Southern China Winter Rainfall Modulated by South China Sea Warming

• Published in: Geophysical research letters Vol. 49; no. 5
• Main Authors: Wang, Qiang, Zhong, Wenxiu, Yang, Song, Wang, Junbin, Zeng, Lili, Chen, Ju, He, Yunkai
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.03.2022
• Subjects: Boundary currents; Climate; Climatic extremes; East Asian monsoon; El Nino; El Nino events; El Nino phenomena; Moisture; Monsoons; Rain; Rainfall; Rainfall forecasting; Southern Oscillation; Transport; Tropical atmosphere; Tropical climate; Wind; Winter; Winter monsoon; South China Sea; China
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL097181

New insight into the contribution of anomalous South China Sea (SCS) warming is proposed to understand strong southern China (SC) winter rainfall. El Niño events, which weaken the East Asian winter monsoon (EAWM), favor SC winter rainfall. However, the changes in SC winter rainfall are not always in phase with the El Niño‐Southern Oscillation, making the prediction of East Asian climate challenging. Here, we show that the increased moisture associated with the warming SCS induced by the weakening western boundary current leads to increased meridional moisture transport to SC. Particularly, during the El Niño mature winter phase, this effect works jointly with a weakened EAWM to determine an increased rainfall over SC. Therefore, we suggest that the thermal state of the SCS should be considered when large‐scale tropical ocean‐atmosphere variability is utilized to predict SC winter rainfall. Plain Language Summary Climate extremes, such as strong southern China (SC) winter rainfall, greatly affect socioeconomic activities and raise great concerns. The South China Sea (SCS) acts as a “portal” to SC and significantly modulates the nonlinear moisture transport to SC. When the SCS is warm enough, the “portal” opens and allows abundant moisture transport toward SC. Particularly during the El Niño mature winter, this effect works jointly with a weakened East Asian winter monsoon to determine increased winter rainfall over SC. Key Points Tropical air‐sea interaction indices sometimes fail to identify strong southern China (SC) winter rainfall The role of the South China Sea (SCS) in modulating SC winter rainfall under large‐scale tropical air‐sea interactions is revealed A warmer SCS supports large nonlinear moisture transport from the SCS toward SC, resulting in strong SC winter rainfall