Impact of season, cloud cover, and air pollution on different spectral regions of ultraviolet and visible incident solar radiation at the surface

Abstract

AbstractThis study deals with the impact of season, cloud cover, and air pollution on spectral regions of incident solar radiation (UVB, UVA, photosynthetically active radiation (PAR) = Blue + Green + Red, 660, 730 nm) and their ratios (Blue/Red, Blue/PAR, Green/PAR, Red/PAR, 660/730 nm, UVB/UVA, UVB/PAR, and UVA/PAR) measured at three measuring stations at two locations in the City of Ostrava, Czech Republic. The mentioned spectral regions are crucial for plants because they influence photosynthesis and photomorphogenesis. However, there is still a lack of published information about the radiation regime in the plants' environment. The measured data underwent a quality check and were divided into 40 groups corresponding to different combinations of season, cloud cover, and air pollution level. Standard statistical characteristics of spectral regions and their ratios were calculated for each combination. Generalized linear models were used to evaluate the effect of air pollutants on spectral regions of incident solar radiation. Average irradiance values in the spectral regions generally decreased with increasing air pollution on both cloudy and sunny days. A mostly decreasing trend of average values of ratios with increasing air pollution is found mainly on sunny days and, for some cases, even on cloudy days. Each ratio shows a specific patterns depending on the season and cloud cover. The generalized linear models confirm previously published results and underline that air pollution affects various spectral regions of incident solar radiation differently.