Temporal and Spatial Change Analysis of the Sensitivity of Potential Evapotranspiration to Meteorological Influencing Factors in China
2011, 66 (5):
Potential evapotranspiration (E0), as an estimate of the evaporative demand of the atmosphere, has been widely discussed in researches on irrigation management, crop water demand and predictions in ungauged basins (PUBs). Analysis of the sensitivity of E0 to meteorological factors is the basic research on the impact of climate change on water resources, and also is important to the optimal allocation of agricultural water resources. In this study, the calculation method of global radiation in Penman-Monteith formula was improved by optimazation, and the sensitivities of Penman-Monteith potential evapotranspiration to the daily maximum temperature (STmax), daily minimum temperature (STmin), wind speed (SU2), global radiation (SRs) and vapor pressure (SVP) were calculated and analyzed based on the long-term meteorological data at 653 meteorological stations in China during the period 1961-2000. The results are obtained as follows. (1) The multiple correlation coefficient between E0 and pan evaporation increased from 0.61 to 0.75 using the improved Penman-Monteith formula. Trend analysis shows that E0 had the decreasing trends in eight basins of China, which indicates that "pan evaporation paradox" common existed in China from 1960 to 2007. (2) Spatially, Tmax was the most sensitive variable in the Haihe River, Yellow River, Huaihe River, Yangtze River, Pearl River and river basins in southeastern China, and VP was the most sensitive variable in the Songhua River Basin, Liaohe River Basin and river basins in Northwest China, while Rs was the most sensitive variable in river basins of Southwest China. For the national average, the most sensitive variable was VP, followed by Tmax, Rs, U2 and Tmin. In addition, the changes in sensitivity coefficients had certain correlation with elevation. (3) Temporally, the maximum values of STmax and SRs occurred in July, while the maximum values of STmin, SVP and SU2 occurred in January. Moreover, trend analysis indicates that STmax had decreasing trends, while STmin, SU2, SRs and SVP had increasing trends.
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