北京天然光总照度变化趋势分析

Trends of Total Illuminance of Natural Light in Beijing

基于北京连续54年太阳辐射数据,结合中国辐射光当量模型,获取北京天然光年总照度值和月总照度值。应用Mann-Kendall检验方法分析北京天然光年和月总照度值年际变化趋势,结果表明:北京天然光年总照度基本变化趋势为明显减少,且在1977年突变发生后其下降趋势明显增加;各月月总照度值基本年际变化趋势为明显减少,其中7月月总照度值下降幅度最大,11月月总照度值下降幅度最小;除5月在1967年发生突变外,其它月份的突变均发生在1975-1981年之间;各月天然光月总照度值年际变化在突变前为不明显波动变化趋势,突变后均为明显增加的下降趋势。云量及由大气污染所产生的气溶胶光学厚度是造成北京年与月总照度值持续下降的重要因素。

Combined with Chinese luminous efficacy model, this paper gets the annual and monthly total illuminance values of the natural light based on the solar radiation data of 54 consecutive years in Beijing. In this paper, the trends of annual and monthly total illuminance levels in Beijing were analyzed by Mann-Kendall trend analysis and Mann-Kendall mutation test. The results showed that the basic trend of annual total illuminance values in Beijing was significantly decreasing and the declining trend became more evident after mutation occurred in 1977. The basic trends of the monthly total illuminance values were significantly decreasing. The monthly illuminace appeared to decline most steeply in July. In contrary, the least decrease happened in November. Only mutations in May happened in 1967. In other months, mutations occurred between 1975 and 1981. The fluctuation of the trends of monthly illuminace values was not apparent before mutation. The declining trend of monthly total illuminance values significantly increased after mutation. The steady decline of annual and monthly total illuminance values in Beijing can be primarily attributed to the aerosol optical thickness caused by cloudiness and atmospheric pollution.