Progress 10/01/11 to 09/30/16
Outputs
Target Audience:Forecasters, scientists, and modelers interested in extreme weather events are interested in our extreme weather work. Our novel analysis techniques interest a wide community of scientists who study future climate change, especially extreme events. Our future work on extremes is likely to interest the public (e.g. farmers), various government agencies (e.g. the California Energy Commission), and industry (e.g. utilities). This work was shared at scientific conferences and through publications, including a report to Federal funding agencies. The reporting period saw publication of the third National Climate Assessment (NCA) after a lengthy period of public comment. Changes/Problems:A new postdoctoral scholar was hired and while he was the best candidate among the applicants, productivity was quite low as he needed much training to continue the work. A graduate student failed her PhD qualifying exam and her progress to that point was acknowledged with a successful MS degree and two publications are in preparation. What opportunities for training and professional development has the project provided?The PI, postdoc, an one graduate student attended the AGU fall meeting in San Francisco, each presenting a poster, providing the postdoc and student with a networking opportunity and exposure to related research by others. The new postdoc arrived with underdeveloped research skills; a lot of time was devoted to training him in critical thinking when analyzing diagnostic calculations; he also learned new statistical techniques like clustering. The new postdoc and graduate students learned about LSMP analysis. How have the results been disseminated to communities of interest?An invited oral presentation by the PI and three posters (one invited) were presented at the AGU 2014 fall meeting PI, postdoc, and graduate student. The PI continued disseminating results as applicable in other forums, such as planning for IAMAS conference symposia (Cape Town, in 2017), the Scientific Advisory Board of the Canadian Network for Regional Climate and Weather Processes, and US CLIVAR. A lengthy, 15-author publication appeared that outlines the state of knowledge, theory, modeling, and open questions associated with LSMPs and precipitation extremes was submitted. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Significant progress was made on our primary goal of the understanding of extreme weather events affecting California. The PI, working with a new postdoctoral scholar examined how a baker's dozen of climate models simulate extreme heat events affecting California's Central Valley (CCV). The simulations of historical events were used to rank the models' skill and to weight each model's contribution to a model average. We applied robust techniques to identify both types of heat wave events, including the large scale meteorological patterns (LSMPs). One key discovery was that the future does not have a greater occurrence of LSMPs but there are more CCV heat waves of one of the two types due to a general increase in temperatures over North America. The PI, working with a graduate student continued analysis of the dynamics leading up to extreme cold air outbreaks affecting California. One key discovery is that there is unusually high sea level pressure in the Gulf of Alaska and the Canadian prairie that: drives warm air into western Alaska thereby displacing cold air from there and that high drives cold air to the CCV via a complex path, some of which crosses over the Pacific parallel to the Canadian coast. Working with another graduate student we have looked at trends of extreme heat across the continental U.S. Additionally, we examine trends in the temperature humidity index (THI) as well as temperature (T). Trends in T can be found in the literature, trends in THI, arguably more important for agriculture are not commonly considered.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Grotjahn, R., and�Y.-Y. Lee�(2016),�On climate model simulations of the large-scale meteorology associated with California heat waves,�J. Geophys. Res. Atmos.,�121,�18 -32. DOI: 10.1002/2015JD024191
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Lee, Y-Y. and R. Grotjahn (2016) California Central Valley summer heat waves form two ways. J. Clim., 29, 1201-1217. DOI: 10.1175/JCLI-D-15-0270.1
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Progress 10/01/14 to 09/30/15
Outputs
Target Audience:Forecasters, scientists, and modelers interested in extreme weather events are interested in our extreme weather work. Our novel analysis techniques interest a wide community of scientists who study future climate change, especially extreme events. Our future work on extremes is likely to interest the public (e.g. farmers), various government agencies (e.g. the California Energy Commission), and industry (e.g. utilities). This work was shared at scientific conferences and through publications, including a report to Federal funding agencies. The reporting period saw publication of the third National Climate Assessment (NCA) after a lengthy period of public comment. Changes/Problems:The postdoctoral scholar working on this project found a permanent job in another country and left the project in August 2015. A new postdoctoral scholar was hired in the next period and is undergoing training to continue the work. What opportunities for training and professional development has the project provided?The PI and postdoc both attended the enormous AGU fall meeting in San Francisco, each presenting a poster, providing the postdoc with a networking opportunity and exposure to related research by others. The graduate student who prepared an extreme value statistical analysis guide for non-statisticians, learned how to use those extreme value statistical analysis techniques; the document is shared with anyone on our website. The PI learned about clustering analysis. The postdoc and graduate students learned about LSMP analysis. How have the results been disseminated to communities of interest?As mentioned above, two posters were presented at the AGU 2014 fall meeting. The PI and an Indonesian collaborator presented results (1 talk and 2 posters) at an IUGG meeting in Prague on this and related work. An invited presentation was made on this work in Montreal. The PI's expertise on extremes were incorporated into his authoring parts of the third National Climate Assessment (NCA) chapter on Agriculture. The NCA document led to ignite talks, such as the October talk available from the NCAR Ignite VI website. The PI continued disseminating results as applicable in other forums, such as planning for IAMAS conference symposia, the Scientific Advisory Board of the Canadian Network for Regional Climate and Weather Processes, and US CLIVAR. A lengthy, 13-author publication appeared that outlines the techniques, theory, modeling, and open questions associated with LSMPs. What do you plan to do during the next reporting period to accomplish the goals?Research will focus in the coming year on dynamical causes of the patterns that lead to cold air outbreaks and continue for extreme heat. How well climate models captures those dynamics of those extreme events continues. Three new publications (a book chapter and 2 journal articles) have already appeared in this next time period. We are also exploring a new area, making initial analyses of climate indicators of specific interest to the agricultural sector. The climate indicators are to be tracked over a lengthy historical period and into the future (to the end of the 21st Century).
Impacts
What was accomplished under these goals?
Significant progress was made on our primary goal of the understanding of extreme weather events affecting California. The PI, working with his postdoctoral scholar examined what leads up to extreme heat events affecting California's Central Valley. We applied a robust technique to identify events within the Valley, we tracked the sources of the heat back in time, including the large scale meteorological patterns (LSMPs), and applied the analysis to assess a dozen different climate models. One key discovery was that these heat waves can arise from two distinct patterns of air motion (one from across the Pacific, one from the SW US deserts). It was discovered that models could capture both types of processes, but the relative proportions of each type of heat wave varied a lot between models. The PI, working with a graduate student continued analysis of the dynamics leading up to extreme cold air outbreaks affecting California. Working with another graduate student we prepared a guide for non-statisticians to make extreme value statistical analysis of a dataset. The PI led the effort on a major paper summarizing current knowledge of data, statistical techniques, theory, modeling, and trends of extreme heat events in different regions of North America.
Publications
- Type:
Book Chapters
Status:
Published
Year Published:
2014
Citation:
Hatfield, J., G. Takle, R. Grotjahn, P. Holden, R.C. Izaurralde, T. Mader, E. Marshall and D. Liverman, 2014. Chapter 6: Agriculture, In: Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 150-174. doi:10.7930/J02Z13FR http://nca2014.globalchange.gov/downloads or file:///C:/Users/fzgrotja/Downloads/NCA3_Full_Report_06_Agriculture_HighRes%20(1).pdf
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Grotjahn, R., R. Black, R. Leung, M. Wehner, M. Barlow, M. Bosilovich, A. Gershunov, W.J. Gutowski, J.R. Gyakum, R.W. Katz, Y-Y. Lee, Y-K. Lim, Prabhat, 2015. North American extreme temperature events and related large scale meteorological patterns: a review of statistical methods, dynamics, modeling, and trends. Climate Dynamics 1-34 (online) DOI: 10.1007/s00382-015-2638-6
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Progress 10/01/13 to 09/30/14
Outputs
Target Audience: Forecasters, scientists, and modelers interested in extreme weather events are interested in our extreme weather work. Our novel analysis techniques interest a wide community of scientists who study future climate change, especially extreme events. Our future work on extremes is likely to interest the public (e.g. farmers), various government agencies (e.g. the California Energy Commission), and industry (e.g. utilities). Our subtropical high work interests researchers of tropical and midlatitude weather interaction; there is also local interest since California weather is strongly influenced by this high Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The PI's postdoc and graduate student both attended the enormous AGU fall meeting in San Francisco, each presenting a poster. We are preparing a guide for non-statisticians to use for statistical analysis of extreme events in any dataset; this document will be shared with other researchers of extreme events, this not only helps others, it is a useful knowledge and writing experience for the student. How have the results been disseminated to communities of interest? A dual author article was published illustrating extreme statistical analysis of our Central Valley highest temperatures and a LSMP-index developed by the PI. Results were presented at 2 workshops and a major international conference. A (sole author) book chapter, two journal articles (one as lead author) are in various stages of completion. The PI's expertise on extremes were incorporated into his authoring parts of the third National Climate Assessment chapter on Agriculture (final release 5/2014). The PI's extremes expertise also led to his appointment to the Scientific Advisory Board of the Canadian Network for Regional Climate and Weather Processes during this reporting period. What do you plan to do during the next reporting period to accomplish the goals? Research will focus in the coming year on dynamical causes of the patterns that lead to extreme heat, how well a suite of climate models captures those dynamics, and extending the analysis into other extreme cold air outbreaks. We shall also be exploring initial analyses of climate indicators of specific interest to the agricultural sector.
Impacts
What was accomplished under these goals?
Significant progress was made on our primary goal of the understanding of extreme weather events affecting California. The PI, working with his postdoctoral scholar examined what leads up to extreme heat events affecting California's Central Valley. We developed a robust technique to identify events within the Valley, we tracked the sources of the heat back in time, including the large scale meteorological patterns (LSMPs), and applied the analysis to assess a dozen different climate models. One key discovery was that these heat waves can arise from two distinct patterns of air motion (one from across the Pacific, one from the SW US deserts). The PI, working with a graduate student started analysis of the dynamics leading up to extreme cold air outbreaks affecting California. Working with another graduate student we are preparing a guide for non-statisticians to use for statistical analysis of extreme events in any dataset. The PI continued to lead the effort on a major paper summarizing current knowledge of data, statistical techniques, theory, modeling, and trends of extreme heat events in different regions of North America.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Katz, R, Grotjahn, R., 2014. Statistical methods for relating temperature extremes to large-scale meteorological patterns. (US CLIVAR) Variations 12 (1): 4-7.
