Sensitivity of the Potential Evapotranspiration to Key Climatic Variables in the Haihe River Basin
海河流域潜在蒸散发的气候敏感性分析

Evapotranspiration is a key process in hydrologic cycle. Sensitivity analysis of potential evapotranspiration (ET0) is helpful in understanding the impact of climate change on hydrologic cycle. In this paper, a non-dimensional sensitivity coefficient was employed to identify the sensitivity of ET0 to the variation of air temperature (Tmean), solar radiation (Rs), vapor pressure (VP) and wind speed (U2) in the Haihe River basin (HRB). ET0 was estimated with the FAO Penman-Monteith equation. The results showed that the reference evapotranspiration was most sensitive to VP, which is followed by TTmean, Rs and U2 on an annual scale. In terms of season, TTmean was the most sensitive variable and U2 was the least sensitive variable in spring and summer, while VP was the most sensitive variable and Rs was the least sensitive variable in autumn and winter. Spatially speaking, the temperature (STmean) and vapor pressure (SVP) of ET0 sensitivity coefficients showed a decreasing trend from plain to hilly region. The coefficients of solar radiation (SRs) decreased from south to north of the HRB, while that of wind speed (SU2 ) increased from south to north. The long-term trend analysis of sensitivity coefficients for the period from 1957 to 2008 showed that , SRs and STmean increased, while SVP decreased.