To assess the sensitivity of forecast verification statistics for atmospheric variables near the land surface (2-m temp and relative humidity, 10-m wind, as well as precipitation) and on land-surface variables (particularly snow water equivalent and snowmelt) to the vertical placement of near-surface sigma levels in the Weather Research and Forecasting (WRF) model, the Developmental Testbed Center (DTC) ran a carefully controlled test and evaluation of forecasts generated with the Advanced Research WRF (ARW) dynamic core using two model configurations that were identical except for the distribution of the nine lowest sigma levels. Both configurations were based on the WRF Rapid Refress (WRF-RR) physics suite and are for general mid-latitude forecasting applications. The domain employed in this test was a Contiguous United States (CONUS) domain with roughly 13-km grid spacing.

This test was conducted during the summer of 2008 in support of the implementation of the WRF-RR at the National Centers for Environmental Prediction (NCEP)