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Forecasters, scientists, and modelers interested in extreme weather events are interested in our extreme weather work. Our novel analysis technique interests a wide community of scientists who study future climate change, especially extreme events. Our future work on extremes is likely to interest the public (e.g. farmers), various government agencies (e.g. the California Energy Commission), and industry (e.g. utilities). Our subtropical high work interests researchers of tropical-midlatitude interaction; there is also local interest since California weather is strongly influenced by this high Changes/Problems: Our main problem was to recruit a capable postdoctoral scholar and a graduate student with sufficient expertise to perform the needed tasks; this was not successful until late summer. What opportunities for training and professional development has the project provided? The PI organized an international workshop (Berkeley, August) that was attended by observational data, extreme statistics, dynamics, synoptics, and modeling experts in this field. The PI's postdoc and graduate student both attended this workshop. The PI collaborated with an expert in extreme statistics who analyzed the PI's diagnostic index data in novel ways, which are to be published in a periodical in early 2014. How have the results been disseminated to communities of interest? A sole author article was published in major journal. Results were presented at 2 workshops and a major international conference. A (sole author) book chapter, two journal articles (one as lead author), an influential technical report, and a periodical article were started and are in various stages of completion. The PI's expertise on extremes were incorporated into his authoring parts of: (a) the just-approved 15 year plan for US CLIVAR (a body that organizes research on climate, with specific input to funding agencies and international efforts) and (b) the National Climate Assessment chapter on Agriculture. What do you plan to do during the next reporting period to accomplish the goals? Research will focus in the coming year on dynamical causes of the patterns that lead to extreme heat, how well a suite of climate models captures those dynamics, and extending the analysis into other extreme weather (cold, precipitation, winds, as time permits).
Impacts
What was accomplished under these goals?
Significant progress was made on our primary goal of the understanding of extreme weather events affecting California. The PI organized an international workshop (Berkeley, August) that was attended by observational data, extreme statistics, dynamics, synoptics, and modeling experts in this field. With his new postdoctoral scholar (who started in September) important progress was made identifying events from a 60 year record. Through diagnostic calculations we identified precursors to heat waves here much further back in time than previously, discovering a connection to tropical divergent winds over Indonesia and Australia. We also discovered links to the North Atlantic/Scandinavia. (At this writing we are using a tool to objectively discern whether more than one mechanism can lead to the extreme heat over California.) A (sole author) book chapter, two journal articles (one as lead author), an influential technical report, and a periodical article were started and are in various stages of completion.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Grotjahn, R., 2013: Ability of CCSM4 to Simulate California Extreme Heat Conditions from Evaluating Simulations of the Associated Large Scale Upper Air Pattern. Climate Dynamics. 41:1187-1197 DOI: 10.1007/s00382-013-1668-1
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: ACTIVITIES: I mentored 1 graduate student (research design and procedures) on weather patterns associated with high ozone events in Sacramento. I analyzed simulations of the hottest days that affected the Central Valley (CV) of California. It brought together statisticians, modelers, and dynamicsts from around the world. In June I attended the annual CESM workshop in Breckenridge (CO) and presented recent work. In July I participated in another US CLIVAR Summit (Newport Beach, CA) and reported on the first-ever working group (WG) on extremes (I am chair of the WG). In August I traveled to Kunming (China) to speak at an ICDM workshop there that I helped organize on Dynamics and Predictability of High-impact Weather and Climate Events. In October I attended the annual UCAR Members Meeting (as a UCD representative). During the fall and winter I began organizing a workshop (Berkeley, summer 2013) on weather patterns associated with extreme events, and sessions on climate extremes at an international conference (Davos, summer 2013). A large NSF proposal I composed during fall 2011 and winter 2012 was funded in August 2012. During 2012 I extensively revised and rewrote articles 3 topics for the second edition of the Encyclopedia of Atmospheric Sciences (book to be published in 2014). - EVENTS: I made presentations about various lines of research during the review period. These include: the Community Earth System Model (CESM) workshop (Breckenridge) on whether that popular climate model produces the conditions needed for CV extreme heat waves; an overview of extreme hot spells affecting California from various meteorological perspectives (Kunming workshop). - SERVICES: I am a member of ICDM (the International Commission for Dynamics Meteorology, a prominent piece of IAMAS which is a part of IUGG). In 2011 I was elected Secretary (a 4 year term that precedes being President). I was on the scientific organizing committee for a major workshop in Kunming China (August, 2012). I was named chair of a workshop on weather patterns associated with extreme temperature and precipitation events (Berkeley, 2013). I am a member of the Predictability, Prediction and Applications Interface (PPAI) panel of U.S. CLIVAR. This committee sometimes coordinates research on specialized topics under the umbrella implied by its name and it also advises federal funding agencies on emerging needs related to those topics. I also serve on the editorial board of the journal Dynamics of Atmospheres and Oceans. Since 1984 I have been UCDavis' member representative to the advisory body for NCAR. During winter and spring 2012 I was a project leader for a county-wide 4-H SET project on Climate and Weather. During 2012 I was a lead author for the next National Climate Assessment (for Chapter 6: Agriculture). PRODUCTS: Publications, presentations, and other materials (graphics, data files) are posted on webpages, including: http://atm.ucdavis.edu/~grotjahn/Pubs/ http://atm.ucdavis.edu/~grotjahn/EWEs/ http://atm.ucdavis.edu/~grotjahn/Arctic/ http://atm.ucdavis.edu/~grotjahn/Subhi/ PARTICIPANTS: If c) is checked, narrative must be entered in this block (below). INDIVIDUALS: Richard Grotjahn (PI and Project Director, UCD) Elena Hanrahan (graduate student, worked on a MS degree on large scale weather patterns and ozone; UCD) COLLABORATORS: Eugene Takle (Professor at Iowa State University) and Jerry Hatfield (USDA) who were convening lead authors on the National Climate Assessment. The NCA is report issued approximately every 4 years. Rick Katz (Senior scientist at NCAR in Boulder CO; assisting with extreme statistics). TARGET AUDIENCES: TARGET AUDIENCES Forecasters, scientists, and modelers interested in extreme weather events are interested in our extreme weather work. Our novel analysis technique interests a wide community of scientists who study future climate change, especially extreme events. Our work on extremes is likely to interest the public (e.g. farmers), various government agencies (e.g. the California ISO), and industry. There is local interest since we focus on California weather extremes. EFFORTS Results from the forecasting work are used in the advanced synoptic meteorology class (ATM111/111L) required of our majors at UCD. The results of all the projects are presented at national and international scientific conferences where we also receive valuable feedback. My 4-H project was the first county-wide SET project and it taught high school 4-H'ers about climate and weather topics relevant to agriculture. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
CHANGE IN KNOWLEDGE AND ACTIONS: We gained a greater understanding of whether an excellent and popular global climate model can simulate the large scale patterns that fosters the formation of the most extreme events. Specifically, we developed a scheme to identify the patterns in model output, applied it to the CESM, and discovered that the model does not develop the pattern often enough for extreme heat and especially for strong sea breeze cooling situations. We learned more about how to analyze these extreme events using extreme statistical methodology. CHANGE OF CONDITIONS: Our approach of emphasizing the large scale pattern was influential in demonstrable ways. Federal funding agencies through US CLIVAR funded my proposal to develop a national working group on this approach involving scientists from across the country. All prior work emphasizes statistical or regional model downscaling, but even the best regional model will not simulate a local process if the large scale patterns (from a global model) driving that regional model are incorrect. By funding the building of an national team (12 core working group members from across the country) and by planning the first-ever workshop on this topic (to be held August 2013) a new understanding certain types of extreme events and a new approach to assessing climate models has been established.
Publications
- No publications reported this period
|
Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: ACTIVITIES: I mentored 1 graduate student (research design and procedures) on weather patterns associated with high ozone events in Sacramento. I analyzed simulations of the hottest days that affected the Central Valley (CV) of California. In June I traveled to Boulder (CO) to speak and be a panel member in a researcher colloquium I helped organize on Statistical Assessment of Extreme Weather Phenomena under Climate Change. It brought together statisticians, modelers, and policy makers from various application sectors. In June I attended the annual CESM workshop in Breckenridge (CO) and presented recent work. In July I attended the once in 4 years IUGG General Assembly in Melbourne Australia; I was an invited speaker, co-convenor of two sessions, session chair; I also participated in the bi-annual ICDM meeting. In August I participated in another US CLIVAR Summit (Woods Hole, MA) and led the effort to create a working group on extremes. In October I attended the annual UCAR Members Meeting (as a UCD representative) and also developed a research plan for a proposal. EVENTS: I made presentations about various lines of research during the review period. These include: extreme weather affecting 10 major California agricultural commodities (Boulder colloquium); the Community Earth System Model (CESM) workshop (Breckenridge) on whether that popular climate model produces the conditions needed for CV extreme heat waves; I gave 2 presentations (one invited) at the IUGG meeting in Melbourne. In March I hosted a workshop on weather demonstrations and made a dinner speech about climate models for Sacramento area public school science teachers (SIRC). SERVICES: I am a member of ICDM (the International Commission for Dynamics Meteorology, a prominent piece of IAMAS which is a part of IUGG). At the Melbourne meeting I was elected Secretary (a 4 year term that precedes being President). I was named to the scientific organizing committee for a major workshop in Kunming China (August, 2012). I prepared and submitted a proposal for student travel support for the Kunming meeting. I prepared a proposal for a new US CLIVAR working group on the topic of temperature and precipitation extremes and named provisionally as co-chair. I am a member of the Predictability, Prediction and Applications Interface (PPAI) panel of U.S. CLIVAR. This committee sometimes coordinates research on specialized topics under the umbrella implied by its name and it also advises federal funding agencies on emerging needs related to those topics. I also serve on the editorial board of the journal Dynamics of Atmospheres and Oceans. Since 1984 I have been UCDavis' member representative to the advisory body for NCAR. I am also a project leader for a county-wide 4-H project. In December I was asked to be a lead author on the next National Climate Assessment (on extreme weather and agriculture) to be written in 2012. PRODUCTS: Publications, presentations, and other materials (graphics, data files) are posted on webpages, including: http://atm.ucdavis.edu/~grotjahn/Pubs/ ; http://atm.ucdavis.edu/~grotjahn/Arctic/ ; http://atm.ucdavis.edu/~grotjahn/Subhi/ ; PARTICIPANTS: INDIVIDUALS: Richard Grotjahn (PI and Project Director, UCD) Elena Hanrahan (graduate student, working on a MS degree on large scale weather patterns and ozone; UCD) COLLABORATORS: Eugene Takle (Professor at Iowa State University; on a report about extreme weather and major US agricultural commodities both irrigated and not). Rick Katz (Senior scientist at NCAR in Boulder CO; assisting with extreme statistics). TARGET AUDIENCES: TARGET AUDIENCES Forecasters, scientists, and modelers interested in extreme weather events are interested in our extreme weather work. Our novel analysis technique interests a wide community of scientists who study future climate change, especially extreme events. Our future work on extremes is likely to interest the public (e.g. farmers), various government agencies (e.g. the California ISO), and industry. Our subtropical high work interests researchers of tropical-midlatitude interaction; there is also local interest since California weather is strongly influenced by this high. EFFORTS Results from the forecasting work are used in the advanced synoptic meteorology class (ATM111/111L) required of our majors at UCD. The results of all the projects are presented at international scientific conferences where we also receive valuable feedback. My workshop for Sacramento area public school science teachers (SIRC) showed them how to construct 19 different weather-related demonstrations from inexpensive materials as well as how each item demonstrated a specific weather principle. I also de-mystified climate models for the SIRC participants. My 4-H project (mainly in 2012) is the first county-wide SET project and it will facilitate learning by high school 4-H'ers about climate and weather topics relevant to agriculture. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
CHANGE IN KNOWLEDGE AND ACTIONS: We gained a greater understanding of whether an excellent and popular global climate model can simulate the large scale patterns that fosters the formation of the most extreme events. Specifically, we developed a scheme to identify the patterns in model output, applied it to the CESM, and discovered that the model does not develop the pattern often enough for extreme heat and especially for strong sea breeze cooling situations. We learned more about how to analyze these extreme events using extreme statistical methodology (GEV, GPD). CHANGE OF CONDITIONS: Our approach of emphasizing the large scale pattern was influential in a small but larger long term way. We were encouraged by Federal funding agency representatives and by the US CLIVAR Director to develop a national working group on this approach involving scientists from across the country. All prior work emphasizes statistical or regional model downscaling, but even the best regional model will not simulate a local process if the large scale patterns (from a global model) driving that regional model are incorrect.
