linear regression, pollutants, solar elevation angle, solar radiation

The dependencies of spectral regions of incident solar radiation in ultraviolet and visible spectra on concentrations of air pollutants were studied. We used two different approaches to conduct linear model analyses. First, linear models with different meteorological factors as explanatory variables were made for the entire data set without division according to solar elevation angle. These models showed no apparent influence of air pollutants on incident solar radiation but did reveal an effect of air pollutants on incident solar radiation in combination with relative air humidity. Secondly, after eliminating the major effect of solar elevation angle, linear models showed a spectrally dependent influence of dust particles PM10 and NOx and increasing effects of the other air pollutants on at least one of the studied spectral regions. Dust particles PM10 caused a significant reduction in almost all spectral regions. We found that air pollutants affect the spectral composition of incident solar radiation, but it is difficult to identify the direct and indirect impacts of air pollutants on solar radiation in its different spectral regions.