P90  Eliminating Spurious Numerical Waves in High Resolution WRF Simulations of Winter Cyclones

Keeler, Jason M., Brian F. Jewett, Bob M. Rauber, and Greg M. McFarquhar, University of Illinois

Previous research and early results from the Profiling of Winter Storms (PLOWS) field campaign indicate that cloud-top precipitation Ògenerating cellsÓ are a critical component of precipitation processes in mid-latitude winter cyclones.  While the PLOWS dataset provides some knowledge of generating cell thermodynamics and 2D structure, numerical simulations are necessary in order to provide a process-oriented understanding of the mechanisms responsible for their development and maintenance.  Due to the small horizontal scale (~1-2 km) of these generating cells, numerical simulations require very high horizontal resolution (dx ~100-200 m).

This paper describes lower resolution (dx = 3 km) simulations conducted with the Weather Research and Forecasting (WRF) model version 3.3.1.  Analyses of the geostrophic momentum field indicated the presence of troposphere-deep wave features, which formed in the middle of the model domain and propagated northward.  These features are not physically realistic, and must be eliminated before conducting even higher horizontal resolution simulations.  We are employing increased vertical resolution (including the 1/100 resolution ratio recommended by Snyder et al. 1993) and Digital Filter Initialization to reduce or eliminate these spurious waves.