Glassmeier, F, Hoffmann, F, Johnson, JS et al. (3 more authors) (2019) An emulator approach to stratocumulus susceptibility. Atmospheric Chemistry and Physics, 19 (15). pp. 10191-10203. ISSN 1680-7316
Abstract
The climatic relevance of aerosol–cloud interactions depends on the sensitivity of the radiative effect of clouds to cloud droplet number N, and liquid water path LWP. We derive the dependence of cloud fraction CF, cloud albedo AC, and the relative cloud radiative effect rCRE=CF⋅AC on N and LWP from 159 large-eddy simulations of nocturnal stratocumulus. These simulations vary in their initial conditions for temperature, moisture, boundary-layer height, and aerosol concentration but share boundary conditions for surface fluxes and subsidence. Our approach is based on Gaussian-process emulation, a statistical technique related to machine learning. We succeed in building emulators that accurately predict simulated values of CF, AC, and rCRE for given values of N and LWP. Emulator-derived susceptibilities ∂lnrCRE/∂lnN and ∂lnrCRE/∂lnLWP cover the nondrizzling, fully overcast regime as well as the drizzling regime with broken cloud cover. Theoretical results, which are limited to the nondrizzling regime, are reproduced. The susceptibility ∂lnrCRE/∂lnN captures the strong sensitivity of the cloud radiative effect to cloud fraction, while the susceptibility ∂lnrCRE/∂lnLWP describes the influence of cloud amount on cloud albedo irrespective of cloud fraction. Our emulation-based approach provides a powerful tool for summarizing complex data in a simple framework that captures the sensitivities of cloud-field properties over a wide range of states.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © Author(s) 2019. This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) (https://creativecommons.org/licenses/by/4.0/) |
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) |
Funding Information: | Funder Grant number NERC NE/I020059/1 Met Office P100199 |
Depositing User: | Symplectic Publications |
Date Deposited: | 14 Aug 2019 11:10 |
Last Modified: | 14 Aug 2019 11:10 |
Status: | Published |
Publisher: | European Geosciences Union |
Identification Number: | 10.5194/acp-19-10191-2019 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:149650 |