Spatiotemporal pattern of the global sensitivity of the reference evapotranspiration to climatic variables in recent five decades over China

Abstract

The impact of climatic variables on reference evapotranspiration (ET0) has been a critical issue for ages. The sensitivities of the FAO56 Penman–Monteith ET0 equation to climate variables in 668 stations of China from 1960 to 2009 were studied using a global sensitivity analysis method, the extended Fourier amplitude sensitivity test. The results showed a large degree of spatiotemporal variation in the sensitivity of ET0 to incoming solar radiation, temperature (T), relative humidity (RH), and wind speed, with the averaged first-order sensitivity index (Si) value of 0.41, 0.18, 0.25, and 0.15, respectively. At annul scale, solar radiation was the most sensitive parameter in southern part of China with the mean Si value reached 0.66, while T and RH were the most sensitive parameter in northeast and north China, both with mean Si of 0.37. In northwest China, the mean Si values of incoming solar radiation, T, and wind speed, were relatively constant around 0.25, while the value of RH trended to be slightly higher than other parameters (=0.28). In Tibetan Plateau, solar radiation and T were the two most sensitive parameters, with averaged Si values of 0.32 and 0.31, respectively. The spatial variation of sensitivity varied seasonally, and was closely related to the geographic location of the stations. In general, stations in the low latitude were more sensitive to solar radiation and less sensitive to T than stations in the high latitude. The merit of the sensitivity results obtained in the current study was that it estimates which climatic parameter variation has the greatest impact on ET0 variation across the entire range of the climatic parameters rather than merely based on their median values, and it is helpful to better understand the potential effects of climate changes on the water management in China.