The Study Of Impact Factors Of Solar Radiation In Particular Areas Of China

Cloud, aerosol and water vapor are the mean impact factors of solar radiation atthe earth’s surface, however, the degree of influence is not the same in different timescales or different regions. What’s more, these three elements are not independent ofeach other. That makes the impact factors more complex. The impact factors ofsurface solar radiation in different time scales are studied in detail in this article, byusing aerosol optical depth (AOD) at550nm from MODIS, total cloud cover (TCC),low cloud cover (LCC), relative humidity (RH), precipitation (PRE) and surface solarradiation (SR) data in2001-2009from57stations in the mainland China.In monthly time scale, SR is affected by TCC, RH and AOD with regionalcharacteristics. According to these characteristics, we devide mainland China into8study areas. In each area, a single factor is identified and other factors are eliminated.Furthermore, the relationship between factors is also studied. Results show that:(1) SR in Xinjiang region is mainly influenced by RH, followed by TCC; Inmid-east of Northwest region and Northeast region, the extinction effect of TCC isgreater than RH; SR is mainly influenced by TCC, the enhancing effect of AOD andthe extinction effect of RH are relatively weak in Inner Mongolia region; In NorthChina, Huanghuai, Jianghan and Jianghuai region, TCC and RH are nearly equalimportance on weakening the SR, the enhancing effect of AOD is relatively weak; SRis mainly influenced by TCC, followed by AOD in Jiangnan region and Southwestregion; In Guangdong and Guangxi region SR is mainly influenced by TCC, theenhancing effect of RH is relatively weak.(2) TCC has a extinction effect on SR in all8areas and the extinction effect isgreater in Southerly areas. In northern China, RH has a weakening effect on SR, andthe effect is relatively weak in Inner Mongolia region. What’s more, it has a enhacingeffect in Guangdong and Guangxi region. The enhancing effects of AOD in4regionsare almost the same.(3) The impact factors of TCC are not the same in different region. The degree ofcorrelation between TCC and RH is better in the south area than the north, and betterin coastal areas than inland areas. However, the degree of correlation between TCC and AOD is better in the north. The correlation analysis showed that the change ofTCC depends mainly on AOD in the northwest and Inner Mongolia region. InNortheast region and North China, Huanghuai, Jianghan and Jianghuai region, RHand AOD are nearly equal importance for the change of TCC. In3southern regionsRH plays a more important role on TCC.In yearly time scale, we discuss the impact factors of the trend and theinterannual variability of SR respectively. Results show that:(1) Impact factor of the long-term trend of solar radiation is complicated. Lineartendency estimation shows that in the southern region of China the trend of SR maybe explained by one or two factors, but in most parts of north region the trend of SR isdifficult to explain.(2) The impact factors of the interannual variability of SR are different indifferent areas. The correlation between SR and TCC is significant negative in thedensely populated area in our country, the correlation between SR and LCC issignificant negative in southern region of China. The correlation between SR and RHis significant negative in North China (Tianjin except), Yunnan, Xinjiang region, thecorrelation between SR and PRE is significant negative in southeast coastal area. Thecorrelation between SR and AOD is significant negative in Beijing-Tianjin-Hebeiregion, but it is significant positive in Qinghai, Sichuan, Chongqing and West ofYunnan area. Moreover, interaction between the factors is not obvious in interannualvariability.(3) In Xinjiang region, SR showed a significant downward trend, which may berelated to the increase of LCC. The significant decrease is difficult to explain in NorthChina, Huanghuai, Jianghan and Jianghuai region. Annual variation of SR depends onTCC more, and the correlation between them is significant negative in most stations.SR and LCC also showed a significant negative correlation in Guangdong andGuangxi region. Since we are short of the AOD data, further research about theimpact factors of the trend and the interannual variability of SR is needed.