中文摘要：

利用2004年4月—2005年6月在中国科学院大气物理研究所铁塔分部的紫外辐射观测数据,分析了北京城市紫外辐射的变化特征,结果表明,紫外辐射的变化规律与太阳总辐射一致,紫外辐射与总辐射的比值变化范围在0.02-0.04之间,晴天恒定在0.03,阴天在0.04左右,在沙尘暴过程中比值最小,为0.02。通过分析紫外辐射与大气质量数和平均晴空指数之间的关系,建立了适合于北京的全天候紫外辐射的估算方程。利用建立的估算方程及观测的总辐射值进行了紫外辐射的估算,紫外辐射的计算相对误差在10%以内。

英文摘要：

The variation characteristics of ultraviolet radiation in Beijing city are analyzed based on observed data from April 2004 to June 2005.The daily,monthly and yearly variation characteristics of ultraviolet radiation are same as those of broadband solar radiation.The ratio of ultraviolet radiation to broadband solar radiation varies from 0.02 to 0.04.The ratio is a constant values of 0.03 under clearly sky condition.The ratios are 0.04 and 0.02 in rainy day and dust day,respectively.Dependence of ultraviolet radiation on the atmospheric clearness index is analyzed.An experiential estimating model based on the relationship of the global broadband hemispherical transmittance（Ks） and optical air mass（m） is developed to calculate ultraviolet radiation in all sky conditions.The estimation equation developed in this study can be used to calculate ultraviolet radiation from broadband solar radiation with a relative error within 10% in Beijing.