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Custom SST and SIC boundary conditions for CAM6

M

mduffy

Margaret Duffy
New Member
Hi,
I am trying to create my own SST and SIC boundary conditions file to run CAM6 simulations. Specifically, I want to take the SST and SIC from CESM2 abrupt4xCO2 simulations and was planning on leaving atmospheric constituents at preindustrial levels. To start, I am comparing the TS and ICEFRAC variables from abrupt4xCO2 to SST_cpl and ice_cov from an existing boundary condition file, and I have a few questions.

1) The reference boundary condition file and model output have very different values over land. Do these affect the results, and if so, where do these values come from?

2) The reference boundary condition file has "prediddle" versions of SST and SIC. I'm trying to figure out whether I need to do this diddling. What is the purpose and does it affect the results?

3) Other than converting to Celsius, is there anything else I might need to do to convert TS and ICEFRAC to CAM6 boundary conditions?

Thanks in advance!
Margaret
 
I

islas

Moderator
Staff member
Hi Margaret,

(1) I'm not sure what the boundary condition file is that you're looking at, but I suspect it's not going to matter. The SST file needs to have something over land (not NaN's) so it may be that someone did some kind of in-filling over the land regions when creating the boundary conditions from SST as opposed to using the actual surface temperature. But that's just a guess.

(2) I think it's best to do the diddling. The model will linearly interpolate between monthly values and the diddling ensures that the monthly mean that the model feels when it's using that interpolation is equal to the monthly mean you're trying to give it. In practise, it may not substantially affect your results depending on what you're looking at, but it's probably worth doing just to be sure. You can find tools do that in ./components/cam/tools/icesst.

(3) I think if you use the tools in that directory you should get the inputs in the right format. I recall there might be something a bit confusing about the units of icefrac and that the diddling code might be expecting an input in % as opposed to something ranging from 0-1 and then it produces the diddled icefrac in the range 0-1. But I may have been using an older version of this script so can't guarantee that's an issue you're going to come across - just something to look out for.

Isla
 
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