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- Title
Asymmetric Efficacies Between Warm and Cold Pacific Meridional Modes in Inducing ENSO.
- Authors
Li, Xumin; Yu, Jin‐Yi; Ding, Ruiqiang; Hu, Jianyu; Tuo, Peng‐Fei
- Abstract
This study investigates boreal spring events of Pacific Meridional Mode (PMM) from 1950 to 2022, revealing that cold PMM is more effective in triggering subsequent La Niña compared to warm PMM's induction of following El Niño. This asymmetry stems from the varying origins and sub‐efficacies of PMM groups. The cold PMM is primarily initiated by pre‐existing La Niña, while the warm PMM is comparably activated by pre‐existing El Niño and internal atmospheric dynamics. PMMs initiated by pre‐existing El Niño or La Niña play a crucial role in determining the efficacies of PMMs in triggering subsequent El Niño‐Southern Oscillation (ENSO). The strong discharge of pre‐existing El Niño hampers warm PMM's induction of subsequent El Niño, whereas weak recharge from pre‐existing La Niña enhances the efficacy of cold PMM in inducing subsequent La Niña. Comprehending not only the PMM phase but also its origin is crucial for ENSO research and prediction. Plain Language Summary: This study investigated the efficacies of warm and cold Pacific Meridional Mode (PMM) events in triggering El Niño and La Niña events from 1950 to 2022. Contrary to previous beliefs, the research concludes that cold PMM are more adept at inducing La Niña. The varying efficacies are linked to the fact that cold PMM are primarily initiated by preceding La Niña occurrences, while warm PMM are comparably activated by the subtropical atmospheric internal dynamics and previous El Niño events. Due to the weaker ocean heat content recharge associated with pre‐existing La Niña compared to the discharge associated with pre‐existing El Niño, La Niña‐induced cold PMM encounters less competition from tropical discharge‐recharge processes in inducing a subsequent La Niña. In contrast, El Niño‐activated warm PMM faces stronger competition in inducing an El Niño. Consequently, the distinct origins of cold and warm PMM phases, along with their competition with tropical discharge‐recharge processes, contribute to their respective efficacies in inducing El Niño and La Niña. Key Points: The cold phase of Pacific Meridional Mode (PMM) has a higher efficacy in inducing following La Niña than warm PMM in inducing El NiñoDisparate efficacies arise from distinct origins of the two PMMs and their varied competition with tropical discharge‐recharge processesCold/warm PMM, induced by a previous La Niña/El Niño, encounters weak/strong competition from recharge/discharge in triggering El Niño‐Southern Oscillation
- Subjects
EL Nino; LA Nina; ATMOSPHERIC circulation; ENTHALPY
- Publication
Geophysical Research Letters, 2024, Vol 51, Issue 12, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2024GL108924