Performance of the Weather Research and Forecasting Model for Month-Long Pan-Arctic Simulations

The performance of the Weather Research and Forecasting (WRF) model was evaluated for month-long simulations over a large pan-Arctic model domain. The evaluation of seven different WRF (version 3.1) configurations for four months (January, April, July, and October 2007) indicated that WRF produces reasonable simulations of the Arctic atmosphere. Ranking of the model error statistics, calculated relative to the NCEP/Department of Energy Global Reanalysis 2 (NCEP-2), for sea level pressure, 500- and 300-hPa geopotential height, 2-m air temperature, and precipitation identified the model configurations that consistently produced the best pan-Arctic simulations. For all WRF configurations considered, large errors in circulation are evident in the North Pacific. The errors in the North Pacific are manifested as an overly weak and westward-shifted Aleutian low and overly strong subtropical Pacific high simulated by WRF. These circulation errors are nearly barotropic, with a slight increase in magnitude with height, and they vary slightly in magnitude and position as the WRF physics options and domain size are changed. It is concluded that the circulation errors are likely due to errors in the treatment of the model-top boundary. The use of a higher model top (10 hPa rather than 50 hPa) or spectral nudging of wavenumbers 1–3 in the top half of the model domain results in significantly reduced circulation biases. Simulations with WRF version 3.2 also show reduced errors.