Characteristics of solar radiation and the impact of clouds at Yangbajing, Tibet

Abstract

Yangbajing (YBJ) is located on the Tibetan Plateau, China. The characteristics of solar radiation and its relationship with clouds at YBJ from April 2009-April 2010 are analyzed in this paper. The annual mean solar radiation was 478.4 W m-2 and annual mean transmittance was 0.713. Atmospheric mean transmittance of clear skies reaches 0.828 when the solar elevation angle (SEA) is greater than 10 degrees. Comparisons with numerical simulations show atmosphere of YBJ is very clean. It was also found that impacts from atmospheric conditions on solar radiation are similar in clear sky during the year because the standard deviation of transmittance in clear skies was less than 0.05 when the SEA was greater than 10 degrees. It helps to understand the impact of clouds on solar radiation without considering other impact factors. At the latter part of the article, we analyzed and established a statistical quantitative relationship between surface solar radiation and cloud fraction.