Preprints
https://doi.org/10.5194/egusphere-2023-1436
https://doi.org/10.5194/egusphere-2023-1436
29 Jun 2023
 | 29 Jun 2023

Global Observations of Aerosol Indirect Effects from Marine Liquid Clouds

Casey James Wall, Trude Storelvmo, and Anna Possner

Abstract. Interactions between aerosols and liquid clouds are one of the largest sources of uncertainty in the historical radiative forcing of climate. One widely shared goal to reduce this uncertainty is to decompose radiative anomalies arising from aerosol-cloud interactions into components associated with changes in cloud-droplet number concentration (Twomey effect), liquid water path adjustments, and cloud-fraction adjustments. However, there has not been a quantitative foundation for simultaneously estimating these components with global satellite observations. Here we present a method for assessing shortwave radiative flux anomalies from the Twomey effect and cloud adjustments over ocean between 55° S and 55° N. We find that larger aerosol concentrations are associated with widespread cloud brightening from the Twomey effect, a positive radiative adjustment from decreasing liquid water path in subtropical stratocumulus regions, and a negative radiative adjustment from increasing cloud fraction in the subtropics and midlatitudes. The Twomey effect and total cloud adjustment contribute -0.77±0.25 W m-2 and -1.02±0.43 W m-2, respectively, to the effective radiative forcing since 1850 over the domain (95 % confidence). Our findings reduce uncertainty in these components of aerosol forcing and suggest that cloud adjustments make a larger contribution to the forcing than is commonly believed.

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Journal article(s) based on this preprint

18 Oct 2023
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Global observations of aerosol indirect effects from marine liquid clouds
Casey J. Wall, Trude Storelvmo, and Anna Possner
Atmos. Chem. Phys., 23, 13125–13141, https://doi.org/10.5194/acp-23-13125-2023,https://doi.org/10.5194/acp-23-13125-2023, 2023
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One of the largest sources of uncertainty in the overall anthropogenic forcing of climate is...
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We use satellite data to investigate how aerosol particles affect the radiative properties of...
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