Earth's radiation balance

The radiation balance of the earth is the most important part of the energy budget of the Earth. While the different household sizes in an equation are mathematically accounted for, while they are also well describes the radiation budget and represents their interactions over the portion of the radiation balance.

Radiation balance

The incident solar radiation is (mostly ) short-wave, so this formula is also referred to as short-wave radiation balance ():

• = Global radiation
• = Direct radiation
• = Diffuse radiation ( sky radiation )
• = Reflected radiation (influence ozone layer, etc.)
• = albedo

The Earth's surface emits thermal radiation ( infrared). Since this radiation is long wavelength, this formula is also referred to as long-wave radiation balance ():

• = Effective radiation
• = Radiance of the earth's surface ( terrestrial radiation )
• = Back radiation (influence of atmospheric gases, aerosols and clouds)

From the two formulas for the radiation absorption and emission of radiation, ie for profit and loss, can be determined now is how much total available ( total radiation balance (), net radiation ):

The performance of the entire atmosphere above the incident solar radiation to the earth is approximately 5.5 million EJ / a (1 EJ = 1018 J ) ( see chart above, 174 PW = 174 • 1015 J / s = > 174 • 1015 J / s • 31.536 • 106 s / a ≈ 5.5 • 1024 J / a). The world energy demand in 2010 was 505 EJ.

Radiation budget

The coming to earth solar energy by clouds, air and soil (in this case especially of snow) to 30% reflected back into space (ie, the albedo of the entire Earth is 0.30 ). The remaining 70 % is absorbed: about 20% of the atmosphere, 50 % from the ground. The latter are made ​​by radiation and by conduction with subsequent convection back to the air sleeve. If this energy is again completely radiated into space, would the average air temperature at -18 ° C, while it actually is 15 ° C.

The difference is explained by the natural greenhouse effect of the atmosphere. The so-called greenhouse gases in the heated atmosphere (mainly water vapor and carbon dioxide) emit infrared radiation - in the direction of Earth. The supplies for the radiated energy by convection and absorption ( a part of the radiation from the Earth's surface in the infrared is absorbed ). The emitted infrared radiation from the atmosphere leads to a warming of the earth's surface to an average of 33 ° C. These figures apply only to the earth as a whole. Local and regional conditions depend on many factors:

• Of the albedo of the earth's surface from 30 - may be vastly % means (eg snow 40 to 90%, 20 to 45% desert, forest 5 to 20 %)
• From the above-mentioned angle of the sun rays and length of exposure
• Of cloudiness and humidity
• The heat transport by wind, air layering etc.

Theoretically, these factors are largely modeled, but not in all details such as congestion effects on mountains or irregular movement of low pressure areas. For good predictions meteorology required except enormous computing power, a world dense grid of measurement data across all layers of the atmosphere, which comes in practice limits.