Separate aerosol particle nucleating effect in CAM5

[starrystarrynighttt]

Dear all,

I am running fixed-SST simulations with CESM version 1.2 (CAM5 + CLM4) to test the impact of sulfate aerosol emissions on the TOA energy budget. The only difference between these simulations is that for one of them I added additional sulfate aerosol emissions. I found that cloud cover changes substantially to aerosols.

Since the cloud fraction change could be due to both additional aerosol particles (service as nuclei) and changes in the vertical motion, I am wondering if there is a way to separate these processes?

For example, the model outputs include the cloud liquid tendency due to various processes and the Morrison microphysics seems to consider the aerosol-cloud interactions. Can I use this variable to represent the aerosol particle nucleating effect?

Thanks very much, and any comments would be very appreciated!

 

[andrew]

Greetings, I think the way to separate them is to look at the changes in aerosol (BURDENSO4 or the various number variables for SO4) and then the changes in vertical velocity, either the grid scale (OMEGA) or the sub-grid velocity from turbulence that feeds activation (WSUB).

MG microphysics does include aerosol affects through changes in the activated number for liquid (NCAL) that then is used to increase cloud drop number.

So these variables should give you some insight as to what is the dominate co-variate here.

Hope that helps!

Regards,

Andrew

 

[starrystarrynighttt]

Greetings, I think the way to separate them is to look at the changes in aerosol (BURDENSO4 or the various number variables for SO4) and then the changes in vertical velocity, either the grid scale (OMEGA) or the sub-grid velocity from turbulence that feeds activation (WSUB).

MG microphysics does include aerosol affects through changes in the activated number for liquid (NCAL) that then is used to increase cloud drop number.

So these variables should give you some insight as to what is the dominate co-variate here.

Hope that helps!

Regards,

Andrew

Dear Andrew,

Thanks very much for your responses.

Yes, I have examined the change related to aerosols (aerosol optical depth and aerosol burden) and the vertical velocity. Both of them show a positive contribution to cloud change (increase in aerosol particles and an increase in the upward motion).

So my previous question is, could I separate their individual contribution quantitatively? It does not seem to me that there is any model output that directly represents such contributions (am I right?). Maybe I can do some correlation calculations instead...

Thanks again.