An emulator approach to stratocumulus susceptibility

Franziska Glassmeier*, Fabian Hoffmann, Jill S. Johnson, Takanobu Yamaguchi, Ken S. Carslaw, Graham Feingold

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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 D 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.

Original languageEnglish
Pages (from-to)10191-10203
Number of pages13
JournalAtmospheric Chemistry and Physics
Volume19
Issue number15
DOIs
Publication statusPublished - 13 Aug 2019

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stratocumulus
albedo
volcanic cloud
cloud droplet
large eddy simulation
surface flux
cloud cover
subsidence
boundary condition
boundary layer
moisture
aerosol
liquid

Cite this

Glassmeier, F., Hoffmann, F., Johnson, J. S., Yamaguchi, T., Carslaw, K. S., & Feingold, G. (2019). An emulator approach to stratocumulus susceptibility. Atmospheric Chemistry and Physics, 19(15), 10191-10203. https://doi.org/10.5194/acp-19-10191-2019
Glassmeier, Franziska ; Hoffmann, Fabian ; Johnson, Jill S. ; Yamaguchi, Takanobu ; Carslaw, Ken S. ; Feingold, Graham. / An emulator approach to stratocumulus susceptibility. In: Atmospheric Chemistry and Physics. 2019 ; Vol. 19, No. 15. pp. 10191-10203.
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Glassmeier, F, Hoffmann, F, Johnson, JS, Yamaguchi, T, Carslaw, KS & Feingold, G 2019, 'An emulator approach to stratocumulus susceptibility', Atmospheric Chemistry and Physics, vol. 19, no. 15, pp. 10191-10203. https://doi.org/10.5194/acp-19-10191-2019

An emulator approach to stratocumulus susceptibility. / Glassmeier, Franziska; Hoffmann, Fabian; Johnson, Jill S.; Yamaguchi, Takanobu; Carslaw, Ken S.; Feingold, Graham.

In: Atmospheric Chemistry and Physics, Vol. 19, No. 15, 13.08.2019, p. 10191-10203.

Research output: Contribution to journalArticleAcademicpeer-review

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T1 - An emulator approach to stratocumulus susceptibility

AU - Glassmeier, Franziska

AU - Hoffmann, Fabian

AU - Johnson, Jill S.

AU - Yamaguchi, Takanobu

AU - Carslaw, Ken S.

AU - Feingold, Graham

PY - 2019/8/13

Y1 - 2019/8/13

N2 - 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 D 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.

AB - 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 D 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.

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DO - 10.5194/acp-19-10191-2019

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VL - 19

SP - 10191

EP - 10203

JO - Atmospheric Chemistry and Physics

JF - Atmospheric Chemistry and Physics

SN - 1680-7316

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ER -

Glassmeier F, Hoffmann F, Johnson JS, Yamaguchi T, Carslaw KS, Feingold G. An emulator approach to stratocumulus susceptibility. Atmospheric Chemistry and Physics. 2019 Aug 13;19(15):10191-10203. https://doi.org/10.5194/acp-19-10191-2019