Contrasting Recent and Future ITCZ Changes from Distinct Tropical Warming Patterns

Journal Article · Sat Nov 28 00:00:00 EST 2020 · Geophysical Research Letters

DOI:https://doi.org/10.1029/2020GL089846· OSTI ID:1761057

Zhou, Wenyu ^[1]; Leung, Lai-Yung  ^[1]; Lu, Jian ^[1]; Yang, Da ^[2]; Song, Fengfei ^[1]

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1. BATTELLE (PACIFIC NW LAB)
2. University of California, Davis

The Intertropical Convergence Zone (ITCZ) is a salient feature of the Earth’s deep-tropical circulation. Here we report and explain the contrasting changes in seasonal ITCZs over recent decades and under future warming. We show that seasonal ITCZs have shifted poleward and narrowed over recent decades but are projected to shift equatorward and widen under future warming. Such contrasting changes are induced by distinct surface warming patterns. Specifically, the equatorial Pacific has cooled over recent decades with phase change in the Pacific Decadal Oscillation (PDO) but in the future it will experience stronger anthropogenic warming than the tropical mean. The effect of surface warming pattern on ITCZ is consistently explained by thermodynamic and energetic theories and is demonstrated through atmosphere-only simulations forced with prescribed SST. In the coming decades, PDO may change into a positive phase. This will enhance the equatorial warming and lead to amplified ITCZ changes that are distinct from recent trends.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1761057
• Report Number(s): PNNL-SA-154107
• Journal Information: Geophysical Research Letters, Vol. 47, Issue 22
• Country of Publication: United States
• Language: English