Sun photometer

A sun photometer is a photometer that is aimed directly at the sun. Current sun photometer consisting of an optical, spectral filters, a photodetector, and a data logger. Automated sun photometers have a controller with the help of the device follows the sun throughout the day. The measured quantity is the direct sunlight.

At the ground and in the atmosphere, the irradiation is lower than in space, as it is attenuated by absorption and scattering. Therefore, the measured radiation flux is a combination of solar radiation and atmospheric effects. The relationship of these two variables describing the Lambert -Beer law.

Atmospheric effects can be removed by a so-called Langley extrapolation. This is inferred from measurements at different positions of the sun at different path lengths through the atmosphere, but constant atmosphere of the irradiation conditions of the outside atmosphere. If the außeratmosphärische radiation is known that sun photometer can be used to investigate the atmospheric conditions, in particular the atmospheric optical thickness. If the radiation measured in several spectral channels suitable, can with the sun photometer aerosol concentration or the vertically integrated concentration of some atmospheric gases such as water vapor and ozone are measured.