Work

Diverse onset pathways of South China Sea summer monsoon driven by SSTA across Indian-Pacific-Atlantic Oceans

Year: 2025

Type: article

Abstract: In climatology, the South China Sea (SCS) summer monsoon (SCSSM) onset features rapid establishment of low-level westerlies and convection across the entire basin, in contrast to Indian summer monsoon onset which begins with northward migration of the Intertropical Convergence Zone (ITCZ). Diverse SCSSM onset pathways complicate subseasonal rainfall forecasts in the surrounding region during boreal spring. Besides simultaneous onset in the SCS, this study recognizes two other types of SCSSM onset: northern-initiated and southern-initiated pathways. In the northern-initiated type, the low-level westerly wind begins over northern SCS, accompanied by a positive Tripole mode in the North Atlantic and El Niño–like SSTAs in the Pacific. This SSTA configuration enhances the extra-tropical meridional cell and tropical Walker circulation to shift the western Pacific subtropical high (WPSH) southward, suppressing (intensifying) westerly wind in the southern (northern) SCS. In contrast, the southern-initiated type features initiation of westerly wind in the southern SCS. This type is ascribed to the tropical southern Indian Ocean cooling and negative Pacific Meridional Mode. The colder Indian Ocean boosts northward migration of ITCZ over Arabian Sea, which strengthens low-level westerly wind over the southern SCS by enhancing cross-equatorial Somali jet and shifts the WPSH northward, thereby suppressing the monsoon onset over the northern SCS. This pattern is developed by the PMM-related easterly wind in the tropical Pacific Ocean. These findings shed new light on SCSSM onset behavior and have significant implications for spring rainfall teleconnections between South China and the Southeast Asia.

Source: Atmospheric Research

DOI: 10.1016/j.atmosres.2025.108611

Authors: Yanan Duan, Boqi Liu

Institutions: Chinese Academy of Meteorological Sciences, University of Chinese Academy of Sciences, State Key Laboratory of Severe Weather

Language: English

Topic: Climate variability and models

Subfield: Global and Planetary Change

Field: Environmental Science

Domain: Physical Sciences

SDG: Climate action

Open Access status: hybrid

Estimated APC paid: $3,310