[MITgcm-support] Student with a question/issue with the KPP package

[Dhruv Balwada]

Hi Taylor,

KPP computes a mixed layer depth that depends on surface forcing, ocean
buoyancy profile, and velocity profile. A Richardson number is calculated
(equation 21 in Large 1994 Rev. of Geophysics), and the Hbl set to the
smallest depth where Richardson number equals some critical value. As you
are doing an offline calculation, I am assuming you have no forcing. Also,
because you use daily averaged velocities, which are presumably smooth, you
don't generate small Ri in the domain. You could try to look at what the
boundary layer depth was in the online simulation that generated the
velocity fields in the first place, if you just want an estimate. If you
care about having a region of enhanced mixing near the surface in the
biogeochem model, then you might need to think of a more clever work
around.

Best,
Dhruv

On Wed, Jun 20, 2018 at 12:41 PM, Taylor Shropshire <tas14j at my.fsu.edu>
wrote:

> Hello,
>
>
> Background:
>
> I am running an offline biogeochemical model using MITgcm for the Gulf of
> Mexico. Flow fields are from previously computed daily averages and are
> prescribed daily in the model.
>
>
> Issue:
>
> I have KPP outputting its variables weekly: KPPviscAz, KPPdiffKzT,
> KPPdiffKzS, KPPGHAT, KPPHBL.
>
>
> When I look at the output of KPPHBL (mixed layer depth) I find that it is
> always 5m at every record at every grid point. Why is this happening in my
> simulations?
>
>
> Thanks for your time,
>
> -Taylor
>
>
>
> *Taylor Shropshire PhD Candidate - Oceanography*
> *Center for Ocean - Atmospheric Prediction Studies*
> *Florida State University*
>
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>
>
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