[Evapotranspiration estimation using three-temperature model and influencing factors of Nanning City, China]

Evapotranspiration is the key element of hydrological energy cycle and climate system. It is of great significance to estimate the spatiotemporal variation of evapotranspiration and its response to climate and land use changes for understanding the effects of water cycle and ecological processes in urban basins. Based on the three-temperature model and MODIS Image, we estimated and analyzed the spatiotemporal variation of evapotranspiration in Nanning City from 2001 to 2018, and examined the influence and driving mode of main climate factors and land use types on evapotranspiration. The results showed that the annual average evapotranspiration of Nanning City ranged from 495.7 to 781.1 mm during 2001-2018, with the inter annual relative variability ranging from -22.5% to 23.1%, showing an overall upward trend. The regional evapotranspiration showed a distribution pattern of high north-south and low middle, with the urban evapotranspiration being significantly lower than suburban area. The evapotranspiration had a significant multiple correlation with climate factors. The influence of temperature on the evapotranspiration was stronger than precipita-tion. Evapotranspiration was temperature driven in suburbs, but was driven by multiple factors in urban area. The average evapotranspiration of different land use types in Nanning was forests (823.4 mm) > grasslands (675.6 mm) > croplands (582.9 mm) > urban area (346.6 mm). The change of land use type was the main underlying surface factor leading to the significant change of regional evapotranspiration.