Investigation of the atmospheric water budget of the BALTEX area using NCEP/NCAR reanalysis data

Abstract

The Baltic Sea Experiment BALTEX is the European regional project of GEWEX. The aim of BALTEX is to improve the knowledge of the water and energy cycle of the Baltic Sea including its catchment area (the BALTEX area). In this study the NCEP/NCAR reanalysis data (Kalnay et al. Bull. Am. Meteorol. Soc., 1996, 77, 437-471) are used to derive the mean atmospheric water budget over the BALTEX area. For this purpose the horizontal water vapour fluxes use calculated. In the long-term mean (here 1948-2000) the vertically integrated divergence of these fluxes must balance evaporation minus precipitation. The latter two are provided by the NCEP/NCAR reanalyses. The water budget over the BALTEX area is, however, not closed. An error estimation is performed. The divergence of the water vapour flux is corrected due to the mass balance correction technique (Alestalo, Tellus, 1981, 33, 360-371). Large differences are obtained between the precipitation given by the NCEP/NCAR reanalysis and by the analysis of the observations by Rubel and Hantel (Meteorol. Atmos. Phys., 2001, 77, 155-166). With these analysed precipitation data and the corrected divergence of the water vapour fluxes the imbalance of the water vapour budget could be remarkably reduced.