how to calculate the average moisture flux over a period of time.

[liuzf406]

Dear Users,
 
I  need to calcualte the average moisture flux at the level 500 hPa over a period of time. I calculated the mean values for 1969 and 1972, respectively, but it seemed that there is no difference between the two years. I don't know why it is. Can anyone please give me a help?
Thanks in advance.
 
 The gs file for calculating average moisture flux  of 1969 is as following:
'reinit'
'set grid off'
'set grads off'
'set poli on'
'set parea 1 10 1 8'
'sdfopen shum.mon.mean.nc'  
'sdfopen uwnd.mon.mean.nc' 
'sdfopen vwnd.mon.mean.nc'
'sdfopen pres.mon.mean.nc'
'set lat 30 90'
'set xlint 40'
'set lon -160 -40'
'set ylint 30'
'set mpdset cnworld mres'
'set map 1 1 1'
'draw map'
'print'
'disable print'
'enable print flux69.gmf'
'set gxout shaded'
'set ylopts 1 4 0.1'
'set xlopts 1 4 0.1'
'set cint 0.5'
*'set ccols 9 14 4 11 5 13 3 10 7 12 8 2 6'
'set ylopts 1 4 0.1'
'set xlopts 1 4 0.1'
'set arrowhead 0.05'
*'set arrscl'
'set lev 500'
'define qu=shum.1*uwnd.2'
'define qv=shum.1*vwnd.3'
'define aqu=ave(qu,t=253,t=264)'
'define aqv=ave(qv,t=253,t=264)'
'define uv=ave(mag(qu,qv),t=253,t=264)'
'd mag(qu,qv)'
'd aqu;aqv'
'set arrscl 0.1 50'
'set arrowhead 0.2'
'run cbar.gs'
'set gxout contour'
'print'
'disable print'
 
 
 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://gradsusr.org/pipermail/gradsusr/attachments/20100401/c4b80017/attachment.html