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Title: A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5

Solar-J is a comprehensive radiative transfer model for the solar spectrum that addresses the needs of both solar heating and photochemistry in Earth system models. Solar-J is a spectral extension of Cloud-J, a standard in many chemical models that calculates photolysis rates in the 0.18–0.8 µm region. The Cloud-J core consists of an eight-stream scattering, plane-parallel radiative transfer solver with corrections for sphericity. Cloud-J uses cloud quadrature to accurately average over correlated cloud layers. It uses the scattering phase function of aerosols and clouds expanded to eighth order and thus avoids isotropic-equivalent approximations prevalent in most solar heating codes. The spectral extension from 0.8 to 12 µm enables calculation of both scattered and absorbed sunlight and thus aerosol direct radiative effects and heating rates throughout the Earth's atmosphere. Furthermore, the Solar-J extension adopts the correlated-k gas absorption bins, primarily water vapor, from the shortwave Rapid Radiative Transfer Model for general circulation model (GCM) applications (RRTMG-SW). Solar-J successfully matches RRTMG-SW's tropospheric heating profile in a clear-sky, aerosol-free, tropical atmosphere. Here, we compare both codes in cloudy atmospheres with a liquid-water stratus cloud and an ice-crystal cirrus cloud. For the stratus cloud, both models use the same physical properties, and we findmore » a systematic low bias of about 3 % in planetary albedo across all solar zenith angles caused by RRTMG-SW's two-stream scattering. Discrepancies with the cirrus cloud using any of RRTMG-SW's three different parameterizations are as large as about 20–40 % depending on the solar zenith angles and occur throughout the atmosphere. Effectively, Solar-J has combined the best components of RRTMG-SW and Cloud-J to build a high-fidelity module for the scattering and absorption of sunlight in the Earth's atmosphere, for which the three major components – wavelength integration, scattering, and averaging over cloud fields – all have comparably small errors. More accurate solutions with Solar-J come with increased computational costs, about 5 times that of RRTMG-SW for a single atmosphere. There are options for reduced costs or computational acceleration that would bring costs down while maintaining improved fidelity and balanced errors.« less
Authors:
ORCiD logo [1] ; ORCiD logo [1] ;  [2] ;  [3] ;  [3]
  1. Univ. of California, Irvine, CA (United States). Dept. of Earth System Science
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Univ. of California, Irvine, CA (United States). Dept. of Computer Science
Publication Date:
Report Number(s):
LLNL-JRNL-732404
Journal ID: ISSN 1991-9603
Grant/Contract Number:
AC52-07NA27344; SC0007021; SC0012536; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Geoscientific Model Development (Online)
Additional Journal Information:
Journal Name: Geoscientific Model Development (Online); Journal Volume: 10; Journal Issue: 7; Journal ID: ISSN 1991-9603
Publisher:
European Geosciences Union
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 97 MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; 54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1374519

Hsu, Juno, Prather, Michael J., Cameron-Smith, Philip, Veidenbaum, Alex, and Nicolau, Alex. A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5. United States: N. p., Web. doi:10.5194/gmd-10-2525-2017.
Hsu, Juno, Prather, Michael J., Cameron-Smith, Philip, Veidenbaum, Alex, & Nicolau, Alex. A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5. United States. doi:10.5194/gmd-10-2525-2017.
Hsu, Juno, Prather, Michael J., Cameron-Smith, Philip, Veidenbaum, Alex, and Nicolau, Alex. 2017. "A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5". United States. doi:10.5194/gmd-10-2525-2017. https://www.osti.gov/servlets/purl/1374519.
@article{osti_1374519,
title = {A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5},
author = {Hsu, Juno and Prather, Michael J. and Cameron-Smith, Philip and Veidenbaum, Alex and Nicolau, Alex},
abstractNote = {Solar-J is a comprehensive radiative transfer model for the solar spectrum that addresses the needs of both solar heating and photochemistry in Earth system models. Solar-J is a spectral extension of Cloud-J, a standard in many chemical models that calculates photolysis rates in the 0.18–0.8 µm region. The Cloud-J core consists of an eight-stream scattering, plane-parallel radiative transfer solver with corrections for sphericity. Cloud-J uses cloud quadrature to accurately average over correlated cloud layers. It uses the scattering phase function of aerosols and clouds expanded to eighth order and thus avoids isotropic-equivalent approximations prevalent in most solar heating codes. The spectral extension from 0.8 to 12 µm enables calculation of both scattered and absorbed sunlight and thus aerosol direct radiative effects and heating rates throughout the Earth's atmosphere. Furthermore, the Solar-J extension adopts the correlated-k gas absorption bins, primarily water vapor, from the shortwave Rapid Radiative Transfer Model for general circulation model (GCM) applications (RRTMG-SW). Solar-J successfully matches RRTMG-SW's tropospheric heating profile in a clear-sky, aerosol-free, tropical atmosphere. Here, we compare both codes in cloudy atmospheres with a liquid-water stratus cloud and an ice-crystal cirrus cloud. For the stratus cloud, both models use the same physical properties, and we find a systematic low bias of about 3 % in planetary albedo across all solar zenith angles caused by RRTMG-SW's two-stream scattering. Discrepancies with the cirrus cloud using any of RRTMG-SW's three different parameterizations are as large as about 20–40 % depending on the solar zenith angles and occur throughout the atmosphere. Effectively, Solar-J has combined the best components of RRTMG-SW and Cloud-J to build a high-fidelity module for the scattering and absorption of sunlight in the Earth's atmosphere, for which the three major components – wavelength integration, scattering, and averaging over cloud fields – all have comparably small errors. More accurate solutions with Solar-J come with increased computational costs, about 5 times that of RRTMG-SW for a single atmosphere. There are options for reduced costs or computational acceleration that would bring costs down while maintaining improved fidelity and balanced errors.},
doi = {10.5194/gmd-10-2525-2017},
journal = {Geoscientific Model Development (Online)},
number = 7,
volume = 10,
place = {United States},
year = {2017},
month = {1}
}