Technical Working Group Meeting, April 2019

MW: Discovered travis test GFDL uses for FMS has been failing for six months. MW fault. Introduced new MPI function. Function doesn’t exist openMPI 1.6, which is what travis uses. Doesn’t show up in MOM5 as changes not in there. Solution was to switch to MPICH. Bleeding edge travis only uses openMPI 1.10.

FMS in MOM5

AH: Link FMS rather than have in repo. NH: I agree. MW: Still think subtree best solution. Now FMS has dedicated automake build can formally install as module? MW: Had a long chat about this with Alistair. Not hot on submodule/subtree. NH: Just have in CMake or a script. AH: Makes sense.

RF: One of my jobs with decadal project is to have MOM5 linked with AM4. Uses a more recent version of FMS. Will be useful for RF. Have to get MOM5 talking with FMS used in AM4. MW: Have run MOM5 with latest FMS. RF: Just making sure no surprises, changes of interfaces. Not just FMS, also other bits and pieces. AH: Auto testing with multiple FMS.

MW: If we go path of building independent libraries, not sure how C world tracks this? ABI changes? How do you manage binary compatibilities? NH: Did that with OASIS, and not sure it was worthwhile. MW: C programs don’t seem to have these issues. NH: Using precompiled libs necessary in linux, for us not reason not to compile FMS when compiling MOM. MW: Not keeping public library? NH: More complexity than necessary. We’re just talking about splitting source code out into separate repo. Good idea. MW: MOM6 has FMS repo, and a macro repo above that the builds everything. Not sure we want to go that way. NH: access om2 works that way too but experiment repos are separate. MW: Maybe submodules / subtrees aren’t so bad. NH: MOM5 repo can have a build script that references a build script for FMS. MW: Doesn’t CMake have some functionality to check it out for you.

AH: Finish off CMake build scripts and add in FMS stuff.

MW: What they do with MOM6 is having issues. Will bring up with them. Maybe some convergence on library dependencies. AH: Don’t favour central lib install with MPI dependencies.

RF: Not much to report. Make sure WOMBAT can be called in MOM-SIS. Only outstanding issue. Just changing a few if statements. MC: Comfortable that it will run in ESM framework? RF: Not sure who is going to test? MC: OM2? RF: Should run in OM2.

MC: Richard Matear went to visit AH. I haven’t run anything yet. With experiments running under payu ready to go. OM2 test with WOMBAT.

AH: Is there a PR for these code changes? Make a PR. RF: Maybe said to do that. Split up testing to avoid duplication.

MC: Hakase wants to run this too I believe?

AK: Set up RYF for Spence. Run 20 years. Looking at test bed for improved config. Improved bathy from RF. Conservative temp. Running at half the cost of previous config. 10Mh/yr, 60-65 KSU. Speed up from higher time ocean tilmestep, and ice is now 2 time steps per ocean timestep, compared to 3. Due to removal of fine cells in bathymetry in tripole. Wanted to use non-mushy ice, but low ice con in Baltic fails to converge thermodynamic temp profile. Should converge in a few steps, but limit at 100 and still doesn’t converge. Paul is using mushy. Had a run with non-mushy up top crash. Spinup7 is mushy spinup8 is non-mushy. 10-15% extra cost for mushy ice. Not sure if we’re CICE or MOM bound. Other resolutions are not using mushy. Want to set up an IAF tenth run starting in 1958. Can afford with cheaper model.

AK: TEOS-10, not sure if we want to use. Need absolute salinity and cons temp.

AK: Noticed gyres are much too weak in all resolutions. Looks have to careful with JRA55. Did a test with 0.25 with abs wind rather than relative. No change. Florida current 65%, EAC about 70%. Gulf stream is not separating properly. Mean position ok, but to variable. Maybe insufficient momentum. Doesn’t go around grand banks properly. Causes SST biases. Not sure how much to fix before IAF.

NH: All resolutions? AK: All resolutions are too weak. Gulf stream separartion is ok in tenth in average, but too much variance. Mean position in 0.25 is really bad. Biases around grand banks similar in all resolutions. NH: Improving separation improve biases? AK: Maybe. SSH is localised in model, but stretched out in obs.

NH: Is this specific to JRA55? Does it happen with CORE forcing as well? AK: Don’t know. Griffies said others find gyres a bit weak with JRA55. It uses scatterometer winds, which are relative to an eddying ocean. Not in the same location as a model. JRA55 paper suggest adding climatological mean current to the wind to force the ocean. AH: Should that be in the product? AK: Griffies says people aren’t too keen on Sujino suggestion. AH: Diagnose wind stress from 0l25 test? AK: yes. 10-20% change in stress in western boundary currents and southern ocean where large mean currents. Stress changes are in quite small areas, not a big effect on gyres.

MC: Do you recall what the EAC numbers were in model compared to obs. I thought we had 20Sv which is similar to OFAM/BRAN. AK: Obs: 18.7, 17.5 and 17.2 Sv about 2000m in models. 22.1 pm 7.5 from a mooring. Florida current is 30% too low. Well observed.

NH: What is big challenge in future? AK: Not sure how much to change before next IAF. Will put out a call for diagnostics. Also explain config and see if people have an issue with that.

AH: Doesn’t MOM5 not fully support TEOS-10? RF: Not obvious to user that can use TEOS-10. Kind of fudged. Proper way is to carry an extra tracer. Have preformed salinity and an adjustment factor to create abs salinity. Another way is to have abs salinity as a single variable and adjustment factor is zero. To use full TEOS-10 in MOM5, need 2 tracers. If you do it the same as the rest of the world would have a zero tracer. Don’t want a wasteful tracer.

RF: There is a newer way to parameterise the equation of state. Need updated. AH: New module? RF: Yes, just switch.

RF: Frazil not being redistributed. Needs fixing. AH: Affect other runs? RF: No just FAFMIP.