Publications
- No publications reported this period
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: ACTIVITIES: I mentored 1 graduate student (research design and procedures). We completed our linear stationary wave (LSW) model procedures including calculations of forcing from CAM3 bias and vice versa and for limited regions of the globe. The work was written up and submitted for publication in a refereed international journal. We developed further our analyses of simulations of the hottest days that affected the Central Valley (CV) of California. In July I traveled to Europe to meet with experts in extreme statistics in Exeter England and Saclay France. I had extensive discussions of the appropriate use of the methodology, these were incorporated into a paper that was submitted and later accepted on using the large scale upper air pattern to pick out rare hottest days. From mid-May to early June I visited the Laboratory for Atmospheric and Geophysical Sciences (LASG) in Beijing China. I had a long-standing invitation visit them, LASG covered the costs, and my sabbatical freed up my time. I worked with 2 senior researchers there on some projects, I advised two of their students on their research design, gave several presentations, and participated in their weekly research meetings. I spent the rest of my sabbatical writing my third book (though an important chunk of the work was lost in a computer malfunction) and in writing 3 proposals. I am supervising a MS student working on weather patterns associated with high ozone events in the Sacramento region. EVENTS: I made presentations about various lines of research during the review period. These include: presentations on 4 different topics at LASG (Beijing, China) in May, the Community Climate System Model (CCSM) workshop (Breckenridge, CO; June), and 3 presentations (same topic) in Europe (July). SERVICES: I am a member of ICDM (a commission of IAMAS which is a part of IUGG). I was placed on the organizing committees for two very large sessions at the 2011 IUGG meeting in Melbourne Australia. I was also selected to co-organize a CLIVAR workshop as part of the National Center for Atmospheric Research (NCAR) 2011 summer colloquium in Boulder Colorado; the workshop is on extreme climate events and their simulation from the perspective of stakeholders (electric power, water resources managers, reinsurance, etc.) In the spring I was appointed as a member of the Predictability, Prediction and Applications Interface (PPAI) panel of U.S. CLIVAR. This committee sometimes coordinates research on specialized topics under the umbrella implied by its name and it also advises federal funding agencies on emerging needs related to those topics. I also serve on the editorial board of the journal Dyn. Atmos. And Oceans. Since 1984 I have been UCDavis' member representative to the advisory body for NCAR. PRODUCTS: The publications, results from experiments, and other materials (graphics, data files, and documents) are posted on webpages that I and my postdoc maintain. These pages include: http://atm.ucdavis.edu/~grotjahn/Pubs/ http://atm.ucdavis.edu/~grotjahn/Arctic/ http://atm.ucdavis.edu/~grotjahn/Subhi/ PARTICIPANTS: INDIVIDUALS Richard Grotjahn (PI and Project Director, UCD) Elena Hanrahan (graduate student, working on MS degree on large scale weather patterns and ozone (UCD) COLLABORATORS Grant Branstator (senior scientist at NCAR in Boulder CO, assisting with Arctic project) Lin Lin Pan (project scientist at NCAR in Boulder CO, assisting with Arctic project) Joe Tribbia (senior scientist at NCAR in Boulder CO, assisting with Arctic project) Renato Vitolo (research faculty member, Univ. of Exeter, England, assisting with extreme statistics) TARGET AUDIENCES: TARGET AUDIENCES Scientists and modelers working in climate simulation and climate change, including polar climate, are served by our Arctic error project. Forecasters as well as researchers interested in west coast extreme weather events are interested in our extraordinary weather work. Our novel downscaling project interests a wide community of scientists who study future climate change, especially extreme events. Our future work on the downscaling project is likely to interest the public (e.g. farmers), various government agencies (e.g. the California ISO), and industry. Our subtropical high work interests researchers of tropical-midlatitude interaction; there is also local interest since California weather is strongly influenced by this high. EFFORTS Results from the forecasting work are used in the advanced synoptic meteorology class (ATM111/111L) required of our majors at UCD. The results of all the projects are presented at international scientific conferences where we also receive valuable feedback. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
CHANGE IN KNOWLEDGE AND ACTIONS: We gained a greater understanding of the large scale pattern that fosters the formation of the most extreme events. Specifically, we understand why a low level heat maximum has to be just offshore for the hottest events (so lower sea level pressure migrates from the CV to the coast). The upper level pattern builds higher pressure over the Great Basin thereby creating a pressure gradient force to oppose cooling sea breezes. The large scale pattern enhances sinking, lowering and intensifying the subsidence inversion over the CV. This happens the night before the hottest days. The subsequently sunshine is mixed only in the shallow layer below the inversion thereby creating the extreme max temperatures in the CV. This picture is complicated by mountain upslope flows from the daytime heating, but those appear to be trapped near the surface (below the inversion). We learned more about how to analyze these extreme events. There is a special branch of statistics devoted to analyzing events at the extreme tails of a distribution. From that information we learned a bit about the return periods (estimated statistically) for events of a given magnitude. CHANGE OF CONDITIONS: None.
Publications
- Grotjahn, R., L-L. Pan, J. Tribbia, 2011: Sources of CAM3 vorticity bias during northern winter from diagnostic study of the vorticity equation. Climate Dynamcis. in press. DOI: 10.1007/s00382-011-0998-0
- Grotjahn, R., 2011 : Identifying extreme hottest days from large scale upper air data : A pilot scheme to find California Central Valley summertime maximum surface temperatures. Climate Dynamcis. in press. DOI: 10.1007/s00382-011-0999-z
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: ACTIVITIES: I completed my mentoring of a postdoc in several activities (proposal preparation, publication preparation, research procedures). He has now found permanent employment out of state. I mentored 2 graduate students (research procedures and publication preparation). One graduate student completed her MS degree at the end of 2009. We completed our linear stationary wave (LSW) model procedures including calculations of forcing from CAM3 bias and vice versa and for limited regions of the globe. We completed work analyzing the vorticity bias equation; that work examined both of the equation term by term, to learn more about biases that affect the Arctic simulation. The work was written up and submitted for publication in a refereed international journal. We developed analyses of simulations of the record-setting 2006 heat wave that affected the Central Valley (CV) of California. The work used a half dozen different types of statistical tests and calculations applied to output from the state of the art WRF forecast model. The study also examined the spatial extent by merging satellite and ground observations. We used our knowledge that heat waves affecting the CV have very large scale patterns in the upper atmosphere to develop an index that predicts heat waves at CV surface stations from the large scale upper air fields. This index was further refined and analyzed using statistical techniques unique to 'extreme' data. I completed a book chapter (on extreme weather) for a popular science book and began working on an advanced book on the general circulation of the atmosphere. EVENTS: I made five presentations about various lines of research during the review period. These include: the Community Climate System Model (CCSM) workshop (Breckenridge, CO; June), the International Association of Meteorology and Atmospheric Science (IAMAS) General Assembly (Montreal, Canada, July), the Climate Diagnostics Workshop (Monterey, CA, October) SERVICES: I am a member of ICDM (a commission of IAMAS which is a part of IUGG). For ICDM I hosted a symposium on subtropical highs; such highs control much of California weather. I also serve on the editorial board of the journal Dyn. Atmos. And Oceans. PRODUCTS: The publications, results from experiments, and other materials (graphics, data files, and documents) are posted on webpages that I and my postdoc maintain. These pages include: http://atm.ucdavis.edu/~grotjahn/Pubs/ ; http://atm.ucdavis.edu/~grotjahn/Arctic/ ; http://atm.ucdavis.edu/~grotjahn/Subhi/ ; http://atm.ucdavis.edu/~lpan/doc1/ ; http://atm.ucdavis.edu/~lpan/doc3/ ; http://atm.ucdavis.edu/~lpan/doc4/ ; http://atm.ucdavis.edu/~lpan/presentation/ PARTICIPANTS: INDIVIDUALS Richard Grotjahn (PI and Project Director, UCD) Lin Lin Pan (postdoctoral scholar, responsible for LSW and CAM3 models and activities related to the Arctic error study, UCD) Elena Hanrahan (graduate student, working on MS degree on large scale weather patterns and air quality (primarily O3, UCD) Aude Valade (graduate student, working on MS degree on simulation and extent of California heat waves, UCD) COLLABORATORS Grant Branstator (senior scientist at NCAR in Boulder CO, assisting with Arctic project) Joe Tribbia (senior scientist at NCAR in Boulder CO, assisting with Arctic project) TARGET AUDIENCES: TARGET AUDIENCES Scientists and modelers working in climate simulation and climate change, including polar climate, are served by our Arctic error project. Forecasters as well as researchers interested in west coast extreme weather events are interested in our extraordinary weather work. Our novel downscaling project interests a wide community of scientists who study future climate change, especially extreme events. Our future work on the downscaling project is likely to interest the public (e.g. farmers), various government agencies (e.g. the California ISO), and industry. Our subtropical high work interests researchers of tropical-midlatitude interaction; there is also local interest since California weather is strongly influenced by this high. EFFORTS Results from the forecasting work are used in the advanced synoptic meteorology class (ATM111/111L) required of our majors at UCD. The book chapter will improve my severe weather class (ATM010) with new diagrams and information. As mentioned above, the results of all the projects are presented at international scientific conferences where we also receive valuable feedback. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
CHANGE IN KNOWLEDGE AND ACTIONS: We learned that the Arctic simulation bias for vorticity (like temperature) was connected to the north Atlantic storm track. In addition the bias in the Beaufort High simulation was linked to erroneous motion of vorticity that the model should have drawn out of Siberia (but instead drew across the Bering Strait). The vorticity and temperature results were linked via thermodynamic arguments such that shallow layer of cold bias led to elevated sea level pressure (and vice versa for shallow warm layer). These results were further reinforced by the linear stationary wave model (LSWM) results. We learned that the LSWM had more limited use as a diagnostic tool than expected. For the 'California' subtropical high, interactions with attendees at the IAMAS (MOCA-09) conference improved our understanding and developed some ideas for why theoretical models and observations do not match. For the CV (California Central Valley) heat waves, we gained a greater understanding of the large scale pattern that fosters the formation of the most extreme events. Specifically, we used the knowledge we gained from our Arctic simulation bias work to understand why a low level heat maximum had to be just offshore for the hottest events (to lower sea level pressure which drives offshore, sinking, winds). We learned more about the skill of the model and developed ideas for how to apply our technique to better understand future climate. We quantified temperature error (as a function of time of day) for the best forecast model; maximum temperature errors were largest. This was partly an issue of the local wind field and partly how soil moisture was handled. CHANGE OF CONDITIONS: We implemented and ran locally a version of the US National Weather Service primary forecast model (WRF).
