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.