Option to use Jordan1991 over glacier land units

[wwieder]

Biases in coupled model Greenland snow melt can be resolved with reverting the snow_thermal_cond_method = 'Jordan1991', but it really reduces snow melt over vegetated columns and will likely bring back our dead arctic vegetation issue. Can we use Jordan over glacier land units and Sturm over all other land units?

@billsacks, @olyson, @ekluzek would any of you be willing to help with this? At first we're looking for simple source mods that can be used for a coupled model test.

[ekluzek]

Hmmm. We should be able to figure out a hack for this I suppose. I'll need to look at the code. @billsacks has a PR on a different thing that hacks behavior over Greenland. He also has notes on how it should be handled longer term, and I think the same kind of thing would apply here.

So we can come up with a PR with a hack. And then if it's important bring it in properly later.

There are glacier behavior namelist items to control different behavior over different glaciers. And that would be the longer term right way to handle it.

[billsacks]

I just looked at the code. This looks like a very easy thing to hack together initially. I can do that and get it to you shortly.

This differs from the previous two hacks I did in that (if I understand right) the behavior difference you want is for all glacier landunits. That's easier than what I did in the earlier hacks.

My understanding is that for this initial hack you don't care about it being runtime controllable, just hard-code:

• If glacier, use the Jordan scheme
• If non-glacier, use Sturm

By the way, in looking quickly at the code, I noticed that Lake is still hard-coded to use the Jordan scheme, regardless of whether Sturm is being used elsewhere. Should that be fixed long-term?

[wwieder]

please see #3072, I'll do a run to check it works as intended.

[wwieder]

@billsacks let me know where the lake issue is? I'd suspect it's not in SoilTemperatureMod.

[billsacks]

It appears in two places for lakes:

CTSM/src/biogeophys/LakeFluxesMod.F90

Line 483 in be65fad

tksur(c) = tkair + (7.75e-5_r8 *bw + 1.105e-6_r8*bw*bw)*(tkice-tkair)

CTSM/src/biogeophys/LakeTemperatureMod.F90

Line 1184 in be65fad

thk(c,j) = tkair + (7.75e-5_r8 *bw + 1.105e-6_r8*bw*bw)*(tkice-tkair)

(Since I saw that the SoilTemperature code was run over non-lake points, I was curious what happened over lakes, so searched for some of the relevant constants in order to find this code.)