Reduced surface fine dust under droughts over the southeastern United States during summertime: observations and CMIP6 model simulations
<p>Drought is an extreme hydroclimate event that has been shown to cause an increase in surface fine dust near source regions, yet the drought–dust relationship in regions predominantly influenced by long-range-transported dust such as the southeastern USA (SEUS) has received less attention. U...
Main Authors: | , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2022-06-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://acp.copernicus.org/articles/22/7843/2022/acp-22-7843-2022.pdf |
Summary: | <p>Drought is an extreme hydroclimate event that has been
shown to cause an increase in surface fine dust near source regions, yet
the drought–dust relationship in regions predominantly influenced by
long-range-transported dust such as the southeastern USA (SEUS) has received
less attention. Using long-term surface fine-dust observations, the weekly US
Drought Monitor (USDM), and the monthly standardized
precipitation–evapotranspiration index (SPEI), this study unmasks spatial
disparity in drought–dust relationships in the contiguous USA (CONUS) where
the SEUS shows a decrease in surface dust concentrations during drought in
contrast to the expected increase in dust found in other CONUS regions.
Surface fine dust was found to decrease by <span class="inline-formula">∼</span> 0.23 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span> with a unit decrease in SPEI in the SEUS, as opposed to an
increase of <span class="inline-formula">∼</span> 0.12 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span> in the west. The
anomalies of dust elemental ratios, satellite aerosol optical depth (AOD),
and dust extinction coefficients suggest that both the emissions and
trans-Atlantic transport of African dust are weakened when the SEUS is under
droughts. Through the teleconnection patterns of the negative North Atlantic
Oscillation (NAO), a lower-than-normal and more northeastward displacement
of the Bermuda High (BH) is present during SEUS droughts, which results in
less dust being transported into the SEUS. At the same time, enhanced
precipitation in the Sahel associated with the northward shift of the
Intertropical Convergence Zone (ITCZ) leads to lower dust emissions therein.
Of the 10 selected models participating in the sixth phase of the Coupled
Model Intercomparison Project (CMIP6), GISS-E2-1-G was found to perform the
best in capturing the drought–dust sensitivity in the SEUS. This study
reveals the mechanism of how droughts influence aerosol abundance through
changing long-range transport of dust.</p> |
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ISSN: | 1680-7316 1680-7324 |