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

[Flynn Ames]

great thanks for this Jeff - this makes sense!

Thanks again,
Flynn
________________________________
From: MITgcm-support <mitgcm-support-bounces at mitgcm.org> on behalf of Jeffery R Scott <jscott at mit.edu>
Sent: 21 March 2023 2:04 PM
To: mitgcm-support at mitgcm.org <mitgcm-support at mitgcm.org>
Subject: Re: [MITgcm-support] Inertial stability criterion in tutorials - Quick question

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
_______________________________________________
MITgcm-support mailing list
MITgcm-support at mitgcm.org<mailto:MITgcm-support at mitgcm.org>
http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support<https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmailman.mitgcm.org%2Fmailman%2Flistinfo%2Fmitgcm-support&data=05%7C01%7Cf.ames%40pgr.reading.ac.uk%7Cd415deabd0b8436c789408db2a156263%7C4ffa3bc4ecfc48c09080f5e43ff90e5f%7C0%7C0%7C638150043553816253%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=v0a2%2FVGZ6MHapH4KHjCDF6Yf7xG0I1OdDbmmu4NemyQ%3D&reserved=0>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20230321/7b412c6c/attachment.html>