Temperature and precipitation variations in Norway 1900-1994 and their links to atmospheric circulation

Abstract

The main aim of the present study was to identify to what degree decadal scale variability and long-term trends in temperature and precipitation in Norway can be attributed to variations in the dominating atmospheric circulation patterns. Empirical models were developed and tested on monthly series of temperature and precipitation in different regions in Norway. The monthly mean sea level pressure (SLP) field over the northern North Atlantic and northern Europe was used as a predictor. Principal components (PCs) deduced from this field were used as a basis for stepwise multiple regression analysis. The downscaling models were developed using 1925–1969 as a training period, while 1900–1924 and 1970–1994 were used as validation periods. Model testing revealed that the temperature variability during 1970–1994 in most cases was better simulated than the variability during 1900–1924. The models reproduced most of the observed trends and decadal scale variability from 1940 to present. They also reproduced the precipitation trends in western Norway before 1940. However, the temperature increase observed over all the country in 1900–1940 was not reproduced. Nor was the increased winter precipitation in southeastern Norway during the same period. It is concluded that the temperature and precipitation changes observed in Norway during the last 40 years can mainly be attributed to variations in the SLP field. Variations in the precipitation conditions in the eastern parts of the country, and in temperature all over the country, during 1900–1940 are probably connected to changes in external forcings and/or atmosphere–ocean interactions. Copyright © 2000 Royal Meteorological Society