[gradsusr] How to calculate the velocity potential for a local domain ?

[Arlindo Meque]

 Dear Jayakrishna,  
I've tried the script but
the problem persists:  
 ga-> define
psi= fish_psi(u,v.2)
Error from fish: rc = 1000
Operation
Error:  Error from fish function
Operation Error:  Error
from fish_psi function
  Error ocurred at column 1
DEFINE
error:  Invalid expression.  
If push comes to shove I'll try the
idea proposed by Bernd Becker  (Thanks for the email !!!)

Arlindo 

 



________________________________
 De: Jayakrishnan P.R <prjayakrishnan at gmail.com>
Para: GrADS Users Forum <gradsusr at gradsusr.org> 
Enviadas: Quinta-feira, 28 de Fevereiro de 2013 19:11
Assunto: Re: [gradsusr] How to calculate the velocity potential for a local domain ?
 

Dear Arlindo,
                I herewith attach a GS file in which velocity potential and stream function is computed from u and v components. I attempted this long back and I am sorry to say that I could not remember the whole steps. Still I hope this may be useful. Also the following link may be useful.
http://opengrads.org/doc/udxt/fish/fish.html#computing_velocity_potential_from_wind_components

'reinit'
'sdfopen /media/JKPRMUSIC/JKPR/DATA/ncep/d/uvw/uwnd.2000.nc'
'sdfopen /media/JKPRMUSIC/JKPR/DATA/ncep/d/uvw/vwnd.2000.nc'
'set lon 0 357.5'
'set lat -90 90'
prompt 'key-in file name for psi:'
pull fname
'set fwrite 'fname
tt=1
while (tt<=10)
'set t 'tt
zz=1
while (zz<=2)
'set z 'zz
'define psi= fish_psi(uwnd,vwnd.2)'
'define one=1+0*lat'
'define upsi=mvadv(one,psi)'
'define vpsi=-muadv(one,psi)'
*'set gxout shaded'
*'display psi/1e7'
*'set gxout stream'
*'display upsi;vpsi'
'set gxout fwrite'
'd psi/1e7'
'd upsi'
'd vpsi'
zz=zz+1
endwhile
tt=tt+1
endwhile
'disable fwrite'

If any suggestions I will again look into my old archives. Best of Luck.

-- 
Sincerely
***********************************************
Jayakrishnan.P.R
Teaching Associate (Atmospheric Science)
Academy of Climate Change Education and Research
Kerala Agricultural University
Vellanikkara-680 656

and also

Research Fellow (Part Time)
Department of Atmospheric Sciences
CUSAT, Cochin-682 016
Kerala, India.
Mob: 09496026547

*********************************************** 
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