Publications
- JOURNAL ARTICLES Parn, L-L., Grotjahn, R., and Tribbia, J., 2009, Sources of CAM3 temperature bias during northern winter from diagnostic study of the temperature bias equation. Climate Dynamics, DOI: 10.1007/s00382-009-0608-6.
- BOOK CHAPTER Grotjahn, R., 2010, 'Extremes', a chapter in The Encyclopedia of Weather and Climate Change, by Fry, J., Graf, H-F., Grotjahn, R., Raphael, M., Saunders, C., and Whitaker, R. (listed alphabetically) UC Press, Berkeley California (in press; March 2010 release date) p. 142-201.
- ABSTRACTS Grotjahn, R., and Pan, L-L., 2009: Northern Hemisphere winter CAM3 bias analysis. 14th CCSM Workshop 15-18 June 2009 Breckenridge, CO. See: http://www.cgd.ucar.edu/csm/events/ws.2009/Agendas/POSTpolar09.pdf (file link: http://atm.ucdavis.edu/~grotjahn/Arctic/ )
- Grotjahn, R., 2009: Large scale weather patterns associated with California extreme heat waves and their link to daily summer maximum temperatures in the Central Valley. MOCA-09 19-29 July 2009 Montreal, Canada. (M08.25) Available at: http://www.moca-09.org/e/documents/IAMAS2009Program15w.pdf (see page 79) (file link: http://atm.ucdavis.edu/~grotjahn/EWEs/ )
- Grotjahn, R., and Pan, L-L., 2009: Temperature and vorticity terms related to CAM3.0 Arctic surface climate simulation bias. MOCA-09 19-29 July 2009 Montreal, Canada. (J02.5) See: http://www.moca-09.org/e/documents/IAMAS2009Program15w.pdf (see page 107) (file link: http://atm.ucdavis.edu/~grotjahn/Arctic/ )
- Grotjahn, R., and Pan, L-L., 2009: On observed associations between the subtropical highs and diabatic heating. MOCA-09 19-29 July 2009 Montreal, Canada. (M10.46) See: http://www.moca-09.org/e/documents/IAMAS2009Program15w.pdf (see page 162)
- Grotjahn, R., 2009: Large scale weather patterns associated with California heat waves and their use in a hindcast and future climate. NOAA Climate Diagnostics and Prediction Workshop, 26-30 October 2009. (9.07) See: http://www.cpc.ncep.noaa.gov/products/outreach/workshops/CDPW34/CDPW3 4_agenda.pdf (file link: http://atm.ucdavis.edu/~grotjahn/EWEs/ )
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: ACTIVITIES: I mentored a postdoc in several activities (proposal preparation, publication preparation, research procedures). I mentored 3 graduate students (research procedures and publication preparation). One graduate student completed her MS degree. We continued to refine our linear stationary wave (LSW) model procedures including calculations of forcing from CAM3 bias and vice versa and for limited regions of the globe. We completed work analyzing the temperature bias equation and made progress on a similar analysis of the vorticity bias equation. That work examined both of these novel equations term by term, to learn more about biases that affect the Arctic. (The connection between remote forcing and the Arctic was established with the LSW analysis.) We also examined diabatic heating both at specific levels, vertically integrated, and partitioned by physical process and found interesting chain of bias properties for storms in the North Atlantic. We developed analyses of the spatial extent of heat waves affecting the Central Valley (CV) of California. The work used about a dozen different types of statistical tests and calculations applied to CV heat waves defined by several criteria. We used our knowledge that heat waves affecting the CV have very large scale patterns in the upper atmosphere to develop an index that predicts heat waves at CV surface stations from the large scale upper air fields. DISSEMINATION EVENTS: We made three presentations about various lines of research during the review period. These include: AGU fall meeting (San Francisco, CA; December), AMWG meeting (Boulder, CO; February), and the CCSM workshop (Breckenridge, CO; June). SERVICES: I am a member of ICDM (a commission of IAMAS which is a part of IUGG). For ICDM I developed a symposium for the next conference in 2009. I also serve on the editorial board of the journal Dyn. Atmos. And Oceans. PRODUCTS: The publications, results from experiments, and other materials (graphics, data files, and documents) are posted on webpages that I and my postdoc maintain. These pages include: http://atm.ucdavis.edu/~grotjahn/Pubs/ ; http://atm.ucdavis.edu/~grotjahn/Arctic/ ; http://atm.ucdavis.edu/~grotjahn/Subhi/ ; http://atm.ucdavis.edu/~lpan/doc1/ ; http://atm.ucdavis.edu/~lpan/doc3/ ; http://atm.ucdavis.edu/~lpan/doc4/ ; http://atm.ucdavis.edu/~lpan/presentation/ PARTICIPANTS: INDIVIDUALS Richard Grotjahn (PI and Project Director, UCD) Lin Lin Pan (postdoctoral scholar, responsible for LSW and CAM3 models and activities related to the Arctic error study, UCD) Brooke Bachmann (graduate student, performed geographic heat wave analysis, Completed MS degree, UCD) Elena Hanrahan (graduate student, working on MS degree on northwind events and air quality, UCD) Aude Valade (graduate student, working on MS degree on simulation and spread of heat waves, UCD) COLLABORATORS Grant Branstator (senior scientist at NCAR in Boulder CO, assisting with Arctic project) Bruce Briegleb (senior scientist at NCAR in Boulder CO, assisting with Arctic project) Joe Tribbia (senior scientist at NCAR in Boulder CO, assisting with Arctic project) Richard Katz (senior scientist at NCAR in Boulder CO, assisting with extreme events statistics) TARGET AUDIENCES: TARGET AUDIENCES Scientists and modelers working in climate simulation and climate change, including polar climate, are served by our Arctic error project. Forecasters as well as researchers interested in west coast extreme weather events are interested in our extraordinary weather work. Our novel downscaling project interests a wide community of scientists who study future climate change, especially extreme events. Our future work on the downscaling project is likely to interest the public (e.g. farmers), various government agencies (e.g. the California ISO), and industry. Our subtropical high work interests researchers of tropical-midlatitude interaction; there is also local interest since California weather is strongly influenced by this high. EFFORTS Results from the forecasting work are used in the advanced synoptic meteorology class (ATM111/111L) required of our majors at UCD. As mentioned above, the results of all the projects are presented at international scientific conferences where we also receive valuable feedback. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
CHANGE IN KNOWLEDGE AND ACTIONS: We learned that the Arctic simulation bias for temperature was connected to the north Atlantic storm track. In addition the simulation of that storm track was contrary: the storms were weaker in terms of the kinetic energy, yet they produced much more precipitation than observed. In following this connection, we expanded our study to include midlatitude bias as well as the Arctic. In showing a connection to transient storms, we have to change our focus to techniques that can assess different states of the storms; specifically we intend to use CAM in a forecast mode instead of the climate simulation mode we've been using. For the CV (California Central Valley) heat waves, we learned that they often extend far north of the CV, with a 1 day lag they are highly correlated with unusual warmth in Washington and Oregon. However, they had less correlation with heat at much closer cities in Nevada. In developing an index connecting extreme heat waves at CV stations (Fresno, Bakersfield, Red Bluff) we found that the index had unexpected skill. The index was designed to identify the highest 1 percent of extremely hot days which it does with good skill. However, the index also is highly correlated with maximum temperature on other summer days as well (r=0.85) which is a higher correlation than obtained using a regional climate model. Such regional climate models are used to downscale output from global scale climate models to individual stations or small regions. Our index represents a new way to do such a downscaling and has the potential to have more skill than the standard procedures used to predict future climate changes locally. We intend to apply this technique to downscaling predictions of future extreme events for various possible future climate scenarios. To do that we need to develop some sophisticated statistics for setting confidence limits on our predictions and we intend to work further with statisticians (such as Dr. Katz) on this point.
Publications
- Grotjahn, R., and L-L. Pan, 2008: Arctic Surface DJF Biases in CAM3 Viewed as Forcing Fields. Joint CCMWG and AMWG meeting, 11-15 February 2008, Boulder CO. Available at: http://www.ccsm.ucar.edu/csm/working_groups/Atmosphere/Presentations/ 2008WG.presentations/v7-cclim_and_AMWGs-agenda-Feb-2008.htm ABSTRACT
- Grotjahn, R., and L-L. Pan, 2008: Sources of CAM Arctic Surface Climate Bias Deduced from the Vorticity and Temperature Equations -- DJF. 13th CCSM Workshop 17-19 June 2008 Breckenridge, CO. Available at: http://www.ccsm.ucar.edu/events/ws.2008/Presentations/Tarn/PCWG/Grotj ahn_CCSM-June08-talk4.pdf ABSTRACT
- L-L. Pan, and R. Grotjahn, 2008: Diagnostic study of the simulation bias in Community Atmospheric Model (CAM3). AGU Fall meeting, Innovative Applications of Satellite and Ground Observations in Evaluating General Circulation Models III, 18 December, San Francisco Abstract available at: http://www.agu.org/cgi-bin/sessions5meeting=fm08∂=A43C&maxhits =400 ABSTRACT
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: ACTIVITIES: I mentored a postdoc in several activities (proposal preparation, publication preparation, research procedures). I mentored 3 graduate students (research procedures and publication preparation). We imported a large atmospheric climate model code (CAM3) and can now run that model locally on a new computer cluster. We continued to refine our LSW model procedures including calculations of forcing from CAM3 bias and vice versa and for limited regions of the globe. We developed analyses of the spatial extent of heat waves affecting a region of California and beyond. With a former student, I completed a project to analyze the large-scale signatures of 4 types of extraordinary weather affecting the southern Sacramento valley: hottest heat wave, coldest freeze, heaviest rainfall, longest duration fog events; the accompanying publication is in press. I completed two articles related to the large scale atmospheric circulation. One is an analysis of the differences between
two global datasets (ERA-40 and NDRA-II) that are frequently used by many researchers around the globe; thus it is a valuable reference work. I also extended my analysis of subtropical highs to include all 5 highs; I presented a comparison/contrast invited talk; a publication is under development. DISSEMINATION EVENTS: We made six presentations about various lines of research during the review period. These include: AMS annual meeting (San Antonio, TX; January), CAM3 AMWG meeting (Boulder, CO; January), CCSM workshop (Breckenridge, CO; June), and IUGG-2007 (Perugia, Italy; July). The publications, results from experiments, and other materials (graphics, data files, and documents) are posted on webpages that I and my postdoc maintain. These pages include: http://atm.ucdavis.edu/~grotjahn/Pubs/ ; http://atm.ucdavis.edu/~grotjahn/Arctic/ ; http://atm.ucdavis.edu/~lpan/doc1/ ; http://atm.ucdavis.edu/~lpan/doc3/ ; and others. SERVICES include membership on ICDM (of IAMAS) and editing 2
special issues of Dyn. Atmos. And Oceans. PRODUCTS: Some interesting results follow. We have proven that the primary sources of many climate models error in the Arctic are local and within the midlatitude storm track. This information will greatly narrow the scope of phenomena that modelers should focus their efforts on to solve these Arctic errors. We found we could reduce the Arctic error with a simple empirical forcing term. While the ERA-40 dataset is superior in many regions and for most variables, it has surprising problems dealing with topography and some other areas, such as the tropical west Pacific. NDRA-II has some surprises, such as a missing Atlantic ICZ during January. Sacramento's severe heat waves are not as widespread across the western US as previously supposed. A tool we developed is a model to deduce the forcing associated with any stationary pattern (the Arctic model error being just one such application) the resultant forcing can be used as a statistical
correction term.
