No abstract

With ongoing global warming, the changes in EA-WNPSM rainfall-feeding over two billion people in East Asia and the Indochina Peninsula-projected by the Coupled Model Intercomparison Project Phase 5 (CMIP5) models show remarkable and unidentified inter-model spread. Here, we reveal the leading inter-model spread of EA-WNPSM changes in 28 CMIP5 models is related to a 'dry north-wet south' dipole in East Asia and a wet Indochina and WNP. This spread pattern of EA-WNPSM changes is induced by the spread of sea surface temperature changes in the equatorial western Pacific, and can be further traced back to an apparent discrepancy among the state-of-the-art models in simulating the tropical Pacific rainfall. An air-sea coupling processes involved with summer background circulation contribute to this robust spread pattern of EA-WNPSM changes. We can constrain the EA-WNPSM rainfall changes based on the current-future relationship and observation that there should be more rainfall increase in North China and the Korean Peninsula and less increase in South China, the Indochina Peninsula and WNP, relative to previous multi-model ensemble projections.

The East Asian summer monsoon (EASM), impacting the lives of more than 1.5 billion people, is a complex climate system independent from the South Asia summer monsoon (e.g.

In phases 5 and 6 of the state-of-the-art Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively) models, there is an apparent excessive rainfall bias with a negative SST bias in the tropical Pacific intertropical convergence zone (ITCZ). The regime of the excessive ITCZ but negative SST bias is inconsistent with the common positive rainfall–SST correlation of climate anomalies over the tropics. Using a two-mode model, we decomposed the rainfall bias into two components and found that the surface convergence (SC) bias is the key factor forming the excessive ITCZ bias in the historical runs of 25 CMIP5 models and 23 CMIP6 models. A mixed layer model was further applied to connect the formation of the SC bias with the SST pattern bias. The results suggest that the meridional pattern of the SST bias plays a key role in forming the SC bias. In the CMIP5 and CMIP6 models, the overall negative SST bias has two apparent meridional troughs at around 10°S and 10°N, respectively. The two meridional troughs in the SST bias drive two convergence centers in the SC bias favoring the excessive ITCZ, even though the local SST bias is negative.