[MITgcm-support] time step problem for cs510?

[Wang, Zhaomin]

Hi,

We have one run probably stopped by numerical instability. We used cube sphere 510 configuration, and initially used deltaT=1200. When the run was stopped, we reduced deltaT to 600. When the one was stopped again, we used deltaT=300. However, the run was also stopped even for this very small time step. We did not try to reduce deltaT further, because the instability may not be caused by a too large time step.  We got the following error message:

***********************
WARNING: r*FacW < hFacInf at       8 pts : bi,bj,Thid,Iter=   1   1   1   1694086
 e.g. at i,j=  24  24 ; rStarFac,H,eta =       NaN  4.281800E+02           NaN -1.058899E+00
STOP in CALC_R_STAR : too SMALL rStarFacW !
WARNING: r*FacS < hFacInf at       8 pts : bi,bj,Thid,Iter=   1   1   1   1694086
 e.g. at i,j=  23  25 ; rStarFac,H,eta =       NaN  4.281800E+02           NaN -8.253981E-01
STOP in CALC_R_STAR : too SMALL rStarFacS !
WARNING: r*FacC < hFacInf at       5 pts : bi,bj,Thid,Iter=   1   1   1   1694086
 e.g. at i,j=  23  24 ; rStarFac,H,eta =       NaN  4.281800E+02           NaN
STOP in CALC_R_STAR : too SMALL rStarFacC !
********************

Thanks.

Zhaomin

British Antarctic Survey
High Cross, Madingley Road
Cambridge, CB3 0ET
UK
Tel: +44(0)1223221488
Fax: +44(0)1223221279

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