Seasonal and interannual variability in urban neighborhood evapotranspiration and its controlling factors in a subtropical city

Abstract

Urban evapotranspiration (ET) plays an important role in mitigating the adverse effects of urbanization and global warming. Precisely measuring urban ET is essential for understanding the mechanisms underlying these mitigation benefits. However, due to the lack of long-term continuous observations, there is limited knowledge regarding the seasonal and interannual variability in urban neighborhood ET and its driving forces, especially for tropical and subtropical cities. In this study, we investigated the dynamics of urban ET using eddy covariance and its influencing factors based on five years of data collected from 2017 to 2021 in Shenzhen, a subtropical megacity in China. Our results highlight the importance of urban neighborhood ET as a significant water consumption in urban areas. Over the five-year period, the mean daily ET value was 1.82 mm day⁻¹, with the lowest value in January and December (< 1 mm day⁻¹) and the highest value between May and August (> 5 mm day⁻¹). The annual ET ranged from 635 mm to 705 mm and averaged 664 mm, accounting for approximately 38 % of the total precipitation. The primary driving force behind urban neighborhood ET was the available energy, while water availability acted as a constraint in such urban environments with substantial annual precipitation (1761 mm). Furthermore, the variability in ET was observed to be influenced by vegetation coverage. These findings have significant implications for urban heat island mitigation and stormwater management.