Simulations of the Climatological Wind Field in the Baltic Sea Area Using a Mesoscale Higher-Order Closure Model

Abstract

A three-dimensional mesoscale numerical model is utilized to investigate the climatological wind field over the Baltic Sea. To cover all synoptic and boundary layer conditions, a large number of model runs have to be made. Since this type of model consumes a rather large amount of computer time, the factors primarily affecting the wind field have been identified to limit the number of model runs. To get accurate results, it was necessary to make simulations representing the four seasons, eight wind directions, and three values of the geostrophic wind speed. The model was run for these 96 conditions with the monthly mean daily temperature variation at screen height over land to include the effects of the thermal stratification. The simulated wind fields were then weighted together using climatological data of the geostrophic wind speed and direction. The model results have been compared with measurements from two lighthouses outside the Swedish coast, as well as with an interpolation of ship measurements. The comparison shows good agreement between the modeled wind field and measurements, with deviations of less than 0.5 m s?1 in the main part of the Baltic Sea. Thus, the small deviations between measurements and simulations suggest that the main flow-forcing parameters, the climatological statistics, and assumptions made are correct.