Stable atmospheric conditions over the Baltic Sea : model evaluation and climatology

The WRF (Weather Research and Forecasting model) was evaluated against flight measurements over the Baltic Sea during stable conditions, focusing on vertical profiles of temperature and wind speed. Six different boundary layer parameterization schemes were used. It is shown that there are generally small differences between the boundary layer schemes, and that all schemes have problems in capturing the strength and height of lowlevel jets. Climatological simulations over the Baltic Sea show that there is a strong seasonality in the stability over the sea with up to 80% stable conditions in spring as compared with 10% in winter. Low-level jets are common, and occur up to 45% of the time in spring. The entire Baltic Sea, not only its coastal areas, is affected by stable stratification.