[Mitgcm-support] RE: about kpp & flt

[mitgcm-support at dev.mitgcm.org]

Salut Jean Michel, actually KPP_ESTIMATE_UREF is supposed to be a
quick-and-dirty, yet-untested fix to problem of assuming that first model
level velocity is the "surface layer" velocity in computation of bulk
Richardson number for determining mixed layer depth for KPP.  Typically, for
wind-driven (not buoyancy) mixed layers, the surface layer is approximately
10% of the mixed layer depth.  So this problem can be exacerbated, not
improved, with lower vertical resolution near the surface ... unless of course
your first model level is deeper than the typical wind-driven mixed layer, in
which case this issue is irrelevant.  At some point I am hoping to come back,
test, and fine-tune this bit of code ... but until then it's a good idea not
to use KPP_ESTIMATE_UREF.  When I get back to it, I will make sure to clean up
code and make it more robust to sign and double-minima issues you raised.

Amicalement, Dimitris