Anthropogenic Aerosols Modulated 20th‐Century Sahel Rainfall Variability Via Their Impacts on North Atlantic Sea Surface Temperature

The Sahel rainfall has a close teleconnection with North Atlantic sea surface temperature (NASST) variability, which has separately been shown to be affected by aerosols. Therefore, changes in regional aerosols emission could potentially drive multidecadal Sahel rainfall variability. Here we combine...

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Vydáno v:	Geophysical research letters Ročník 49; číslo 1; s. e2021GL095629 - n/a
Hlavní autoři:	Zhang, Shipeng, Stier, Philip, Dagan, Guy, Wang, Minghuai
Médium:	Journal Article
Jazyk:	angličtina
Vydáno:	Washington John Wiley & Sons, Inc 16.01.2022 John Wiley and Sons Inc
Témata:	20th century Abrupt/Rapid Climate Change Aerosol effects Aerosols Aerosols and Particles aerosol‐cloud‐interactions African monsoon Air/Sea Constituent Fluxes Air/Sea Interactions Anthropogenic factors Atmosphere Atmospheric Atmospheric Composition and Structure Atmospheric Effects Atmospheric Processes Atmospheric Science Avalanches Benefit‐cost Analysis Biogeosciences Biosphere/Atmosphere Interactions Climate Climate and Interannual Variability Climate Change and Variability Climate Dynamics Climate Impact Climate Impacts Climate models Climate Variability Climatology Clouds Computational Geophysics Cryosphere Datasets Decadal Ocean Variability Disaster Risk Analysis and Assessment Earth System Modeling Earthquake Ground Motions and Engineering Seismology Effusive Volcanism Emissions Evolution of the Atmosphere Evolution of the Earth Explosive Volcanism Fluxes General Circulation Geodesy and Gravity Geological Global Change Global Change from Geodesy Global climate Global climate models Gravity and Isostasy Human influences Hydrological Cycles and Budgets Hydrology Impacts of Global Change Informatics Land/Atmosphere Interactions Marine Geology and Geophysics Marine Pollution Mass Balance Megacities and Urban Environment Modeling Monsoon rainfall Mud Volcanism Natural Hazards North Atlantic variability Numerical Modeling Numerical Solutions Ocean influence of Earth rotation Ocean models Ocean Monitoring with Geodetic Techniques Ocean/Atmosphere Interactions Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions Oceanic Oceanography: Biological and Chemical Oceanography: General Oceanography: Physical Oceans Paleoceanography Physical Modeling Policy Sciences Pollution: Urban and Regional Pollution: Urban, Regional and Global Precipitation Process management Radiation Radiation-cloud interactions Radio Oceanography Radio Science Rain Rainfall Rainfall simulators Rainfall variability Regional Climate Change Regional Modeling Research Letter Risk Sahel rainfall Sea Level Change Sea Level: Variations and Mean Sea surface Sea surface temperature Sea surface temperature variability Seismology Simulation Solid Earth Sulfates Surface fluxes Surface temperature Surface Waves and Tides Tectonophysics Temperature variability Theoretical Modeling Tsunamis and Storm Surges Urban Systems Variability Volcanic Effects Volcanic Hazards and Risks Volcano Monitoring Volcano Seismology Volcano/Climate Interactions Volcanology Water Cycles
ISSN:	0094-8276, 1944-8007
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Popis
Shrnutí:	The Sahel rainfall has a close teleconnection with North Atlantic sea surface temperature (NASST) variability, which has separately been shown to be affected by aerosols. Therefore, changes in regional aerosols emission could potentially drive multidecadal Sahel rainfall variability. Here we combine ensembles of state‐of‐the‐art global climate models (the CESM and CanESM large ensemble simulations and CMIP6 models) with observational data sets to demonstrate that anthropogenic aerosols have significantly impacted 20th‐century detrended Sahel rainfall multidecadal variability through modifying NASST. We show that aerosol‐induced multidecadal variations of downward solar radiative fluxes over the North Atlantic cause NASST variability during the 20th century, altering the ITCZ position and dynamically linking aerosol effects to Sahel rainfall variability. This process chain is caused by aerosol‐induced changes in radiative surface fluxes rather than changes in ocean circulations. CMIP6 models further suggest that aerosol‐cloud interactions modulate the inter‐model uncertainty of simulated NASST and potentially the Sahel rainfall variability. Plain Language Summary Sahel rainfall experienced significant multidecadal variability over the 20th century, with large societal implications. However, the drivers of this variability remain debated. Here we show that anthropogenic aerosols largely contributed to the Sahel rainfall variability. We propose a process chain, from changing sulfate emissions from Europe and North America, to changes in North Atlantic surface net radiative fluxes, via North Atlantic sea surface temperature variability to a shift of ITCZ and changes in West African monsoon, and finally Sahel rainfall variability. This process chain is consistently evidenced by ensembles of state‐of‐the‐art global climate models as well as observational data sets. We show that aerosol‐radiation interactions and aerosol‐cloud interactions are both important processes in this chain. These findings highlight the importance of accurate representation of regional aerosol‐cloud‐radiation interactions for the simulation of Sahel rainfall variability. Key Points A process chain from anthropogenic aerosol emissions to the Sahel rainfall is proposed Large ensemble and CMIP6 simulations suggest that this link is mediated by aerosol impacts on North Atlantic SST Both aerosol‐cloud interactions and aerosol‐radiation interactions are important in this chain process
Bibliografie:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 content type line 23
ISSN:	0094-8276 1944-8007
DOI:	10.1029/2021GL095629