EXCH_M is zero everywhere

[TJ12345]

I use WRF with options
bl_pbl_physics = 2
sf_sfclay_physics = 2

Values of EXCH_M (exchange coefficient for momentum) in wrfout files are zero everywhere.
Is there any way to output EXCH_M for Mellor-Yamada-Janjic scheme?

 

[Ming Chen]

Which version of WRF did you run? can you upload your full namelist.input for me to take a look? thanks.

 

[TJ12345]

I use WRF-4.1.1

I have attached my namelist.input.

If I set
sf_sfclay_physics = 1,
bl_pbl_physics = 1,
EXCH_M fields in wrfout are realistic, not zero.

 

[Ming Chen]

Hi,
This is because exch_m is not output from MYJ PBL. If you look at the code "module_bl_myjpbl.F, you will find :

     SUBROUTINE MYJPBL(DT,STEPBL,HT,DZ                                &
     &                 ,PMID,PINT,TH,T,EXNER,QV,QCW,QCI,QCS,QCR,QCG    & !BSF
     &                 ,U,V,RHO,TSK,QSFC,CHKLOWQ,THZ0,QZ0,UZ0,VZ0      & !BSF
     &                 ,LOWLYR,XLAND,SICE,SNOW                         &
     &                 ,TKE_MYJ,EXCH_H,USTAR,ZNT,EL_MYJ,PBLH,KPBL,CT   &
     &                 ,AKHS,AKMS,ELFLX,MIXHT                          &   !PLee (3/07)
     &                 ,RUBLTEN,RVBLTEN,RTHBLTEN,RQVBLTEN,RQCBLTEN     &
     &                 ,RQIBLTEN,RQSBLTEN,RQRBLTEN,RQGBLTEN            & !BSF
     ....
     ....

Note that exch_m is not listed as a dummy argument for output later. You may modify the codes, list this variable as a dummy argument and output it.

Please let me know if you have any question.