What Is Atmospheric Radiation?

At the same time that the atmosphere absorbs long-wave radiation from the ground, it also radiates energy outwards in a radiating manner. This method of radiating energy outwards is called atmospheric radiation. Because the temperature of the atmosphere itself is also low and the wavelength of the radiated radiant energy is long, it is also called atmospheric long-wave radiation.

The direction of atmospheric radiation is both upward and downward. The downward part of the atmospheric radiation

When the temperature is greater than absolute zero, gases in the atmosphere (mainly oxygen and water vapor), water droplets (clouds, rain and fog), and ice droplets (mainly in ice clouds) all radiate electromagnetic energy and generate thermal radiation noise. In the microwave band, this characteristic of thermal radiation noise is usually characterized by the brightness temperature. The ratio of the brightness temperature to the thermodynamic temperature is called the emissivity. When the electrons in a molecule transition from a high energy state to a low energy state, they emit electromagnetic energy and form radiation. Molecules absorb incident electromagnetic energy, causing electrons to transition from a low energy state to a high energy state, forming absorption. A molecule has a certain number of energy states. Therefore, its radiation spectrum and absorption spectrum are the same. according to

1 The atmosphere has little absorption of short-wave radiation, allowing a large amount of short-wave radiation from the sun to reach the ground, but very little transmission of ground radiation.

(2) The absorption of long-wave radiation by the atmosphere is very strong. The absorption effect is not only related to the distribution of absorbing substances, but also to the temperature and pressure of the atmosphere. In the entire long-wave radiation band, except for the 8-12 m band, the rest of the absorption rate is basically close to 1.8-12 m. The maximum transmittance is therefore called this band. The radiation in this band is just where the ground's radiation ability is the strongest, so 20% of the ground radiation's energy is directed into the space through this window.

(3) Water vapor, liquid water, carbon dioxide, and ozone in the atmospheric components are the main absorbers of long-wave radiation, and they have selective absorption of long-wave radiation.

4 A part of the atmospheric radiation escapes into the universe, and about 62-64% is directed to the ground. This part of the atmospheric radiation that is directed to the ground is called atmospheric reverse radiation.

(5) Atmospheric radiation is infrared long-wave radiation.

Atmospheric reverse radiation will warm the ground, which in turn will increase ground radiation.

Atmospheric radiated noise can affect receiving systems, especially

If you can know their temperature, you can use the Stephen Boltzmann formula to calculate the amount of long-wave radiation in the atmosphere, but this is very difficult. Therefore, many scientists have developed some empirical formulas for directly estimating atmospheric long-wave radiation using the air temperature inside the meteorological station louver.

Theoretical basis: The vast majority of atmospheric long-wave radiation comes from the 100m atmosphere closest to the ground, where most of the water vapor, carbon dioxide, etc. are concentrated, and their temperature changes to a large extent with the change of near-surface air temperature.

The formula is divided into two types: clear sky and cloudy sky.

Solar radiation is the premise and basis of atmospheric radiation. Solar radiation is an electromagnetic wave composed of three parts: ultraviolet, visible, and infrared. Its energy is mainly concentrated in the visible part. Solar radiation is a kind of short-wave radiation, which has two effects: light effect and heat effect. ^[2]

Solar radiation Atmospheric radiation has the same points between the two radiations: they both transmit energy in the form of electromagnetic waves and have thermal effects.

The differences between solar radiation and atmospheric radiation are shown in the following table:

different	Sun radiation	Atmospheric radiation
wavelength	Short-wave radiation	Long wave radiation
ingredient	UV, visible, infrared	infrared
Light effect	Have	no