Directorate

• Contents
• EXECUTIVE SUMMARY
• 1. SCOPE OF THE PROGRAM
• 2. IMPROVING OUR UNDERSTANDING OF EARTH-SYSTEM PROCESSES
• 2.1 Scale Interactions Associated with Precipitating Convective Systems
• 2.2 Understanding the Dynamics and Predictability of Weather Systems on Time Scales of 0-48 h
• 2.3 Fundamental Research on Precipitation Processes, with an Emphasis on their Improved Representation in Numerical Models
• 2.4 Understanding the Dynamics, Physics and Chemistry of Multi-Scale Atmospheric Chemical Constituent and Particulate Transport, Dispersion and Transformations
• 2.5 Fundamental Research in Boundary Layers and their Interfacial Interactions
• 3. ADVANCING THE SCIENCE OF ATMOSPHERIC PREDICTION
• 3.1 Advancing Short-Range Weather Prediction
• 3.2Advancing Data Assimilation Research
• 3.3 Improving Forecasting of Pollutants and Hazardous Materials
• 4. ADVANCED COMMUNITY RESEARCH TOOLS
• 4.1 WRF Community Model
• 4.2 Community Data Assimilation Techniques
• 4.3 Nested Community Climate Model
• 5. SUMMARY
• Acronym List
• Print Version
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Mesoscale & Microscale Meteorology Division Science Plan:

3.1 Advancing Short-Range Weather Prediction

Goal: To lead the development and testing of the WRF advanced analysis and forecasting system at scales that resolve convective systems scale, including systematic evaluation, improvement of model numerics and physics, development of appropriate verification techniques, and extensions for broader applications.

The WRF system has now matured to the stage of operational testing within NCEP and AFWA, and its acceptance by academia as a widely used community mesoscale model that is replacing MM5. This model has been developed and is being extended as a continuing collaborative effort among NCAR, NCEP, FSL, CAPS, AFWA, NRL, the FAA, and a number of university scientists. Our common goal is to improve the forecast accuracy of significant weather features across scales ranging from cloud to synoptic, with priority emphasis on horizontal model grids of <10 km. The model now incorporates:

• Advanced numerics and data assimilation techniques;
• A multiple relocatable nesting capability;
• Numerous state-of-the-science physics options; and,
• Treatment of complex terrain.

WRF is thus well suited for a broad range of applications, from idealized research to operational forecasting. This applications benefit has been gained without compromising flexibility to accommodate future enhancements and user experimentation.
Within MMM, priorities in WRF model development are focused on providing capabilities to facilitate the advancement of our research objectives and similar needs in the research community, and on promoting the transfer of research advances into operational use. In collaboration with the Developmental Test Center (DTC) of the Research Applications Laboratory (RAL), we will evaluate the performance of WRF in both real-time and retrospective forecast experiments. We will collaborate with DTC visitors and staff in developing further enhancements to the modeling system. We will also continue to interact with the WRF operational partners (NCEP, AFWA, and NRL) as well as foreign operational centers to develop advanced systems that can form the basis of the next generation of operational forecast models. As the replacement for the MM5, WRF is certain to become an important facility for university researchers, which has already gained wide usage.
WRF is a highly modular, single source code with plug-compatible modules, and is transportable, extensible, and efficient in a massively parallel computing environment. We will continue to provide software infrastructure support to WRF scientific partners and collaborators to facilitate development and integration of new and enhanced capabilities into the WRF system. WRF will have the ability to operate as a coupled application within the Earth System Modeling Framework (ESMF) and will employ other aspects of ESMF software as appropriate and feasible. In this regard, we will collaborate with other NCAR modelers to build upon the capabilities of ESMF and the WRF software framework, with the aim of enhancing the interoperability of the major NCAR community models by operating within a common framework. We will also continue efforts to improve WRF performance and scaling, and to develop and maintain comprehensive developer documentation and other user-support material.

The single most damaging weather phenomenon is the landfalling tropical cyclone. This arises from both the damage done at landfall by a combination of winds, waves, storm surge and riverine flooding, and the subsequent effects of heavy rainfall and widespread flooding extending well inland. The important societal need for improved forecasts of landfalling tropical cyclones has been recognized by the emphasis placed in this area by the USWRP, the World Weather Research Program and the WMO Tropical Meteorology Research Program. Real-time forecasts of landfalling hurricanes from the 2004 season have shown that the WRF model holds considerable promise for improved forecast of track and intensity, together with the precipitation and surface wind field structure. These forecast improvements are seen to apply at both the critical landfall location and during the subsequent weakening and transformation to a rain depression over land. Our research in this area will focus on the internal dynamics of tropical cyclones and hurricanes and on developing WRF enhancements to improve its accuracy and efficacy for this important forecast issue. Research and WRF enhancements will be directed toward a number of related science issues including: improved cloud microphysics, ocean and land surface coupling, assimilation of satellite data, assimilation of both land-based and airborne Doppler radar data, more sophisticated techniques for adaptive movable grids, and new bogusing strategies for model initialization. Tropical cyclone research is also a focus of the division’s efforts described under the sections 2.2 and 2.3, respectively.

