长江中下游地区太阳辐射变化及其对光合有效辐射的影响

Variation of solar radiation over the middle and lower reaches of the Yangtze River and its influence on photosynthetically active radiation

利用太阳辐射、日照时数及大气气溶胶光学厚度等资料,采用线性趋势、Mann-Kendall检验等分析方法,研究了近50年长江中下游地区太阳辐射变化特征、原因及其对光合有效辐射(PAR)的影响。结果显示:1961～2010年长江中下游地区总辐射在1991年前、后呈先下降后上升趋势;整个时期,散射辐射占总辐射的比重不断增加,直接辐射占总辐射的比重不断减少;受太阳辐射及其组成变化的影响,1961～2010年该地区PAR呈下降趋势,但PAR占总辐射的比例明显上升。进一步分析结果表明,1991年以前总辐射下降的主要原因是日照时数减少造成直接辐射量下降;1991年以后,受直接辐射强度增强的影响,直接辐射量的下降趋于平缓,该时段内总辐射的上升主要和大气气溶胶增加所引起的散射辐射量上升有关。

Based on the climatic observational data including the surface solar radiation, sunshine duration and the aerosol optical depth, the variation and its causes of the surface solar radiation over the middle and lower reaches of the Yangtze River in recent 50 years as well as its influence on photosynthetically active radiation （PAR） were analyzed in this paper by using linear trend estimation, moving average and Mann-Kendall test. The results show that the total solar radia-tion over the middle and lower reaches of the Yangtze River presented significant declining trend from 1961 to 1991, and then gradually increased after 1991. In addi- tion, significantly increase （decrease） trend was observed in the ratio of diffuse （direct） solar radiation from 1961 to 2010. Influenced by the variation of total, direct and dif- fuse solar radiation, the photosynthetically active radiation over the middle and lower reaches of the Yangtze River ex- hibited significant declining trend from 1961 to 2010. However, the ratio of photosynthetically active radiationwas found to significantly increase in this period, which helped to improve the crop light use efficiency. Reason analysis of the variations of the solar radiation over the middle and lower reaches of the Yangtze River indicated that before 1991, the decline of total solar radiation was mainly caused by the decrease of direct solar radiation, due to the decrease of sunshine duration and the increase of cloudy days. However, influenced by the increase of direct solar radiation intensity, the decli- ning trend of direct solar radiation was not significant after 1991, and the increase of total solar radiation was closly related to the increase of diffuse solar radiation resulted from the increase of aerosol.