Including two missing physics for a more realistic representation of 
cloud-surface longwave radiative coupling in the earth system model

Fan, Chongxing; Chen, Yi-Hsuan; Chen, Xiuhong; Lin, Wuyin; Huang, Xianglei; Yang, Ping

doi:10.57757/IUGG23-0192

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Including two missing physics for a more realistic representation of cloud-surface longwave radiative coupling in the earth system model

Authors

Fan, Chongxing
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Chen, Yi-Hsuan
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Chen, Xiuhong
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Lin, Wuyin
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Huang, Xianglei
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Yang, Ping
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

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Citation

Fan, C., Chen, Y.-H., Chen, X., Lin, W., Huang, X., Yang, P. (2023): Including two missing physics for a more realistic representation of cloud-surface longwave radiative coupling in the earth system model, XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) (Berlin 2023).
https://doi.org/10.57757/IUGG23-0192

Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5016293

Abstract

Climate models often ignore cloud scattering and surface emissivity in the longwave (LW) for computational efficiency. Such approximations can cause biases in radiative fluxes and affect simulated climate, especially in the Arctic. We implemented treatments to both physics into the DoE Energy Exascale Earth System Model (E3SM) version 2 and assessed their impacts on the simulated mean-state global climate as well as climate sensitivity. By turning on and off the switches in the modified E3SMv2 model, we studied the changes in mean-state climate due to cloud LW scattering and surface emissivity effects. Cloud LW scattering warms the entire global troposphere by ~0.4 K on average; the warming is stronger in the Arctic (~0.8 K) than in the tropics due to the Arctic amplification phenomenon. When realistic emissivity is incorporated into the model, the surface skin temperature increases by 0.36 K instantaneously on a global average. Surface skin temperature, as well as surface air temperature and tropospheric temperature, further increases by 0.19 K due to the inclusion of surface spectral emissivity. The mean-state climate changes due to both effects are linearly additive. We carried out simulations under the abrupt 4xCO2 scenario and found that total global-mean climate feedback does not change significantly after including either or both physics. Nevertheless, radiative feedbacks in the tropics can change up to 10%. Our study suggests that both processes should be included for a faithful representation of the LW radiative coupling between surface and cloud.