北京地区城市化对太阳辐射的影响-趋势分析

本文根据太阳辐射在大气中的传输削弱原理,采用逐项扣除方法计算分析了北京地区冬季大气污染对太阳直接辐射通量的削弱(S_a)及其逐年变化,同时计算分析了Linke浑浊因子(T)、湿浑浊因子(W)和污染浑浊因子(R)等大气透明度特征量及其逐年变化.计算结果表明,在冬季晴天条件下,S_a平均占太阳常数的21％,而理想大气削弱和水汽吸收削弱只分别占17％和7％.S_a具有明显的逐年增加的总趋势,平均从60年代初的0.30cal/cm~2·min增加到80年代初的0.51cal/cm~2·min,S_a的净增量占太阳常数的11％.在同样条件下算出的T的多年平均值为3.20,水汽、理想大气和污染物对T的贡献分别为0.54、1和1.66,近似比例为1:2:3,污染物对T的贡献占50％.T和R也都具有明显的逐年增加的总趋势,分别从60年代初的2.7和1.1增加到80年代初的3.7和2.1.分析表明.造成以上变化趋势的主要原因是城市化引起的大气污染的加重,现有的污染控制措施还未能有效地改变这种趋势.

INFLUENCE OF URBANIZATION IN BEIJING REGION ON INCOMING DIRECT SOLAR RADIATION

Based upon the transfer principle of solar radiation in the atmosphere and by means of the stepwise deduction method, the attenuation of direct solar radiation with normal incidence due to the atmospheric pollutants in Beijing region, Sa, the Linke turbidity factor T, the humid turbidity factor W, the residual (or pollutant) turbidity factor R, and their yearly variations over the last 26 years (1957-1982) is computed and analysed.Results of computation indicate that, in wintertime when midday and cloudless, on an average of 26 years, Sa amounts to 21% of the solar constant S0, but attenuation by ideal atmosphere and water vapor is only 17% and 7 %, respectively. With regard to yearly variation, Sa tends to increase gradually, from 0.30 cal/cm²-min early in 1960s to 0.51 cal/cm²· min early in 1980s. The net increment of Sa is 11% of S0. In the same way, the average value of T is 3.20; values of W, R and ideal atmosphere turbidity factor are 0.54,1.66 and 1, respectively. Contribution of R to T is about 50%. T and R also have a significant increasing trend over years, from 2.7 and 1.1 early in 1960s to 3.7 and 2.1 early in 1980s.By such analysis this paper tends to conclude that the trend on the rise is mainly due to the increasing atmospheric pollution by urbanization of Beijing these years. The air-pollution control measures taken now are still not effective enough to improve the situation.