Lawrence Livermore National Laboratory

Sample image of NARAC WRF model illustrating atmospheric conditions over the continental United States via 500-mb geopotential heights and absolute vorticity.
This higher resolution regional NARAC WRF model simulation shows the effect of NY harbor on the speed and direction of the wind at 10 meters above the surface.

NARAC performs in-house numerical weather prediction simulations using the National Center for Atmospheric Research's (NCAR's) Weather Research & Forecast (WRF) atmospheric model to generate high-resolution wind fields when observations or available numerical weather prediction model output data are insufficient for accurate dispersion modeling in complex conditions. The large selection of physics options available in WRF to parameterize sub-grid scale phenomena such as convective processes and planetary boundary layer turbulent mixing allows NARAC to tailor the model configuration to optimize forecasting skill for specific scenarios.

Important features of the WRF model include:

  • Grid system based on a continuous-terrain representation and variable-resolution sigma vertical coordinate system (Arakawa-C grid)
  • Multiple, nested grid capability
  • Non-hydrostatic compressible dynamics (Klemp and Wilhelmson, JAS 1978) with second-order advection and fourth-order diffusion
  • Large selection of sub-grid scale atmospheric physics parameterizations for radiation (Harshvardhan, JGR 1987), explicit moist physics (Rutledge and Hobbs, JAS 1983), convective precipitation physics (Kain and Fritsch, JAS 1990; Kuo, JAS 1979), boundary layer physics (Mellor and Yamada, 1982), and surface layer physics (Louis, 1979)
  • Variety of meteorological data assimilation methods: multivariate optimum interpolation analysis of winds and temperature, time-dependent boundary conditions (Daview, QJRMS 1976; Perkey and Krietzberg, MWR 1976)