Study of ratio of photo synthetically active radiation to solar radiation under clear and overcast conditions in Mongolia

This study focuses on the solar photosynthetically active radiation (PAR) in Mongolia, which is investigated last more than 10 years. The quantitative characteristics of solar radiation, such as direct, diffuse and global radiation are evaluated in the study through the long term trend. The mean pattern of a seasonal variation of PAR at Mongolian grain farm region shows that the global (direct + diffuse) PAR is 68.9plusmn7.6 MJ/(m²month) in December as a yearly minimum and 307.5plusmn10.3 MJ/(m²month) in May as a yearly maximum through the observation period. The yearly summation is 2.22plusmn0.07 GJ/(m²yr) and is very stable compared with monthly variations.