[RegCNET] how to calculate these

[BI XUNQIANG]

Dear Shekhar:

On Mon, 14 Nov 2005, M.Sudhanshu Shekhar wrote:

> I want to calculate velocity potential, stream function, rotational and
> divergence winds from the model result. How to proceed for the same ?
> 
Since GrADS mainly serves for global Lat-Lon grid datasets, I don't
know whether the function hcurl (for vorticity), hdivg (for horizontal 
divergence), and set gxout stream (for streamlines) work with the 
projected (with pdef line in your ctl file) data or not. I am afraid
that GrADS is not that smart (but I am not sure, does someone knows ?)


If you just want to use GrADS, the safe way would be:

Firstly, just choose one Lat-Lon window size inside your domain (your
interier interest region), and use "set gxout fwrite" way output u &
v fields for this Lat-Lon domain to one file, and you prepare the ctl
file (no pdef line in it) for this new data file of yours.

Then open the new file in GrADS, and use hcurl, hdivg and use
set gxout stream (for streamlines).

Does someone know a way to get velocity potential and stream function
in GrADS ?
I will try to find my FORTRAN code to calculate velocity potential
and stream function later.

Best regards,
Xunqiang (in Pragua) 
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~  Dr. Xunqiang Bi         email:bixq at ictp.it  ~ 
~  Physics of Weather and Climate Group        ~
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