McCoy, DT orcid.org/0000-0003-1148-6475, Bender, FA-M, Mohrmann, JKC et al. (3 more authors) (2017) The global aerosol-cloud first indirect effect estimated using MODIS, MERRA, and AeroCom. Journal of Geophysical Research: Atmospheres, 122 (3). pp. 1779-1796. ISSN 2169-897X
Abstract
Aerosol-cloud interactions (ACI) represent a significant source of forcing uncertainty in global climate models (GCMs). Estimates of radiative forcing due to ACI in Fifth Assessment Report range from −0.5 to −2.5 W m−2. A portion of this uncertainty is related to the first indirect, or Twomey, effect whereby aerosols act as nuclei for cloud droplets to condense upon. At constant liquid water content this increases the number of cloud droplets (Nd) and thus increases the cloud albedo. In this study we use remote-sensing estimates of Nd within stratocumulus regions in combination with state-of-the-art aerosol reanalysis from Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA2) to diagnose how aerosols affect Nd. As in previous studies, Nd is related to sulfate mass through a power law relationship. The slope of the log-log relationship between Nd and SO4 in maritime stratocumulus is found to be 0.31, which is similar to the range of 0.2–0.8 from previous in situ studies and remote-sensing studies in the pristine Southern Ocean. Using preindustrial emissions models, the change in Nd between preindustrial and present day is estimated. Nd is inferred to have more than tripled in some regions. Cloud properties from Moderate Resolution Imaging Spectroradiometer (MODIS) are used to estimate the radiative forcing due to this change in Nd. The Twomey effect operating in isolation is estimated to create a radiative forcing of −0.97 ± 0.23 W m−2 relative to the preindustrial era.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2017. American Geophysical Union. All Rights Reserved. Reproduced in accordance with the publisher's self-archiving policy. |
Keywords: | microphysics; aerosol; cloud; climate |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst for Climate & Atmos Science (ICAS) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 04 Apr 2017 12:15 |
Last Modified: | 25 Jul 2017 00:38 |
Published Version: | https://doi.org/10.1002/2016JD026141 |
Status: | Published |
Publisher: | American Geophysical Union |
Identification Number: | 10.1002/2016JD026141 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:114472 |