[MITgcm-support] Identifying location from processor & i,j

[Martin Losch]

Hi Dafydd,

you should be able to figure out/print out the values of XC,YC at these points, which tell you where on the sphere you are.

In my experience, this type of error (crash after a few years of simulation) is related to the sea ice thickness piling up over time and depressing etaN until the ocean cells become too thin. This happens often in the “single grid bays” into which ice is pushed and where ice cannot move out easily. I “advocate” turning off the pressure replacement method (because that tends to make immobile thick ice very weak and prone to further convergence/compression), i.e. set SEAICEpressReplFac=0., in data.seaice, but you can also cap the load of the sea ice on the water column (#define SEAICE_CAP_ICELOAD, but checkout seaice_growth.F where the ice load is limited to 1/5 of the surface grid cell thickness, l344, can be made larger).

Martin

> On 25. Oct 2021, at 19:27, Dafydd Stephenson <dafydd at ucar.edu> wrote:
> 
> Hi everyone,
> all of my runs seem to eventually (after a few model decades) exit with the error “ STOP in CALC_R_STAR : too SMALL rStarFac[C,W,S] ! ”. I am running the ECCOv4r4 configuration with CORE Normal Year Forcing.
>  
> I have enabled monitoring at the timestep frequency, and, as the forcing repeats yearly, comparing the monitoring statistics with those of the previous year seems useful. Plotting them shows that they are comparable until the point of the error (at which point one of the line plots stops suddenly while the other continues), so I don’t believe there to be a CFL violation or any sort of runaway instability. Similarly, I have balanceEmPmR=.TRUE., so I don’t think that a cell is running dry.
>  
> Nevertheless, the error seems to occur in the same location every time (processor 94 of 192 [or 47 of 96, depending on the config], at i,j=2,13), and I think it would be useful to know exactly where this is. Is there some way I could get from this CPU,j,i location to an index of the llc90 grid?
>  
> Thanks in advance for any help,
> Dafydd
>  
>  
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