Some questions about od550aer data in CMIP6

[Naive]

Greetings,

In CMIP6, I found od550aer data in CESM2. However, I have a question about this variable.

When I looked up the literature on CMIP6, I found that in the literature "AerChemMIP: quantifying the effects of chemistry and aerosols in CMIP6 ", "Another problem is which ambient humidity in the model is picked to compute AOT. Some models compute an all-sky AOT, including AOT in cloudy fractions with high humidities, while others restrict output to clear-sky AOT. The latter is preferred here, because it may be compared to that AOT which is observed under clear-sky conditions from satellites and sun photometers. Aerosol–radiation interactions are also most effective in clear-sky scenes, and it is thus more relevant to base forcing efficiencies on clear-sky AOT. If models compute normally an all-sky AOT using high relative humidities in cloudy fractions of the grid box, they are asked to also compute a clear-sky AOT (od550csaer) using clear-sky relative humidities."

Therefore, I would like to know whether the variable od550aer output in CESM2 is all-sky AOT?
If yes, does CESM2 have an output clear-sky AOT? (I did not find the od550csaer of CESM2 in CMIP6)

I'd appreciate it if you could answer me.

 

[strandwg]

Greetings,

In CMIP6, I found od550aer data in CESM2. However, I have a question about this variable.

When I looked up the literature on CMIP6, I found that in the literature "AerChemMIP: quantifying the effects of chemistry and aerosols in CMIP6 ", "Another problem is which ambient humidity in the model is picked to compute AOT. Some models compute an all-sky AOT, including AOT in cloudy fractions with high humidities, while others restrict output to clear-sky AOT. The latter is preferred here, because it may be compared to that AOT which is observed under clear-sky conditions from satellites and sun photometers. Aerosol–radiation interactions are also most effective in clear-sky scenes, and it is thus more relevant to base forcing efficiencies on clear-sky AOT. If models compute normally an all-sky AOT using high relative humidities in cloudy fractions of the grid box, they are asked to also compute a clear-sky AOT (od550csaer) using clear-sky relative humidities."

Therefore, I would like to know whether the variable od550aer output in CESM2 is all-sky AOT?
If yes, does CESM2 have an output clear-sky AOT? (I did not find the od550csaer of CESM2 in CMIP6)

I'd appreciate it if you could answer me.

CMIP6 "od550aer" is the CAM output field "AODVISdn", defined as "Aerosol optical depth 550 nm, day night". I can't tell you how that correlates to the comments from CMIP6 above.

I've moved this to the CAM forum.

 

[Naive]

CMIP6 "od550aer" is the CAM output field "AODVISdn", defined as "Aerosol optical depth 550 nm, day night". I can't tell you how that correlates to the comments from CMIP6 above.

I've moved this to the CAM forum.

Thank you very much.

 

[brianpm]

I **think** that AODVISdn is the "all-sky" calculation. But I'm not totally confident that CAM has a clear-sky version that would be usefully different. I'm looking at CAM/src/physics/cam/modal_aer_opt.F90 at cam_cesm2_1_rel · ESCOMP/CAM

Maybe someone from the chemistry side can chime in on this.

 

[Naive]

I **think** that AODVISdn is the "all-sky" calculation. But I'm not totally confident that CAM has a clear-sky version that would be usefully different. I'm looking at CAM/src/physics/cam/modal_aer_opt.F90 at cam_cesm2_1_rel · ESCOMP/CAM

Maybe someone from the chemistry side can chime in on this.

Yes, I used data from models that output both aod550aer (all-sky) and aod550csaer (clear-sky) in CMIP6, and I drew some graphs to compare and found that they were exactly the same. But I can't understand why.