Downward Solar Radiation at the Surface Difference<br>
aer_opt2angssa minus standard case<br>
4-km domain, forecast hour 24<br>
aer_opt2angssa Case uses:<br>
 GEOS 3-hourly aerosol optical depth<br>
 GEOS 3-hourly aerosol angstrom exponent<br>
 GEOS 3-hourly aerosol single scattering albedo from TOTSCATAU/TOTEXTTAU<br>
 fixed aerosol asymmetry parameter = 0.9<br>