Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Contrasting Recent and Future ITCZ Changes From Distinct Tropical Warming Patterns

TitleContrasting Recent and Future ITCZ Changes From Distinct Tropical Warming Patterns
Publication TypeJournal Article
Year of Publication2020
JournalGeophysical Research Letters
Volume47
Number22
Abstract / Summary

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.

URLhttp://dx.doi.org/10.1029/2020gl089846
DOI10.1029/2020gl089846
Journal: Geophysical Research Letters
Year of Publication: 2020
Volume: 47
Number: 22
Publication Date: 11/2020

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.

DOI: 10.1029/2020gl089846
Citation:
Zhou, W, L Leung, J Lu, D Yang, and F Song.  2020.  "Contrasting Recent and Future ITCZ Changes From Distinct Tropical Warming Patterns."  Geophysical Research Letters 47(22).  https://doi.org/10.1029/2020gl089846.