Changing Trend of Pan Evaporation and Its Cause over the Past 50 Years in China
Pan evaporation, as a measurement of atmospheric evaporative demand, has traditionally been used for agricultural water management. The changing trend of pan evaporation also attracts attentions from the hydrological community worldwide due to its indicative meaning in hydrological cycles. In this study, the changing trend of pan evaporation in China over the past 50 years was analyzed by using Mann-Kendall test method. The results show that there is a decreasing trend in most of the observations on pan evaporation in China, with an average rate of 17.2 mm/10a in China. In the humid region, the decreasing rate was 29.7 mm/10a, presenting the most significantly decreasing trend, while the decreasing rate were 17.6 mm/10a and 5.5 mm/10a in the semi-arid/sub-humid region and arid region, respectively. Temporally, most significant decreases occur in summer with a rate of -16.2 mm/10a; then, -9.7 mm/10a in spring; the decreasing rates in autumn and winter are relatively low. On the attribution, we calculated the complete correlation coefficients of 7 climate factors with pan evaporation. And decreases in diurnal temperature range and wind speed were found to be the main influencing factors leading to the decrease of pan evaporation. The decrease in diurnal temperature range might relate to the increase of aerosol as well as the other pollutants under the circumstance of global warming, which is one of the main features in the context of climate change; and the lowering of wind speed might be associated with the weakening of the Asian winter and summer monsoon under the global climate warming.
Chinapan evaporationdiurnal temperature rangewind speedMann-Kendall test
NETL
NSTL
万方数据
维普