PARTICIPANTS: INDIVIDUALS Richard Grotjahn (PI and Project Director, UCD) Lin Lin Pan (postdoctoral scholar, responsible for LSW and CAM3 models and activities related to the Arctic error study, UCD) Brooke Bachmann (graduate student, performing historical heat wave analysis for MS degree, UCD) Elena Hanrahan (graduate student, working on MS degree, UCD) Aude Valade (graduate student, working on MS degree, UCD) COLLABORATORS Grant Branstator (senior scientist at NCAR in Boulder CO, assisting with Arctic project) Bruce Briegleb (senior scientist at NCAR in Boulder CO, assisting with Arctic project) Joe Tribbia (senior scientist at NCAR in Boulder CO, assisting with Arctic project)
TARGET AUDIENCES: TARGET AUDIENCES Scientists and modelers working in climate simulation and climate change, including polar climate, are served by our Arctic error project. Forecasters as well as researchers interested in west coast extreme weather events are interested in our extraordinary weather work. Our global datasets work interests a wide community of scientists who use such data. Our subtropical high work interests researchers of tropical-midlatitude interaction; there is also local interest since California weather is strongly influenced by this high. EFFORTS Results from the forecasting work are used in the advanced synoptic meteorology class (ATM111/111L) required of our majors at UCD. The general circulation survey article forms the main basis of an 90 minute lecture in a graduate level course (ATM240) at UCD. As mentioned above, the results of all the projects are presented at international scientific conferences where we also receive valuable feedback.
Impacts
CHANGE IN KNOWLEDGE AND ACTIONS: Some of the new fundamental knowledge is summarized above. For the Arctic simulation error work, that new knowledge led us to make a parallel study of three relevant governing equations, evaluating the error of each term. Since each term represents a physical process, this procedure allows us to identify the specific processes that are in error and to match the process with elements of the forcing found by the LSW model. Our analysis of the heat waves of Sacramento led us to revise our procedures several times. We are analyzing extremes, which are rare, and common statistical procedures do not apply to rare events. We also had to revise our statistical approach to improve how we extract information from the links. Even the ranking of the worst heat waves varied notably depending on the criteria selected (by hottest temperature? By hottest 3 day average? by longest duration?). The preparation of the paper (with Faure) on extraordinary
weather helped us identify procedures for a follow up study (proposal submitted). Our use of the LSW model spurred our interest in a follow up study of tropical-midlatitude interaction (proposal submitted). CHANGE IN CONDITIONS: The extraordinary weather work provides local forecasters with guidance on how to interpret weather maps produced by computer forecast models by identifying key structures. Our study of the Arctic simulation error is beginning to provide model developers with key information about what to target for improvement (if not to use an empirical correction). Since the Arctic is most sensitive to global climate change, our results are potentially very useful to many individuals and agencies.
Publications
- Grotjahn, R., 2007: Observational study of subtropical highs (invited) IUGG XXIV, IAMAS session MS011 on the Dynamics of Eastern Tropical Oceans and Subtropical Highs. 4 July, 2007, Perugia, Italy. Available at: http://www.iugg2007perugia.it/abstractDetails.asp?inObj=3470
- Grotjahn, R., 2007: Large Scale Signatures of Extreme Weather Events in the California Central Valley IUGG XXIV, IAMAS session MS015 on Extreme Weather and Climate Events: Past Occurrences and Future Likelihoods. 9-11 July, 2007, Perugia, Italy. Available at: http://www.iugg2007perugia.it/abstractDetails.asp?inObj=3470
- Pan, L.-L., T. Li, and R. Grotjahn, 2007: Synoptic eddy feedback and tropical ISO-midlatitude connection. The 4th AOGS annual meeting, July 30-August 4, Bangkok, Thailand. (session AS10-A0028) Available at: http://www.asiaoceania.org/society/public.asp?)
- Grotjahn, R., 2007, Different Data, Different General Circulations? A Comparison of Selected Fields in NCEP/DOE AMIP-II and ECMWF ERA-40 Reanalyses. Dyn. of Atmos. and Oceans, in press.
- Grotjahn, R., 2007, Preface to part 2. Dyn. of Atmos. and Oceans, in press.
- Grotjahn, R., and L-L. Pan, 2007: Forcing fields derived from Arctic surface biases in CAM3. AMWG meeting, 29-30 January 2007, Boulder CO. Available at: http://www.ccsm.ucar.edu/working_groups/Atmosphere/Agendas/amwgmeetin gagenda2006Jan.html
- Grotjahn, R., and L-L. Pan, 2007: Sources of CAM3 Arctic Surface Bias from Parsing the Temperature Equation. 12th CCSM Workshop 19-21 June 2007 Breckenridge, CO. Available at: http://www.ccsm.ucar.edu/events/CCSMAnnualWorkshop2007/posterabstract handout3.pdf
- Grotjahn, R., 2007: Comparison of basic fields in ERA-40 and NCEP/DOE Reanalysis II Datasets. IUGG XXIV, IAMAS jointly with IAHS and IAPSO session JMS011 on Assessing & Exploiting Re-analysis Data Sets. 4 July, 2007, Perugia, Italy. Available at: http://www.iugg2007perugia.it/abstractDetails.asp?inObj=3470
- Grotjahn, R., and Osman, M., (2007) Remote weather associated with North Pacific subtropical sea-level high properties. Int. J. Climatol. 27:587-602.
- Grotjahn, R., (2007) Preface to part 1. Dyn. of Atmos. and Oceans 43:1-2. doi:10.1016/j.dynatmoce.2006.10.001
- Grotjahn, R., (2007) Deducing the general circulation from basic concepts and a few empirical facts. Dyn. of Atmos. and Oceans 43:3-15. doi:10.1016/j.dynatmoce.2006.05.002
- Grotjahn, R., and G. Faure, 2007, Composite Predictor Maps of Extraordinary Weather Events in the Sacramento California Region. Wea. Anal. and Forecasting, in press.
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Progress 01/01/06 to 12/31/06
Outputs
Dr. Grotjahn supervised 4 graduate students and 1 postdoc during this year. We pursued 4 lines of research: a) We have started a new line of research that applies our earlier work into forecasting extraordinary events in 5 categories: severe freezes, long duration fog, extreme heat waves, heat wave termination, and heavy rain. We learned that those events are associated with large scale weather patterns. Since those patterns have a scale resolvable by climate models, we can apply our techniques to climate model output and have a completely new way to assess the occurrence frequency and other statistics of these events in future climate. A paper is under revision at this writing as are 2 grant proposals. b) We continue our study of what maintains the subtropical highs. Further work with observations led to connections between strength of high and remote forcing. Our work has shown some theories to lack observational support, several theories have the correct
connections, but reverse cause and effect. Work on the North Pacific high (NP high) has been published (on line). The NP high has a different mix of remote interactions compared to the SP high. Frontal cyclone forcing dominates the NP high time series requiring special filtering techniques to identify any other forcing factors. c) NSF continues to fund our work to understand why most climate models have similar errors in their simulated Arctic surface climate (ASC). The atmospheric errors are subtle, resist obvious solutions, and cause significant errors in the simulated sea ice distribution. We identified several remote forcing links between the ASC and other observed and simulated variables. To investigate the physics behind this statistical connection we are using a highly sophisticated linear stationary wave model running at UCD. As one student graduated during the period, the work has been picked up by a new postdoctoral scholar and the rate of progress has greatly improved. We
are presently refining the robustness of the overall simulation prior to interrogating the remote and local connections. Other observational and model data analysis continues. d) I am editing two special issues of Dynamics of Atmospheres and Oceans on the atmospheric general circulation. My overview paper has been accepted and my other paper, making a needed comparison between the general circulations in two popular datasets, is under revision at this writing. During the review period, 2 refereed publications have been accepted and 2 more are in revision. 2 conference abstracts were prepared and 1 presentation was made.
Impacts
The project increases our understanding of the extraordinary events that often have major economic impact to our region (especially hard freezes, heavy rain events that cause flooding, and severe heat waves). With improved understanding comes improvement in forecasting and future planning for these important weather events. The subtropical highs strongly influence our weather and are a continuing focus of study. Our Arctic climate simulation work is important to understanding global change. In models, the Arctic region responds more strongly to global warming than do middle and tropical latitudes. The utility of such global warming predictions hinges on understanding (and hopefully reducing) errors in the Arctic simulation.
Publications
- GROTJAHN, R., and M. OSMAN, 2006. Remote weather associated with North Pacific subtropical sea level high properties. International Journal of Climatology, DOI: 10.1002/joc.1423 (published online 12 October).
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Progress 01/01/05 to 12/31/05
Outputs
Dr. Grotjahn supervised three graduate students during this year. We pursued 4 lines of research: a) I used a nonlinear model and coherent localized initial structures to test a popular conceptual model of cyclone formation. A key result showed that the conceptual model did illustrate a significant growth process, but for reasons that differed from the commonly-believed basis for that conceptual model. (See publication list) b) We continue our study of what maintains the Pacific subtropical highs. Further work with observations led to connections between strength of high and remote forcing by precipitation in midlatitude cyclone tracks and tropical convection equatorward of the highs. Our work has shown some theories to lack observational support. Work on the North Pacific high (NP high) has been submitted, reviewed, and is currently under revision. The NP high has a different mix of remote interactions compared to the SP high. Frontal cyclone forcing dominates the NP
high time series requiring special filtering techniques to identify any other forcing factors. c) NSF continues to fund our work to understand why most climate models have similar errors in their simulated Arctic surface climate (ASC). The atmospheric errors are subtle, resist obvious solutions, and cause significant errors in the simulated sea ice distribution. We identified a remote forcing link between the ASC and precipitation in the eastern tropical Indian ocean ICZ. Interestingly, Arctic SLP is sensitive to slight shifts of the ICZ in that region and those shifts are consistent with the ICZ location error in the model. To investigate the physics behind this statistical connection we have finally gotten a highly sophisticated linear stationary wave model running at UCD. This model allows us to interrogate remote forcing as well as work the connection backwards. Other observational and model data analysis continues. d) My Editorial Board duties for Dynamics of Atmospheres and
Oceans, led me to commence a lengthy process of editing a special issue on the very broad topic of the general circulation. This includes my own: overview and research papers. The latter makes a needed comparison between the general circulations in two popular datasets. During the review period, 1 refereed publication appeared and 1 more was in revision. 3 conference abstracts were prepared and 3 presentations were made.
