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

Jan Lenaerts jtmlenaerts at gmail.com
Thu Jun 8 05:49:27 MDT 2017


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 <mailto: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 <mailto: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 <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><mailto: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.
>> 
>> 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><mailto: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/>








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