Massexchange processes on the Earths surface and in the atmosphere

Zonal distribution of the radiation balance of the 'Earth-atmosphere' system is dictated by the key role of astronomical factors: altitude of the Sun above the horizon and sunlight hours per year. As an example, Fig. 10.3 presents mean values by latitude of the thermal balance components of this system. Analysis shows that the expenditure part of the thermal balance mainly consists of heat consumption for evaporation at the surface and for turbulent heat flow between the Earth and atmosphere. Shortage or excess of incoming or outgoing heat are carried away by horizontal motions in the atmosphere. An important item of the 'Earth-atmosphere' thermal balance is absorption or yield of heat by oceans. In tropical or temperate latitudes the absolute values exceed the value of residual radiation, i.e. the radiation balance. Absorption or yield of heat by the lithosphere is only a small portion of the system's thermal balance for a season.

Table 10.1 gives the values of the Earth's surface thermal balance obtained by different authors experimentally both in temperate and polar latitudes. The data of Table 10.1 show that absolute values of each compo

Wm 2

Fig. 10.3. Average latitudinal values of components of thermal balance of the 'Earth-atmosphere' system (according to G.N. Vitvitskiy): 1 - radiation balance of the 'Earth-atmosphere' system; 2 - variations of heat content (accumulation or loss of heat for the period under consideration) of hydrosphere; 3 - phase transitions of moisture; 4 - re-distribution of heat by horizontal motion of the atmosphere and oceans.

Fig. 10.3. Average latitudinal values of components of thermal balance of the 'Earth-atmosphere' system (according to G.N. Vitvitskiy): 1 - radiation balance of the 'Earth-atmosphere' system; 2 - variations of heat content (accumulation or loss of heat for the period under consideration) of hydrosphere; 3 - phase transitions of moisture; 4 - re-distribution of heat by horizontal motion of the atmosphere and oceans.

nent vary during a year. Maximum values of the radiation balance, heat consumption for evaporation and turbulent heat exchange are typical for the middle of the summer period, while minimum values are typical for the middle of the winter period. Maximum heat flow into the soil occurs in the early summer, while maximum yield by the soil occurs in the early winter. This displacement as to maximum inflow and outflow of heat at the surface is associated with a high heat consumption for thawing of snow cover Q^},.

On the territory of the former USSR the radiation balance of the surface varies from zero on the remotest Arctic islands to 200 kJ cm2 in the foothills of Central Asia. In mountains of the Russian North-East, its value is lower,

Table 10.1. Seasonal sum and percentage relationship between arrival (+) and consumption ( — ) of heat balance of the Earth's surface on the open areas of plains (after M.K.Gavrilova)

Summer Winter

Components -

of heat 104 kJ 104kJ Landscape, soil balance cm-2 % cm-2 % composition

Summer Winter

Components -

of heat 104 kJ 104kJ Landscape, soil balance cm-2 % cm-2 % composition

Zagorsk (Moscow region)

0 0

Post a comment