北京晴天紫外辐射的传输、损失及其长期变化

基于北京1990年晴天太阳辐射和气象观测资料的分析,考虑了影响紫外辐射(UV)的主要因子——臭氧、光化学、散射等对UV能量的吸收、利用和散射作用,发展了晴天UV的经验模式.研究表明,1990和1991年UV计算值与UV测量值吻合较好,二者相对偏差的平均值分别为3.68％、3.83％.利用此经验模式计算了大气上界的UV,计算结果较为合理.采用经验模式及考虑太阳活动、轨道参数、大气成分等因素的订正,计算了北京1979-1998年晴天的UV,其表现为下降趋势,年均下降率为0.20％.1979-1998年晴天,受臭氧、光化学和散射等因子影响,损失于大气中的各个UV能量都表现出增长趋势,年增长率分别为6.93％、7.56％、7.13％;损失于大气的UV能量以吸收和利用作用为主,并表现为冬季最大的特征.

The transmission, loss and long term variation of UV in clear skies in Beijing

Based on the analysis of observations of solar radiation and meteorology in clear skies in Beijing, the effects of UV absorption, photochemical reactions and scattering were considered in a developed empirical model of UV for clear skies. The calculated UV agreed well with that observed in clear skies in 1990 and 1991, with their relative biases about 4%. The empirical model predicted the UV at the top of the atmosphere reasonably well. Considering variations of solar activity, the Earth's orbit and the atmospheric components, the empirical UV model was modified and used for clear skies in Beijing from 1979 to 1998. The UV showed a decreasing trend, with its annual decreasing rate of 0.20%. During 1979-1998, UV losses associated with O₃, photochemical and scattering factors indicated increasing trends in clear skies with their annual increases about 7%. UV energy loss in the atmosphere in clear skies was assumed to be mainly a result of absorption and consumption of atmospheric substances, with the highest in winter.