Urbanization impacts on evapotranspiration change across seven typical urban agglomerations in China

Evaluating the differences in evapotranspiration between urban and surrounding non-urban areas (i.e., SET) has critical implications for urban ecological planning and water resources management. However, it is unclear how the magnitude of changes in SET caused by urbanization varies under different climatic conditions in China. Here, using the remotely ET estimates at 1 km spatial resolution, we firstly estimated the magnitude of changes in SET and then quantified the main driving factors influencing variations in SET of 7 national-level urban agglomerations (UAs) across China during 2003-2020. Results showed that all annual ETurban values were smaller than ETnon-urban of 7 UAs, and the absolute SET values of cities in South China were generally higher than those in North China. There is an apparent effect of urbanization on SET increase in Guanzhong Plain City Group, Central Plain UA and Guangdong-Hong Kong-Macao Greater Bay Area (GHKMGBA), while SET decrease in Chengdu-Chongqing City Group and Yangtze River Delta (YRDUA) were primarily due to the climate change. The suppressing effects of temperature and NDVI on SET decrease in YRDUA were enhanced, and the promoting effect of GDP on SET increase in GHKMGBA was weakened. Considering nonstationary features, urbanization appears to heighten extreme SET by 0.83 %, 4.83 % and 10.39 % under 5-year, 20-year, and 50-year return periods over all the 7 UAs, respectively. Collectively, our findings confirm that urbanization is a significant factor that leads to SET increase, and the factors affecting the response of urban water circulation system need to be deeply decomposed.