Understanding the response of tropical overturning circulations to greenhouse gas and aerosol forcing

While observational records provide evidence for strengthening of the Pacific Walker circulation and the boreal winter Hadley cell over the last few decades, the underlying causes are not well understood. This study investigates the radiative effects of CO 2 and anthropogenic aerosols on regional va...

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Bibliographic Details
Published in:Environmental Research: Climate 2024-12, Vol.3 (4), p.45009
Main Authors: Kalik, Vishisth, Krishnan, R, Ayantika, D C, Swapna, P, Manmeet, Singh, Sandeep, N, Vellore, Ramesh, Brahmananda Rao, V
Format: Article
Language:English
Subjects:
anthropogenic aerosols
climate change
greenhouse gases
IITM-ESM
ITCZ
subtropical aridity
tropical meridional and zonal overturning circulations
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Summary:While observational records provide evidence for strengthening of the Pacific Walker circulation and the boreal winter Hadley cell over the last few decades, the underlying causes are not well understood. This study investigates the radiative effects of CO 2 and anthropogenic aerosols on regional variations in the intensity of tropical meridional (Hadley-like) and zonal (Walker-like) overturning circulations, based on a suite of experiments using the IITM Earth System Model (IITM-ESM) along with supplementary analysis of observed and reanalysis datasets. Two key findings emerge from our study (i) strengthening of the Pacific Walker circulation with enhanced zonal sea surface temperature gradients and precipitation increase over the tropical Indo-Pacific, in response to global warming via ocean-atmosphere coupled feedbacks (ii) aerosol-induced intensification of regional meridional overturning circulation over the ( 0 − 120 ∘ E) longitudinal domain resulting from inter-hemispheric energy imbalance and southward shift of the southern hemispheric (SH) rainfall belt extending eastward from Africa across the Indian Ocean. Our results suggest that the combined radiative influence of increased CO 2 and northern hemispheric (NH) anthropogenic aerosols reinforces the regional meridional overturning circulation, by enhancing convection over the SH and promoting widespread descent over the NH subtropics and mid-latitudes covering northern Africa, Mediterranean, parts of middle-East, West and South Asia. The present findings have important implications for the regional water resources, agriculture and environment.
ISSN:2752-5295
2752-5295
DOI:10.1088/2752-5295/ad6f3c