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

Mesoscale Modeling

Researchers in MMM are leading the development efforts toward creating an 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 Weather Research and Forecasting system (WRF) has now matured to the stage of operational testing within NCEP and AFWA, and is widely used by academia as a community mesoscale model. 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 less than 10 km.

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 the collaborative experience of previous research into mesoscale modeling in polar regions by MMM, the Polar Meteorology Group of the Byrd Polar Research Center (The Ohio State University), and the Pennsylvania State University (PSU), the National Center for Atmospheric Research (NCAR) Fifth-generation Mesoscale Model (MM5) has been modified for use in polar regions. The Antarctic Mesoscale Prediction System model (AMPS), runs twice per day (00Z and 12Z initializations), and cover progressively finer domains ranging from 90-km (covering most of the Southern Hemisphere) to 3-km (covering the region immediately surrounding McMurdo Station, the base of USAP operations).

LES (Large Eddy Simulation)

The planetary boundary layer (PBL) is a critically important region in atmospheric and oceanic flows. Turbulence and in particular coherent structures embedded in PBL turbulence determine important fluxes of momentum, heat, and scalars at the surface and entrainment zone of the PBLs which in turn impact larger scale motions. MMM studies three-dimensional, time-dependent, PBL turbulence using turbulence-resolving numerical simulations and in particular Large-Eddy Simulation (LES) for a wide variety of geophysical flows. The current NCAR LES code was first built in 1984 by Moeng (1984) to study clear convective PBLs and since then has continuously evolved to include a variety of physical processes, eg, clouds, chemistry, shear and stable stratification, vegetative surface canopies, and Langmuir cells and wave breaking in the ocean mixed layer, and has been adopted by outside researchers to study a variety of geophysical flows.

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, contact Piotr Smolarkiewicz.

The Clark - Hall Model

The three-dimensional, non-hydrostatic anelastic meteorological model described by Clark (1977), Clark and Hall (1991), and Clark et al. (1996), exploits features such as two-way interactive grid nesting and vertically-stretched terrain-following coordinates. The model uses a bulk parameterization for both the liquid and ice phase. The liquid phase is parameterized according to a modified version of the Kessler (1969) scheme, with Simpson and Wiggert's (1969) autoconversion formula. In this scheme, liquid water exists as cloudwater and rainwater. The ice phase parameterization uses the Koenig and Murray (1976) ice microphysical scheme. The Koenig-Murray formulation treats two types of ice particles: pristine ice (Ice A) - ice crystals initially formed by heterogeneous nucleation or ice splinter processes due to riming, and ice particles (Ice B) - also called graupel and initially formed by the freezing of raindrops or the interaction of Ice A particles with raindrops. This ice scheme is described, in detail, by Bruintjes et al. (1994). In summary, the model carries microphysical variables of water vapor, cloud water mixing ratio, rain water mixing ratio, and number concentration and mixing ratio for two types of ice particles. For more information, contact Bill Hall (hallb@ucar.edu).

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...