[MITgcm-support] mitgcm seaice

[Jinlun Zhang]

Hi Mike,

The 0.25 value is used to prevent water drag from being too small in 
order to avoid possible instability. Water drag is often higher than 
0.25, so the insensitivity might not come from this. Otherwise, the ice 
V or ocean V might be a bit too small.

Cheers,

Jinlun

On 11/23/2022 9:02 AM, Michael A Spall wrote:
> Hi All,
> I am doing a problem with the MITgcm and the seaice package. The results are nearly insensitive to the value of SEAICE_waterDrag.
> I see in the code that if a certain condition is met then the drag is set to 0.25, which I suspect is being met in my calculations (I am
> checking this).  Can someone explain the reasoning behind this limit?
>
> from MITgcm_c67c, seaice_oceandrag_coeffs.F:
>
>             IF ( SEAICE_waterDrag.LE.0. ) THEN
>              CwatC(I,J,bi,bj)=0.
>             ELSEIF ( TEMPVAR.LE.(0.25 _d 0/SEAICE_waterDrag)**2 ) THEN
>              CwatC(I,J,bi,bj)=0.25 _d 0
>             ELSE
>              CwatC(I,J,bi,bj)=SEAICE_waterDrag*SQRT(TEMPVAR)
>             ENDIF
>
> Thanks,
> Mike
>
> ==================================================================
>
> Michael A. Spall
> Senior Scientist
> Clark 323A
> Department of Physical Oceanography
> Woods Hole Oceanographic Institution
> 360 Woods Hole Road MS #21
> Woods Hole, MA 02543
>
> 508-289-3342
> mspall at whoi.edu
> https://urldefense.com/v3/__https://www2.whoi.edu/staff/mspall__;!!K-Hz7m0Vt54!nS_Dw_xQpzrotMZ2-NkZZ2MwbO4ort_7yY9DyiMC6iuck-GyACH2psYlBuH2mbOXELbNedtpD81SnnU$
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> https://urldefense.com/v3/__http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support__;!!K-Hz7m0Vt54!nS_Dw_xQpzrotMZ2-NkZZ2MwbO4ort_7yY9DyiMC6iuck-GyACH2psYlBuH2mbOXELbNedtp8fziL7Q$