Establishment of high-resolution aerosol parameterization and its influence on radiation calculations

Abstract To accurately simulate the effects of aerosols on the atmospheric radiation budget, we here establish an aerosol optical parameterization scheme with high spectral resolution (974-band) for radiative transfer model(BCC_RAD); this scheme includes sulfate (SF), black carbon (BC), organic carbon (OC), dust (SD), and sea salt (SS) aerosols. The results of the 974-band scheme are compared with those obtained using a low-resolution 17-band scheme. Our results show the 974-band scheme more accurate in its representation of the aerosols’ optical properties. The largest relative differences in the volume extinction coefficient(Kex) between the 974-band and 17-band schemes range from 5.87% to 54.64%, with BC (41.13%) and SF (54.64%) showing the largest values at 1.91 and 2.7 μ m, respectively. The single scattering albedo of hygroscopic aerosols (SF, SS, and OC) show minimal values at 2.84 and 6.01 μ m, respectively, in the 974-band scheme due to light absorption; however, the low spectral resolution of the 17-band scheme prevents these features from being resolved. Specifically, the relative difference between the two schemes approaches 72.72% at 2.84 μ m for SF. Thus, improved spectral resolution may be required for some aerosols. We also compare the effects of aerosols on the radiation budget in East Asia simulated by 974-band and 17-band BCC_RAD models. Under clear-sky conditions, the simulation results indicate a relative difference in the radiation flux of 0.28–5.93% for the two schemes. The 974-band and 17-band schemes show daily mean direct radiative forcings (DRFs) due to all aerosols of − 16.97 and − 17.13 W/m2 at the surface and − 7.12 and − 6.93 W/m2 at the top of the atmosphere, respectively. Additionally, the 974-band model generally simulates a larger DRF for BC and smaller DRFs for scattering aerosols such as SF; these differences become greater for smaller zenith angles.