CAM4: Aerosol direct and semidirect effects treatment.

[amatcaos@caos_iisc_ernet_in]

Hello,

I am using CESM1.0.4 and the E1850CN component set. I am trying to understand the aerosol effects and the earth's temperature response when additional aerosols are pescribed (especially sulfate and black carbon) at 15 km (~ 200 hPa) in the model vertical layer. My questions are:

Q1: What aerosols effects are modelled in this component set?
I think they are only the aerosol direct and semi-direct effects.

Q2: In which .F90 file in the model code the aerosol direct and semidirect effects are treated?
I guess the code will be in the /home/angshuman/Documents/CESM1.0.4/atm/cam/src/physics/rrtmg folder.

Many Thanks
Angshuman

 

[eaton]

The E1850CN compset uses the cam4 physics package which uses prescribed bulk aerosols, the old camrt radiation package (not RRTMG), and the RK microphysics.  There are no indirect or semidirect aerosol effects in this package, only direct aerosol effects.  The bulk optical properties for the bulk aerosols are computed in cam/src/physics/cam/aer_rad_props.F90 

 

[amatcaos@caos_iisc_ernet_in]

Thanks 

 

[amatcaos@caos_iisc_ernet_in]

Is it possible that when the aerosols are modified in the troposphere, the indirect effects will turn on? Actually I am attempting to modify aerosols (add extra SO4 aerosols) near the troposphere, I find significant cooling. This is only possible if the indirect effect is present.Many thanksAngshuman 

 

[santos]

The CAM4 microphysics doesn't allow aerosols to affect drop size at all, so whatever you're seeing is not the cloud albedo effect. I don't know what you mean when you say you see cooling, though. Where, over what time period, after what specific change?