[gradsusr] level dimension didn't vary in gs file

[resmi ea]

Dear all users
this is my gs file; the  ctl file is given below. i want to file u-wind
anomaly fro the grid 0-90N and 0-357.5
at 1000 t0 10 hPa level for a single day(time= 1feb2008)
The grd file has shows the output at a single level
The problem is output result didnot vary at different levels

'reinit'
'sdfopen /media/resmi-1/windows/ncep/uwnd/200h_uwnd/uwnd.2000_10.nc'
'set lat 0 90'
'set lon 0 357.5'
*'set lev 850'
'set time 1feb2008'

'set gxout fwrite'
'set fwrite stj850_26j.grd'
n=1
while(n<=17)

'set z 'n
'define tt=uwnd(time=1feb2000)'
'define tt1=uwnd(time=1feb2001)'
'define tt2=uwnd(time=1feb2002)'
'define tt3=uwnd(time=1feb2003)'
'define tt4=uwnd(time=1feb2004)'
'define tt5=uwnd(time=1feb2005)'
'define tt6=uwnd(time=1feb2006)'
'define tt7=uwnd(time=1feb2007)'
'define tt8=uwnd(time=1feb2008)'
'define tt9=uwnd(time=1feb2009)'
'define tt10=uwnd(time=1feb2010)'

'define daymean=(tt+tt1+tt2+tt3+tt4+tt5+tt6+tt7+tt8+tt9+tt10)/11'
*'d daymean'
'define dayanom=tt9-daymean'
*'d dayanom'

n=n+1
endwhile
'disable fwrite'

Control file

 DSET  /media/resmi-1/windows/ncep/uwnd/200h_uwnd/stj850_26j.grd
 undef -999.99
 xdef 144 linear 0 2.5
 ydef 37 linear 0 2.5
 zdef 17 levels 1000 925 850 700 600 500 400 300 200 250 150 100 70 50 30
20 10
 tdef 1 linear 01feb2008 1dy
 TITLE  stj850_26j.grd  144x37 grd
 vars 1
 uwnd  0 -999 uwnd temperature
 endvars
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