5.5    A Comprehensive Evaluation of Polar WRF Forecast     Performance in the Antarctic

Bromwich, David, Francis Otieno, Keith Hines, Ohio State University, Kevin Manning, NCAR, and Elad Shilo, Israel Meteorological Service

Recent polar versions of the Weather Research and Forecasting (Polar WRF) model are evaluated over an Antarctic domain at 60 km. The impact of model improvements, large scale circulation variability, and uncertainty in the initial and lateral boundary conditions are examined. Model skill is found to be robust even without nudging and not very sensitive to interannual variations. Forecast skill differs more between seasons than between recent versions. The forecasts exhibit a cold summer and a warm winter bias in 2-m air temperatures. Dew point temperature statistics are similar but smaller in magnitude. Biases in both forecast wind speed and surface pressure are positive. Deficiencies in model cloud representation enhance longwave radiative loss from the surface and lead to the summer cold bias. The winter warm bias results from an anomalously large sensible heat flux toward the surface generated by the positive wind speed bias in the stable boundary layer. The most skillful forecasts are those using ERA-Interim reanalysis for initial and lateral boundary conditions.