[MITgcm-support] ECCOv4 Configurations: R-Star Coordinate Error with Modified Wind Forcing

[Martin Losch]

Hi Yohei,

if this is related to sea ice and if you are using the ECCOv4-r2 sea ice parameters (thi is what I found: https://github.com/gaelforget/ECCOv4/blob/master/input/data.seaice), then you could try to set 
 SEAICEpressReplFac = 0.,
and rerun (from the beginning). I have also tried to get rid of landpoints where wind forcing “pushes” ice into corners where it cannot escape. The eccov4-r2 data.seaice contains large (400) diffusivities for seaice variables, which probably were used to alleviate this problem (@Gael, correct me if I’m wrong). In my experience, this is no longer necessary with SEAICEpressReplFac = 0.,

Martin


> On 11. Feb 2024, at 18:00, Yohei Takano - BAS <yokano at bas.ac.uk> wrote:
> 
> Dear all,
> 
>    I am working on setting up a simulation with the ECCOv4-r2 configuration. The first step is to
> run (spin-up) the model with this configuration, except I detrended the atmospheric wind forcing
> (including zonal, meridional wind stress and surface wind speed). The model ran for a while (~ 10 years)
> but stops after that with "STOP ABNORMAL END: S/R CALC_R_STAR", which is related to the r* coordinate
> from my understanding. More specifically it is "too SMALL rStarFac[C,W,S]" and I see very small 
> hFactorC (from diagnostics) at a grid point near the continent (or perhaps sea ice related since it is in the Southern Ocean).
> 
>    The reason behind the error is this modified atmospheric wind forcing but I am a bit stuck on how I can
> fix this issue (i.e. how can I further modify the forcing to prevent this error) and would like to ask for advice on dealing with
> this issue. I saw comments in the previous question (in this list) lowering deltaT but I don't think that will solve the issue in this case. 
> 
>     rStarFac error actually happens quite often in my case modifying the atmospheric forcing and for those
> who have experienced similar challenge, I would like to ask for some advice how to deal with this.
> Thank you in advance.
> 
> Regards,
> 
> Yohei
> 
> 
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