Optical "dimming" of cloud medium due to interaction with CO2 laser radiation

It is shown theoretically that, under certain conditions, a considerable supersaturation may occur in the vicinity of a large water drop being evaporated by heating with CO₂ laser radiation. This supersaturation may result in the condensation of the. vapor and formation of a large number of fine particles. The possibility of heterogeneous and, under conditions of substantial overheating ( > 70°C), homogeneous condensation is considered. The growth of drops in a laser radiation field under supersaturation conditions is discussed. It is shown that the total attenuation cross section of the new drops may exceed, in the visible range, the attenuation cross section of the original drop and this may result in optical "dimming" of the interaction zone. Experimental results support the formation of a train of fine particles alongside evaporating large cloud particles at subzero temperatures. "Dimming" as a result of the interaction of CO₂ laser radiation with a crystalline cloud medium is reported and the dependences of this dimming on the radiation intensity, size of cloud particles, attenuation coefficient, and temperature of the medium are accounted for. The experimental results are in qualitative agreement with the theory.