Variations of potential evapotranspiration from 1961-2000 in Xinjiang, China

Potential evapotranspiration (PET) was estimated by applying Penman-Monteith Method recommended by FAO with climatic data from 96 stations during 1961 to 2000 in Xinjiang. The spatial and temporal variations of the potential evapotranspiration in Xinjiang are analyzed. The whole potential evapotranspiration has decreased in all seasons. The average annual evapotranspiration rate decreases by 29.87 mm/decade. Superimposed on this general decline are fluctuations with above average rates in the 1970s and 1980s. Decreasing PET rates are more pronounced in spring and summer as compared to autumn and winter. Through correlation analysis, the major climate factors that affect the temporal change of the potential evapotranspiration are analyzed. Changes in relative humidity and to a lesser degree wind speed and sunshine duration were found to be the most important meteorological variables affecting PET trends in Xinjiang while changes in temperature played an insignificant role. Negative evapotranspiration trends are thought to a general decrease under global warming scenarios.