radiation parameterizations R Pincus University of Colorado Eli Mlawer Atmospheric and Environmental Research and coauthors This study reports on a recent intercomparison of radiation codes ID: 377481
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Assessing climate model radiation parameterizationsR. Pincus, University of Colorado; Eli Mlawer, Atmospheric and Environmental Research, and co-authors
This study reports on a recent intercomparison of radiation codes used in climate models. Tests were performed for current atmospheric conditions and the sensitivity to quadrupled CO2 concentrations. Key results are:The current generation of codes has improved relative to previous generations, but important state-dependent errors remain. Absorption of solar radiation is underestimated by most codes.Errors for present-day conditions are essentially unrelated to errors in sensitivity to changes in CO2 concentrations.This study motivates a more ambitious evaluation of code error, to be done as part of a Radiative Forcing activity associated with the next Coupled Model Intercomparison Project (CMIP6).
Errors with respect to LBLRTM reference model in top-of-atmosphere (TOA) net broadband longwave flux under present-day conditions (left panel) and error in TOA forcing from CO2 concentrations quadrupled from present-day values (right), for a variety of reference models (squares) and codes used in climate models (circles). Older versions are denoted by open shapes. Reference values are listed. Codes that have been updated since CMIP5 are more accurate than their predecessors (compare filled and open circles).
Reference: Pincus et al., 2015: Radiative flux and forcing parameterization error in aerosol-free clear skies. Geophys. Res. Lett., doi:10.1002/2015GL064291.
Changes in the flux of atmospheric radiant energy that arise from increasing levels of greenhouse gases are the driving forces behind climate change. The prediction of future climate depends critically on how accurately parameterizations within
climate models compute this radiative flux and its sensitivity to increasing gas concentrations.