Longwave radiation budget at the Baltic Sea surface from satellite and atmospheric model data

The net longwave radiation flux LW↑↓ in the Baltic Sea in 2001 has been subjected to spatial and temporal analysis. Maps of the mean monthly LW↑↓ over the Baltic were drawn using the new semi-empirical formula for the Baltic Sea (Zapadka et al. 2007). The input data for the formula, such as sea surface and air temperatures, and cloud cover, were obtained from the Tiros N/NOAA and METEOSAT 7 satellites and from the UMPLfo recast model (see http://meteo.icm.edu.pl). The mean annual LW↑↓ for 2001 was estimated at 63 W m−2 and compared with available data from other sources. The monthly maps of the net flux LW↑↓ over the Baltic show that the total values reach a minimum (LW↑↓≈50 W m−2) in April, September, October and a maximum (LW↑↓≈80 W m−2) in November. The statistical error of daily maps, on which the monthly maps were based, is no more than 18 W m−2.