Upper-Troposphere MM5 and WRF Temperature Error and Vertical Velocity Coupling

Abstract

he fifth-generation Pennsylvania State University?National Center for Atmospheric Research Mesoscale Model (MM5) and the Weather Research and Forecasting Model (WRF) have been employed to predict troposphere temperatures for atmospheric study and operational decision making with positive results. Temperature bias in MM5 and WRF has been noted in previous troposphere studies through radiosonde vertical profile comparison; however, long-range horizontal in situ temperature observations have never been utilized to assess MM5 and WRF upper-troposphere temperature prediction. This study investigates upper-troposphere temperature forecasting of MM5 and WRF utilizing long-range in situ observations linking temperature error to forecast vertical velocity within the upper troposphere over surface elevation changes and different surface types. Temperature observations were taken during flights over North America, Europe, and southwest Asia between 6000 and 7600 m above sea level and compared with MM5 and WRF upper-troposphere forecasts. Regression analysis indicated MM5 and WRF upper-troposphere temperature forecast errors were related to changes in forecast vertical velocities within 100 km laterally of the modeled flight tracks between 39° and 59°N latitude. Temperature error and forecast vertical velocity coupling occurred in MM5 and WRF forecasts over land, while no evidence of temperature error and forecast vertical velocity coupling in MM5 or WRF forecasts was found over water. Evaluation of MM5 and WRF forecasts displayed varying results of temperature error and forecast vertical velocity coupling between specific surface elevations above sea level, vegetative cover, and urban influences.