[Liwg-core] Fwd: Re: non-bfb 289 to 291

Bill Sacks sacks at ucar.edu
Thu Apr 19 09:06:48 MDT 2018


Hi Laura,

Thanks a lot for this! This is good to hear.

Regarding this:
>
> #289 outputs ‘acab’ in m/year; and #291 has ‘smb’ in mmWE/year.
This came in with the new CISM version (which was related to the changed 
initial conditions file).

Thanks,
Bill S


On 4/19/18, 9:02 AM, Laura Muntjewerf - CITG wrote:
> Hi Bill,
>
> On differences in SMB between #289 and #291, they don’t seem that large.
> Integrated mean SMB over simulation years 25-54 is 406.97 Gt/yr in 
> #289 vs. 403.79 Gt/yr in #291.
>
> Most of the effect is on the west margin ablation zone; here SMB in 
> #291 is more negative than in #289.
> In the link there is time series of the % ablation area and the 
> integrated SMB over simulation years 25-54; and spatial maps of SMB 
> mean and difference: 
> https://drive.google.com/open?id=1lMHm0Dgu7s3D-1kwhi0o-mY5GXNSEE7o
>
> #289 outputs ‘acab’ in m/year; and #291 has ‘smb’ in mmWE/year.
> I suppose this came with the changed initial conditions file?
>
> Laura
>
>
>
>
>
>
>> On 11 Apr 2018, at 15:44, Bill Sacks <sacks at ucar.edu 
>> <mailto:sacks at ucar.edu>> wrote:
>>
>> Okay, thanks for these thoughts!
>>
>> On 4/11/18, 7:37 AM, Laura Muntjewerf - CITG wrote:
>>>
>>> Hi Bill,
>>>
>>> Good catch, and thanks for the detailed information.
>>>
>>> So we can expect differences in SMB fields. Based on the input 
>>> fields you pointed to, I am expecting some difference in the 
>>> integrated SMB. However, I am more curious to see to what degree 
>>> this makes spatial differences. I agree with you that it is a good 
>>> idea to make a comparison.
>>>
>>> From a quick look on how the snow developed in 289, the snow pack 
>>> over the northern tundra takes ~20 years to equilibrate.
>>> I’d say run 50 years, that provides 30 years to look at the SMB 
>>> climate.
>>> Definitely next week I have time to look at the output, I am curious 
>>> to see the implications.
>>>
>>> Laura
>>>
>>>
>>>
>>>> On 11 Apr 2018, at 13:38, Bill Sacks <sacks at ucar.edu 
>>>> <mailto:sacks at ucar.edu>> wrote:
>>>>
>>>> Good news: It turns out that my concern about large water and 
>>>> energy fluxes in the first year was unfounded. i.e., this was wrong:
>>>>> Incidentally: this problem with CISM initial conditions means that 
>>>>> (I think) we also would have seen big, fictitious water and energy 
>>>>> fluxes from Greenland in the first year of any simulation done 
>>>>> since June which pointed to a land initial conditions file taken 
>>>>> directly from an offline spinup. I'm not sure how many of the runs 
>>>>> over the last year were set up in this way (as opposed to using a 
>>>>> land file from a hybrid case, which would be consistent with the 
>>>>> buggy CISM).
>>>> It turns out that the fluxes are all generated in time step -1 – a 
>>>> time step that CLM does before the real start of the simulation, 
>>>> and fluxes generated in that time step apparently do not feed back 
>>>> to the rest of the system.
>>>>
>>>> So it seems that the only issue is the different glacier cover 
>>>> around the margin of the Greenland ice sheet (and slightly 
>>>> different glacier elevations).
>>>>
>>>> Bill
>>>>
>>>> On 4/10/18, 12:40 PM, Bill Sacks wrote:
>>>>> Hi all,
>>>>>
>>>>> We discussed this issue at the co-chairs meeting today. I'm 
>>>>> pasting in notes about that and other notes from today's co-chairs 
>>>>> meeting, below.
>>>>>
>>>>> Cecile is starting a run to look at the impact of using incorrect 
>>>>> glacier cover in all runs since last June. This will probably be 
>>>>> run #293, which will be #289 + fixed glacier cover over Greenland. 
>>>>> To the extent that there are diffs, those diffs will probably show 
>>>>> up most over Greenland, including possibly affecting SMB 
>>>>> diagnostics. Would anyone have the time to do a comparison of #293 
>>>>> vs. #289 (once #293 has run far enough) to see if there are 
>>>>> significant diffs? How long would Cecile need to run #293 for you 
>>>>> to do diagnostics on it?
>>>>>
>>>>> Thanks,
>>>>> Bill S
>>>>>
>>>>>
>>>>> *April 10, 2018 *
>>>>> *
>>>>> *
>>>>> *Problematic issue found from non-bfb analysis, comparing #289 and 
>>>>> #291*
>>>>> *
>>>>> *
>>>>> One big thing Bill S was concerned about was runs since June, 2017 
>>>>> that used buggy CISM init with CLM finidat from offline spinup. 
>>>>> These runs would have had big fluxes in the first year. But, 
>>>>> fortunately, it turns out that there weren't very many runs that 
