中国北方近50年潜在蒸发的变化

利用彭曼-蒙梯斯公式和常规气象资料计算中国北方地区潜在蒸发(也称蒸发力)变化,分析实测蒸发皿蒸发的变化,结果表明:自20世纪50年代以来,潜在蒸发和蒸发皿蒸发呈波动下降趋势。日照百分率、风速下降和湿度增加影响了潜在蒸散和蒸发皿蒸发量的变化。从能量观点来说,太阳总辐射的下降是潜在蒸发和蒸发皿蒸发减小的主要原因之一,大气湿度增加和人类对于能源消耗的增加导致到达地面的太阳总辐射下降。因太阳总辐射的下降引起潜在蒸发的减小量约占总潜在蒸发减小量的78%左右。

Changes of Potential Evaporation in Northern China over the Past 50 Years

The authors estimated the changes of potential evaporation in northern China over the past 50 years (1950-2000) by using the Penman-Monteith model and also analyzed the observation pan evaporation data in the same regions in this paper.The results showed that the potential evaporation and pan evaporation amount had a same decreasing tendency in recent 50 years.The main reasons for the decrease of potential evaporation and pan evaporation amount were due to the decrease of sunshine percentage and wind speed and increase of air humidity during this period of time.From the viewpoint of the energy,the solar radiation reduction was also one of the main reasons for evaporation decrease.The present research indicated that the air humidity increase and the increase in energy resources consumption owing to anthropogenic activities were the two important factors affecting total solar radiation reduction.According to the estimation by Penman-Monteith model the decreased amount of potential evaporation induced by reduction of solar radiation reaching the earths surface accounted for 78% of the total amount of evaporation decreased.