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Title: Improved Representation of Surface Spectral Emissivity in a Global Climate Model and Its Impact on Simulated Climate

Abstract

Surface longwave emissivity can be less than unity and vary significantly with frequency. However, most climate models still assume a blackbody surface in the longwave (LW) radiation scheme of their atmosphere models. This paper incorporates realistic surface spectral emissivity into the atmospheric component of the Community Earth System Model (CESM), version 1.1.1, and evaluates its impact on simulated climate. By ensuring consistency of the broadband surface longwave flux across different components of the CESM, the top-of-the-atmosphere (TOA) energy balance in the modified model can be attained without retuning the model. Inclusion of surface spectral emissivity, however, leads to a decrease of net upward longwave flux at the surface and a comparable increase of latent heat flux. Global-mean surface temperature difference between the modified and standard CESM simulation is 0.20 K for the fully coupled run and 0.45 K for the slab-ocean run. Noticeable surface temperature differences between the modified and standard CESM simulations are seen over the Sahara Desert and polar regions. Accordingly, the climatological mean sea ice fraction in the modified CESM simulation can be less than that in the standard CESM simulation by as much as 0.1 in some regions. Finally, when spectral emissivities of sea ice andmore » open ocean surfaces are considered, the broadband LW sea ice emissivity feedback is estimated to be -0.003 W m -2 K -1, assuming flat ice emissivity as sea ice emissivity, and 0.002 W m -2 K -1, assuming coarse snow emissivity as sea ice emissivity, which are two orders of magnitude smaller than the surface albedo feedback.« less

Authors:
 [1];  [1];  [1];  [2];  [3];  [3]
  1. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Climate and Space Sciences and Engineering
  2. Texas A & M Univ., College Station, TX (United States). Dept. of Atmospheric Sciences
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Division of Climate and Ecosystem Sciences
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of Michigan, Ann Arbor, MI (United States); Texas A & M Univ., College Station, TX (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1464167
Alternate Identifier(s):
OSTI ID: 1432584
Grant/Contract Number:  
AC02-05CH11231; SC0012969; SC0013080
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Climate
Additional Journal Information:
Journal Volume: 31; Journal Issue: 9; Journal ID: ISSN 0894-8755
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; energy budget/balance; feedback; longwave radiation; radiative transfer; climate models; land surface model

Citation Formats

Huang, Xianglei, Chen, Xiuhong, Flanner, Mark, Yang, Ping, Feldman, Daniel, and Kuo, Chaincy. Improved Representation of Surface Spectral Emissivity in a Global Climate Model and Its Impact on Simulated Climate. United States: N. p., 2018. Web. doi:10.1175/JCLI-D-17-0125.1.
Huang, Xianglei, Chen, Xiuhong, Flanner, Mark, Yang, Ping, Feldman, Daniel, & Kuo, Chaincy. Improved Representation of Surface Spectral Emissivity in a Global Climate Model and Its Impact on Simulated Climate. United States. doi:10.1175/JCLI-D-17-0125.1.
Huang, Xianglei, Chen, Xiuhong, Flanner, Mark, Yang, Ping, Feldman, Daniel, and Kuo, Chaincy. Tue . "Improved Representation of Surface Spectral Emissivity in a Global Climate Model and Its Impact on Simulated Climate". United States. doi:10.1175/JCLI-D-17-0125.1.
@article{osti_1464167,
title = {Improved Representation of Surface Spectral Emissivity in a Global Climate Model and Its Impact on Simulated Climate},
author = {Huang, Xianglei and Chen, Xiuhong and Flanner, Mark and Yang, Ping and Feldman, Daniel and Kuo, Chaincy},
abstractNote = {Surface longwave emissivity can be less than unity and vary significantly with frequency. However, most climate models still assume a blackbody surface in the longwave (LW) radiation scheme of their atmosphere models. This paper incorporates realistic surface spectral emissivity into the atmospheric component of the Community Earth System Model (CESM), version 1.1.1, and evaluates its impact on simulated climate. By ensuring consistency of the broadband surface longwave flux across different components of the CESM, the top-of-the-atmosphere (TOA) energy balance in the modified model can be attained without retuning the model. Inclusion of surface spectral emissivity, however, leads to a decrease of net upward longwave flux at the surface and a comparable increase of latent heat flux. Global-mean surface temperature difference between the modified and standard CESM simulation is 0.20 K for the fully coupled run and 0.45 K for the slab-ocean run. Noticeable surface temperature differences between the modified and standard CESM simulations are seen over the Sahara Desert and polar regions. Accordingly, the climatological mean sea ice fraction in the modified CESM simulation can be less than that in the standard CESM simulation by as much as 0.1 in some regions. Finally, when spectral emissivities of sea ice and open ocean surfaces are considered, the broadband LW sea ice emissivity feedback is estimated to be -0.003 W m-2 K-1, assuming flat ice emissivity as sea ice emissivity, and 0.002 W m-2 K-1, assuming coarse snow emissivity as sea ice emissivity, which are two orders of magnitude smaller than the surface albedo feedback.},
doi = {10.1175/JCLI-D-17-0125.1},
journal = {Journal of Climate},
number = 9,
volume = 31,
place = {United States},
year = {Tue Apr 10 00:00:00 EDT 2018},
month = {Tue Apr 10 00:00:00 EDT 2018}
}

Journal Article:
Free Publicly Available Full Text
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