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[GEMPAK #ULU-782715]: how to get wind component

To answer your first question, you can simply use SFPARM = UWND;VWND (for wind 
in meters/second) or SFPARM = UKNT;VKNT (for knots) in the SF programs to find 
the U and V components of the wind, provided your surface file has the wind 
speed and direction parameters.

See the SFPARM man page for more information:

http://www.unidata.ucar.edu/cgi-bin/gempak/manual/variables_index?sfparm

As for your second question, you can check if UWND and VWND are in your grid 
files with the program GDINFO

http://www.unidata.ucar.edu/cgi-bin/gempak/manual/programs_index?gdinfo

Finally, UREL and VREL are in meters per second, as defined in the grib product 
they are decoded from,  using table $GEMTBL/grid/wmogrib2.tbl.  This table 
defines the parameter names, units and scaling for the grib parameter id from 
the model output.

To output in knots, you can use KNTV(UREL) and KNTV(VREL)



-Michael



> dear sir:
> 
> I'm very thanks for your advice to help me solve the problem creating
> correct surface file .  however there 3 questions to want you help.
> 
> First question, I want to get the wind components u and v by wind
> dircetory and speed.could you told me what should I do ?
> 
> sceond question ,are both uwnd and vwnd  in the grd files if I want to
> draw a streamline by gdstream program?
> 
> finally, could you told me the difference between uwnd and urel?
> 
> thanks
> 
> 2009-08-17
> 
> 
> 
> gcs
> 
> 


Ticket Details
===================
Ticket ID: ULU-782715
Department: Support GEMPAK
Priority: Normal
Status: Open