Anthropogenic Intensification of East Asia Summer Monsoon Frontal Precipitation System

Abstract

Summer monsoon precipitation provides crucial water resources for agriculture, industry, and life in East Asia (EA). Meanwhile, it causes disasters when occurring over highly populated regions. Recently, we have witnessed a series of extreme precipitation events in South Korea, China, and Japan during the summer monsoon season. It remains uncertain whether these events and the EA summer monsoon precipitation system are affected by the ongoing climate changes. The summer precipitation in EA is contributed by various extra-tropical cyclones, fronts, and other weather systems. Here, we focus on the stationary front-induced precipitation, which accounts for more than 30% of EA summer precipitation. Based on objectively detected frontal systems, we found that the intensity of observed frontal rainfall increased by 19.8% during 1991–2015. It was further shown that the intensity increase of frontal rainfall is mainly attributed to anthropogenic greenhouse gas forcing on the basis of the Community Earth System Model Large Ensemble simulations. We found that the reinforced western North Pacific subtropical high makes enhanced water vapor convergence in the lower troposphere along its rim. This study confirms that the frontal summer monsoon precipitation system over EA has been intensified significantly by human-induced global warming, which will likely enhance further in the future.