Improvement of the Simulation of Cloud Longwave Scattering in Broadband Radiative Transfer Models
Abstract
Abstract Cloud longwave scattering is generally neglected in general circulation models (GCMs), but it plays a significant and highly uncertain role in the atmospheric energy budget as demonstrated in recent studies. To reduce the errors caused by neglecting cloud longwave scattering, two new radiance adjustment methods are developed that retain the computational efficiency of broadband radiative transfer simulations. In particular, two existing scaling methods and the two new adjustment methods are implemented in the Rapid Radiative Transfer Model (RRTM). The results are then compared with those based on the Discrete Ordinate Radiative Transfer model (DISORT) that explicitly accounts for multiple scattering by clouds. The two scaling methods are shown to improve the accuracy of radiative transfer simulations for optically thin clouds but not effectively for optically thick clouds. However, the adjustment methods reduce computational errors over a wide range, from optically thin to thick clouds. With the adjustment methods, the errors resulting from neglecting cloud longwave scattering are reduced to less than 2 W m−2 for the upward irradiance at the top of the atmosphere and less than 0.5 W m−2 for the surface downward irradiance. The adjustment schemes prove to be more accurate and efficient than a four-stream approximationmore »
- Authors:
-
- Department of Atmospheric Sciences, Texas A&M University, College Station, Texas
- Department of Physics and Astronomy, Texas A&M University, College Station, Texas, Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas
- Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, Michigan
- Atmospheric and Environmental Research, Inc., Cambridge, Massachusetts
- Space Science and Engineering Center, University of Wisconsin–Madison, Madison, Wisconsin
- Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, Colorado, Department of Atmospheric Sciences, Texas A&M University, College Station, Texas
- Publication Date:
- Research Org.:
- Univ. of Michigan, Ann Arbor, MI (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Biological and Environmental Research (BER)
- OSTI Identifier:
- 1454654
- Alternate Identifier(s):
- OSTI ID: 1541833
- Grant/Contract Number:
- SC0012969
- Resource Type:
- Published Article
- Journal Name:
- Journal of the Atmospheric Sciences
- Additional Journal Information:
- Journal Name: Journal of the Atmospheric Sciences Journal Volume: 75 Journal Issue: 7; Journal ID: ISSN 0022-4928
- Publisher:
- American Meteorological Society
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 54 ENVIRONMENTAL SCIENCES; Meteorology & Atmospheric Sciences
Citation Formats
Tang, Guanglin, Yang, Ping, Kattawar, George W., Huang, Xianglei, Mlawer, Eli J., Baum, Bryan A., and King, Michael D. Improvement of the Simulation of Cloud Longwave Scattering in Broadband Radiative Transfer Models. United States: N. p., 2018.
Web. doi:10.1175/JAS-D-18-0014.1.
Tang, Guanglin, Yang, Ping, Kattawar, George W., Huang, Xianglei, Mlawer, Eli J., Baum, Bryan A., & King, Michael D. Improvement of the Simulation of Cloud Longwave Scattering in Broadband Radiative Transfer Models. United States. https://doi.org/10.1175/JAS-D-18-0014.1
Tang, Guanglin, Yang, Ping, Kattawar, George W., Huang, Xianglei, Mlawer, Eli J., Baum, Bryan A., and King, Michael D. Mon .
"Improvement of the Simulation of Cloud Longwave Scattering in Broadband Radiative Transfer Models". United States. https://doi.org/10.1175/JAS-D-18-0014.1.
@article{osti_1454654,
title = {Improvement of the Simulation of Cloud Longwave Scattering in Broadband Radiative Transfer Models},
author = {Tang, Guanglin and Yang, Ping and Kattawar, George W. and Huang, Xianglei and Mlawer, Eli J. and Baum, Bryan A. and King, Michael D.},
abstractNote = {Abstract Cloud longwave scattering is generally neglected in general circulation models (GCMs), but it plays a significant and highly uncertain role in the atmospheric energy budget as demonstrated in recent studies. To reduce the errors caused by neglecting cloud longwave scattering, two new radiance adjustment methods are developed that retain the computational efficiency of broadband radiative transfer simulations. In particular, two existing scaling methods and the two new adjustment methods are implemented in the Rapid Radiative Transfer Model (RRTM). The results are then compared with those based on the Discrete Ordinate Radiative Transfer model (DISORT) that explicitly accounts for multiple scattering by clouds. The two scaling methods are shown to improve the accuracy of radiative transfer simulations for optically thin clouds but not effectively for optically thick clouds. However, the adjustment methods reduce computational errors over a wide range, from optically thin to thick clouds. With the adjustment methods, the errors resulting from neglecting cloud longwave scattering are reduced to less than 2 W m−2 for the upward irradiance at the top of the atmosphere and less than 0.5 W m−2 for the surface downward irradiance. The adjustment schemes prove to be more accurate and efficient than a four-stream approximation that explicitly accounts for multiple scattering. The neglect of cloud longwave scattering results in an underestimate of the surface downward irradiance (cooling effect), but the errors are almost eliminated by the adjustment methods (warming effect).},
doi = {10.1175/JAS-D-18-0014.1},
journal = {Journal of the Atmospheric Sciences},
number = 7,
volume = 75,
place = {United States},
year = {Mon Jun 18 00:00:00 EDT 2018},
month = {Mon Jun 18 00:00:00 EDT 2018}
}
https://doi.org/10.1175/JAS-D-18-0014.1
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