REFLECTIVITY OF CUMULONIMBUS CLOUDS IN THE VISIBLE WAVELENGTH RANGE
Recently, studies of microphysical processes in the clouds, in particular, investigations of the mechanisms of cloud element formation, the phase change of the clouds, etc have been intensively carried out to diagnose the characteristics of the cloud. It is known that the main electrical characteristic of any medium is the dielectric constant. However, in the visible part of the optical wavelength range, the permittivity of ice and water has a weak dispersion and, in fact, the diagnosis of the cloud by studying its variation in this range is not informative. A different situation arises when considering the scattering of light waves by particles contained in a cloud, since the nature of the scattering of an electromagnetic wave by a dispersive medium of a cloud, consisting of droplets of water and ice crystals depends on the ratio of the wavelength and the size of the scattering particles, thereby having certain information about the basic characteristics of the cloud. On this basis, the reflectivity of cumulonimbus C<sub>b</sub> clouds in the visible wavelength range is studied in this paper. The cases of light scattering at different stages of life cycle of the C<sub>b</sub> cloud are considered based on the statistical data of meteorological observations and conventional models. It is shown that the reflectivity is only due to rayleigh scattering from shallow water droplets in the early stage of the C<sub>b</sub> cloud formation. By laser probing in the visible wavelengths these clouds can be distinguished from those from wich no precipitation fall (C<sub>u hum</sub>, clouds of good weather). The reflection is due to diffuse scattering from large particles at the "mature" stage of life cycle of the cloud, and appears on the shortwave of the visible spectrum if it contains hailstones. The analytical expression is obtained, which connects the intensity of reflected radiation from the cloud with the effective diameter and the concentration hailstones. The algorithm for calculating the glaciness of the C<sub>b</sub> cloud is given based on the gamma-function distribution of hailston sizes.