Calculating & displaying meridional stream function

[Miller, Tim]

Hi all,
I have global wind data at 1.25 degrees resolution and need to calculate
and display a mean meridional wind stream function in GrADS.  I'm
calculating a zonal mean meridional wind as vbar=ave(v,x=1,x=288) and can
display it.  Then I want to calculate and display psi, where psi(z)=psi(z-
1)+vbar(times weighting factor).  I'm having trouble figuring out a way to
structure this within GrADS.  Psi needs to be a 2-D array, but I want to
calculate it one level at a time, referring to the result of the level
below.  Any suggestions, or a script for me to use?  Thanks.
Tim Miller
NASA/MSFC