Sensitivities of cloud radiative effects to large-scale meteorology and aerosols from global observations

Andersen, Hendrik, Cermak, Jan, Douglas, Alyson, Myers, Timothy A., Nowack, Peer ORCID:, Stier, Philip, Wall, Casey J. and Wilson Kemsley, Sarah (2023) Sensitivities of cloud radiative effects to large-scale meteorology and aerosols from global observations. Atmospheric Chemistry and Physics, 23 (18). 10775–10794. ISSN 1680-7324

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The radiative effects of clouds make a large contribution to the Earth's energy balance, and changes in clouds constitute the dominant source of uncertainty in the global warming response to carbon dioxide forcing. To characterize and constrain this uncertainty, cloud-controlling factor (CCF) analyses have been suggested that estimate sensitivities of clouds to large-scale environmental changes, typically in cloud-regime-specific multiple linear regression frameworks. Here, local sensitivities of cloud radiative effects to a large number of controlling factors are estimated in a regime-independent framework from 20 years (2001-2020) of near-global (60° N-60° S) satellite observations and reanalysis data using statistical learning. A regularized linear regression (ridge regression) is shown to skillfully predict anomalies of shortwave (R2Combining double low line0.63) and longwave cloud radiative effects (CREs) (R2Combining double low line0.72) in independent test data on the basis of 28 CCFs, including aerosol proxies. The sensitivity of CREs to selected CCFs is quantified and analyzed. CRE sensitivities to sea surface temperature and estimated inversion strength are particularly pronounced in low-cloud regions and generally in agreement with previous studies. The analysis of CRE sensitivities to three-dimensional wind field anomalies reflects the fact that CREs in tropical ascent regions are mainly driven by variability of large-scale vertical velocity in the upper troposphere. In the subtropics, CRE is sensitive to free-tropospheric zonal and meridional wind anomalies, which are likely to encapsulate information on synoptic variability that influences subtropical cloud systems by modifying wind shear and thus turbulence and dry-air entrainment in stratocumulus clouds, as well as variability related to midlatitude cyclones. Different proxies for aerosols are analyzed as CCFs, with satellite-derived aerosol proxies showing a larger CRE sensitivity than a proxy from an aerosol reanalysis, likely pointing to satellite aerosol retrieval biases close to clouds, leading to overestimated aerosol sensitivities. Sensitivities of shortwave CREs to all aerosol proxies indicate a pronounced cooling effect from aerosols in stratocumulus regions that is counteracted to a varying degree by a longwave warming effect. The analysis may guide the selection of CCFs in future sensitivity analyses aimed at constraining cloud feedback and climate forcings from aerosol-cloud interactions using data from both observations and global climate models.

Item Type: Article
Additional Information: Funding information: HA and JC have received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement no. 821205 (FORCeS) and the Deutsche Forschungsgemeinschaft (DFG) in the project Constraining Aerosol-Low cloud InteractionS with multi-target MAchine learning (CALISMA), project number 440521482. PS was supported by the European Research Council project RECAP under the European Union’s Horizon 2020 research and innovation programme (grant no. 724602) and by the FORCeS 5 project under the European Union’s Horizon 2020 research programme with grant agreement no. 821205. PN and SWK were supported through the UK Natural Environment Research Council (NERC) grant number NE/V012045/1. CJW received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101019911. T.A.M. was supported by the NOAA Cooperative Agreements with CIRES, NA17OAR4320101 and NA22OAR4320151, and by the NOAA/ESRL Atmospheric Science for Renewable Energy program.
Uncontrolled Keywords: atmospheric science,sdg 13 - climate action ,/dk/atira/pure/subjectarea/asjc/1900/1902
Faculty \ School: Faculty of Science > School of Environmental Sciences
University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups: Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Faculty of Science > Research Groups > Climatic Research Unit
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Depositing User: LivePure Connector
Date Deposited: 30 Aug 2023 12:30
Last Modified: 19 Oct 2023 03:38
DOI: 10.5194/acp-23-10775-2023


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