>>>>> were configured that way.
>>>>>
>>>>> The other issue here is incorrect glacier cover over Greenland. 
>>>>> This probably doesn't have too large of an effect on global 
>>>>> climate, but concern is that any change could affect the Lab Sea.
>>>>>
>>>>> One concern is that this will affect the SMB analyses that have 
>>>>> been done by the LIWG over the last year.
>>>>>
>>>>> Next step: start a new run with the new code base with a CLM 
>>>>> initial file from 2 timesteps into #291, to look at diffs due to 
>>>>> glacier cover over Greenland. But actually, we might fold WACCM 
>>>>> forcing updates into this new run, too, so that the new run has 
>>>>> everything we want and can be used in the spinup process.
>>>>>
>>>>> ----
>>>>>
>>>>> *Run #290*
>>>>>
>>>>> Background on what motivated this: WACCM put in a check that 
>>>>> aborts if co2 goes above 720, because that goes past the end of a 
>>>>> lookup table. The point of this abort was to warn users not to try 
>>>>> to do (e.g.) a 4x CO2 run with this configuration. But the check 
>>>>> was triggered even for preindustrial, leading to the discovery of 
>>>>> a problem with diffusion.
>>>>>
>>>>> These same numeric issues affect anything being transported – 
>>>>> including H2O and aerosols.
>>>>>
>>>>> Run #290 has a fix to diffusion which has been confirmed to fix 
>>>>> this issue.
>>>>>
>>>>> Note that Lab Sea is warmer in this run, which could be a good 
>>>>> thing. In addition, ocean temperature and salinity look better 
>>>>> over Lab Sea.
>>>>>
>>>>> Feeling is that this looks promising... will look further into 
>>>>> whether to use this change moving forward.
>>>>>
>>>>> ----
>>>>>
>>>>> *Release planning*
>>>>> *
>>>>> *
>>>>> For fully-coupled compsets: The two scientifically-supported 
>>>>> compsets will be a preindustrial (which is a cmip6 preindustrial) 
>>>>> and historical compset – but this historical will NOT be a cmip6 
>>>>> historical. There will be other compsets that are functionally but 
>>>>> not scientifically supported.
>>>>>
>>>>> The CESM2.0.0 release won't be a "cmip6" release, but the plan is 
>>>>> for it to support cmip6 pre-industrial. A follow-up release (e.g., 
>>>>> CESM2.0.1) will add support for cmip6 historical & future scenarios.
>>>>>
>>>>> JF (ecohed by Dave L): Feels that priority should be supporting 
>>>>> the fully-coupled. Shouldn't spend a lot of time on standalone 
>>>>> compsets if this detracts from having the fully-coupled release 
>>>>> done in time.
>>>>>
>>>>> What is the timeline for having the final values of tuning 
>>>>> parameters in place? It's possible that these tuning parameters 
>>>>> won't all be finalized even by the June workshop, but sense is 
>>>>> that we really want to have a release by the June workshop.
>>>>>
>>>>> One feeling from a number of people is that we shouldn't try to 
>>>>> have /any/ cmip6 science support, even for preindustrial, in the 
>>>>> CESM2.0.0 release. We would still provide scientific support for 
>>>>> preindustrial and historical in CESM2.0.0, but they wouldn't be 
>>>>> called cmip6.
>>>>>
>>>>> The differences for preindustrial in the cmip6 release update may 
>>>>> just be ocean BGC parameters. There are also some WACCM forcing 
>>>>> changes in the pipeline, but those should be ready by May 11.
>>>>>
>>>>> ----
>>>>>
>>>>> *Next meeting: Friday*
>>>>> *
>>>>> *
>>>>> *Please look at run #290 for that.*
>>>>>
>>>>>
>>>>>
>>>>> On 4/9/18, 10:09 PM, Bill Sacks wrote:
>>>>>> For those not on cesm2control:
>>>>>>
>>>>>> -------- Original Message --------
>>>>>> Subject: 	Re: non-bfb 289 to 291
>>>>>> Date: 	Mon, 09 Apr 2018 22:02:51 -0600
>>>>>> From: 	Bill Sacks <sacks at ucar.edu>
>>>>>> To: 	Jim Edwards <jedwards at ucar.edu>
>>>>>> CC: 	cesm2control <cesm2control at cgd.ucar.edu>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Jim: Again, thank you very much for tracking down the diffs 
>>>>>> between 289 and 291, and for tracking them back to fields sent 
>>>>>> from CISM.
>>>>>>
>>>>>> I have some good news and some bad news. I'm bringing 
>>>>>> cesm2control into the loop for the bad news. For the executive 
>>>>>> summary, just read the parts in bold.
>>>>>>
>>>>>> One piece of good news is that I think I understand the (or at 
>>>>>> least a) source of the 289-291 diffs. Another piece of good news 
>>>>>> is that these particular diffs are limited to Greenland. The bad 
>>>>>> news is that the changes here are non-negligible over Greenland, 
>>>>>> and indicate that all of the runs done since about last June have 
