Key variables required for aerosol direct radiative forcing estimates are aerosol optical thickness (AOT), ngstrm Exponent (AE) and single scattering albedo (SSA), which are determined not only by aerosol amount but also by physical and optical parameters such as size distribution, hygroscopicity, mixing state of the particles, and refractive index especially of absorbing particles such as black carbon (BC) and dust. As the values of these parameters are often assumed in climate models, we investigate how the variations in these prescribed parameters can explain the differences in AOT, AE and SSA between the simulation by an aerosol global model and the ground-based remote sensing observation, AERONET. We conclude that the differences between our simulations and AERONET observations of AOT, AE and SSA are larger than sampling errors but can be generally explained by the uncertainty of the assumed parameters, although some simulations have clear biases that may be caused by errors in both emission and transport by the model. The uncertainty of sulfate sizes significantly dominates the uncertainty of AOT, AE and SSA, whereas the uncertainty of dust refractive indices and mixing states of organic carbon and BC is dominates the uncertainty of SSA.
All Science Journal Classification (ASJC) codes
- General Earth and Planetary Sciences