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

Bette Otto-Bliesner ottobli at ucar.edu
Tue Jun 6 12:30:01 MDT 2017


Hi Jan,

How does the accumulation, rain and snow, look in south and southeast
Greenland. Rain looked a bit high in SE Greenland but possibly
canceled by negative snow anomalies?

Thanks,
Bette



> On Jun 6, 2017, at 12:40, Lenaerts, J.T.M. (Jan) <j.lenaerts at uu.nl> wrote:
>
> Hi Bill and others,
>
> I already looked at #173 (yr 2-21).
>
> Greenland SMB is ~500 Gt/yr, which is consistent with previous (good) simulations. I would argue that Greenland melt is a bit too low (but hard to say as this is 1850). Also consistent is the lack of N-Greenland runoff.
>
> Antarctic melt looks great, which is also in line with previous simulations. Overall, no big red flags or alarm bells based on this preliminary analysis.
>
> Please note that the land diagnostic set already includes the ice sheets, so everyone can take a look: http://webext.cgd.ucar.edu/B1850/b.e20.B1850.f09_g17.pi_control.all.173/lnd/b.e20.B1850.f09_g17.pi_control.all.173-obs.11_30/setsIndex.html
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> Cheers,
>
> Jan
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> On 6 Jun 2017, at 19:09, Bill Sacks <sacks at ucar.edu<mailto:sacks at ucar.edu>> wrote:
>
> 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.
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> Bill S
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> ----
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> Snow albedos
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> Peter Lawrence: before tweaking land albedos, albedos were significantly higher than MODIS both in high latitudes and desert regions
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> 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
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> 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.
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> 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.
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> ----
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> Plan for runs
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> • Keep #173 going – this includes atmosphere changes without land snow changes
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>  *   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
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> • 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)
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> • 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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> - - - - - - - - - - - - - - - - - - - - - - - - - - -
> Jan Lenaerts
> IMAU, Utrecht University || University of Colorado
> @lenaertsjan<https://twitter.com/lenaertsjan> || website<http://www.colorado.edu/lab/icesheetclimate/>
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> <spatial_GrIS_b.e20.B1850.f09_g17.pi_control.all.173_year.pdf>
> <spatial_AIS_b.e20.B1850.f09_g17.pi_control.all.173_year.pdf>


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