Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 12 2 2008 10.5194/hess-12-405-2008 http://www.hydrol-earth-syst-sci.net/12/405/2008/ http://www.hydrol-earth-syst-sci.net/12/405/2008/hess-12-405-2008.html http://www.hydrol-earth-syst-sci.net/12/405/2008/hess-12-405-2008.pdf 405 414 2008-03-05 Influence of summer and winter climate variability on nitrogen wet deposition in Norway L. R. Hole lrh@nilu.no H. A. de Wit W. Aas Norwegian Institute for Air Research (NILU), P.O. Box 100, 2027 Kjeller, Norway Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, 0349 Oslo, Norway Norwegian Meteorological Institute, Forecasting Division for Western Norway, Allegt. 70, 5007 Bergen, Norway Dominating wind patterns around Norway may change due to climate warming. This could affect transport of polluted air masses and precipitation. Here, we study relations between reactive nitrogen wet deposition and air mass transport during summer and winter expressed in the form of climate indices, at seven sites in Southern Norway for the period 1980–2005. Atmospheric nitrate concentrations decreased with 0 to 50% in the period, particularly at sites with little precipitation, and mostly during 1990–2005. For comparison, reported reductions in emissions of oxidised nitrogen in Europe in 1989–2003 were 23%. Climate indices explained up to 36% of the variation in winter nitrate deposition at the western and northern sites – and also explained 60% of the variation in winter precipitation (R=0.77). This suggests that the variation in nitrate wet deposition is closely related to variation in precipitation, and that the climate indices seem to also partly control the variation in atmospheric nitrate concentrations (R=−0.45 at coastal sites). 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