We present the results of direct comparisons between the calculations, performed by the Monte Carlo radiative transfer code, and measurements of solar downward radiation. To reflect the specificity of different geographical regions, we have chosen the measurements carried out at the Southern Great Plains, Tropical Western Pacific and North Slope of Alaska as well as the measurements at Meteorological Observatory of Moscow State University. The comparisons have been fulfilled using our own aerosol models and estimates of NO2 column amount derived from the collocated and simultaneous AERONET data. Besides, the additional observations of the sky were used for the selection of cloudless cases. In fact, no significant difference between calculations and observations for all stations was apparent. Mean bias did not exceed 1-1.5 % of the TOA incident flux.