More biomass burning aerosol is being advected westward over the southern tropical Atlantic since 2003

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Authors

Tyler Tatro, Paquita Zuidema 

Abstract

Each year, agricultural fires in southern continental Africa emit approximately one third of the world’s biomass burning aerosol. This is advected westward by the prevailing circulation winds over a subtropical stratocumulus cloud deck. The radiative effects from the aerosol and aerosol-cloud interactions impact regional circulations and hydrology. Here we examine how concurrent changes in the burning season and regional climate in southern Africa over the past 18 years (2003-2020) impact the southeast Atlantic. We combine satellite-derived burned area datasets with ECMWF-reanalysis carbon monoxide, black carbon, and meteorology from the biomass burning season (May-October) in southern Africa. The burning season begins in May in woody savannas in the northwest and shifts to open savanna and grassland fires in the southeast, with small fires (less than 1 km2) contributing significantly to total burned area. In the most recent decade, more small fires are occurring in the middle of the biomass burning season and the overall season is shorter, corroborated by reanalysis carbon monoxide fields. Significantly increased free tropospheric winds, shifted southward, transport smoke aerosol further southwest over the southeast Atlantic. The increased aerosol advection is coupled with a southern shift in the south Atlantic subtropical high and an increase in the low cloud fraction on the southern edge of the stratocumulus cloud deck. While smoke emissions sources have not changed significantly, changes in the smoke transport pathway, attributed to increasing surface temperatures in southern Africa and tropical expansion, combined with an altered low cloud distribution, explain how the regional radiation balance has shifted to more top-of-atmosphere cooling over the southeast Atlantic in recent decades. 

DOI

https://doi.org/10.31223/X5PD95

Subjects

Atmospheric Sciences, Climate

Keywords

southern African easterly jet, tropical expansion, biomass burning, CAMS reanalysis

Dates

Published: 2024-07-26 09:37

Last Updated: 2024-11-04 21:24

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License

CC-BY Attribution-NonCommercial 4.0 International

Additional Metadata

Conflict of interest statement:
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data Availability (Reason not available):
All data used is feely available - links are listed under the Acknowledgements section (page 21)