Variability In Atmospheric Circulation In The Arctic Between 1939 And 1990

It is impossible to evaluate the causes of variability in T and P in the Arctic without research on variability in atmospheric circulation therein. As is widely known, the role of this circulation in determining climate is much greater here than at lower geographical latitudes. It is especially significant during cool seasons, when the inflow of solar radiation is insignificant. The thermal equilibrium of the polar climatic system in its present form would be impossible without a constant inflow of heat from lower geographical latitudes. Atmospheric and oceanic circulations serve as the heat conveyors. The results of recent research in the field show that as much as 95% of heat advection reaches the Arctic by way of atmospheric circulation (and not 66%, as had earlier been assumed), and only 5% is brought by oceanic circulation (Alekseev et al. 1991). During the polar night these are the only heat fluxes that reach the Arctic and protect it from cooling. All of this, together with the fact that the change in synoptic processes is 1.5 times quicker here than at lower latitudes (Vangengeim 1952, 1961), support the thesis that the climate of the Arctic is much more sensitive to changes in atmospheric circulation than the climate of other areas of the globe. That is why considerable attention will be devoted to this issue in this work.

The variability of atmospheric circulation in the Arctic over the period 1939-1990 was investigated using types and groups of synoptic processes in the Arctic as provided by Dydina (1958, 1982), and macrotypes of circulation in the Northern Hemisphere according to the Vangengeim-Girs typology (Girs 1960, 1971, 1974). The aforementioned data for the period 1948-1974 were taken from a calendar of types of synoptic processes in the Arctic published by Dydina (1982), and for the remaining years they were obtained from G.K. Zubakin at the Arctic and Antarctic Research Institute at St. Petersburg.

Dydina (1958) identifies 16 basic and 9 complementary circulation types, mainly taking into consideration the similarity in the arrangement of isobaric fields and their kinematic characteristics in the Arctic, as well as the relative similarity of those fields in lower latitude areas. On the basis of general characteristics of the arrangement of basic isobaric fields in the Arctic, all the types of circulation were generalised and 6 groups of synoptic processes were created: A, B, W, G, D, and K (Dydina 1982).

The analysis in the present work covers 16 basic types and 6 groups of circulation in the Arctic as well as 3 macrotypes of circulation (Vangengeim

Figure 4.1. Examples of synoptic situations for particular types of atmospheric circulation according to the typology of Dydina (1982). Letters denote macrotypes of circulation.

L - cyclone, H - anticyclone, continuous arrows - tracks of cyclones, dashed arrows - tracks of anticyclones

Figure 4.1. Examples of synoptic situations for particular types of atmospheric circulation according to the typology of Dydina (1982). Letters denote macrotypes of circulation.

L - cyclone, H - anticyclone, continuous arrows - tracks of cyclones, dashed arrows - tracks of anticyclones

Circulation Arctic
Figure 4.1. cont.
Scroll Saw Rocket Pattern
Figure 4.1. conl.

1961; Girs 1977): western (W), meridional (C), and eastern (E). Examples of synoptic situations for particular types of atmospheric circulation are shown in Figure 4.1. What follows is a shortened description of the general arrangement of isobaric fields in the Arctic for each circulation group. In parentheses are the types which belong to a given group:

Group A (I and II) - development of cyclone activity over the majority of the Arctic basin and anticyclone activity over the area of Canadian Arctic Archipelago,

Group B (III-V) - development of anticyclone activity over the majority of the Arctic,

Group W (VI-X) - development of cyclone activity over the western Arctic and anticyclone activity over the eastern Arctic,

Group G (XI) - development of cyclone activity over the eastern Arctic, and anticyclone activity over the western Arctic, i.e. these synoptic processes are contrary to those of group W,

Group D (XII-XIII) - development of cyclone activity over the area of the Kara Sea and the Laptev Sea or to the north, while anticyclone fields are formed west and east of the area of cyclone activity,

Group K (XIV-XVI) - synoptic processes of this group are contrary to those of group D as far as the arrangement of isobaric fields is concerned, i.e. development of anticyclone activity over the Kara and Laptev seas, and cyclone activity to the west and east of them.

A team of meteorologists working at the Arctic and Antarctic Research Institute, particularly Dydina (1958, 1964), identified the relationships between different types (groups of types) of circulation and the most important elements of weather in the Arctic. Dydina also found significant connections between the types of synoptic processes in the Arctic and the macrotypes of atmospheric circulation in the Northern Hemisphere. The results obtained enabled the production of a medium range weather forecast for the Arctic and its parts. Later, she published a number of studies concerning this problem (Dydina 1982 and references therein).

Dydina's classification of synoptic processes in the Arctic is very well known among Russian meteorologists and climatologists and has been accepted by leading Russian experts investigating different environmental problems in the Arctic. For example, both in the Atlas Okeanov: Polarnyj Severnyj Okean (Gorshkov 1980) and Atlas Arktiki (1985), the atmospheric circulation in the Arctic is depicted using the synoptic processes identified by Dydina.

The subjective character of this classification is its main weakness and some researchers are sceptical as to the authenticity of Dydina's types and groups of synoptic processes in the Arctic. However, the correctness of Dydina's classification using 'objective' synoptic typing techniques (principal component and cluster analyses) was confirmed by Vanda and Lyamzin (1978) and Vanda (1978). They obtained statistically significant relationships (Chuprov coefficient of correspondence 0.633) between the groups of synoptic processes in the Arctic identified by Dydina and the groups ofatmospheric circulation distinguished by them as a result of the above mentioned 'objective' method of classification. This allows us to state that Dydina's classification does have an objective character to a significant degree. The validity of this classification was also confirmed by good results obtained in operational weather forecasts for the Arctic.

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