[Liwg-core] co-chairs notes 1-3-17

Marcus Löfverström marcusl at ucar.edu
Tue Jan 3 11:56:34 MST 2017


Hi Bill,
one clarification, do you mean if we want to change the rain-snow
partitioning within the CAM/CLM gridcells based on the surface slope (as
Julio suggested a while ago) or are you referring to something else?

// Marcus

On Tue, Jan 3, 2017 at 1:37 PM, Bill Sacks <sacks at ucar.edu> wrote:

> One specific question is whether we want to change the rain-snow
> partitioning at all at this point. If so, we'll need to decide that soon.
>
> Bill
>
> On Jan 3, 2017, at 11:21 AM, Bill Sacks <sacks at ucar.edu> wrote:
>
> Hi all,
>
> Here are the notes from today's meeting. Many relevant notes so I'm just
> including everything. Some of these notes will make more sense when
> accompanied by the slides – and there is some good information on the
> slides that I didn't duplicate here – specifically about the latest
> atmosphere developments. I assume JF will send out the slides soon.
>
> One item I'd like to call your attention to: There was some question as to
> whether Julio's latest runs – specifically GRNL03 – are acceptable in terms
> of Greenland precipitation. The general feeling was that there might not be
> much more we can do if the answer is "no", but they'd still be interested
> in your answer.
>
> Bill S
>
>
>
> * January 3, 2017 *
>
> *CSL*
>
> JF: These numbers may not be updated correctly. We should see our new
> Cheyenne allocation reflected.
>
> Jim E: Nothing official on the timing of Cheyenne, but he heard the week
> of the 20th.
>
> ----
>
> *Summary of where we stand*
>
> Angular momentum: Decision has been made to turn off the changes to
> angular momentum. It is available as an option, but it will be off for
> CESM2: there was too much uncertainty with this, given everything else
> going on.
>
> ----
>
> *Sub-grid orography changes*
>
> Propose just making this change over Greenland.
>
> Julio: While this feels somewhat arbitrary, it is somewhat justifiable
> based on the conditions over Greenland.
>
> Julio did some runs where he also applied this over Antarctica. It didn't
> improve things much there, and he's concerned that it might have
> detrimental effects in other parts of the model (e.g., WACCM). So he feels
> that the best thing is to just apply this over Greenland, admitting that
> we're making this local adjustment.
>
> This has NOT been tested with WACCM. We need to do that.
>
> Joe: Ideally, we would apply this globally; we should just be up-front
> that we're doing this over Greenland because we care about the evolution of
> land ice in Greenland. Julio agrees, but also feels that there is at least
> some physical justification for this.
>
> There was some discussion of whether / how this will work with
> an interactive ice sheet. Most of the CMIP6 runs will NOT have an
> interactive ice sheet. Those that do (for ISMIP6) can (at least in
> principle) regenerate CAM subgrid orography following the same method as
> Julio has used. (Note that CISM has topography at 4 km, which is
> sufficiently high resolution for this.) Note that Julio's scheme doesn't
> use any information about the ice sheet edge – assuming that some of this
> effect comes from the rough topography left behind as the ice sheet
> retreats.
>
> Are ice sheet modelers happy with the final precip? Unsure... feeling is
> it's probably barely acceptable, but not totally sure.
>
> ----
>
> *Supersaturation*
>
> Andrew: The instances of unphysical supersaturations are infrequent. They
> are going to let these unphysical supersaturations stay, because removing
> them led to too high climate sensitivity. We don't have time to do this
> right, so are going to live with these infrequent unphysical events.
>
> ----
>
> *Angular momentum fixes*
>
> WACCM QBO could probably be improved again via tuning. But this would take
> time and the WACCM group was uncomfortable with this since they don't have
> a good physical understanding of why these things would change.
>
> ----
>
> *CAM - model skill*
>
> SST: Overall Rich feels like this isn't too bad. We've done better, but
> this isn't bad.
>
> Too much cloud over tropical land: We can probably tune this. If not, we
> could live with it as is.
>
> JF: Do you expect any impact on ENSO? Rich: Unsure... we can look.
>
> Climate sensitivity: Based on just 6 years: seems we have lower
> sensitivity than 119, but the question is: is it low enough.... Run has
> been updated to 12 years, and now there seem to be bigger differences. In
> addition, RESTOM is dropping in the new run as we'd want it to (which we
> didn't see in 119). Overall, the new 4xCO2 looks more like what we've seen
> in the past (as opposed to 119).
>
> ----
>
> *Some other changes that need to come in*
>
> *• *CLM:
>
>    - Dave L: Can bring in latest tunings once other components are ready
>    - Working on new transient data sets
>    - Overall, nothing in the way of us finishing soon
>
>
> • Ocean:
>
>    - Need to change coupling from 2-hour to 1-hour
>    - Caspian Sea needs to be brought in
>
>
> • Chemistry
>
>    - Need to update the emissions
>
>
> • BGC
>
>    - Keith: There's a lot on the MarBL development side that needs to
>    come onto the trunk. Small amount of development needed for marginal seas
>    - Needs some tuning, but there's a chain of dependencies:
>    e.g., waiting for dust retuning, which is waiting on land retunings.
>
>
> • CISM
>
>    - Bill S: New grid in place, including new mappings. Will come in in
>    alpha06a. (New projection, and slight update to glacier cover.)
>    - There are still some other changes needed, but they will have 0
>    impact on these runs with a diagnostic ice sheet.
>
>
> • CIME
>
>    - Mariana: In good shape. The biggest need right now is documentation.
>
>
> ----
>
> *Estuary Box Model*
>
> John T brought up the question of whether we want to keep the EBM – which
> we originally brought in because it fixed the Lab Sea Ice – now that it
> looks like we have a somewhat warmer climate there, and this may not be
> needed
>
> Rich: Shouldn't count on the warmer climate – may be decadal variability
>
> Gokhan: Asks himself that question, too. But feels we should keep EBM
> because it's more physically realistic anyway.
>
> ----
>
> *Integrations*
>
> 125 continuing
>
> 4xCO2 continuing
>
> We should do runs with some of the other changes, but save Caspian Sea
> change for later, since there were some issues with that.
>
>    - Rich feels we should do Julio's changes separately, so we can have a
>    run with final atmosphere, and then do other changes on top of that.
>
>
> Dave L feels we can shoot for new land with updated parameters around the
> end of the week.
>
>
>
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>


-- 
Marcus Löfverström (PhD)
Post-doctoral researcher
National Center for Atmospheric Research
1850 Table Mesa Dr.
80305 Boulder, CO, USA

https://sites.google.com/site/lofverstrom/
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