Contrasting Recent and Future ITCZ Changes From Distinct Tropical Warming Patterns. Issue 22 (20th November 2020)

• Record Type: Journal Article
• Authors: Zhou, Wenyu; Leung, L. Ruby; Lu, Jian; Yang, Da; Song, Fengfei
• Is Part Of: Geophysical research letters. Volume 47:Issue 22(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-20
• Subjects: ITCZ -- tropical circulation -- climate change and variability -- tropical warming pattern -- PDO; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL089846
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: This study synthesizes the observed trends and projected changes in the Intertropical Convergence Zones (ITCZs). Under future warming, the seasonal ITCZs are projected to shift equatorward, widen, and weaken. The equatorward‐shifted seasonal ITCZs cause a squeeze of the annual‐mean zonal‐mean tropical ascent. Over 1979–2014, however, the seasonal ITCZs have shifted poleward in South Pacific and generally narrowed and strengthened. The observed annual‐mean zonal‐mean changes are largely opposite to the future squeeze. Such contrasting ITCZ changes are attributed to the distinct tropical warming patterns. Specifically, the equatorial Pacific has cooled following a phase change in the Pacific Decadal Oscillation (PDO) but will warm more than the tropics in future. The ITCZ response to tropical warming pattern is consistent with thermodynamic/energetic theories and demonstrated through SST‐forced experiments. In the coming decades, a positive PDO can act jointly with anthropogenically forced equatorial warming, leading to substantial ITCZ changes that are distinct from recent trends. Key Points: Under anthropogenically forced enhanced equatorial warming, the seasonal ITCZs are projected to shift equatorward, widen, and weaken Over 1979–2014 with a positive‐to‐negative PDO phase change, the seasonal ITCZs have shifted poleward in SH and sharpened generally In the coming decades, a positive PDO can enhance the equatorial warming and amplify the anthropogenically forced ITCZ changes