High-latitude, low-altitude stratospheric aerosol injection reshapes West African monsoon rainfall and associated dynamics - Preprint

[Geoengineering News]

https://www.researchsquare.com/article/rs-9315964/v1

Authors: Kwesi Twentwewa Quagraine, Kwesi Akumenyi Quagraine, Emmanuel Akalanyabah, Francis Nkrumah, Nana Ama Browne Klutse

22 April 2026

Abstract

Stratospheric aerosol injection (SAI) is proposed as a near-term intervention to offset warming, yet its regional impacts remain uncertain. We assess the response of the West African Monsoon (WAM) to high-latitude, low-altitude SAI (HiLLA-SAI) using WACCM6 and UKESM1 simulations. Both models reproduce the seasonal cycle but exhibit systematic biases in rainfall magnitude and extremes. Under SAI, precipitation responses are spatially heterogeneous, with the largest anomalies in July–August. WACCM6 projects widespread wet biases extending inland from the Guinea Coast, whereas UKESM1 produces weaker and more heterogeneous responses, including drying over the Guinea Highlands and Nigeria. Both models show reduced wet spell persistence along the coast and increased dry spell duration over the Sahel. Dynamically, SAI reduces the meridional temperature gradient and shifts the African Easterly Jet southward, consistent with a reduced northward extent of the rain belt. However, responses differ markedly across models, indicating strong model dependence and heterogeneous responses of SAI to WAM conditions.

Source: ResearchSquare