Climate fluctuations in Sweden 1860-1987.

Type: Report
Author: Alexandersson, Hans., Eriksson, Bertil


We are living in a time when there is a great concern and anxiety on climate changes, induced by man or natural. Figures showing trends or abrupt changes may not seldom be based on rather poor climate records. Thus we have started a climate project at SMHI where we have taken great care to avoid non- homogeneous records and where we have limited our aims to the period of instrumental records (mainly from 1860 in Sweden but a few stations have data from about 1750). Three elements have been studied extensively: temperature, precipitation and air pressure. Two main areas within Sweden were selected. In order to avoid non- homogeneous data the temporal analysis was preceded by a spatial homogeneity test which revealed several discontinuities and artificial trends. Long- term fluctuations were visualized by using a Gaussian low pass filter. One interesting feature is that the pressure difference northern to southern Sweden showed a decrease by about 10% around 1930. The corresponding decrease of the zonal wind may to some extent explain the quite large frequency of cold winters in later decades as high winter temperatures in Scandinavia is strongly connected with westerly and southwesterly inflow of mild and humid Atlantic air-masses. Another interesting but still somewhat questionable feature is the dry early decades.