P36 Performance of the Air Force's operational configuration for version 3.5.1 and proposed configuration for version 3.8.1 using the Weather Research and Forecasting model

Hertneky, Tracy, Michelle Harrold, Jamie Wolff, and Christopher Williams, National Center for Atmospheric Research and Developmental Testbed Center

To assist the Air Force (AF) with making an evidence-based decision in regards to updating their operational configuration, the Developmental Testbed Center (DTC) conducted a testing and evaluation (T&E) activity to compare the performance of a proposed WRF version 3.8.1 configuration against a configuration using version 3.5.1 that was previously tested for the AF. Major updates to version 3.8.1 included the use of the Thompson aerosol-aware microphysics scheme and the updated Rapid Radiative Transfer Model (RRTMG) long wave and short wave schemes, along with various other changes to physics and dynamics options. A 15 km contiguous US grid was employed for this test, with forecasts initialized every 36 hours during the winter and summer seasons of 2011-2012 and included a total of 123 cases. The Model Evaluation Tools (MET) software package was used to conduct a full objective verification analysis of surface and upper air model data using a variety of verification metrics. In addition, pair-wise differences between the two configurations were used to determine statistical significance (SS) and practical significance (PS), a measure of whether the differences are large enough to be of practical value. During this presentation, an overview of the analysis will be described with emphasis placed on PS differences. Briefly, when assessing surface temperature and dew point temperature bias results, version 3.8.1 performed better at most forecast lead times, with differences being PS. Differences in upper air temperature generally favored version 3.8.1 with PS during the summer, in particular across the Western US region, while version 3.5.1 was the preferred configuration for upper air dew point temperature over the Western US during both seasons.