[Wrf-users] TKE equation and model tendency

[Maria Vittoria Guarino]

Dear All,


I am interested in calculating each individual term of the TKE equation that the model uses to compute the total TKE given in output.

In my simulations I am not using a PBL scheme but I am letting the model explicitly solve the turbulent mixing by using the prognostic TKE equation (km_opt=2).


Following the Technical Notes and having a look at the code in module_diffusion.em I managed to calculate shear production and buoyancy production/destruction by extracting from the model output each component of the deformation tensor (D11, D22, D33 etc..) and the eddy viscosity Kmv, Kmh, Khv. However, the dissipation term seems to be more difficult to calculate and I got some very high values that I don't trust.


In addition, what I have at the moment is, for example, the shear production per unit mass per second (m^2/s^3) but If I want to compare it with the (total) TKE in output (m^2/s^2) I need to know the model tendencies.

I saw the variable tke_tend is in the Registry file but it is a i1 variable (not a state one) so even if I edit the Registry adding an "h" tke_tend is not present in wrfout.

I also tried to add a new line to Registry, this time defining tke_tend as a state variable, by doing this I do get the variable in the output but it is zero everywhere.


Summarizing, I have two questions:


- did someone extract the tke tendencies? if yes, how?  do I have to make some changes to the model code?

- did someone calculate each term of the tke equation? if yes, I would be glad if I could double check the method I am using to do it with this someone.



Thank you very much,


Regards.


Vittoria


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Maria Vittoria Guarino
PhD Student
Mountain wave breaking in atmospheric flows with directional wind shear
Room 306, Lyle Building
Department of Meteorology
University of Reading, Earley Gate, Reading, RG6 6BB
Email: m.v.guarino at pgr.reading.ac.uk
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