About excess absorption of optical radiation in the visible and infrared

Based on field data on spectral atmospheric transmission along the extended near-ground paths in an arid zone and in a region of the West Siberia, excess continuous absorption of radiation in the 0.44-11.5 mu m wavelength region has been revealed, which nonlinearly depends on the absolute air humidity. Its value, under assumption of quadratic dependence on absolute air humidity, is about 1000-1450 g(-2)cm(5), far in excess of the continuous absorption by water vapor; and the character of its spectral dependence suggests that it is related to the finely dispersed soot aerosol. The absorption coefficients obtained on the near-ground and slant paths are compared. The comparison made shows quite satisfactory agreement between them. The presence of the finely dispersed aerosol in the atmosphere is considered one of the important factors causing the anomalous absorption of optical radiation by clouds.