[Liwg-core] proposal

Bill Sacks sacks at ucar.edu
Thu Mar 30 08:37:31 MDT 2017


Hi Miren,

As this falls into the category of ingesting a new spatial map into CLM, this is not feasible to get onto the CLM trunk in time for the spinup run: Getting a new spatial map into CLM involves either (a) adding a new "stream" input (substantial code development), or (b) adding a new field on CLM's surface dataset (moderate code development plus some tedious work of regenerating new surface datasets for every resolution). Either one takes more time than we have.

Since you seem keen on doing some resetting over the ice sheet, I'll suggest one other option: Rather than trying to get this resetting to work out-of-the-box on the CLM trunk, you or Raymond or someone else could implement this in a one-time fashion, and then process the single CLM restart file that will be used for Task 2A next week. This would be easier than the more general solution, because you could possibly do this with some python/ncl/etc. scripts rather than trying to embed it in the CLM code. However: This would mean that this option wouldn't be available out-of-the-box, and if it needs to be redone for any reason, you would need to redo this processing. Unfortunately, I don't think I can commit much time to help with this option, because there does not seem to be consensus that it is worth doing. But if you're willing to do this yourselves, then it could be a feasible option.

Bill S

> On Mar 30, 2017, at 8:18 AM, Miren Vizcaino <M.Vizcaino at tudelft.nl <mailto:M.Vizcaino at tudelft.nl>> wrote:
> 
> Hi Bill, 
> 
> The proposal is to use two variables from the latest run from Raymond - so it is based on inherent CESM2 model behavior.
> 
> output is here /glade/scratch/raymonds/archive/b.e20.B1850.f09_g16.pi_control.all.134_reset35_n05rep/lnd/hist
> 
> We rejected the idea of the ELA because
> 
> 1) we don’t have SMB output per EC
> 
> 2) prescribing an “observation-based" ELA falls into the problem of “baking" the answer
> 
> We propose to take the model output, and reset wherever Hsnow (t=20) - annual mean snow melt (average t=10-20) < 2 m w.e.  for the Greenland ice sheet. 
> 
> Reset over tundra and all small glaciers 
> 
> No reset for AIS, since we don’t aim to simulate ablation areas there 
> 
> The idea is that this CESM run has 20 years, so enough time for the driest-with-no-melt areas to build 2 m w.e. 
> 
> and we permit that grid cells with high accumulation and high melt (e.g. SE) can join the club of producing runoff 
> 
> Given we have so little time, this seems like a handy solution - Is this feasible to implement? 
> 
> Thanks, 
> 
> miren
> 

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