Recipient Organization
RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY
3 RUTGERS PLZA
NEW BRUNSWICK,NJ 08901-8559
Performing Department
Environmental Sciences
Non Technical Summary
Currently, the tools that weather forecters use to forecast thunderstorms do not account for the fact that the air outside a thunderstorm can mix with the air inside a thunderstorm as the storm develops and matures. In some cases, this mixing of air could prevent a storm from advancing beyond the stage of being a small cloud. As a result, thunderstorms are occasionally forecast that do not materialize. This can then lead to lost economic opportunities (e.g., a farmer decides not to plant because of the forecast for storms that don't actually happen). This research project is investigating the best way to incorporate the mixing process into thunderstorm forecasting techniques without it getting so complicated as to be intractable. Software that is commonly used by weather forecasters will be modified to incorporate the mixing process, and particular forecasts will be re-examined with the new tools. Ultimately, forecasts of thunderstorms should improve as a result.In a similar vein, new techniques are also being researched in the realm of forecasting nor'easters. Again, software in common use is being tweaked and validated, with the overall goal being an improvement in weather forecasting. For both weather phenomena (thunderstorms and nor'easters), results will be communicated at professional conferences of meteorologists as well as in the classroom to the next generation of meteorologists.
Animal Health Component
40%
Research Effort Categories
Basic
20%
Applied
40%
Developmental
40%
Goals / Objectives
This work has two objectives, one involving the diagnosis of convective environments, and the other involving nor'easter studies. These are further discussed below.1) Diagnosis of convective environmentsThis work will extend parcel theory by including the effects of entrainment on the calculation of standard diagnostics such as CAPE, CIN, LFC, LNB, and others. Since there is no one way to include entrainment, a variety of approaches will be tested to determine which best reflects reality for the midlatitude, continental convection this work is concerned about. Past casestudies from the literature will be reevaluated in light of the new diagnostics. Finally, the diagnostics will be used to repeat previous climatological studies. To summarize, new diagnostics of convection will allow for improved analyses and predictions of convection, and may lead to statistical analyses of environments favorable for convection that are more powerful in discriminating between those environments conducive for convection, and those environments that are not, both for current and future climates.2) Nor'easter studiesThe objective of the nor'easter studies is to improve our understanding of the dynamics and thermodynamics of nor'easters. The objective can be divided into two parts. In one part of the study, a collection of nor'easters is studied so that conclusions may be drawn about nor'easter dynamics most generally. Questions related to this objective include the following: How sensitive is the modeled nor'easter development to the assimilation of COSMIC RO data? How does nor'easter development depend on the way the microphysics is parameterized in simulations? Additionally, particular focus is made on a high-impact March 2010 storm. In that case, it is equally important to understand the source of the model errors that led to a terrible wind forecast. Would additional observations (say, from COSMIC) improve the forecast? More generally, how does the model analysis need to be changed to improve the forecast?
Project Methods
This section begins with an outline of the methods to be used for the two project objectives, followed by a general description of the efforts that will be used to affect the target audiences, as well as how the overall project will be evaluated.I) Outline of methodsA) Diagnosis of convective environmentsA number of approaches to incorporating entrainment in parcel theory will be used to determine the optimal choice. The goal is to add as little to standard parcel theory as possible to allow the new approach to be tractable in an educational setting and also to prevent overfitting various parameters associated with entrainment. The first challenge is to implement basic parceltheory. Even here, there is a wide variation in standard practice. Although highly accurate ways of computing parcel ascent paths (with no entrainment) are known, many standard tools such as N-SHARP (the National Sounding/Hodograph Analysis and Research Program) and its Python-based replica SHARPPy (https://github.com/sharppy/SHARPpy) use a highlyinaccurate method. Thus, the first decision is whether to incorporate entrainment into an existing tool despite the issues over accuracy or "reinvent the wheel" to some degree for better accuracy. A related question is whether to conserve moist static energy, the approach many studies of tropical convection take, or to conserve equivalent potential temperature, as most studies of midlatitude convection do.Studies in the literature have outlined a number of detailed methods and parameterizations for entrainment, which will be investigated, but for simplicity a constant entrainment rate may be all that is necessary for the purposes of this project. It is important to point out that entrainment is highly variable, dependent on the size of the convection, the organization of the convection, and other