Abstract:

Based on the sunshine duration,rainfall,cloudage,and mean wind speed data of 93 stations in the Lowermiddle Reaches of the Changjiang River during 1961-2010 with modern statistical diagnostic methods such as climatic trend rate,abrupt detection,and correlation analysis,the temporal/spatial characteristics and cause of yearly,seasonal,and monthly sunshine duration in the Lowermiddle Reaches of the Changjiang River were investigated in this paper.The results showed that the spatial distribution of yearly,seasonal,and monthly sunshine duration in the northeast of the Lowermiddle Reaches of the Changjiang River was more than that in the southwest of the reaches.The sunshine duration was most in summer,and next in autumn,spring,and winter.The yearly sunshine duration in the Lowermiddle Reaches of the Changjiang River in the recent 50 years was obviously widespread declined (682 h/10a),and the decline was more than that of the national average in the same period.The significant decadal change was in the early 1980s.The yearly sunshine duration was extremely excessive in 1963 and 1971,which caused by much summer sunshine duration,but no extremely deficient was observed in this period.The sunshine duration in spring,summer, autumn and winter also declined at the rate of 27 h/10a,375 h/10a,108 h/10a,165 h/10a respectively,especially in summer, autumn, and winter(p＜005).The most declination was in summer,and next in winter,autumn,and spring.The reduction rate of the sunshine duration in year,summer,autumn,and winter in recent 30 years reduced,but the sunshine duration in spring increased at the rate of 147 h/10a in the same time.The abrupt change of the yearly sunshine duration in the midsouth of Hubei,north of Hunan,north of Jiangxi,north of Anhui,Southeast of Zhejiang appeared in the 1980s.Factors leading to the decreases in yearly sunshine duration varied greatly over different regions.The reduction of the yearly sunshine duration in the north of the Lowermiddle Reaches of the Changjiang River had close relationship with the increase of the rainfall and the reduction of the mean wind speed. Moreover the effect of the lowlevel cloudage in the south of the Lowermiddle Reaches of the Changjiang River was also important