Atmospheric Transmittance

Transmittance, Atmospheric


(also, atmospheric transparency), the capacity of the atmosphere to transmit electromagnetic energy. Atmospheric transmittance is dependent on the air mass penetrated by rays, as well as on the amount of water vapor and dust in the air. It varies for radiations of different wavelengths; the smaller the atmospheric absorption and scattering of light, the greater the atmospheric transmittance.

Atmospheric transmittance may be characterized either by the transmission coefficient, which is equal to the fraction of radiation that passes through the atmosphere when rays fall vertically, or by the turbidity factor, which indicates the extent to which the transmittance of an actual atmosphere under given conditions differs from the transmittance of an ideal (ideally clean and dry) atmosphere.

The atmospheric transmittance of the rays of a celestial body decreases as the body approaches the horizon because the length of the path of the rays in the air increases, which is expressed by the optical air mass.

Atmospheric transmittance varies at different points on the earth’s surface. The most transmissive air is in polar countries because it contains the least amount of dust and moisture. Changing humidity and the dust content in the air at a given point throughout the year determine the annual atmospheric transmittance at that point. Thus, for example, in Pavlovsk, near Leningrad, the minimum atmospheric-transmission coefficient, which is equal to 0.759, is observed in July, and the maximum transmission coefficient, which is equal to 0.806, is observed in December (for the same optical air mass, equal to 2). Thus, the atmosphere is most transmissive in winter and least transmissive in summer.

A significant decrease in atmospheric transmittance is observed as a result of increasing air pollution, especially when the dust content increases.


Kondrat’ev, K. Ia. Aktinometriia. Leningrad, 1965.
Berliand, M. E., and K. Ia. Kondrat’ev. Goroda i klimat planety. Leningrad, 1972.
Zuev, V. E. Rasprostranenie vidimykh i infrakrasnykh voln ν atmosfere. Moscow, 1970.
References in periodicals archive ?
The Meteorological Atmospheric Measurement Bolometer Array (MAMBA) is an all-sky sensor designed to characterize atmospheric transmittance to support tactical and space sensors testing and operations.
In addition, meteorological data recorded close to the Landsat 8 pass over the studied area were used, in order to determine the atmospheric transmittance used in the atmospheric correction.
This fraction of radiation reaching the earth's surface depends on local weather conditions, which characterize the atmospheric transmittance for the short-wave radiation (Borges et al.
Hargreaves & Samani (1982) were the first to propose a predictive model of incident solar radiation from the air temperature, using the atmospheric transmittance from Eq.
Perhaps the best sub-orbital solution is to make observations from a high-altitude balloon where the atmospheric transmittance exceeds 99 % over most wavelengths of interest.
Following Kieffer and Stone (5), observations of many stars will provide atmospheric transmittance at various sky locations throughout the night.
Technical information on radiometry, MTF theory, EOMUX and EMUX, atmospheric transmittance and target discrimination are also explained.
Cloud cover indices for the images are calculated from Eq(1) and atmospheric transmittance factors are obtained from Eq(3) applying the cloud cover indices and regression coefficients values.
Clear sky radiation on the earth's surface can be estimated by calculating the atmospheric transmittance for beam radiation, [[tau].
atmospheric transmittance due to Rayleigh scattering (dimensionless)
2) Atmospheric transmittance of solar blind UV below the ozone layer is limited by scattering due to other atmospheric constituents and absorption by surface ozone (a common urban pollutant).
Common module systems, EOMUX systems, EMUX systems, two-dimensional MTF, resolution, image quality, sampled-data systems, atmospheric transmittance, atmospheric MTF, target signatures, sensitivity and noise, system performance models, target discrimination and range predictions.

Full browser ?