Projected change of East-Asian winter precipitation related to strong El Nino under the future emission scenarios

It has been demonstrated that the increased CO2 concentration would influence El Nino and its connected precipitation anomaly over East Asia (EA). Based on the model simulations from CMIP5 and CMIP6, this study investigates projected change of the boreal winter precipitation anomaly in EA during strong Eastern-Pacific type El Nino (EP-El Nino) responding to different emission scenarios and further examines the possible mechanisms. Features of the EA precipitation anomaly associated with EP-El Nino can be reasonably captured by most of the CMIP5 models, but not substantially improved by the CMIP6 models. As emissions increase, the positive precipitation anomalies over the northern EA (NEA) during strong EP-El Ninos tend to be more intense, while the precipitation anomalies decrease over southern EA (SEA). Such a change pattern is generally consistent between CMIP5 and CMIP6 models, which can be intimately related to the changes of circulation and moisture transport. That is, the changed cyclonic (anticyclonic) anomaly pattern over NEA (SEA) is favorable (unfavorable) for the formation of precipitation pattern with the associated enhanced (weakened) moisture supply anomaly. Further analysis shows that the strong EP-El Nino itself acts to increase precipitation anomaly over most of NEA compared with historical simulations, while its induced combination mode contributes to the relatively large inconsistency over SEA between CMIP5 and CMIP6.

Automated summary

It has been shown that the increased CO2 concentration has an impact on El Nino and its associated precipitation anomaly over East Asia. This study, using CMIP5 and CMIP6 model simulations, investigates the projected change of boreal winter precipitation anomaly in East Asia during strong Eastern-Pacific type El Nino events, considering different emission scenarios and examining the possible mechanisms. The CMIP5 models can reasonably capture the features of the precipitation anomaly associated with the El Nino events, but the CMIP6 models show minimal improvement. As emissions increase, the precipitation anomalies over northern East Asia intensify during strong El Nino events, while they decrease over southern East Asia. This pattern of change is consistent between the CMIP5 and CMIP6 models and can be attributed to changes in circulation and moisture transport.