How to implement localized ocean albedo modification?

[abhanawat]

Hi everyone!

I am new to CESM2 so pardon me if I sound naive.

I would like to to predict the effect of non-uniform ocean albedo manipulation, i.e. different albedo at different parts of various oceans, on the global climate using the CESM2 climate model. Could someone let me know how to do that? I have geospatially varying ocean albedo data that I want to use as input into the climate model for the simulations. Any help would be greatly appreciated!

Thank you!

 

[dbailey]

The ocean albedo is computed in the coupler routine drivers/mct/main/seq_flux_mct.F90 in the subroutine seq_flux_ocnalb_mct assuming you are using MCT. This is where you would have to modify the code.

 

[abhanawat]

The ocean albedo is computed in the coupler routine drivers/mct/main/seq_flux_mct.F90 in the subroutine seq_flux_ocnalb_mct assuming you are using MCT. This is where you would have to modify the code.

Thank you so much @dbailey ! I will look further into it and let you know again!

 

[abhanawat]

The ocean albedo is computed in the coupler routine drivers/mct/main/seq_flux_mct.F90 in the subroutine seq_flux_ocnalb_mct assuming you are using MCT. This is where you would have to modify the code.

Hi @dbailey Could you also let me know how to find the value of the lats(n) and lons(n) used in the seq_flux_ocnalb_mct subroutine?

In the seq_flux_ocnalb_mct subroutine, I found that

do n = 1,nloc_o
lats(n) = dom_o%data%rAttr(klat,n)
lons(n) = dom_o%data%rAttr(klon,n)
enddo

Also, the dom_o is defined as:

dom_o => component_get_dom_cx(ocn) ! dom_ox

I basically want to modify the albedo in those specific latitudes and longitudes already used in the subroutine. Can you please help me with that?

 

[dbailey]

You need to add an if block that checks lats and lons. I believe there is already a latitude dependency in the code you have highlighted.

 

[abhanawat]

You need to add an if block that checks lats and lons. I believe there is already a latitude dependency in the code you have highlighted.

Thanks @dbailey ! Actually, what I meant is that I want to know the exact latitude and longitudes values already being used in the subroutine. The data that I want to input most likely has a different map resolution than the one already being used in the subroutine. Therefore, if I can find the values of lats(n) and lons(n), I can change the resolution of my input data.

 

[dbailey]

I guess what I was saying is you add code like:

if (lats(n) > 50.) then
...
endif

You let the code figure out what gridcells it is applied to.

 

[abhanawat]

I guess what I was saying is you add code like:

if (lats(n) > 50.) then
...
endif

You let the code figure out what gridcells it is applied to.

I see! Thanks!! I will try this way and let you know! Also, I am curious: Do you know what the resolution usually is for CESM simulations? Is there like a default resolution for the gridcells?

 

[dbailey]

There is not really a default resolution. We do tend to use an approximately one-degree resolution for our workhorse CMIP simulations.