Impacts
The project increases our understanding of the dynamics of frontal cyclones; those cyclones are the primary weather producer for our region. With improved understanding comes improvement in forecasting these important weather systems. The subtropical highs strongly influence our weather and are a continuing focus of study. Our Arctic climate simulation work is important to understanding global change. In models, the Arctic region responds more strongly to global warming than do middle and tropical latitudes. The utility of such global warming predictions hinges on understanding (and hopefully reducing) errors in the Arctic simulation.
Publications
- GROTJAHN, R., 2004. On type B cyclogenesis in a quasi-geostrophic model. Quarterly Journal of the Royal Meteorological Society, 131: 109-124.
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Progress 01/01/04 to 12/31/04
Outputs
Dr. Grotjahn supervised two graduate students during this year. We have pursued 3 lines of research: a) Our work using a nonlinear model and coherent localized initial structures was applied to testing a popular conceptual model of cyclone formation. An important result was to show that the conceptual model did illustrate a significant growth process, but for reasons that differed from the commonly-believed basis for that conceptual model. b) We continued our study of what creates the Pacific subtropical highs. Further work with observations led to connections between high strength and remote forcing by precipitation in midlatitude cyclone tracks and tropical convection equatorward of the highs. A popular current theory was revised by its authors because it lacked observational support; their revised theory is now more in line with our previously reported results. Others advanced a theory that also lacks observational support. To address these problems our major
publication (4 years in development) appeared regarding the South Pacific high (SP high). Work on the North Pacific high (NP high) is now being written up for publication. The NP high has a different mix of remote interactions compared to the SP high. Frontal cyclone forcing dominates the NP high time series requiring filtering techniques to identify any other forcing factors. c) Our third line of research seeks to understand why most climate models have similar errors in their simulated Arctic surface climate (ASC). The atmospheric errors are subtle, but cause significant errors in the simulated sea ice distribution. During this year NSF awarded us a large grant to study the simulated ASC. We have begun identifying remote factors that influence the ASC in observations and a popular climate model. Early results show linkage to remote forcing, such as frontal cyclone simulation errors is either subtle or present in a nonlinear feedback. Observational and model data analysis is ongoing.
We are developing an iteration pair of stationary wave and storm track models to study the nonlinear feedback. During the review period, 1 refereed publication appeared and 1 more was accepted. 3 conference abstracts were prepared and 3 presentations were made.
Impacts
The project increases our understanding of the dynamics of frontal cyclones; those cyclones are the primary weather producer for our region. With improved understanding comes improvement in forecasting these important weather systems. The subtropical highs strongly influence our weather and are a continuing focus of study. Our Arctic climate simulation work is important to understanding global change. In models, the Arctic region responds more strongly to global warming than do middle and tropical latitudes. The utility of such global warming predictions hinges on understanding (and hopefully reducing) errors in the Arctic simulation.
Publications
- GROTJAHN, R., 2004. Remote weather associated with south Pacific subtropical sea-level high properties. International Journal of Climatology 24: 823-839.
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Progress 01/01/03 to 12/31/03
Outputs
Dr. Grotjahn supervised one graduate student during part of this year. We have pursued 3 lines of research this year. The research projects include: a) Our work using a nonlinear model and coherent localized initial structures was written up and published. Localized structures are more similar to real weather features than tested by any prior theoretical model. An important result is that nonlinear forcing of growing linear modes often exceeds linear mechanisms. Also, the nonmodal growth hypothesis does not dominate the growth, while the normal mode growth appears to be applicable locally. We submitted an application of the work to nonlinear advection upon a standard conceptual model of cyclone formation. b) We continued our study of forcing of the Pacific subtropical highs. Further work with observations led to connections between high strength and remote forcing by precipitation in midlatitude cyclone tracks and tropical convection equatorward and west of the highs.
A popular current theory was revised by its authors because it lacked observational support; their revised theory is now more in line with our previously reported results. A major publication (4 years in development) is under review regarding the South Pacific high. Work on the North Pacific high is on going. c) A third line of research seeks to understand why most climate models have similar errors in their simulated Arctic surface climate. The atmospheric errors are subtle, but cause significant errors in the simulated sea ice distribution. Surface climate errors raise concerns about global warming simulations that show the largest changes in the Arctic. Simplified dynamical models suggest that the Arctic surface climate error is connected to storm track simulation errors thousands of km away. Compositing and 1-point correlations and autocorrelations are being examined to pursue this proposed connection in observations and climate models. During the review period, 2 refereed
publications appeared and 2 more were submitted. 3 conference abstracts were prepared and 3 presentations were made.
Impacts
The project increases our understanding of the dynamics of frontal cyclones; those cyclones are the primary weather producer for our region. With improved understanding comes improvement in forecasting these important weather systems. The subtropical highs also strongly influence our weather and are a continuing focus of study. Our Arctic climate simulation work is important to understanding global change. The Arctic region responds more strongly to global warming than do middle and tropical latitudes. So, the utility of global warming predictions is amplified by understanding (and hopefully reducing) errors in the Arctic simulation.
Publications
- HODYSS, D., and R. GROTJAHN, 2003. Nonmodal and unstable normal mode baroclinic growth as a function of horizontal scale. Dynamics of Atmos. and Oceans, 37: 1-24.
- GROTJAHN, R., D. HODYSS, and S. IMMEL, 2003. A technique for creating linearly stable localized atmospheric features with an application to nonlinear cyclogenesis. Dynamics of Atmos. and Oceans, 37: 25-54.
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Progress 01/01/02 to 12/31/02
Outputs
Dr. Grotjahn supervised one graduate student during part of this year. We have pursued 3 lines of research this year. The student project was funded by a grant from the University of California, Davis. The research projects include: a) We concluded our investigation of nonmodal and normal mode growth as a function of perturbation scale in Cartesian geometry. A resulting publication was accepted. b) Our work using a nonlinear model and coherent localized initial structures was written up and submitted for publication. A revised manuscript is under review at this time. Localized structures are more similar to real weather features than tested by any prior theoretical model. An important result is that nonlinear forcing of growing linear modes often exceeds linear mechanisms. Also, the nonmodal growth hypothesis does not dominate the growth, while the normal mode growth appears to be applicable locally. c) We continued our study of forcing of the Pacific subtropical
highs. Further work with observations led to connections between high strength and remote forcing by precipitation in midlatitude cyclone tracks and tropical convection equatorward and west of the highs. A popular current theory was revised by its authors because it lacked observational support; their revised theory is now more in line with our previously reported results. d) We initiated a new line of research during Dr. Grotjahn's sabbatical. We seek to understand why most climate models have similar errors in their simulated Arcitc surface climate. The atmospheric errors are subtle, but cause significant errors in the simulated sea ice distribution. Compositing and 1-point correlations and autocorrelations were examined for various observed quantities. A simple zonal mean model was developed for use in testing some of the hypotheses. During the review period, 2 refereed publications appeared and 1 more was submitted. 1 conference abstract was prepared and 3 presentations were
made.
Impacts
The project increases our understanding of the dynamics of frontal cyclones; those cyclones are the primary weather producer for our region. With improved understanding comes improvement in forecasting these important weather systems. The subtropical highs also strongly influence our weather and are a continuing focus of study. Our Arctic climate simulation work is important to understanding global change. The Arctic region responds more strongly to global warming than do middle and tropical latitudes. So, the utility of global warming predictions is amplified by understanding (and hopefully reducing) errors in the Arctic simulation.
Publications
- GROTJAHN, R., and C. CASTELLO, 2002. Nonmodal growth on a sphere at various horizontal scales. Geophys. Astrophys. Fluid Dynamics, 96: 223-238.
- HODYSS, D., and R. GROTJAHN, 2002. Nonmodal and unstable normal mode baroclinic growth as a function of horizontal scale. Dynamics of Atmos. and Oceans, in press.
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Progress 01/01/01 to 12/31/01
Outputs
Dr. Grotjahn supervises one graduate student currently. We have pursued six lines of research this year. The student projects were funded by grants from UCDavis. The research projects include: a) Investigation of nonmodal and normal mode growth as a function of perturbation scale in Cartesian geometry. Nonmodal growth was largest for short modes, but at observed scales it was less important. Also, horizontally tilted troughs form in a uniform flow (which makes the flow nonuniform). Two ms were prepared. Part 1 appeared this year. Part 2 was revised recently and re-submitted; acceptance is pending. b) A student successfully developed a spherical coordinates pair of linear models (initial value and eigenvalue). The models include a meridionally-varying jet. Nonmodal growth had not been previously examined in these coordinates; the results were similar to those in "a)". A ms describing this work has recently been accepted. c) A follow-up study to a 1999 conference
presentation uses a nonlinear model and coherent localized initial structures. Localized structures are more similar to real weather features than tested by any prior theoretical model. An important result is that nonlinear forcing of growing linear modes often exceeds linear mechanisms. A ms was recently submitted. d) An initial study of forcing of the subtropical high led to connections between high strength and remote forcing by precipitation in midlatitude cyclone tracks and tropical convection equatorward and west of the highs. Some doubt was cast upon the current theory. Work is continuing. A conference presentation was made. During the review period, a refereed publication appeared and 3 more were submitted. 2 conference proceedings and 2 major technical reports were prepared.
Impacts
The project increases our understanding of the dynamics of frontal cyclones; those cyclones are the primary weather producer for our region. With improved understanding comes improvement in forecasting these important weather systems. The subtropical highs also strongly influence our weather and are a new focus of study.
Publications
- CASTELLO, C., and R. GROTJAHN, 2001. Initial Value and Eigenvalue QG Models for Studying Cyclogenesis in Spherical Coordinates. UCD Atm. Sci. Tech Rpt 100018. 196 pp.
- FAURE, G., and R. GROTJAHN, 2001. Forecast Guidance of Significant Weather Events in Sacramento Area Using Historical Analogs. UCD Atm. Sci. Tech. Rpt. 10019. 174 pp.
- GROTJAHN,R., and S. IMMEL, 2001. Observational study of the remote forcing of Pacific Subtropical Highs. 13 Conf. Atmos. Ocn. Fluid Dyn., AMS, Breckenridge, p. 16-17.
- HODYSS, D., and R. GROTJAHN, 2001. Diagnosing cyclogenesis by partitioning energy and potential enstrophy in a linear quasi-geostrophic model. TELLUS A, 53: 567-577.
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Progress 01/01/00 to 12/31/00
Outputs
Dr. Grotjahn supervises two graduate students currently. We have pursued six lines of research this year. The student projects were funded by a grants from NSF and Cal-Space. The research projects include: a) Investigation of nonmodal and normal mode growth as a function of perturbation scale in Cartesian geometry. Nonmodal growth was largest for short modes, but at observed scales it was less important. Also, horizontally tilted troughs form in a uniform flow (which makes the flow nonuniform). b) A student successfully completed a Master?s Thesis (exam plan). This student developed a spherical coordinates pair of linear models (initial value and eigenvalue). The models include a meridionally-varying jet. Nonmodal growth had not been previously examined in these coordinates; the results were similar to those in "a)". c) A follow-up study to a 1999 MS thesis uses a nonlinear model and coherent localized initial structures. Localized structures are more similar to real
weather features than tested by any prior theoretical model. An important result is that nonlinear forcing of growing linear modes often exceeds linear mechanisms. d) A study of frontal cyclone observed scale change and kinetic energy distribution. Upper and lower features have differing size changes; the lower feature grows to match the upper, thus facilitating overall storm growth. e) Initial study of forcing of the subtropical high led to connections between high strength and remote forcing by precipitation in midlatitude cyclone tracks and tropical convection equatorward and west of the highs. Some doubt was cast upon the current theory. Work is continuing. f) We updated pedagogical materials regarding the general circulation observations and energetics, and baroclinic instability. It shall appear shortly in a major review work.