>>>>>> used somewhat wrong glacier cover over Greenland; run 291 finally 
>>>>>> fixed this (unknowingly).
>>>>>>
>>>>>> I'll start with the impact, and then describe the problem in more 
>>>>>> detail.
>>>>>>
>>>>>> The impact can be seen by diffing a CLM h0 file between these two 
>>>>>> cases and looking at the fields PCT_LANDUNIT (% of each landunit 
>>>>>> on the gridcell) and PCT_GLC_MEC (% of each glacier elevation 
>>>>>> class) (both fields are constant in time, so it doesn't matter 
>>>>>> which file you choose). See 
>>>>>> /glade/scratch/sacks/cism_comparison/diff.291_289.clm2.h0.0001-01.nc. 
>>>>>> I am attaching images showing the difference in % glacier; they 
>>>>>> are the same data, just with different color bars.
>>>>>>
>>>>>> As you can see from this figure, there are substantial 
>>>>>> differences in % glacier around the margin of the Greenland ice 
>>>>>> sheet. If we just consider the points with differences, here are 
>>>>>> statistics:
>>>>>>
>>>>>> In [13]: summarize(pct291[0,3,:,:][w]-pct289[0,3,:,:][w])
>>>>>> count    302.000000
>>>>>> mean     -10.491008
>>>>>> std       13.153102
>>>>>> min      -48.280025
>>>>>> 25%      -18.350363
>>>>>> 50%       -7.774761
>>>>>> 75%       -1.507887
>>>>>> max       30.457689
>>>>>>
>>>>>> That is, there are 302 grid cells over Greenland with differences 
>>>>>> in % glacier, and in those grid cells that differ, the percent of 
>>>>>> the grid cell covered by glacier is about 10% lower in 291 than 
>>>>>> in 289, on average. There are also diffs in mean glacier 
>>>>>> elevation in these and probably other grid cells in Greenland 
>>>>>> (not shown).
>>>>>>
>>>>>> How did this difference come about? In all of these runs, the ice 
>>>>>> sheet model (CISM) is static in time, but it dictates CLM's 
>>>>>> (static) glacier cover over Greenland in initialization. CISM's 
>>>>>> glacier cover can be set either from a restart file or from 
>>>>>> observed initial conditions, and we've gone back and forth in 
>>>>>> terms of how we do this in the CESM2 test runs.
>>>>>>
>>>>>> For all runs since about June, 2017, we've been doing a hybrid 
>>>>>> start with a refcase whose CISM restart file can be traced back 
>>>>>> to the refcase, 
>>>>>> /glade/p/cesmdata/cseg/inputdata/ccsm4_init/b.e20.B1850.f09_g17.pi_control.all.149.cism/0103-01-01/. 
>>>>>> I added a CISM restart file to that refcase to make it usable in 
>>>>>> configurations with CISM. Unfortunately, as I just discovered 
>>>>>> tonight, I did not give enough thought to the choice of CISM 
>>>>>> restart file used there: The CISM restart file we've been using 
>>>>>> was 2 years into a software test with an evolving ice sheet. (I 
>>>>>> should have used a restart file from a run with a non-evolving 
>>>>>> ice sheet; I'm not sure why I chose this one.) While ice sheets 
>>>>>> do not generally evolve much in 2 years, it is common for us to 
>>>>>> see a large jump in the first year of the simulation, and that's 
>>>>>> what is reflected here.
>>>>>>
>>>>>> In the latest CISM version (cism2_1_50, in cesm2_0_alpha10b and 
>>>>>> later), I found a way to do what we've really wanted all along: 
>>>>>> forcing CISM to use observed initial conditions whenever it's 
>>>>>> running in no-evolve mode. This wouldn't have changed answers if 
>>>>>> the refcase were set up correctly, but since I put a bad restart 
>>>>>> file into the refcase we've been using, it resulted in the answer 
>>>>>> changes that we're seeing.
>>>>>>
>>>>>> I guess this will have to be the first test case for the 
>>>>>> question, "Will we allow this answer-changing bug fix?". The 
>>>>>> refcase we've been using is definitely buggy in this respect. 
>>>>>> Furthermore, it is not directly usable in the new version of CISM 
>>>>>> (which was the motivation for making the behavior change in 
>>>>>> cism2_1_50). We could back out the change in cism2_1_50 and 
>>>>>> instead produce a patched-up refcase that gives bit-for-bit 
>>>>>> answers with #289 and works with the new version of the code. But 
>>>>>> in addition to carrying forward the bug, this path will cause 
>>>>>> problems for anyone doing hybrid runs off of other refcases. So 
>>>>>> my preference is to allow this answer change, but I recognize 
>>>>>> that this needs higher-level sign-off.
>>>>>>
>>>>>> Bill
>>>>>>
>>>>>
>>>>
>>>> _______________________________________________
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>>>
>>
>

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