factors. The intent here is not to diagnose the true CAPE experienced by each individual cloud, but rather to develop a technique that allows forecasters to identify situations where neglecting entrainment could lead their forecast to go astray. If the technique indicates that neglecting entrainment does not degrade from the forecast (perhaps because the lifting mechanism is expected to be so strong that parcels will reach their LFC anyway), then all of the standard thresholds and rules of thumb applied to traditional convective indices can still be applied.These various entrainment techniques will then be tested on a variety of cases previously examined in the literature, some of which were situations where convection failed to occur when forecast, and others for which the forecast was reasonable. Through these analyses, the way to incorporate entrainment that best adds value to diagnostics such as CAPE will be determined, and ways in which the new diagnostics can be incorporated into a forecast process will be able to be determined.Finally, past climatological studies will be repeated to determine the impact the new diagnostics have on the results.B) Nor'easter studiesIn the proposed study, the latest version of the WRF-ARW Model will be used for three forecast domains. These domains (at 45-, 15- and 5-km grid spacing, respectively) will have two-way interaction to allow the air-sea exchanges modeled on the inner domains to feed back to the larger scale circulations. Seven nor'easter cases have been chosen for further study based upon three constraints: All cases must have occurred after April 2006 (when COSMIC launched), must cover a wide array of months, and must have affected the Northeast. All cases remained offshore, except some storms clipped Cape Cod, and one hugged the Long Island coast. All events were close enough to land to produce significant impacts to society.For each case, simulations will be run for 180 hours, starting roughly 72 hours prior to the first precipitation impacts in the highly populated Mid-Atlantic US and associated cyclogenesis. This time frame serves to focus attention exclusively on cyclone initiation and its later impact on this region. A 72-hour lead time will allow simulations to spin up, establish baroclinicity between the cooler eastern US and warmer Gulf Stream, and simulate surface latent heat fluxes along theexpansive (>1000 km) northern edge of the Gulf Stream, which are all vital for nor'easter simulations. Specifically, model initialization will be 72 hours prior to the first nor'easter-related 0.5 mm (~0.02 inch) precipitation reading from the New Jersey Weather and Climate Network. A New Jersey-centric approach was chosen due to its high population density (461.6 km-2), significant contribution ($473 billion) to the US gross domestic product, and importance to the mission of the New Jersey Agricultural Experiment Station. Additionally the simulation period is long enough to cover the entire event duration. The drawback of such a long forecast length is the significant forecast error that is expected to develop over the 180-h period. However, the assimilation of COSMIC data should mitigate this risk.Before running any nor'easter cases, it is necessary to choose appropriate physics parameterizations. Preliminary work to determine an optimal configuration was completed using many tens of 12-hour WRF model runs. The optimal combination of WRF physics parameterizations were determined to be those that qualitatively produced the best results, yet allowed a 180-h WRF Model run to complete in no more than 18 hours on the computational resources available. Based on this analysis, the following WRF physics parameterizations have been selected:• Microphysics: Goddard Cumulus Ensemble Model scheme,• Longwave radiation: RRTM longwave radiation scheme,• Shortwave radiation: MM5 Dudhia shortwave,• Surface layer: MM5 similarity,• Land surface: NOAH LSM,• Planetary boundary layer: BouLac PBL, and• Cumulus parameterization: Grell-Devenyi ensemble scheme.All of these parameterizations are identical for each domain. The only exception is that the innermost domain does not use a cumulus parameterization.To determine the importance of COSMIC assimilation, two WRF configurations will be used for each nor'easter case, a control run with no COSMIC assimilation, and an experimental run with COSMIC assimilation (using WRFDA). To investigate BMPS influence upon nor'easter simulations, five BMPS will be used. In particular, the three, six-class, three-ice, single-momentschemes known as the Lin, Goddard Cumulus Ensemble (GCE6), and WRF single moment (WSM6) will be used, as well as a seven-class, four-ice, single-moment scheme (GCE7), and finally, a six-class, three-ice, double-moment scheme [WRF double-moment, six class (WDM6)]. The March 2010 nor'easter will be further analyzed by varying the other parameterizations used to determine the sensitivity of the forecast to these choices. Note that, although the initial conditions certainly already include COSMIC observations indirectly, these retrospective forecasts do not include further information from COSMIC (unless assimilated via WRFDA).II) Efforts and evaluationEfforts that will be used to change the target audience will include talks at conferences including annual meetings of the American Meteorological Society, as well as lectures to meteorology undergraduate students.This project will be evaluated by peer reviewers when pieces are submitted for publication as research articles, as well as by students through teaching evaluations.