| Summary: | 碩士 === 國立臺灣大學 === 大氣科學研究所 === 103 === The effect of agricultural irrigation on the environment has long been a critical concern. Anthropogenic water management can change surface-energy budgets and the water cycle. In this study, we focused on the impacts of Asian low-latitude irrigation on regional and global climates during boreal wintertime. We used a state-of-the-art earth system model to simulate land–air interaction processes affected by water management and the consequent responses in atmospheric circulation. Modeling without considering irrigation underestimates evapotranspiration in the Indo-Gangetic Plain during winter. Perturbed experiments show that wet-soil-moisture anomalies at low latitudes can lower the surface Bowen ratio and reduce the surface temperature to a continental scale through atmospheric feedback. The intensity of prevailing monsoon circulation becomes stronger because of larger land–sea thermal contrast. In addition, anomalous tropical precipitation and midlatitude climatic changes indicate tropical–extratropical teleconnections. The wintertime Aleutian low is deepened and shifts eastward, and an anomalous warm surface temperature is found in North America, although there is little irrigation over North America in the winter. Previous studies have noted this warming but left it unexplained, and we provide a plausible mechanism for these remote impacts, which come from the irrigation over Asian low-latitude regions.
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