A La Niñaâ Like Climate Response to South African Biomass Burning Aerosol in CESM Simulations

The climate response to atmospheric aerosols, including their effects on dominant modes of climate variability like El Niñoâ Southern Oscillation (ENSO), remains highly uncertain. This is due to several sources of uncertainty, including aerosol emission, transport, removal, vertical distribution, a...

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Bibliographic Details
Published in:Medical Council
Main Authors: Amiri‐farahani, Anahita, Allen, Robert J., Li, King‐fai, Nabat, Pierre, Westervelt, Daniel M.
Format: Article in Journal/Newspaper
Language:unknown
Published: Cambridge University Press 2020
Subjects:
teleconnection
Africa
La Nina
climate model
aerosol
biomass
Atmospheric and Oceanic Sciences
Science
Pacific
Arctic
Online Access:https://hdl.handle.net/2027.42/154503
https://doi.org/10.1029/2019JD031832
Description
Summary:The climate response to atmospheric aerosols, including their effects on dominant modes of climate variability like El Niñoâ Southern Oscillation (ENSO), remains highly uncertain. This is due to several sources of uncertainty, including aerosol emission, transport, removal, vertical distribution, and radiative properties. Here, we conduct coupled oceanâ atmosphere simulations with two versions of the Community Earth System Model (CESM) driven by semiempirical fineâ mode aerosol direct radiative effects without dust and sea salt. Aerosol atmospheric heating off the west coast of Africaâ most of which is due to biomass burningâ leads to a significant atmospheric dynamical response, including localized ascent and upperâ level divergence. Coupled Model Intercomparison Project version 6 (CMIP6) biomass burning simulations support this response. Moreover, CESM shows that the anomalous aerosol heating in the Atlantic triggers an atmospheric teleconnection to the tropical Pacific, including strengthening of the Walker circulation. The easterly trade winds accelerate, and through coupled oceanâ atmosphere processes and the Bjerknes feedback, a La Niñaâ like response develops. Observations also support a relationship between south African biomass burning emissions and ENSO, with La Niña events preceding strong south African biomass burning in boreal fall. Our simulations suggest a possible twoâ way feedback between ENSO and south African biomass burning, with La Niña promoting more biomass burning emissions, which may then strengthen the developing La Niña.Key PointsSouth African biomass burning aerosol locally warms the atmosphereThis heating drives local ascent and divergence, triggering a teleconnection to the PacificThe Pacific Walker circulation strengthens, and a La Niñaâ like response develops Peer Reviewed https://deepblue.lib.umich.edu/bitstream/2027.42/154503/1/jgrd56111_am.pdf https://deepblue.lib.umich.edu/bitstream/2027.42/154503/2/jgrd56111-sup-0001-Figure_SI-S01.pdf ...

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