The water aerosol (fogs and clouds) clearing under conditions of the thermal blooming of a laser beam vaporizing particles is under study. The diffraction spreading, relative motion of the beam and the medium, absorption and scattering of the radiation, and the particle size distribution are taken into account. The transparency function is investigated in dependence of the initial optical thickness, clearing and thermal blooming parameters, and the Fresnel number for a slit beam. The comparison with experimental data is carried out.