Impacts
The project increases our understanding of the dynamics of frontal cyclones; those cyclones are the primary weather producer for our region. With improved understanding comes improvement in forecasting these important weather systems. The subtropical highs also strongly influence our weather and are a new focus of study.
Publications
- GROTJAHN,R., 2000. Multiple waterspouts at lake Tahoe. BUL. AMER. MET. SOC., 81: 695-702.
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Progress 01/01/99 to 12/31/99
Outputs
Dr. Grotjahn supervises three graduate students currently. We have persued five lines of research work this year. The student projects were funded by a grant from the NSF. The research projects include: a) A fourth student successfully completed a Master?s Thesis using a linear model of frontal cyclone development. We developed a novel way of creating an eigenvalue (linear) problem from a low-order linear and nonlinear model. Some important results: quantified the relative importance of two proposed mechanisms of cyclone development and discovered that horizontally tilted troughs can form in a uniform flow (which make the flow nonuniform). b) A follow-up study to the completed MS thesis using a nonlinear model and coherent localized initial structures. Localized structures are more similar to real weather features than tested by any prior theoretical model. An important interim result is nonlinear forcing of growing linear modes. c) A study of frontal cyclone observed
scale change and kinetic energy distribution. Upper and lower features have differing size changes, the lower feature grows to match the upper, thus facilitating overall storm growth. d) A follow-up to the completed Master?s thesis: using spherical geometry and a meridionally varying jet. Models are currently under development. e) Initiating study of forcing of the subtropical high.. An analytical model using diabatic heating cast in spherical coordinates is under development. A extensive proposal to fund this work was submitted to the NSF. An analysis of an unusual outbreak of waterspouts at Lake Tahoe was submitted for publication.
Impacts
The project increases our understanding of the dynamics of frontal cyclones; those cyclones are the primary weather producer for our region. With improved understanding comes improvements in forecasting these important weather systems.
Publications
- GROTJAHN, R., and C. CASTELLO, 1999. A study of frontal cyclone surface and 300 hPa geostrophic kinetic energy distribution and scale change. MON. WEA. REV., IN PRESS.
- HODYSS, D., and R. GROTJAHN, 1999. Some effects of meridional structure upon the initial growth of a baroclinic wave. In: 12th Conference on Atmospheric and Oceanic Fluid Dynamics. 253-254.
- GROTJAHN,R., and D. HODYSS 1999. On initial growth using localized atmospheric vortices. In: 12th Conference on Atmospheric and Oceanic Fluid Dynamics. 77-78.
- GROTJAHN,R., and C. CASTELLO 1999. Do frontal cyclones change size as they grow? In: 17th Conference on Weather Analysis and Forecasting. 72-73.
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Progress 01/01/98 to 12/01/98
Outputs
Dr. Grotjahn supervises two graduate students currently. We have pursued three lines of research work this year. One student project was funded by a grant from COMET. This project implemented an automated Internet web page displaying simulations from a forecast model developed at UC Davis by Prof. Soong. The current website URL is: http://www-atm.ucdavis.edu/mascast/masmain.html The other student successfully implemented a novel way of creating an eigenvalue (linear) problem from a low-order nonlinear model. We are investigating how some basic theoretical properties of frontal cyclone change when examined in more than one dimension. NSF funds this project. We completed our third project: analysis of frontal cyclone scale change during their life cycle. Cyclones double in size near the earth's surface, but the upper level portion does not. Most theoretical studies assume cyclones do not change size, while many people have the subjective impression that the storms do
increase in size as they mature. This year we have completed development of two independent series of protocols by which to perform the analysis (one uses wavelets, the other radial averaging). During the review period, one publication has appeared.
Impacts
(N/A)
Publications
- GROTJAHN, R., D. HODYSS, and C. CASTELLO, 1998. Do frontal cyclones change size? Observed widths of north Pacific lows. MON. WEA. REV.,
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Progress 01/01/97 to 12/01/97
Outputs
Dr. Grotjahn supervises two graduate students currently. They are performing two lines of research work individually, and a third project together. The first student project is funded by a grant from the federal agencies interested in weather prediction. This project shall implement an automated internet web page displaying simulations from a forecast model developed at UC Davis by Prof. Soong. The second individual project has progressed to successfully implement a novel way of creating an eigenvalue (linear) problem from a low-order nonlinear model. We are currently applying the technique to more advanced model equations. This project is funded by an NSF grant recieved during this review period. The joint project is carried over from the previous year: wavelet analysis of frontal cyclones during their life-cycle. This project is intended to answer the question of whether cyclones change size as they mature. Whatever the result, the work has important implications
for how theoretical models of these weather systems are designed. Most theoretical studies assume cyclones do not change size, while many people have the subjective impression that the storms do increase in size as they mature. After much experimentation, we have recently completed development of an acceptable series of protocols by which to perform properly the wavelet analysis. Preliminary results will be available soon. During the review period, two publications appeared (one was "in press" last year).
Impacts
(N/A)
Publications
- GROTJAHN, R., and J. EASH, 1997. (Physalis peruviana) Uncommon but not forgotten. Fruit Gard., 28, pp. 5-7.
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Progress 01/01/96 to 12/30/96
Outputs
Dr. Grotjahn competed an observational study used for background to a new line of research using more advanced mathematical models that previously used to study midlatitude theoretical dynamics. The more advanced models use the true "primitive" equations. The observational work focused on the "vorticity equation" and demonstrated that there should be noteworthy changes in theoretical models that use the true primitive equations. That work is published in the first paper listed below. He also wrote an NSF proposal to fund further work developing and applying these new models. (As of this writing, verbal notification of successful funding has be received.) Dr. Grotjahn wrote an invited publication honoring one of his teachers from two decades ago. The short article includes some anecdotes but also provided a means to illustrate some simple answers to several fundamental equations in midlatitude dynamics. (For Example: are frontal cyclones powered by baroclinic
instability or by latent heating. Answer: both, about equally.) Dr. Grotjahn has two new graduate students beginning at the end of this review period. The will perform work along the lines described in the five year extension of this project.
Impacts
(N/A)
Publications
- Grotjahn, R., 1996. Vorticity equation terms for extratropical cyclones. Mon. Wea. Rev., 124, pp. 2843-2858.
- Grotjahn, R., 1997 Simplifying a complex subject: Some thoughts on teaching the general circulation. Dyn. Atmos. Oceans, in-press.
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Progress 01/01/95 to 12/30/95
Outputs
Dr. Grotjahn completed a sabbatical visit to NCAR in Boulder Colorado. During the second half of this sabbatical, completed a ms (in press) describing the evolution of 28 cyclones near the east coast of Asia. Observations were studied to prove that 3 terms in the full vorticity equation which are commonly neglected in theoretical studies are in fact not negligible; one is the second largest term! The manuscript describing the study of the vorticity equation is currently under review. The 3 significant terms in the vorticity equation motivates use of a higher-order theoretical model to study cyclone evolution. So, an existing oceanographic (balance equations) model was converted to simulate atmospheric conditions. Simulations with the model are continuing at this writing. Other projects included initiation of work that applies the tools of wavelet transforms to determine if cyclones change their size during evolution. Collaborative work was begun to search for
connections between air quality and climate diagnostic parameters. The initial survey of the subject focuses on ozone (summer conditions) in the South Coast (LA basin and environs) and San Francisco Bay areas. The goal of the project is to establish (or not) the connection to climate variables that may be forecastable months in advance.
Impacts
(N/A)
Publications
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Progress 01/01/94 to 12/30/94
Outputs
A demonstration project combining observations to confirm some theoretical notions was completed. The work used a simple theoretical model to demonstrate that a simple property of the atmosphere prior to cyclogenesis could indicate which of two proposed mechanisms to explain the growth was more relevant. The theoretical work was developed in the two articles listed below. The simple property was whether the upper and lower troughs were connected and if so, whether the axis had upstream tilt. We examined observations of the troughs structure prior to development and determined that one mechanism (baroclinic instability) was more relevant to the real atmosphere than the other (nonmodal growth). The work was reported on at a major conference in Bergen Norway. The conference abstract is listed below. Since that time, Dr. Grotjahn commenced a sabbatical visit to NCAR in Boulder Colorado. During the first half of his stay, he looked at more observations and concluded that
the case reported upon in Bergen was typical of most cyclogenesis. Other observational work was concerned with proving that 3 terms in the full vorticity equation which are commonly neglected in theoretical studies are in fact not negligible. One of the 3 is the second largest term! We propose to consider a more complete set of equations (which includes these terms) and to see how the theory of the past 40 years must be modified. One report on this work is to be published in the following year; it other ms in the works will be repor.
Impacts
(N/A)
Publications
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Progress 01/01/93 to 12/30/93
Outputs
Preliminary work began on the effects of intense tropical convection upon the dynamics of flows in midlatitudes (including frontal cyclones). All prior related studies specify the midlatitude flow rather than allowing that flow to interact with the tropics. Two branches of groundwork are currently being laid: development of the coupled mathematical (computer) model and analysis of the appropriate observed balance. Adding interaction with the tropics adds new terms to the governing equations in our models. The extra terms prompt us to check that other terms being kept (or neglected) are consistent with the level of the approximation being made. The check analyzes the observed balance. Preliminary results suggest a different group of terms should be included than those kept in the standard theoretical analysis. All the extra terms have made the computer model harder to develop and have lengthened the time until our first results. Pedersen finished his masters thesis on
effects of friction upon the development of initial conditions that simulate early stages of frontal cyclone development. This work's importance is to sort out which of two competing theories best describes the observed process. We uncovered several flaws with one theory that has recently obtained much publicity. A proposal was prepared to study the connection between air pollution in the Los Angeles area and atmospheric weather events on a larger scale. Large scale influences include the cyclone storm tracks over the western U.S.
Impacts
(N/A)
Publications
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Progress 01/01/92 to 12/30/92
Outputs
The research by the PI, during this period, can be grouped into 3 categories. Production was delayed on a book announced last year. The PI needed to work out numerous, lengthy and tedious details. The book has finally come out in January 1993. The full reference follows. The midlatitude jet streams are maintained and shaped by tropical circulations and by midlatitude frontal systems. We began to investigate a higher order dynamical formulation that allows the jets to partially interact with the frontal systems. While there are appealing dynamical (theoretical) reasons for looking at higher order, we spent the past year laying groundwork by examining observations. Observations help resolve two questions: what type of behavior would we expect to find in the theoretical work; what higher order terms are the most important (allowing consistent simplification of the equations). Progress on these questions was slow because we had difficulty obtaining sufficiently complete
datasets. By the end of the period we had acquired useful observational data, had developed the necessary suite of programs and were performing calculations on the individual cases. During the next year we intend to report upon this work. A Masters Student has nearly completed his research into the initial dynamical growth of midlatitude atmospheric systems (i.e. frontal systems). We have been concerned with sorting out hydrodynamical instability (HI) from another source of amplitude change called "phase superposition" growth (PSG).
