Abstract This study examines the climate response to a sea surface temperature (SST) warming imposed over the southwest Tropical Indian Ocean (TIO) in a coupled ocean-atmosphere model. The results indicate that the southwest TIO SST warming can remotely modulate the atmospheric circulation over the western North Pacific (WNP) via inter-basin air-sea interaction during early boreal summer. The southwest TIO SST warming induces a “C-shaped” wind response with northeasterly and northwesterly anomalies over the north and south TIO, respectively. The northeasterly wind anomalies contribute to the north TIO SST warming via a positive Wind-Evaporation-SST(WES) feedback after the Asian summer monsoon onset. In June, the easterly wind response extends into the WNP, inducing an SST cooling by WES feedback on the background trade winds. Both the north TIO SST warming and the WNP SST cooling contribute to an anomalous anticyclonic circulation (AAC) over the WNP. The north TIO SST warming, WNP SST cooling, and AAC constitute an inter-basin coupled mode called the Indo-western Pacific ocean capacitor (IPOC), and the southwest TIO SST warming could be a trigger for IPOC. While the summertime southwest TIO SST warming is often associated with antecedent El Niño, the warming in 2020 seems to be related to extreme Indian Ocean Dipole in 2019 fall. The strong southwest TIO SST warming seems to partly explain the strong summer AAC of 2020 over the WNP even without a strong antecedent El Niño.
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Low Cloud–SST Feedback over the Subtropical Northeast Pacific and the Remote Effect on ENSO Variability
Abstract Low clouds frequent the subtropical northeastern Pacific Ocean (NEP) and interact with the local sea surface temperature (SST) to form positive feedback. Wind fluctuations drive SST variability through wind–evaporation–SST (WES) feedback, and surface evaporation also acts to damp SST. This study investigates the relative contributions of these feedbacks to NEP SST variability. Over the summer NEP, the low cloud–SST feedback is so large that it exceeds the evaporative damping and amplifies summertime SST variations. The WES feedback causes the locally enhanced SST variability to propagate southwestward from the NEP low cloud deck, modulating El Niño–Southern Oscillation (ENSO) occurrence upon reaching the equator. As a result, a second-year El Niño tends to occur when there are significant warm SST anomalies over the subtropical NEP in summer following an antecedent El Niño event and a second-year La Niña tends to occur when there are significant cold SST anomalies over the subtropical NEP in summer following an antecedent La Niña event The mediating role of the NEP low cloud–SST feedback is confirmed in a cloud-locking experiment with the Community Earth System Model, version 1 (CESM1). When the cloud–ocean coupling is disabled, SST variability over the NEP weakens and the modulating effect on ENSO vanishes. The nonlocal effect of the NEP low cloud–SST feedback on ENSO has important implications for climate prediction.
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- Award ID(s):
- 2105654
- NSF-PAR ID:
- 10426248
- Date Published:
- Journal Name:
- Journal of Climate
- Volume:
- 36
- Issue:
- 2
- ISSN:
- 0894-8755
- Page Range / eLocation ID:
- 441 to 452
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1175/JCLI-D-21-0902.1
