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

Andrew Gettelman andrew at ucar.edu
Thu Jun 8 10:45:48 MDT 2017


Yes, I would expect that reducing LWP a bit by raising the vapor deposition
efficiency is creating less liquid and less liquid precipitation. I'm glad
this is positive for land ice.

Cheers,

Andrew

On Thu, Jun 8, 2017 at 5:49 AM, Jan Lenaerts <jtmlenaerts at gmail.com> wrote:

> Hi Bette,
>
> See attached, comparing LENS, 125, 169 and 173 (now years 20-49). Page 1
> are the absolute numbers, page 2 is the relative bias (in %) with respect
> to RACMO2. The other plot shows the seasonal cycles.
>
> Overall, 173 is very comparable to 125 in snowfall, and looks a bit better
> than 169. Andrew, rainfall is really much better (i.e. ~100% reduced
> integrated over the ice sheet) in 169 and 173 compared to 125 (without
> repartitioning)!
>
> Cheers,
>
> Jan
>
>
>
>
>
>
>
> On 6 Jun 2017, at 20:30, Bette Otto-Bliesner <ottobli at ucar.edu> wrote:
>
> 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
>
> Cheers,
>
> Jan
>
>
>
>
>
>
>
>
>
>
> On 6 Jun 2017, at 19:09, Bill Sacks <sacks at ucar.edu<mailto:sacks at ucar.edu
> <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.
>
> 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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> Liwg-core at cgd.ucar.edu<mailto:Liwg-core at cgd.ucar.edu
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>
> - - - - - - - - - - - - - - - - - - - - - - - - - - -
> Jan Lenaerts
> IMAU, Utrecht University || University of Colorado
> @lenaertsjan<https://twitter.com/lenaertsjan> || website<
> http://www.colorado.edu/lab/icesheetclimate/>
>
>
>
>
>
>
>
>
> <mime-attachment>
> <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>
>
>
> - - - - - - - - - - - - - - - - - - - - - - - - - - -
>
> *Jan Lenaerts *IMAU, Utrecht University || University of Colorado
> @lenaertsjan <https://twitter.com/lenaertsjan> || website
> <http://www.colorado.edu/lab/icesheetclimate/>
>
>
>
>
>
>
>
>
>
>


-- 
Dr. Andrew Gettelman   andrew at ucar.edu
http://www.cgd.ucar.edu/staff/andrew/
+1.303.497.1887
National Center For Atmospheric Research
3090 Center Green Drive,
Boulder, Colorado 80301, USA
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