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Irrigated area has rapidly expanded over the North China Plain (NCP), over the second half of the twentieth century. Simultaneously, there has been an observed increase in specific humidity and precipitation and a decrease in surface temperature during summer. The impacts of irrigation on regional climate in Eastern China are investigated using the Massachusetts Institute of Technology-Regional Climate Model with irrigation module. The results of our experiments clearly support that surface cooling as well as enhanced precipitation are attributable to irrigation over the NCP. The irrigation-induced soil moisture change simulated over the NCP during summer resulted in cooler surface temperatures by 1 similar to 4 degrees C over this region, which led to a reduction of the planetary boundary layer, higher surface pressure, and significant changes in low-level circulation. Our results indicate that moisture convergence is enhanced over Hebei and Henan province along the Taihang-Mountain, which generated a significant increase in precipitation by 20 similar to 40% over this region.

Plain Language Summary The North China Plain is the largest irrigated area in Eastern China. During the second half of the twentieth century, there was an observed increase in irrigation extent, humidity, and precipitation, with a concurrent decrease in surface temperature. The Massachusetts Institute of Technology-Regional Climate Model, including the irrigation module, was used to investigate the impact of irrigation on regional climate over Eastern China. Massachusetts Institute of Technology-Regional Climate Model experiments clearly support that the irrigation extension altered local climate through surface cooling and enhanced precipitation over the North China Plain during the boreal summer time.