Abstract:
The changes of atmospheric circulation patterns in the Northern Hemisphere and in the Arctic for the period 1939–1990 were investigated. For this purpose, the seasonal and annual frequencies of occurrence of W, E and C macrotypes according to the Vangengeim–Girs typology and groups of synoptic processes in the Arctic (A, B, W, G, D and K) according to the Dydina classification have been computed. Spatial and seasonal patterns of the mean diurnal temperature range (DTR) in the Arctic are presented, based on the data from 33 Arctic stations for the period 1951–1990. The relationships between the DTR in the Arctic and the atmospheric circulation changes in the Northern Hemisphere and in the Arctic have been investigated. The seasonal mean DTR for each macrotype of circulation and group of circulation was calculated using daily data from ten Arctic stations for the period 1951–1990. These stations represent all climatic regions and subregions identified by the authors of Atlas Arktiki (1985. Gla6noye Upra6lenye Geodeziy i Kartografiy, Moskva, p. 204). In addition, the correlation coefficients between DTR in the Arctic and both the North Atlantic Oscillation Index (NAO) and the Zonal Index (ZI) have been computed. Statistically significant changes of atmospheric circulation in the Northern Hemisphere (mainly in low and moderate latitudes) since the mid-1970s, which are also reported by other researchers, have been confirmed. In the Arctic, the atmospheric circulation has also undergone changes in recent decades; however, these changes are significantly smaller. Both the annual and the seasonal mean DTR values have been found to be the highest in the centre of the southernmost parts of the Canadian and Russian Arctic and the lowest in the Norwegian Arctic. Based on the seasonal means, four types of annual course of the DTR in the Arctic have been identified. The results pertaining to the relationship between DTR and atmospheric circulation provide some evidence that, in recent decades, both the large-scale changes of the atmospheric circulation in the Northern Hemisphere and its changes in the Arctic have led to the damping of the cool half-year DTR in the Arctic.
