Regional mesoscale forecast models are becoming increasingly important tools for the forecasting of local weather. Forecasting of precipitation is a particularly challenging problem since mesoscale models rely on bulk microphysical parameterization schemes that do not fully represent the physical processes involved in the production of precipitation.

The IMPROVE Project being carried out at the University of Washington, is designed to improve the microphysical parameterization of cloud and precipitation processes in mesoscale models by obtaining detailed measurements of those processes in a variety of systems.

Brief descriptions will be given of the measurements obtained in the winter of 2000-2001 of frontal systems approaching Washington coast, and in winter 2001-2002 of orographic systems over the Oregon Cascade Mountains. The ways in which these data are being used to evaluate present microphysical parameterization schemes and to develop improved schemes will be described.