Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment
Atmospheric Chemistry and Physics European Geosciences Union (2013)
Authors:
CA Randles, S Kinne, G Myhre, M Schulz, P Stier, J Fischer, L Doppler, E Highwood, C Ryder, B Harris, J Huttunen, Y Ma, RT Pinker, B Mayer, D Neubauer, R Hitzenberger, L Oreopoulos, D Lee, G Pitari, G Di Genova, J Quaas, Fred G Rose, S Kato, ST Rumbold, I Vardavas, N Hatzianastassiou, C Matsoukas, H Yu, F Zhang, H Zhang, P Lu
Abstract:
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.
