[Liwg-core] relevant co-chairs notes 6-6-17

Bill Sacks sacks at ucar.edu
Tue Jun 6 11:09:20 MDT 2017

Here are the most relevant notes from today's co-chairs meeting.

My executive summary:

(1) Based on Jan's analysis of the snow albedo changes, we won't go with that change – instead, the land group will try to get lower albedos by changing the snow cover fraction parameterization, which shouldn't impact the ice sheets much

(2) Run #173 (currently 30 years in) is a possible candidate for a "final, good" configuration. Once that gets a little further along (maybe in the next day or two?) it would be good for someone from the LIWG to look at some diagnostics for Greenland in that run.

Bill S


Snow albedos

Peter Lawrence: before tweaking land albedos, albedos were significantly higher than MODIS both in high latitudes and desert regions

Dave L: However, lowering albedos degrades simulation of ice sheet melt over Antarctica (and maybe Greenland?). So we don't want to do an extreme change to the albedos

Dave L: Expects we can get a similar response by changing snow cover fraction – and that probably wouldn't have negative impacts on the ice sheets.

Dave L: Also note that land albedos are actually a bit lower than CCSM4. It may still be that CLM's albedos are too high, but he doesn't have a lot of faith in the MODIS albedos.


Plan for runs

• Keep #173 going – this includes atmosphere changes without land snow changes
Look at this – particularly over Greenland and throughout the Arctic, because that's where a lot of the changes are.
If this looks good, then do a 20th century with this

• Start another run with land snow changes – probably get decreased albedos by changing snow cover fraction parameterization, rather than changing snow albedos more directly, because this will be better for the ice sheets. (#174)

• Start another run with new land snow changes plus the atmosphere changes (#174 changes on top of #173)


Tentative meeting Friday at 10 am
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