We look forward to strong collaborations with university researchers and scientists at the NOAA Hurricane Research Division in these efforts.
Improved accuracy in short-range (0-48 h) forecasting of convective and mesoscale weather, and in particular high impact weather and hazards, provides the potential for enormous economic and societal benefits, and is a major objective of the USWRP. Recent high resolution forecasts conducted by MMM in support of the BAMEX field program demonstrated an encouraging potential to forecast the formation, structure, and propagation of convective systems. This program especially emphasized the importance of being able to directly parameterize cloud physics rather than the bulk properties of convection that is used in coarser resolution forecasts. We will continue to advance the capabilities for high-resolution forecasting through the evaluation and enhancement of model physics (especially cloud microphysics, boundary layer, and land-surface processes), assimilation of small-scale observations such as Doppler radar data, and further refinement of model numerics.

Experimental real-time forecast exercises at resolutions that enable explicit convective processes will continue to be critical for:

• Transferring new results and capabilities to the operational WRF model; and,
• Eliciting important feedback from research and forecast communities to drive further research activities.

We will be working closely with the DTC on real-time experiments with model configurations, model physics and assimilation methods to test their capacity for transformation to operations. Ongoing collaborations with the Storm Prediction Center (SPC) and NWS offices nationwide also will expand and will include the development of forecaster education and training material on methods to interpret such new, high-resolution forecast guidance and ensemble forecast output (discussed in the following section).

An important new aspect of our research will be investigations of the very short-range (0-6 hour) forecast problem. At present the initial conditions of mesoscale NWP models do not contain information at the convective scales, which take several hours to spin up, with the result that the first few hours of the forecast are not usable. Progress in the area of very short range forecasting thus requires development and testing of:

• Techniques to initialize convective-scale structures in NWP models; and,
• Accurate numerical and physical schemes.

Our work on techniques that can be utilized for initializing convective-scale structures, for example 3D-Var/4D-Var and the Ensemble Kalman filter, are described in more detail in Section 4.2. Since the primary source for observations on the convective scale is Doppler radar, the main focus will be on methods to assimilate Doppler radar data into WRF. We will further develop our work on accurate numerical and physical schemes that can adequately describe processes that act on very short time and space scales.

The development of these techniques for very short-range forecasting will also provide guidance for improving the early behavior in short-range forecast models.

Proper development of high-resolution prediction of mesoscale weather systems and atmospheric constituents requires new efforts in model verification. Because of the highly intermittent and localized nature of mesoscale weather systems, traditional measures of forecast accuracy developed for synoptic-scale forecasts are inadequate. To enable meaningful evaluation of high-resolution forecasts, we will explore new verification techniques that consider the physical character of mesoscale systems as well as the nature of the prediction (deterministic vs. stochastic). A promising new approach using spectral analysis to assess the characteristics of the forecasts against observations will be further developed as a tool to assess the realism of scales represented in the model forecasts. In addition, we will explore new object-oriented methodologies and other nontraditional techniques. The verification of fine-scale weather features is further complicated by the lack of datasets representing the details of mesoscale systems over regional domains. In collaboration with RAL, we will continue to develop and maintain regional datasets from WSR-88D radar, satellites, profilers, rawinsondes, and other local measurements to provide the observations needed to implement and evaluate new verification techniques.

In collaboration with CGD, other government laboratories, and university scientists, we will develop a regional climate modeling system based on WRF. Our plans are for this to be a 2-way nested model as we consider that the upscale contribution of, for example, mesoscale convective system details, could be a critical factor in the global scale interactions that affect both regional weather and climate. This development will be done in conjunction with the basic research on scale interaction described in Section 2.1 and will lead to the Nested Climate Model described in Section 4.3. To further expand capabilities to study regional climate influences with WRF, we will collaborate with other NCAR scientists and software engineers to consider formulations for a global non-hydrostatic version of WRF. The desirable formulations being considered include local refinement techniques for high-resolution regional forecasts and techniques that would be suitable for future use as a global, cloud-resolving model. We will begin by developing simple non-hydrostatic prototypes for promising approaches and test the comparative behavior of differing numerics and coordinate frameworks.

We plan to interact with the THORPEX program in this endeavor. With the assistance of CGD, we are also porting physics packages from the CCSM to WRF, and plans are being developed both to nest WRF within CCSM and to couple WRF with a regional ocean model. This interaction will be facilitated by the adoption of the ESMF across the NCAR model systems.

Next section: Advancing Data Assimilation Research

 

 

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