why i can not find wrf_helicity in WRFUserARW.ncl script in NCL 6.0

hi everyone.
 I am reading same ncl sample functions scripts and WRFUserARW.ncl in
NCL6.0. I found
 that there are not the key parameter about "wrf_helicity" in the
WRFUserARW.ncl .But
 in the sample script wrf_helicity_1.ncl ,the only load ncl scripts
are gsn_code.ncl
and WRFUserARW.ncl.
Can anyone tell me why and where is the wrf_helicity ?thanks

-- 
TANG Jie

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Received on Fri Feb 17 08:22:33 2012