Water vapor weak lines contribution to the shortwave radiative transfer in the real atmospheric conditions

At present some differences are observed between measured and calculated fluxes of solar radiation at the Earth’s surface. According to recent investigations these differences correlate with columnar water vapor. The results of calculation of the contribution of numerous weak absorption lines of water vapor, which usually are not taken into account as applied to atmospheric radiation problems, to the irradiance of the Earth’s surface and spectral brightness of sky are considered. Spatial-angular brightness was modeled in several spectral intervals of near IR and visible ranges at different vision directions and Sun positions. Irradiance of the Earth’s surface was estimated in the range of 4000-20000 cm -1 under different aerosol conditions. It was performed comparative calculations for the HITRAN2000k spectral lines database and Partridge-Schwenke data. The calculated results have shown that the neglect of the contribution of weak absorption lines of water vapor in the near IR and visible regions can lead to errors (to 2% in the 100 cm -1 intervals) in calculation of the diffuse radiation.