[Wrf-users] I have a confusion on the use of Smagorinsky and TKE coefficients when i have to use them for real case Masoscale to Large-eddy simulations

[KPAIKPAI Batebana]

Dearmembers,


 I'm using WRFV3.8,
Ihave a confusion on the use of Smagorinsky and  TKE coefficients when ihave to apply them for real case Mesoscale to Large-eddy simulation.

In .. /WRFV3/test/em_les/namelist.input,  Smagorinsky coeff and  TKE coeff arerespectively 
 c_s                               = 0.18

 c_k                               = 0.10


 
While, in ../WRFV3/test/em_real/README.namelist c_s                               = 0.25     ; Smagorinsky coeff

 c_k                               = 0.15     ; TKE coeff

This is new in WRFV3.7 but this coefficientswere not listed in the namelist.input from em_real directory

There is also no detail on these coefficents inthe user's guide.


 
1) I would like to understand the meaning of thedifference between these coefficients from Large-eddy simulation to real casesimulation2) Can i set these coefficients in my simulationin real case test? If yes then are they always together or one can make achoice to set on one of them?


 
3) My confusion has increased when i have seenthe details on eddy coefficient options (km_opt) fromWRFV3/test/em_real/README.namelist which purpose is to specify the turbulenceparameterization. So i couldn't know how  c_s and c_k arerelated to km_opt when i have to use 2D Smagorinsky and 3D TKE1.5. 

I may be grateful if anyone can give me somedetails about my concern
Regards,

 
M. KPAIKPAI Batebana,Ex-Président de l'ASETOC
Doctorant au Laboratoire de Microphysiques et Précipitation Orageuse,
Institue de physiques de l’Atmosphère,
Université de l’Académie des Sciences de Chine (CAS),Pékin – Chine   
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