FHIST : SST forcing file (values over Land)

[bidyut]

Hi,

I have a general question regarding the SST forcing file for the FHIST run. I see that the SST file has values over land as well. What are these values ... Land surface temperatures? In an AMIP run (compset=FHIST), does CAM see these temperatures or ignore them?

Thanks.

 

[nusbaume]

Hi Bidyut,

CAM should ignore any SST values over land, as all land surface temperature values will be provided to CAM by CLM.

In terms of what the land values actually are, I believe they are just interpolated values from the observed SST fields. However, I am not entirely sure about this, so I have gone ahead and moved this thread to the CAM forum in case someone who knows these data sets better than I do would like to clarify.

Hope that helps, and have a great day!

Jesse

 

[bidyut]

Hi Jesse,

Thanks for the reply.

The reason I asked the question is, I wanted to do an experiment to see the response of the atmosphere to land-surface temperatures (like what is done in this paper Ackerley and Dommenget 2016 (Atmosphere-only GCM (ACCESS1.0) simulations with prescribed land surface temperatures)). Do you have any suggestion on this?

Thanks.

 

[nusbaume]

Hi Bidyut,

I am not aware of any officially-supported way to prescribe land surface temperatures to CAM, as CAM in general will only run in either idealized setups (e.g. aquaplanet) or coupled to CLM, which will then calculate the land surface temperatures.

That being said, you might be able to modify the source code to have CAM always receive prescribed surface temperature values. This would likely be done in the file located here:

<CESM_DIR>/components/cam/src/cpl/atm_import_export.F90

where <CESM_DIR> is wherever you downloaded the CESM code. In that source file the variables cam_in(c)%ts(i) and cam_in(c)%tref(i), which set the surface temperature and reference temperature received by CAM, could be modified such that they are set to some prescribed value over certain regions. You could also modify the exported surface temperature values from CLM instead, which should be contained in CLM's own atm_import_export.F90 file.

Finally, you could try posting this question in the simpler models forum as well:

Simpler Models

This forum is for technical and scientific questions related to the simpler model configurations within CESM, such as aquaplanet, dynamical core, SCAM etc http://www.cesm.ucar.edu/models/simpler-models/

bb.cgd.ucar.edu

To see if there are any specialized configurations that might also work.

Anyways, I hope that helps, and good luck!

Jesse

 

[bidyut]

Hi Jesse,

Thanks for the reply. This is really helpful.

If it is not too much to ask, can you please briefly explain, "the variables cam_in(c)%ts(i) and cam_in(c)%tref(i), which set the surface temperature and reference temperature received by CAM, could be modified such that they are set to some prescribed value over certain regions".

Can you please point me to the route CAM reads the SST input? Maybe I can adopt a similar approach to make land surface temperature forcing.

Thanks anyway for your help.

Bidyut

 

[hannay]

The SSTs over land are calculated by an interpolation with the poisson_grid_fill function. As as Jesse says, the value over land are ignored but they need to be there.

 

[bidyut]

Hi Cecile,
Thanks for your reply. Is it possible to make the model "not ignore them" and use them instead? If yes, How do I do it? In that can I can prepare a forcing file with land surface temperatures in place of interpolated dummy SST values.

My goal is to force the atmospheric model with SST and TS.

Thanks.

 

[hannay]

As far as I know, you cannot force the model with TS over land.