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Obukhov length in wrfout?

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Is there a way to compute the Obukhov length using wrfout variables. I see friction velocity as an output, but not turbulent temperature flux.

If you output the variable RMOL, which will give the inverse of the Monin-Obukhov length, so you could calculate it from that.

This variable is not currently set to output in the history files. There are 2 ways to turn it on:
1) Modify the WRF/Registry/Registry.EM_COMMON file. In this line:
state    real  RMOL             ij      misc        1         -      r        "RMOL"                  "1./Monin Ob. Length"                      ""

You'll need to add an 'h' for 'history in the I/O column, so that it reads:
state    real  RMOL             ij      misc        1         -      rh        "RMOL"                  "1./Monin Ob. Length"                      ""

The downfall with this option is that you will have to clean, reconfigure, and recompile the model.

2) A simpler option may be to use the Runtime I/O option. You can read more about that here: