[MITgcm-support] KPP diffusivities

[Stefano Querin]

Hi,
I'm having some problems with the KPP eddy viscosity/diffusivity profiles.
I'm running the MITgcm model with kpp, obcs, exf and cal packages to study a very shallow gulf (max depth 25 m). The model domain is 88 x 128 x 28 points, with resolution of 250 x 250 x (0.5 for the 6 upper layers, 1.0 for the remaining 22) m.
I attach a time-depth plot of temperature (filled color) and KPP temperature eddy diffusuvity (contours). The simulated event is a strong wind episode after some days of hot summer weather (strongly stratified water column): the wind breaks the initial stable thermohaline stratification. During all the simulation, it seems that the increase in turbulent motions due to night surface cooling is shifted to noon and (even stranger...) to the bottom of the water column!!!

Regarding the exf pkg, I'm using the configuration specified below:


c    WIND |TEMP |DOWN |BULK |EVAP |            actions
c    -----|-----|-----|-----|-----|-------------------------------------

...

c     def | def |  -  | def |  -  | Read-in uwind, vwind, atemp, aqh,
c         |     |     |     |     | swflux, lwflux, precip, and runoff.
c         |     |     |     |     | Compute ustress, vstress, hflux,
c         |     |     |     |     | and sflux.
c         |     |     |     |     |

The sign and magnitude of surface fluxes is right (I checked it twice against the  exf_fields.h  values), also because the temperature plot seems reasonable (surface warming during the day). I'm rather sure that the diffusivity plot is not flipped: the increase of turbulent motions caused by the wind is near the surface, as it should...
It seems that the turbulent activity due to wind is computed correctly, while the one caused by convection is somehow inverted (in time and depth).
I'm also rather sure that I made some mistakes somewhere but I really don't know where! Probably it's something trivial (shame on me...)!
Any guess? In the meantime, I will contine to look into the KPP related routines...

Thanks!

Stefano

P.S.: have a nice and frightening Halloween!
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