TY - JOUR
T1 - An Investigation Into Biases in Instantaneous Aerosol Radiative Effects Calculated by Shortwave Parameterizations in Two Earth System Models
AU - Freidenreich, S.
AU - Paynter, D.
AU - Lin, P.
AU - Ramaswamy, V.
AU - Jones, A. L.
AU - Feldman, D.
AU - Collins, W. D.
N1 - Funding Information:
The author would like to acknowledge the many helpful suggestions from the various coauthors as well as those from two internal reviewers. A. L. Jones is funded by DOE award DE-SC0012313, “Collaborative Research: Centralized activities in support of the Radiative Forcing Model Intercomparison Project” and Princeton University's Cooperative Institute for Climate Studies (CICS). The material from co-authors Feldman and Collins is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research and Regional and Global Model Analysis under contract number DE-AC02-05CH11231. This report was prepared by Pu Lin under award NA18OAR4320123 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration, or the U.S. Department of Commerce.
Funding Information:
The author would like to acknowledge the many helpful suggestions from the various coauthors as well as those from two internal reviewers. A. L. Jones is funded by DOE award DE‐SC0012313, “Collaborative Research: Centralized activities in support of the Radiative Forcing Model Intercomparison Project” and Princeton University's Cooperative Institute for Climate Studies (CICS). The material from co‐authors Feldman and Collins is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research and Regional and Global Model Analysis under contract number DE‐AC02‐05CH11231. This report was prepared by Pu Lin under award NA18OAR4320123 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration, or the U.S. Department of Commerce.
Publisher Copyright:
© 2021. American Geophysical Union. This article is a U.S. Government work and is in the public domain in the USA.
PY - 2021/6/16
Y1 - 2021/6/16
N2 - Because the forcings to which Coupled Model Intercomparison Project - Phase 5 (CMIP5) models were subjected were poorly quantified, recent efforts from the Radiative Forcing Model Intercomparison Project (RFMIP) have focused on developing and testing models with exacting benchmarks. Here, we focus on aerosol forcing to understand if for a given distribution of aerosols, participating models are producing a radiometrically-accurate forcing. We apply the RFMIP experimental protocol for assessing flux biases in aerosol instantaneous radiative effect (IRE) on two participating models, GFDL AM4 and CESM 1.2.2. The latter model contains the RRTMG radiation code which is widely used among CMIP6 GCM's. We conduct a series of calculations that test different potential sources of error in these models relative to line-by-line benchmarks. We find two primary sources of error: two-stream solution methods and the techniques to resolve spectral dependencies of absorption and scattering across the solar spectrum. The former is the dominant source of error for both models but the latter is more significant as a contributing factor for CESM 1.2.2. Either source of error can be addressed in future model development, and these results both demonstrate how the RFMIP protocol can help determine the origins of parameterized errors relative to their equivalent benchmark calculations for participating models, as well as highlight a viable path towards a more rigorous quantification and control of forcings for future CMIP exercises.
AB - Because the forcings to which Coupled Model Intercomparison Project - Phase 5 (CMIP5) models were subjected were poorly quantified, recent efforts from the Radiative Forcing Model Intercomparison Project (RFMIP) have focused on developing and testing models with exacting benchmarks. Here, we focus on aerosol forcing to understand if for a given distribution of aerosols, participating models are producing a radiometrically-accurate forcing. We apply the RFMIP experimental protocol for assessing flux biases in aerosol instantaneous radiative effect (IRE) on two participating models, GFDL AM4 and CESM 1.2.2. The latter model contains the RRTMG radiation code which is widely used among CMIP6 GCM's. We conduct a series of calculations that test different potential sources of error in these models relative to line-by-line benchmarks. We find two primary sources of error: two-stream solution methods and the techniques to resolve spectral dependencies of absorption and scattering across the solar spectrum. The former is the dominant source of error for both models but the latter is more significant as a contributing factor for CESM 1.2.2. Either source of error can be addressed in future model development, and these results both demonstrate how the RFMIP protocol can help determine the origins of parameterized errors relative to their equivalent benchmark calculations for participating models, as well as highlight a viable path towards a more rigorous quantification and control of forcings for future CMIP exercises.
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U2 - 10.1029/2019JD032323
DO - 10.1029/2019JD032323
M3 - Article
AN - SCOPUS:85107489422
SN - 2169-897X
VL - 126
JO - Journal of Geophysical Research: Atmospheres
JF - Journal of Geophysical Research: Atmospheres
IS - 11
M1 - e2019JD032323
ER -