The Effect of Tropical Pacific Air‐Sea Coupling on the Rainfall Response to Quadrupled CO ₂ Forcing

Journal Article · 03 August 2023 · Geophysical Research Letters

DOI: https://doi.org/10.1029/2023gl103466 · OSTI ID:2421271

Hsu, Tien‐Yiao  ^[1]; Magnusdottir, Gudrun  ^[2]; Primeau, Francois  ^[2]

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1. Univ. of California, San Diego, CA (United States). Scripps Inst. of Oceanography; OSTI
2. Univ. of California, Irvine, CA (United States)

We perform quadrupled CO₂climate simulations with the Community Earth System Model version 1 (CESM1) to study how air-sea coupling affects the response of tropical rainfall under global warming. We use a hierarchy of ocean models to separate the effects of seasonal mixed-layer entrainment, wind-driven Ekman flows directed perpendicular to the wind, and the near-equator frictional flows directed in the same direction as the wind. We show that the Pacific Ocean's enhanced equatorial warming pattern (EEW) and equatorward ITCZ contraction observed in previous climate simulations emerge when the ocean model includes wind-driven Ekman and frictional flows. Furthermore, the near-equator frictional flow contributes more than half of the heat convergence in the equatorial Pacific Ocean. Finally, we show that although Ekman flow and near-equator frictional flow can both result in EEW, their coupled interactions with the Hadley circulation lead to opposite feedbacks on EEW's strength.

• Research Organization: Univ. of California, Irvine, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: SC0019407
• OSTI ID: 2421271
• Journal Information: Geophysical Research Letters, Journal Name: Geophysical Research Letters Journal Issue: 15 Vol. 50; ISSN 0094-8276
• Publisher: American Geophysical Union (AGU)Copyright Statement
• Country of Publication: United States
• Language: English