ROMS<kshedstrom version> blowing-up with ' REASON: KEchar = NaN, PEchar = NaN' report

[yangwu1215]

I'm recently studying the kshedstrom version <https://github.com/kshedstrom/roms/tree/master>, and trying to set the vertical s-coordinate manually.
However, if I set the s-coordinate with an intersified surface layer, the model blow up with the 'REASON: KEchar = NaN, PEchar = NaN' report. The following is the s-coordinate, error report , and running log.

While, if I set the s-coordinate following the 'vtransform=2, vstretching=4' option, the model works successfully. The following is the s-coordinate, which has a uniform vertical spacing of 0.03.

Hope to get some help with this problem. Great thanks!

[kate]

That's a very intensified surface layer. Did you try a shorter timestep? There are numerical limitations on the vertical operations which can cause blow-ups like that.

[yangwu1215]

Thank for for the suggestion. The model works if I reduce the dt from 300s to 10s.