From Community Mesoscale Models for Weather Prediction to Nested Regional Climate modeling

Mesoscale Numerical Weather Prediction

MMM scientists and software engineers continue to lead development and community support efforts for an advanced numerical weather analysis and forecasting system. This is the Weather Research and Forecasting (WRF) model, and areas of ongoing system advancement areas include numerics and physics, software performance and computational efficiency, data assimilation capabilities, model evaluation, and extensions for broader applications. The WRF system is operational at various NWP centers throughout the world (e.g., NCEP, AFWA) and is the most popular (based on number of registered users) mesoscale model in the global research community. WRF was originally developed through a collaboration among NCAR, NOAA/NCEP, NOAA/ESRL, the Air Force Weather Agency (AFWA), the Naval Research Lab (NRL), Oklahoma University (OU/CAPS), the FAA, and university scientists. The common goal has been to improve the accuracy of the simulation of weather across scales ranging from the cloud to synoptic. In recent years, WRF's application has been extended into regional climate modeling.

Coupling Mesoscale Models and Climate Models to Create Better Prediction of Regional Climate

Climate varies across a wide range of temporal and spatial scales. Yet, climate modeling has long been approached using global models that can resolve only the broader scales of atmospheric circulations and their interactions with convection, land, ocean surface, and sea ice. Clearly, large-scale climate determines the environment for mesoscale and microscale processes that govern the weather and local climate; but, likewise, processes that occur at the regional scale may have significant impacts on the large-scale circulation. This is an important issue for climate and weather scales. Additionally, resolving such interactions will lead to much improved understanding of how climate both influences, and is influenced by, human activities. MMM is working with CGD and its climate model, to develop a Nested Regional Climate Model (NRCM) for community use.

Other Modeling Efforts

AMPS (Antarctic Mesoscale Prediction System)

Based on mesoscale model research and testing in polar regions by MMM, collaborator The Ohio State University, and others, the Advanced Research WRF model, with Version 3.1, has been modified for use in polar regions. This runs in the Antarctic Mesoscale Prediction System (AMPS) at NCAR, an experimental, real-time NWP system over Antarctica providing guidance to forecasters of the United States Antarctic Program and for science and logistics uses worldwide. AMPS produces two runs daily, with forecast times out to five days. The system's configuration features six nested grids with sizes from 45 km (covering most of the Southern Ocean) to 1.67 km (covering the McMurdo Station region). AMPS output may be viewed at http://www.mmm.ucar.edu/rt/amps.

LES (Large Eddy Simulation)

Large-Eddy Simulation (LES) is a state-of-the-art numerical technique to study turbulence and its coherent structures and statistics. The technique has been widely used to simulate geophysical turbulent flows, particularly turbulence in the planetary boundary layer (PBL). The PBL is a critically important region of the Earth's system: It promotes transport of momentum, heat, moisture, chemical species and gases; it links human activities, for example land use and generation of pollutants, with larger scale atmospheric motions; it is where land, air and sea interact. Thus, the PBL strongly impacts weather and climate. In MMM, we have used LES to study clear and cloudy PBLs, daytime and nighttime PBLs, chemical transport, turbulence/vegetation interactions, ocean waves and wave breaking, dispersion of pollutants, turbulence over surface heterogeneities such as hills, valleys and land use, and turbulence in deep convection systems. The original NCAR LES code uses a pseudospectral representation in the horizontal directions and finite-differencing in the vertical. This code has been adopted by many outside researchers who adapt the code to their particular topic within geophysical turbulence. LES capabilities also exist in the Weather-Research Forecast model (WRF-LES), which is based on the WRF framework and uses finite-differencing in horizontal and vertical directions.

All-scale Anelastic Model for Geophysical Flows

An adaptive, grid-refinement approach for simulating geophysical flows on scales from micro to planetary. The model is nonoscillatory forward-in-time (NFT), nonhydrostatic, and anelastic. The major focus in this effort to date has been the design of a generalized mathematical framework for the implementation of deformable coordinates and its efficient numerical coding in a generic Eulerian/semi-Lagrangian NFT format. For more information, please visit the EULAG web page.

Jenny Sun (sitting) talks with colleagues who are working to assimilate radar data into WRF. The team includes (left to right): Qingnong Xiao, Bill Kuo, Andrew Crook, So-Young Ha, Dale Barker, and Soichiro Sugimoto. ...more...