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This study aims to better understand the ENSO impacts on climate anomalies over East Asia in early winter (November–December) and late winter (January–February). In particular, the possible mechanisms during early winter are investigated. The results show that ENSO is associated with a Rossby wave train emanating from the tropical Indian Ocean toward East Asia (denoted as tIO-EA) in early winter. This tIO-EA wave train in El Niño (La Niña) is closely related to a weakening (strengthening) of the East Asian trough, and thereby a weakened (strengthened) East Asian winter monsoon and warm (cold) temperature anomalies over northeastern China and Japan. By using partial regression analysis and numerical experiments, we identify that the formation of tIO-EA wave train is closely related to precipitation anomalies in the tropical eastern Indian Ocean and western Pacific (denoted as eIO/wP). In addition, the ENSO-induced North Atlantic anomalies may also contribute to formation of the tIO-EA wave train in conjunction with the eIO/wP precipitation. The response of eIO/wP precipitation to ENSO is stronger in early winter than in late winter. This can be attributed to the stronger anomalous Walker circulation over the Indian Ocean, which in turn is caused by higher climatological SST and stronger mean precipitation state in the Indian Ocean during early winter. [ABSTRACT FROM AUTHOR]

Understanding the link between future changes in East Asian summer monsoon (EASM) and global warming levels is of great importance for regional climate change adaptation and mitigation in East Asia. Here, we analyze the projected changes in EASM circulation and precipitation under different warming levels from 1.5 to 5 °C above the preindustrial global mean temperature, using large‐ensemble simulations conducted with Canadian Earth System Model version 2. We find that the model projects enhanced monsoon circulation and precipitation with global warming. The 850‐hPa meridional winds, precipitation, and 500‐hPa vertical ascending motion will be enhanced nonlinearly, while the total column precipitable water will increase quasi‐linearly. The increase in precipitable water in the wet EASM region is only slightly greater than global average but the increase in precipitation is much greater than global one, with enhanced 500‐hPa vertical ascending motion contrary to global mean. The increased low‐level land‐sea thermal contrast leads to the enhanced EASM meridional circulation and thus bring a large amount of moisture into Eastern China, providing favorable conditions for additional increase in precipitation. A simplified moisture budget analysis shows that the dynamic component related to strengthening monsoon circulation plays dominant role in the increase in EASM precipitation when the global temperature increases by more than approximately 2 °C, while the thermodynamic component caused by increased water vapor is important when the warming is smaller. Plain Language Summary: Changes in East Asian summer monsoon (EASM) circulation and precipitation have great impacts on human society, agriculture and energy in East Asia. Previous studies rarely investigated EASM circulation and precipitation changes under specific global mean temperature increases, such as 1.5 to 5 °C of warming. Here, we focus on EASM circulation and precipitation changes linked with different global warming levels. Four EASM metrics (850‐hPa meridional wind, precipitation, precipitable water, and 500‐hPa vertical velocity) are examined to reflect EASM system changes based on Canadian Earth System Model version 2 large‐ensemble runs. We find that EASM low‐level meridional wind, precipitation, and midlevel vertical ascending motion will be enhanced nonlinearly with warming, while precipitable water will increase quasi‐linearly with warming. The increase in EASM precipitation is greater than global average, accompanied by increasing vertical ascending motion and strengthened southerly winds. When global mean near‐surface air temperature increases by more than 2 °C, the dynamic component plays dominant role in the increased EASM precipitation, while the thermodynamic factor plays a secondary role. These results provide useful information for developing strategies for climate change policy in East Asia. Key Points: East Asian summer monsoon (EASM) circulation and precipitation are projected to increase nonlinearly with warmingThe EASM circulation is projected to enhance mainly driven by increased thermal contrasts in the lower troposphere rather than in upper layerBoth dynamic and thermodynamic components contribute to precipitation increase but dynamic change is more important at high warming level [ABSTRACT FROM AUTHOR]