Impacts
(N/A)
Publications
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Progress 01/01/91 to 12/30/91
Outputs
The PI completed an advanced textbook-monograph on the atmospheric general circulation. The book should appear in mid-1992. The book combines observations with theories of the large scale atmospheric flows and thermodynamics. Each ch of diverse literature. While preparing this text, the PI devised a new idea for future research in midlatitude dynamics.
Impacts
(N/A)
Publications
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Progress 01/01/90 to 12/30/90
Outputs
During the past year applied and primarily theoretical research was accomplished. APPLIED: The first two publications listed below arose from this area. The first publication examines how the uneven distribution of observing stations creates a bias in longitudinal averages. The bias turns out to be fortuitously small. The second report shows that the ECMWF global weather forecast model has spurious high skill in the South Pacific. The previously unreported problem is due to comparing the model with itself, instead of with observations. THEORETICAL: Several efforts were pursued. Grotjahn and Lai (1991) uses a 3-D, nonlinear, spectral, general circulation (GC) model to study the nonlinear effects of surface temperature anomalies upon midlatitude cyclones. The research proved a hypothesis that enhanced growth should occur over warm anomalies due to static stability changes. 2) The linear effects of a large scale mountain ridge upon cyclone development was completed
and is reported in Grotjahn and Wang (1990). Both of these publications are listed below. Topographic effects on stationary flows and on nonlinear evolution were completed and should be published next year.
Impacts
(N/A)
Publications
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Progress 01/01/89 to 12/30/89
Outputs
During the past year applied and primarily theoretical research was accomplished. Applied: Work was completed regarding the predictability and the error characteristics of forecasts for the Australia-New Zealand region. Work was begun to adapt the same tools to study forecasts over California. The first two publications listed below arose from this area. Theoretical: Four efforts were pursued; two MS students finished. 1) A lengthy proposal was filed for federal funding to continue the work another three years. 2) One MS student completed her degree with a project investigating the effects of complete (instead of the commonplace partial) specification of friction upon the eigen-solutions of stratified geophysical flow instability. An important result was the complete destruction of the previously highly-touted 'continuum modes'. A paper has been submitted to a journal on this. 3) A second MS student completed development of the 3-D, nonlinear, spectral, GC
model discussed in prior progress reports. He completed his MS research into the nonlinear effects of surface temperature anomalies upon mid-latitude cyclone. An important result was the enhanced growth over warm anomalies and its linkage to static stability changes. 4) Finally, research into the linear effects of a large scale mountain ridge upon the cyclone development was completed, with a paper submitted and reviewed by a journal (final revisions are now being made in response).
Impacts
(N/A)
Publications
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Progress 01/01/88 to 12/30/88
Outputs
Observational, theoretical and applied research into midlatitude weather patterns are emphasized during this year. Observational work: The observational work focussed mainly upon the North Pacific. 1) Frontal cyclones preferentially form near the east coast of Asia. We proposed a mechanism to explain this preference based upon theoretical concepts. Our mechanism was verified by calculating 3-D trajectories. Pub. 2 below shows how a two-step process accounts for this central problem in midlatitude weather. 2) Storm tracks were deduced by an objective means and some statistical properties calculated. Two publications were submitted that discuss: how the storm tracks vary with important climate anomalies and how the fractal dimensions (affecting predictive skill) vary. One important result is that negative "PNA" climate anomaly broadens the storm track, bringing more rainfall to California. Theoretical work: We continued to develop a limited-area, super-computer model.
Research into linear instability of 3-D, spherical geometry, flows over topography were started. Both of these projects will end by mid 1989. Applied work: While on sabbatical, the PI began new work analyzing forecast model errors. Two ms were submitted. We invented a new technique to stratify errors on the basis of weather pattern and other dynamical properties. We discovered a hidden error in the world's best forecast model. We examined a method to anticipate forecast model error.
Impacts
(N/A)
Publications
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Progress 01/01/87 to 12/30/87
Outputs
This project examines theoretical and observational aspects of large-scale atmospheric motions, especially midlatitude frontal cyclones. The observational work included the completion of the two reports. The major work is a report showing novel displays of the three-dimensional structure of frontal cyclones. This report culminates 5 years effort and includes the most advanced computer graphics available. Traditional, "two-dimensional" graphs are also included to bridge the gap between the old and new ways of depicting detaails of these storms. This report is widely distributed andshould greatly advance synoptic meteorology instruction. The second report accompanies a 16mm film; it describes features of a severe storm to strike California. Other observational work, in progress, traces the source of air in cloud masses and relates that to the oceanic influence upon frontal cyclone development. The theoretical work proceeds along two lines. A linear model was
developed; it is described in pub. 3. The model is a vary large (1 million element) matrix eigenvalue problem that is solved on a supercomputer. A unique feature of this model is the use of orthogonal basic functions to represent the vertical structures in the model. The large matrix size results from the nonseparability of the three-dimensional hydrodynamic instability problem being posed on a sphere.
Impacts
(N/A)
Publications
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Progress 01/01/86 to 12/30/86
Outputs
This project examines theoretical and observational aspects of large-scale atmospheric motions. Observational work: The atlas mentioned in the 85 CRIS report is now being written. Most of the diagrams have been completed, the last set of highest-level computer graphics will be finished 1/87. Publ. #3 is an animated computer graphics filmstrip of the case study used in the atlas. A student completed implementation of the NCAR graphics package on the campus computers. Two graduate students are calculating frontal-cyclone storm tracks and surface heat fluxes, over the North Pacific. Years when the oceanic Kuro Shio current is very different are being compared. The storms form near the Kuro Shio and so their evolution may be strongly altered by changes in the ocean current. Finally, two studies of the global radiosonde weather observation network were completed. The network has remarkable little error when zonal averages are calculated. The time sampling causes large
errors from the semi-diurnal tide. These tides must be filtered from forecast models that include a diurnal cycle. Theoretical work: A high resolution version of the linear model (see 85 CRIS report) was tested and implemented on a new CRAY-XMP supercomputer. Experiments are now underway. Applied work: The main application is to improve weather forecasting. But, what forecast variables does agriculture need most? To answer this, a survey, was completed.
Impacts
(N/A)
Publications
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Progress 01/01/85 to 12/30/85
Outputs
Study continues into observational and theoretical aspects of large-scale atmospheric motions. Observational Work: The atlas of selected atmospheric circulations mentioned in my 83 and 84 CRIS reports remains in hiatus. But, a proposal was sent to OASC at NSF for supercomputer funds to redo many of the atlas diagrams using the world's highest level graphics software. A student is implementing "middle level" (NCAR) graphics at UCD; publication #2 below is one result. The PI is examining the global weather observation network for certain temporal and spatial biases; two articles are in preparation. Theoretical Work: The main thrust remains the effects of anomalous surface temperature patterns on the nonlinear life-cycle of midlatitude cyclones. A "nonlinear package" (consisting of 3 computer programs) was developed and tested this year. A "linear model" that helps to start-up and to analyze the end products of the nonlinear package was also developed. The linear
model is a large computer program which solves for normal (eigen) modes for 3-dimensional basic states in spherical geometry including topography. The linear model was tested extensively. This model can be used for the analysis technique described in publication #3 below. Other projects: The survey of farmers' weather forecast needs (see CRIS report for 84) was largely completed. It was expanded to encompass many crops (besides stone fruit) but reduced to interviews of farm advisors.
Impacts
(N/A)
Publications
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Progress 01/01/84 to 12/30/84
Outputs
Study is continuing into observational and theoretical aspects of large-scale atmospheric motions. Observational Work: See discussion in CRIS report of 1983; the atlas mentioned in that report has been reviewed but publication contingent upon better computer graphics of some of the figures. A student is presently trying to modify a higher-level graphics package for that purpose. A publication (#1 below) described some related work in computer animation of this data. Theoretical Work: The main area is an examination of the effect of anomalous surface heat flux upon the life-cycles of midlatitude cyclonic storms. (See 1983 CRIS report). The global computer model is now being modified for the task. Background work in linear instability has been completed, culminating in publications 2 and 3 below. The nonlinear eigenvector analysis has proven quite difficult to implement, completion of a series of tests has been delayed by an inadequate commercial software package
for the eigenvector calculation. (This delay does not slow up the global model development.) Other projects: Another student is using the newly developd "total variation diminishing" (TVD) finite difference schemes to improve numerical simulation of flows over sharp topography. Finally, a survey has been prepared of the forecast needs of various California farmers; the forecast categories are divided into periods ranging from a day to a season in advance.
Impacts
(N/A)
Publications
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Progress 01/01/83 to 12/30/83
Outputs
Study is continuing into observational and theoretical aspects of the large-scale motions of the atmosphere. Observational Work: This work focusses upon understanding temporal changes and three-dimensional structures. The major work has culminated in an atlas of selected circulations that has just been submitted to U.C. Press. The atlas describes: wave-cyclone storms over North America and over Europe; the global jet streams and the summer monsoon. Computer animated films of these circulations are planned or in progress. See discussion in CRIS report from 1982. Comparison of isentropic, isobaric and three-dimensional trajectories are also underway. Theoretical Work: This work focusses upon the effects of asymmetric surface heat fluxes on the life-cycles of midlatitude wave-cyclonic storms. Computer simulations with a global, spectral, high-resolution, primitive equation model are planned. Dynamical instability of these storms in curving flow as been studied (1
pub, 2 submitted). A new tool for solving linear hyperbolic equations using eigenfunction basis functions has been invented by the PI and is currently being tested. (1 pub).
Impacts
(N/A)
Publications
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Progress 01/01/82 to 12/30/82
Outputs
I have been perfecting some computer animation techniques for meteorological data. These techniques allow a scientist to efficiently preview vast amounts of observed or model generated data. Relationships between different variables can be easily investigated in three dimensions and over time. Two conference presentations were made as well as 16 films. One conference introduced me to some new holographic techniques which I plan to use in the future. These computer programs are being used to produce some maps for an upcoming atlas. The atlas will provide new and dramatic views of major atmospheric circulation patterns including: the global jet streams, the Indian Monsoon and midlatitude cyclonic storms. Nearly all the raw diagrams are completed. Among the new features of this work are three dimensional perspective and stereo views of: The principal atmospheric jet streams in all seasons, and the development of an atmospheric front over the eastern United States.
Three dimensional trajectories were also calculated showing the actual motion of the air (which can be quite different from the two dimensional trajectories commonly calculated). I completed analyses of the hydrodynamic instability of some three-dimensionally varying mean flows. This analysis included previously overlooked sources of energy for developing cyclones that can be locally important.
Impacts
(N/A)
Publications
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