黄淮海流域蒸发量的变化及其原因分析

利用研究区1956-2000年117个气象台站的小型蒸发皿观测资料,分析了黄淮海流域蒸发量的变化趋势及其可能原因。结果表明,近50年来本区蒸发量减少十分显著,其变化速率一般在-50 mm/10a,平原地区最大变化速率达到-80mm/10a以上。蒸发量下降最明显的季节是春季和夏季,其中春季减少最大区域主要在海河流域的东南部和黄河下游,而夏季的减少主要在淮河流域。造成蒸发量减少的直接气候原因可能是日照时数及太阳辐射的减少,平均风速和气温日较差的降低可能也起着重要的作用。

Recent change of pan evaporation and possible climate factors over the Huang-Huai-Hai watershed, China

The tendency and the possible causes of the pan evaporation change over the Huang-Huai-Hai watershed from 1956 to 2000 are analyzed by using the observed monthly data.The results show a significant decrease in the pan evaporation in the area.The rate of decrease is about-50 mm/10a,and the maximum rate of decrease reaches-80mm/10a over the plain area.It is also found that the maximum decrease of the pan evaporation occurred in the southeast of the Haihe basin and the lower Yellow River during spring,and in the Huaihe basin during summer.The main climatic factors for the change of the pan evaporation are analyzed by studying the relationship between the pan evaporation and such elements 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.It is thus obvious that the decrease of the pan evaporation was mainly caused by the weakening solar radiation and the sunshine duration.The arerage wind speed and the DTR may also play an important role in an unknown mechanism.