东江流域蒸发皿蒸发量时空演变特征及其原因分析

Recent Spatio-temporal Change Characteristics of Pan Evaporation and Possible Climate Factors in Dongjiang River Watershed,South China

利用东江流域1956~2000年15个气象台站的小型蒸发皿观测资料,分析了流域蒸发皿蒸发量的变化趋势及其可能原因。结果表明,东江流域年蒸发皿蒸发量整体的下降趋势非常显著,在1986年前后发生了非常明显的下降突变,下降速率达30.9 mm/10a,45年来下降了约139.0 mm;流域下降趋势存在明显的区域差异性和较大的空间异质性。东江蒸发量下降的原因主要是日照时数和平均风速的显著下降,抵消了气温上升所引起的蒸散量的上升,反而使蒸散量呈现为显著下降趋势;平均日较差的显著下降在蒸发皿蒸发量减少趋势中可能也起着重要作用。

Recent spatio-temporal change characteristics of pan evaporation and possible climate factors in Dongiang River watershed from 1956 to 2000 are analyzed by using the observed monthly data.The results show a significant decrease in the pan evaporation in Dongjiang River watershed.The rate of decrease is about-30.9 mm/10a.And there exists an abrupt decrease in yearly mean pan evaporation in the year 1986.The main climatic factors for the change of the pan evaporation are analyzed by studying the relationship between the pan evaporation and climate elements such as the sunshine duration,the average wind speed,the diurnal temperature range（DTR）,the mean maximum and minimum temperature,the mean temperature and the precipitation,and so on.It is thus obvious that the decrease of the pan evaporation was mainly caused by the decreasing solar radiation,the sunshine duration and average wind speed.The DTR may also contribute a lot to the decrease in the pan evaporation in Dongiang River watershed.