Spatial and temporal patterns of chloride deposition in Southern Sweden

Monthly bulk deposition of chloride at 49 stations in Southern Sweden betwe en 1989 and 1995 was used to produce quarterly and annual deposition maps t hrough ordinary block kriging. Generally, deposition decreases from the wes t coast and eastward and displays a large annual variation, governed by the frequency and intensity of midlatitude cyclones. The 1st quarter dominates the temporal pattern all years except 1992. The 4th quarter is the second most important and the 2nd and 3rd quarters have generally low deposition. The spatial deposition maximum was often displaced from the west coast to t he western fringe of the South Swedish highland, due to orographic enhancem ent of precipitation. On the western rise of the highland, deposition almos t entirely co-variates with precipitation. On the west coast and in the eas tern part of Southern Sweden, the temporal pattern is a more complex result of precipitation and frequency of strong westerlies. Comparing the quarter ly total dataset with precipitation and frequency of westerly gales shows t hat both the 3rd and 4th quarters have higher mean precipitation than the 1 st quarter, but lower deposition, while the second quarter has substantiall y lower precipitation but almost equal deposition to the 3rd quarter. The f requency of westerly gales shows a clearer, linear relationship to quarterl y deposition. The 1st quarter has the highest variability in deposition and precipitation as well as in frequency of westerly gales. The importance of single highly salt laden cyclones to the annual deposition is obvious in t he 1st quarter of 1993. Changes in cyclone activity due to climate change i s therefore of vital importance for the chemical characteristics of the mid latitude atmosphere.