Evaporation paradox in China

It is now well established that the surface of Earth has,on average,warmed over the past 50 years. One expected consequence of this warming is that the air near the surface should be drier,which should result in an increase in the rate of evaporation from terrestrial open water bodies. However,lots of observations show that the rate of evaporation from open pans of water has been steadily decreasing all over the world over the past 50 years,and it is similar for the reference evapotranspiration. The contract between expectation and observation is called the evaporation paradox. Based on the data of 353 weather stations from 1956 to 2005,the trends in pan evaporation,air temperature and precipitation are obtained,and then the evaporation paradox and the relation between precipitation and evaporation are analyzed. The conclusions include:(1) in the past 50 years,the air temperature increased and the pan evaporation decreased,therefore the evaporation paradox actually exist in China;(2) the paradox is not consistent in space or time,for example,the pan evaporation in northeast and after 1980s increased with the increasing of air temperature;and (3) in the past 50 years,the precipitation and the pan evaporation exhibit contrary trend in rest areas.