[MITgcm-support] Inertial stability criterion in tutorials - Quick question

[Jeffery R Scott]

Hi Flynn,

In the past few years we’ve updated and improved the first few tutorials, including expressing the stability criteria more specific to the time-stepping scheme  being used (Adam Bashforth II, the model default). The global tutorial has not yet been updated; presently, we’re working on an improved coarse global setup. The inertial stability criterion in this older tutorial is more general, ie not specific to the ABII scheme, and as such, a bit more lenient.

Best,
Jeff


On Mar 20, 2023, at 9:30 AM, Flynn Ames <f.ames at pgr.reading.ac.uk<mailto:f.ames at pgr.reading.ac.uk>> wrote:

Dear MITgcm community,

Hello -  I have a very quick question regarding stability criterion in the MITgcm tutorial experiments I was wondering if someone could answer?

In the first three MITgcm tutorials, the stability criterion for inertial oscillations using Adams Bashforth is stated as:      f*delta_t >  0.5 for stability.

However in a later tutorial - the global ocean simulation - the inertial stability criterion is stated as:          f^2*delta_t^2 > 1.0 for stability.

I.e., the inertial stability criterion in the global ocean simulation is much more lenient.
As far as I can tell, this tutorial also uses the Adams Bashforth time-stepping scheme. So i'm wondering if anyone could explain why a different inertial stability criterion applies here? and under what circumstances either version of this criterion should be used?


Thank you for your time!
Flynn
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