Advances in the Weather Research and Forecasting (WRF) Model

Since its inception ten tears ago, the overall goal of the WRF Model project has been to develop a next-generation mesoscale forecast model and data-assimilation system that will advance both the understanding and prediction of mesoscale weather, and will accelerate the transfer of research advances into operations. The WRF model has been designed to improve forecast accuracy across scales ranging from cloud to synoptic, with priority emphasis on horizontal grid resolutions of 1-10 kilometers. The WRF software has a modular, hierarchical design that provides good portability and efficiency across a range of foreseeable parallel computer architectures, and has demonstrated good parallel scaling in simulations on as many as 10,000 processors. The model incorporates advanced numerics, and currently supports two dynamic cores and numerous state-of-the-art physics options. Since the first release of a beta version in December 2000, over 5,000 users from some 90 countries have registered to download the WRF code. Annual workshops and frequent tutorials are offered to assist a rapidly growing user base. The WRF model has been adopted for use as the primary regional operational forecast model at NCEP and AFWA, and is being implemented for international operational forecasting in Korea, India, Taiwan, and Israel. Numerous real-time forecasting experiments are also being conducted to evaluate WRF performance in a variety of forecast applications. The WRF data-assimilation system (WRF-Var) is a unified (global/regional, multi-model, 3/4D-Var) model-space variational package that has been developed in tandem with the model and is also freely available to the general community. The 3D-Var implementation is run operationally at AFWA and is being adopted for international operations in Korea, China, Taiwan, and India. The 4D-Var system will be made available in the next WRF release later this year.

In the recent community release of Version 2.2, major new features have been added to the modeling system, including a new WRF Preprocessing System (WPS), a multiple relocatable nesting capability, an urban canopy model as part of the NOAH LSM, both grid and obs nudging FDDA, and new microphysics and radiation packages. As the model has matured, its use in research has expanded into a wide range of applications. For the past several years, extensive convection-resolving real-time forecast experiments have been conducted during the convective season by NCAR, NSSL, SPC, NCEP, and the University of Oklahoma to evaluate the capabilities and limitations of explicit convective forecasts. Hurricane forecasting on convection-resolving grids has also received considerable attention, utilizing moving nested grids to concentrate high resolution in the vicinity of the hurricane. The WRF system has been coupled with atmospheric chemistry modules (WRF-Chem) to conduct air-chemistry and air-quality research, and has been adopted for regional-climate applications to investigate the downscaling of global climate influences on regional scales and the upscaling influences of regional processes (particularly moist convection) in global climate circulations. Future developments for WRF will by guided by the strategic plan on Research-Community Priorities for WRF-System Development prepared by the WRF Research Application Board.