And the space pattern of change is: Pan evaporation declined least in the Northeast China,when moving westward,its decrease trend gradually increase.

To comparatively analyze the variation trends of meteorological variables,including air temperature,net radiation,relative humidity,wind speed,and their influences on pan evaporation with different climate conditions in the Laoha river Basin,the observed data during 1970 to 2005 from the Dianzi and Chutoulang subbasins are analyzed and evaluated.

Pan evaporation, an indictor of potential evaporation, has decreased during the last several decades in many parts of the world; the trend is contrary to the expectation that global warming will be accompanied by an increase in evapotranspiration, known as the pan evaporation paradox.

Estimation of reference crop evapotranspiration by Chinese pan;

Experimental study on the fractionation mechanism of hydrogen and oxygen stable isotopes in evaporation from water surface of evaporation pans;

Measurements both from eddy correlation system and evaporation pan are used to derive aerodynamic resistance over bare soil surface as well as maize field.