Distribution of permafrost and spatial variations of its mean annual temperature

The great extent of the territories of the former USSR from west to east and from north to south, the complexity of orographic, geological, tectonic and hydrogeological structures, of landscape and of climate, together with the changes in the late Cenozoic, are responsible for the variety of geocryological conditions in their different parts.

The zonal distribution of permafrost in the territory of the former USSR is associated with two main circumstances:

1. the history of the cryogenic development of the upper layers of the Earth's crust in Neogene-Quaternary time during which the stage was set for the present geocryological conditions;

2. the present conditions of heat exchange at the surface and in the ground. The mean annual ground temperature for the particular period, including for short-period fluctuations, indicates the level of heat-exchange for every climatic sequence.

The present heat-exchange conditions under which the mean annual ground temperatures are being formed, are defined by the following basic factors and conditions:

1. the dependence on latitude of the incoming solar radiation, upon which depends the radiation balance at the Earth's surface;

2. the effect of the Atlantic, Arctic and Pacific oceans on the atmospheric circulation, which gives the regional nature of climate;

3. the distance between the territory and sea basins and the position of the territory within the continent, this being responsible for the climatic continentality, i.e. for the amplitude of the annual fluctuation of temperature of the air and of the Earth's surface;

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