Rowell, DP, Fitzpatrick, RGJ, Jackson, LS orcid.org/0000-0001-8143-2777 et al. (1 more author) (2021) Understanding Intermodel Variability in Future Projections of a Sahelian Storm Proxy and Southern Saharan Warming. Journal of Climate, 34 (2). pp. 509-525. ISSN 0894-8755
Abstract
Projected changes in the intensity of severe rain events over the North African Sahel—falling from large mesoscale convective systems—cannot be directly assessed from global climate models due to their inadequate resolution and parameterization of convection. Instead, the large-scale atmospheric drivers of these storms must be analyzed. Here we study changes in meridional lower-tropospheric temperature gradient across the Sahel (ΔTGrad), which affect storm development via zonal vertical wind shear and Saharan air layer characteristics. Projected changes in ΔTGrad vary substantially among models, adversely affecting planning decisions that need to be resilient to adverse risks, such as increased flooding. This study seeks to understand the causes of these projection uncertainties and finds three key drivers. The first is intermodel variability in remote warming, which has strongest impact on the eastern Sahel, decaying toward the west. Second, and most important, a warming–advection–circulation feedback in a narrow band along the southern Sahara varies in strength between models. Third, variations in southern Saharan evaporative anomalies weakly affect ΔTGrad, although for an outlier model these are sufficiently substantive to reduce warming here to below that of the global mean. Together these uncertain mechanisms lead to uncertain southern Saharan/northern Sahelian warming, causing the bulk of large intermodel variations in ΔTGrad. In the southern Sahel, a local negative feedback limits the contribution to uncertainties in ΔTGrad. This new knowledge of ΔTGrad projection uncertainties provides understanding that can be used, in combination with further research, to constrain projections of severe Sahelian storm activity.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2020 American Meteorological Society. This is an open access article. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst for Climate & Atmos Science (ICAS) (Leeds) |
Funding Information: | Funder Grant number NERC (Natural Environment Research Council) NE/M017176/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 02 Feb 2021 15:03 |
Last Modified: | 02 Feb 2021 15:03 |
Status: | Published |
Publisher: | American Meteorological Society |
Identification Number: | 10.1175/jcli-d-20-0382.1 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:170660 |