合肥地区无云晴天地表太阳短波辐射特征

Characteristics of Solar Shortwave Radiation on Clear Days in Hefei Region

利用SKYNET合肥站1999年9月至2005年8月期间285个无云晴天地面辐射收支观测资料,计算分析了合肥地区地表太阳短波辐射特征。结果表明,地表太阳短波辐射各个分量的日变化均呈上下午近似对称的倒“U”型分布,中午变化较平缓并出现最大值;漫射辐射与总辐射之比KDF呈“U”型日分布。太阳短波辐射各个分量的年最小值均出现在12月份,6月份总辐射、地表太阳短波净辐射和漫射辐射最强,7月份太阳直接辐射和地面反射的短波辐射最强但漫射辐射出现相对低谷。漫射辐射春季最强、夏季次之;太阳短波辐射其它各分量的季节变化均为夏季最强、春季次之、冬季最弱,而且冬夏差异较大。<KDFd>在1月份最大, 7月份值最小并有明显的突变现象;其季节变化特征为夏季最小,冬季最大;其七年平均值为38．4％。

The characteristics of solar shortwave radiation components over grassy marshland are discussed based on the data observed at SKYNET Hefei site on 285 clear days from Sep. 1999 to Aug. 2005. The results showed that, the diurnal variations of all shortwave radiation components exhibit nearly symmetrical converse ＂U＂ shape, with maximal values at solar noon. As to diffuse fraction of global solar irradiance, the opposite occurs. Every component shows the smallest value in December. The monthly mean daily total values such as global solar irradiance, net shortwave and diffuse irradiance are maximal in June, while the maximal values of direct and surface upwelling shortwave irradiance appear in July, and there is a relative weak extremum of diffuse solar irradiance. 〈 Ed~ 〉 of spring is stronger than that of summer and winter months. Seasonal variations of other components are obviously marked by the highest （lowest） value in summer （winter）, and the discrepancies between summer and winter months are remarkable. The maximal value of 〈 KDF^d 〉 appears in January and there has a remarkable ＂jump＂ change in July. Its seasonal variation is the lowest （highest） value appears in summer （winter） and its seven-year-averaged value is 38.4%.