Sansom, R.W.N. orcid.org/0000-0001-6020-2884, Carslaw, K.S. orcid.org/0000-0002-6800-154X, Johnson, J.S. et al. (1 more author) (2024) An Emulator of Stratocumulus Cloud Response to Two Cloud‐Controlling Factors Accounting for Internal Variability. Journal of Advances in Modeling Earth Systems, 16 (9). e2023MS004179. ISSN 1942-2466
Abstract
Large uncertainties persist in modeling shallow, low clouds because of many interacting nonlinear processes and multiple cloud‐controlling environmental factors. In addition, sharp changes in behavior occur when environmental thresholds are met. Model studies that follow a traditional approach of exploring the effects of factors “one‐at‐a‐time” are unable to capture interactions between factors. We simulate a stratocumulus cloud based on the Second Dynamics and Chemistry of Marine Stratocumulus field study using a large‐eddy simulation model coupled with a two‐moment cloud microphysics scheme. The simulations are used to train a Gaussian process emulator, which we then use to visualize the relationships between two cloud‐controlling factors and domain‐averaged cloud properties. Only 29 model simulations were required to train the emulators, which then predicted cloud properties at thousands of new combinations of the two factors. Emulator response surfaces of cloud liquid water path and cloud fraction show two behavioral regimes, one of thin and patchy yet steady stratocumulus and one of thick, growing stratocumulus with cloud fraction near 1. Internal variability (initial‐condition uncertainty) creates unrealistic “bumpy” response surfaces. However, we show that the variability causing the bumpiness can be characterized in an emulator “nugget term” that is adjusted to match the distribution of a small number of initial‐condition ensemble simulations at various points on the surface, thereby allowing a smoother, deterministic response surface to be constructed. Accounting for variability allows the transition between regimes, and the joint interactions of parameters, to be visualized in a more deterministic way that has not been done before.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2024 The Author(s). Journal of Advances in Modeling Earth Systems published by Wiley Periodicals LLC on behalf of American Geophysical Union. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
Keywords: | Gaussian process emulation; stratocumulus clouds; natural variability; large-eddy simulation; cloud process understanding; emulator response surfaces |
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 (Natural Environment Research Council) NE/P016421/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 05 Sep 2024 09:47 |
Last Modified: | 05 Sep 2024 09:47 |
Status: | Published |
Publisher: | American Geophysical Union |
Identification Number: | 10.1029/2023ms004179 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:216652 |