MMM SEMINAR NCAR
Kinetic Energy Spectra in
High-Resolution Limited-Area Forecasts:
Resolving the Transition
National Center for
Atmospheric Research
Boulder, CO
During several forecast experiments conducted over the past 3 years, the nonhydrostatic WRF model with grid-spacing less than 5 km was used to produce daily 36-48 h forecasts. Based on subjective evaluations, it appears that the model possesses some skill in predicting mesoscale phenomena, particularily convective events. Using kinetic energy spectra computed from the forecasts, we examine the energetics of the model forecasts and the resolution capabilities of the model. The forecast kinetic energy spectra clearly show the observed transition from a wavenumber dependence of k**(-3) at large scales to k**(-5/3) in the mesoscale, along with other characteristics found in atmospheric observations. Additionally, the model spectra decay at the highest resolved wavenumbers compared with observations, indicating energy removal by the model's dissipation mechanisms and denoting the model's effective resolution. Various dissipation mechanisms used in NWP models are tested in WRF model simulations to examine the mechanisms' impact on a model's effective resolution, and spectra from other NWP models are also examined. We consider the implications of these results for
numerical weather prediction.
Thursday, 17 March 2005,
3:30 PM
Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg 2 Auditorium (Rm1022)