Dynamics of photosynthetic solar active radiation in Ukraine over 1986 - 2015

Abstract

Photosynthetically active solar radiation (PSR) – solar radiation within the wavelength range of 380 ¼710 nm – forms a basis of plants' life that determines their photosynthesis. No measurements of photosynthetically active solar radiation (PSR) take place in Ukraine due to the lack of standard devices. Direct, scattered and total PSR is calculated via transition measurements and coefficients, whereas total PSR is measured via sunshine duration – using the indirect method. The purpose of the research is to determine PSR and its dynamics during specific months and the warm period of the year (April-October). The components of the radiation regime within the network of actinometric and meteorological observations in Ukraine for 1986 - 2015, 1986 - 1995, 1996 - 2005, 2006 - 2015 were obtained using mathematical statistics and climatological methods. In the course of the research changes in the PSR during specific months and the warm period over specific decades were determined. During the months of the warm period over 1986 -2015, direct, diffused, total PSR and total PSR calculated via sunshine duration tend to increase from the west, northwest or Ukrainian Carpathians to the southern steppe zone and Crimea. During the warm period over 1986 - 1995, the amount of direct PSR varies within 472 ¼ 891 MJ/m², diffused radiation – 887 ¼ 1156 MJ/m², total radiation – 1457 … 1917 MJ/m², total PSR calculated based on sunshine duration – 1621 … 2056 MJ/m²; over 1996 - 2005 the amount of direct PSR varies within – 469 … 1030 MJ/m², diffused – 802 … 1004 MJ / m², total – 1305 … 1973 MJ/m², total PSR calculated based on  sunshine duration – 1654 … 2192 MJ/m²; over 2006 - 2015 the amount of direct PSR varies within 485 ¼ 1065 MJ/m², diffused radiation – 737 ¼ 951 MJ / m², total PSR – 1270 … 1977 MJ / m², total PSR calculated based on sunshine duration – 1649 … 2233 MJ / m². The increase in integrated direct solar radiation over 1996 - 2005 compared to 1986 - 1995, as well as over 2006 - 2015 compared to 1996 - 2005, led to an increase in direct PSR; the decrease in diffused solar radiation led to a decrease in diffused PSR; and ambiguous changes in the components of total solar radiation led to fluctuations in total PSR; increase in sunshine duration is accompanied by an increase in total PSR calculated based on sunshine duration. The research is relevant due to the factor of modern climate variability at the global and regional levels. The study of PSR changes is an urgent task of modern agrometeorology. It enables long-term effective planning of agricultural development.