1. Constrained Projections Indicate Less Delay in Onset of Summer Monsoon over the Bay of Bengal and South China Sea.
- Author
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Cheng, Yifeng, Wang, Lu, Chen, Xiaolong, Zhou, Tianjun, Turner, Andrew, and Wang, Lijuan
- Abstract
The summer monsoon onset over the Bay of Bengal and South China Sea signals the beginning of the Asian summer monsoon, critical for local fisheries, agriculture and livelihoods, so communities are concerned about its potential changes under global warming. Previous projections have suggested a delay, but the extent of this delay remains uncertain, undermining the reliability of the projections. Here, we show a significant correlation between the projected shift in Bay of Bengal/South China Sea monsoon onset and present‐day sea surface temperature (SST) simulation over the western Pacific (WP). This emergent relationship arises from the spread of the precipitation response over the western‐central Pacific to WP SST, as more precipitation induces stronger tropical upper‐tropospheric warming, increasing westerly vertical shear near South Asia, and facilitating the onset delay. The rectified projections indicate that the delayed shift is almost halved compared to raw projections, and the intermodel uncertainty is reduced by 30%. Plain Language Summary: The summer monsoon onset over the Bay of Bengal and South China Sea is a crucial time for fishing, agriculture and livelihood, and is important for the further advance of the monsoon rains over tropical Asia. Previous studies have suggested that monsoon onset in these seas will be delayed in the future, but there is large uncertainty between models, undermining the reliability of the projection. This study finds that the projected shift in the onset is strongly related to a model's representation of sea surface temperatures over the western Pacific Ocean in the present day. Based on the relationship found in observations, we adjust or "constrain" the future projections of the monsoon onset. The delay to the monsoon onset using this adjustment is almost half of the original projection, and the uncertainty between models is also reduced. We suggest that a more accurate simulation of sea‐surface temperatures in the present‐day climate of the western Pacific Ocean is crucial for reliable future projections of the monsoon onset. Key Points: An observational constraint is identified for projected changes in summer monsoon onset date over the Bay of Bengal and South China SeaModels with a warmer sea surface temperature bias over the tropical western Pacific tend to project a more delayed monsoon onset in the futureThe emergent constraint indicates that the delay of monsoon onset over the Bay of Bengal and South China Sea is overestimated [ABSTRACT FROM AUTHOR]
- Published
- 2024
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