Effects Of Aerosol Optical Depth On The Solar Radiation In The Yangtze Delta Region

Atmospheric aerosol can lead to the decrease of total solar radiation and the increase of scattering radiation which cause the change of climate and productivity of terrestrial ecosystem. Yangtze River Delta is one of the most developed areas in China and becomes one of the most polluted areas of fog and haze with the fast development of industry, sharp increase of population and emission of pollutions. While as the important agricultural region, quantitative research of the relations between aerosol optical depth （AOD） and solar radiation can provide scientific evidences for regional climate change simulation, influence of haze on growth and productivity of crops, etc. This study analyzed the changing pattern of solar radiation and AOD in Yangtze River Delta, the influences of AOD on solar radiation and scattering radiation through simulation experiments and established calibration method of MERRA reanalysis data by using clearness index and AOD. The main results concluded:（1） The annual mean of total solar radiation was significantly decreasing from 1961 to 1980 in Yangtze River Delta with the value of 0.98-1.4 MJ m^-2d^-1 per 10 years, then slowly increased in 1980 with 0.17-0.36 MJ m^-2d^-1 per 10 years. Scattering radiation overall slowly grew from 1961 to 2012 in in Yangtze River Delta and the proportion of scattering radiation in total solar radiation was markedly increased with 20% in 50 years and the increasing trend was relatively slowed down after 1990. The annual mean of AOD showed the pattern of apparent increase with 0.17-0.39 per 10 years and had a declining trend but not so obvious.（2） PE plastic film could simulate fog and haze and not change spectrum characteristics and anisotropies of solar radiation. The AOD standard presented by PE plastic film would decrease with the increasing proportion of scattering radiation which means the clearer the sky was, the standard of PE plastic film can present would be higher. PE plastic film with 12 silks and 3 sheets can make decrease of 30% of total solar radiation and 20% increase of scattering radiation with the AOD standard of 0.5 which can present heavy haze.（3） With the increase of AOD, the direct radiation obvious decreased linearly, scattering radiation obvious increased linearly and the significant correlation between scattering radiation and AOD showed scattering radiation could affect by AOD shapely.（4） MERRA reanalysis data were overall higher than observations, annual mean of simulated total solar radiation was 3-4 MJ m-2d-! higher than observations while these two changing pattern were almost the same. Annual mean of scattering radiation simulated by MERRS was mainly lower than measurements with 0.3-1.5 MJ m^-2d^-1 and measurements showed increasing pattern and the pattern of simulation was not clear.（5） Clearness index and AOD could calibrate solar radiation values simulated by MERRA. The results showed the clearness index could calibrate simulations of total solar radiation preferable and AOD performed better on scattering radiation simulations and the more time period was, the better correction would get.