Abstract: Based on the daily meteorological data of 710 stations from 1970 to 2017, authors apply the Mann-Kendall test method and contribution analysis method, analyze the variation characteristics of annual ET_o (potential evapotranspiration) and its sensitive factors, further quantify the contribution of meteorological factors to ET_o variation in different climate regions. The results showed that, (1) among 710 meteorological stations, 177 stations showed a significant increase trend (0.51 to 5.55mm·y⁻¹, P<0.05), 147 stations showed a significant decrease trend (−0.65 to −5.00mm·y⁻¹, P<0.05), and 386 stations showed no-significant change trend. T and U showed an increasing trend, while RH and RN showed a decreasing trend in different climate regions. (2) The sensitivity factors of ET_o to meteorological variables were differ in climate regions, in extreme arid region, arid region and semi-arid region ET_o was most sensitive to net radiation(RN), and most sensitive factor change to relative humidity(RH) in the semi-humid region and humid region, also the sensitivity of ET_o to RH and RN increased with the increase of humidity. (3) The change trend of ET_o was influenced by the sensitivity of climate factors and the relative rate of change. The rise of ET_o in extreme arid region, arid region, semi-arid region and semi-humid region were mainly caused by the increase of T, while the decrease of ET_o was mainly caused by the decrease of U, the change of ET_o in humid region was caused by its high sensitivity to RH and RN. In summary, compared with the sensitivity coefficient, the contribution index considering the relative rate of change is more indicative of the influence of climate factors on ET_o change. This study is conducive to for scientific understanding of regional climate change and hydrological cycle response mechanism.

Key words: Climate regions, Potential evapotranspiration, Contribution amount, Sensitivity coefficient, Relative rate of change