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Summer monsoon rainfall supplies over 55% of annual precipitation to global monsoon regions. As shown by more than 70% of models, including 30 models from CMIP5 and 30 models from CMIP6 under high-emission scenarios, North American (NAM) monsoon rainfall decreases in a warmer climate, in sharp contrast to the robust increase in Asian- African monsoon rainfall. A hierarchy of model experiments is analyzed to understand the mechanism for the reduced NAM monsoon rainfall in this study. Modeling evidence shows that the reduction of NAM monsoon rainfall is related to both direct radiative forcing of increased CO2 concentration and SST warming, manifested as fast and slow responses to abrupt CO2 quadrupling in coupled GCMs. A cyclone anomaly forms over the Eurasian-African continental area due to enhanced land-sea thermal contrast under increased CO2 concentration, and this leads to a subsidence anomaly on its western flank, suppressing the NAM monsoon rainfall. The SST warming acts to further reduce the rainfall over the NAM monsoon region, and the El Niño-like SST warming pattern with enhanced SST warming over the equatorial Pacific plays a key role in suppressing NAM rainfall, whereas relative cooling over the subtropical North Atlantic has no contribution. A positive feedback between monsoon precipitation and atmospheric circulation helps to amplify the responses of monsoon rainfall. [ABSTRACT FROM AUTHOR]

Abstract: Volume transport in the Taiwan Strait is usually northward for most of the year and varies seasonally because of the adjustment of the East Asian monsoon. Based on model simulations, the influence on this northward transport of every typhoon formed during the period 2005–2009 was examined. The results showed that there were four typhoons which enhanced northward transport during these five years. The current measurements, obtained from a buoy deployed in the Taiwan Strait, matched these events exactly. These typhoons had special moving tracks and life histories. They traveled westward in the area south of the strait or moved northward from the south to the north. Under the influence of such a typhoon, the prophase southward atmospheric forcing in the strait was weak and the anaphase northward atmospheric forcing (mainly along-strait wind stress) was strong, which is necessary and crucial in enhancing the northward transport. The ageostrophic process, another important driving factor in transport change, was generated mainly by local atmospheric forces inside the strait under the typhoon weather conditions and its effect on transport magnitude was comparable to that of direct atmospheric forcing. It first stored some energy from the atmospheric forcing to restrain the transport change, and then released the stored energy to prolong and even to intensify the enhanced northward transport. [Copyright &y& Elsevier]