Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

Abstract

In this study we examine the performance of 31 global model radiative transfer schemes in cloud-free conditions with prescribed gaseous absorbers and no aerosols (Rayleigh atmosphere), with prescribed scattering-only aerosols, and with more absorbing aerosols. Results are compared to benchmark results from high-resolution, multi-angular line-by-line radiation models. For purely scattering aerosols, model bias relative to the line-by-line models in the top-of-the atmosphere aerosol radiative forcing ranges from roughly −10 to 20%, with over- and underestimates of radiative cooling at higher and lower sun elevation, respectively. Inter-model diversity (relative standard deviation) increases from ~10 to 15% as sun elevation increases. Inter-model diversity in atmospheric and surface forcing decreases with increased aerosol absorption, indicating that the treatment of multiple-scattering is more variable than aerosol absorption in the models considered. Aerosol radiative forcing results from multi-stream models are generally in better agreement with the line-by-line results than the simpler two-stream schemes. Considering radiative fluxes, model performance is generally the same or slightly better than results from previous radiation scheme intercomparisons. However, the inter-model diversity in aerosol radiative forcing remains large, primarily as a result of the treatment of multiple-scattering. Results indicate that global models that estimate aerosol radiative forcing with two-stream radiation schemes may be subject to persistent biases introduced by these schemes, particularly for regional aerosol forcing

Impact of Coupled NOx/Aerosol Aircraft Emissions on Ozone Photochemistry and Radiative Forcing

“…Mie optical parameters for aerosols are computed using wavelength-dependent refractive indices from the OPAC database and the aerosol size distributions from the ULAQ model. The ULAQ model's photolysis rates, surface and top-of-atmosphere radiative fluxes have been validated in the framework of SPARC-CCMVal and AeroCom inter-comparison campaigns [75,76].…”

Regional and monthly and clear-sky aerosol direct radiative effect (and forcing) derived from the GlobAEROSOL-AATSR satellite aerosol product

“…However, the code used has recently been included in an intercomparison study by Randles et al (2012), and this demonstrated that the uncertainty compared to state-of-the-art radiative transfer models is likely around 1-2 % for the TOA radiative flux. This is considerably smaller than most of the other sources considered here.…”

Optical properties of Saharan dust aerosol and contribution from the coarse mode as measured during the Fennec 2011 aircraft campaign

“…The setup is designed to be as simple as possible to illustrate the effect of SSA and size distribution on radiative fluxes and atmospheric heating rates; further studies will employ more detailed radiative transfer models. We use the Edwards and Slingo radiative transfer model (Edwards and Slingo, 1996;Randles et al, 2012) with a plane-parallel atmosphere and model irradiance from 0.2 to 10 µm with 220 spectral bands. A standard tropical atmosphere was used for vertical profiles of atmospheric gases (Anderson et al, 1986).…”