Abstract: Based on the FAO Penman-Monteith equation,sensitivity coefficients of ET₀ in growing season to air temperature,wind speed,relative humidity and shortwave radiation were studied in 126 stations in Northwest China using a 49-year dataset. The temporal-spatial variations of sensitivity coefficients of ET₀ were also analyzed. The results showed that shortwave radiation was the most sensitive variable to ET₀ in general for the region,followed by relative humidity and air temperature. Wind speed had the least impact. The sensitivity coefficients to all climate variables indicated large spatial variability. The high value area of sensitivity coefficients to air temperature and wind speed was in the westerly climatic region,while the high value area of sensitivity coefficients to relative humidity was in the relatively moist region. The sensitivity coefficients to shortwave radiation were higher in the south study area than in the north. In the growing season,the highest sensitivity coefficients to air temperature and shortwave radiation were in July,while the lowest sensitivity coefficient to wind speed was in July. The absolute sensitivity coefficients to relative humidity increased from April to October. The sensitivity coefficients to shortwave radiation and relative humidity indicated significant increasing and decreasing trends respectively during the 49 years. But the yearly change trends of sensitivity coefficients to air temperature and wind speed were not obvious.

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