Information on aerosol optical properties files for CAM4

[chris_fletcher@utoronto_ca]

Hi, could anyone tell us how the aerosol optical properties file for sulfate was produced (specifically: sulfate_camrt_c080918.nc)?

In the NetCDF header for that file it says 'source = "OPAC + miev0"', but the standard OPAC model [Hess et al. 1998] doesn't seem to output optical properties for anthropogenic sulfate.

Furthermore, on Pg 120 of the CAM4 technical description I found:

The optics for black and organic carbon are identical to the optics for soot and water-soluble aerosols in the Optical Properties of Aerosols and Clouds (OPAC) data set [Hess et al., 1998]. The optics for dust are derived from Mie calculations for the size distribution represented by each size bin [Zender et al., 2003]. The Mie calculations for sulfate assume that it is comprised of ammonium sulfate with a log-normal size distribution. The dry size parameters are a median radius of 0.05 μm and a geometric standard deviation of 2.0.

From this passage it wasn't totally clear which model was used to compute the Mie calculations for sulfate. The standard OPAC model doesn't seem to take median radius or geometric standard deviation as inputs.

Thanks; any insight would be much appreciated.