Weather in a Geo-Engineered Climate: Extratropical Cyclones and Monsoon Dynamics - Thesis

[Geoengineering News]

https://studenttheses.uu.nl/items/60422706-0fe9-472d-897e-7fd722f87d47

Authors: Nooij, Meike de

Abstract

This thesis investigates how extratropical cyclones (ETCs) and monsoon systems respond to stratospheric aerosol injection (SAI), using high-resolution CESM simulations under three scenarios: a reference, a high-emission, and an SAI scenario. We assess storm-track changes and ETC structure using Lagrangian cyclone tracking, Eulerian diagnostics, and extreme-event analyses. We analyse monsoon responses by assessing changes in onset and retreat, supported by regional moisture-budget analyses for three monsoon systems: the South Asian, West African, and Equatorial American Monsoon.

SAI produces asymmetric ETC responses: the North Atlantic storm track shifts poleward, while the North Pacific shifts equatorward. Cyclone intensity metrics show subtle, basin-dependent changes. Under CP8.5, ETC-associated winter precipitation increases by 7% in the Northern Hemisphere and 34% in the Southern Hemisphere. SAI overcompensates for these increases, producing decreases of 7% and 3%, respectively.

Monsoon responses to SAI are strongly region-specific, but the three regions all show

decreased precipitation. The South Asian monsoon increases in duration, while the West African monsoon shows a large spatial redistribution in duration. The Equatorial American monsoon shows reduced precipitation in both scenarios. Analysis of the moisture budget shows that RCP8.5-induced changes are largely thermodynamic, while SAI-induced changes are dynamic.

Overall, the results demonstrate that SAI does not simply reverse warming-induced changes but induces distinct circulation adjustments with regionally varying impacts.

Source: Utrecht University