The radiation balance of the earth's surface is the algebraic sum of radiation fluxes in a certain volume or on a certain surface, that is, the difference between the absorbed radiation and the effective radiation of this surface [1] . Its annual values for the Earth as a whole are positive. One of the climate-forming factors, the most important characteristic of the microclimate of crops and the conditions of their photosynthesis .
Content
Components
For the earth's atmosphere, the radiation balance consists of the positive part — absorbed direct ( S ' ) and diffuse solar radiation ( D ), as well as the absorbed long-wave radiation (infrared) of the earth’s surface , and the expendable part — heat loss due to the long-wave radiation of the atmosphere in the direction of the earth’s surface (the so-called counter-radiation of the atmosphere) and into space [2] . The positive part of the radiation balance of the underlying surface consists of the direct and diffuse solar radiation absorbed by the underlying surface, as well as the absorbed atmospheric counter-radiation. The expenditure part consists of heat loss by the underlying surface due to its own thermal radiation.
The formula of the radiation balance (elements in W / m2) [3] :
B = (S '+ D - R) - (E with - b · E a ) = Q · (1-A k ) - E ef
- B is the radiation balance;
- S 'is direct solar radiation;
- D - diffuse solar radiation;
- R - reflected solar radiation
- Q - total solar radiation;
- E with - radiation of the earth's surface;
- E a - anti-radiation of the atmosphere;
- b is the absorption coefficient of the underlying surface;
- A k is the albedo of the underlying surface;
- E eff - the effective radiation of the underlying surface.
Factors
The radiation balance depends on the height of the sun above the horizon, due to the time of day, time of year , geographic latitude , as well as the albedo of the earth's surface, the transparency of the atmosphere , and cloudiness .
Dynamics
During the day, the radiation balance is positive, at night - negative. The reversal of the radiation balance sign occurs about an hour after sunrise and an hour before sunset. Positive radiation balance means excess heat on the surface of the earth, which is compensated by the outflow of energy in the form of turbulent flows and heat transfer , the cost of heat for phase transitions . Negative balance means lack of heat, replenished by the flow of energy from the atmosphere and from the depths of the soil or water. The value of the radiation balance, its spatial heterogeneity determines the areas of heating or cooling of air above the surface, which affects the mode of atmospheric circulation .
Measurement
Radiation balance in the field is measured using a balance meter designed by Yu. D. Yanishevsky, consisting of two plates (radiation receivers) installed horizontally: the first is toward the zenith, the second is toward the earth's surface. Due to the difference in radiation falling on the plates, a temperature difference is created, which generates an electric current , which is recorded by a galvanometer .
Value
Radiation balance is an integral part of the thermal balance of the atmosphere and underlying surface. On Earth, the radiation balance varies widely: its largest values are in tropical oceans (up to 1 kW / m2), the smallest are in the deepest regions of Antarctica (negative all year round).
See also
- Earth's heat balance
Notes
- ↑ Geography. Modern illustrated encyclopedia / ed. prof. A. P. Gorkina. - M .: Rosmen, 2006.
- ↑ Template: VRE M Template: VRE (Ros.) Template: VRE
- ↑ (rus.) (Rus.) Agricultural Encyclopedic Dictionary / Editor-in-Chief V.K. Month. - M .: Soviet encyclopedia, 1989.
Literature
- Voloshina A.P. Reference manual on glaciometeorology . - M. , 2006.