[gradsusr] Request is completely outside file limits

[Chidzambwa Simba]

Dear Users,
I am computing average zonal wind shear for Dec73-Feb74 from NetCDF
files with DJF months only for all years. I am looking at shear between
850mb (first file) and 200mb (second file).  My grads script is as
follows;
 
'reinit'
'sdfopen uwndDJF_1900_2008.cdf'
'sdfopen uwndDJF_200_1900_2008.cdf'
'set background 1'
'set annot 0 6'
'set map 0 1 8'
'set xlopts 0 4'
'set ylopts 0 4'
'set lat -60 0'
'set lon 100 180'
'set gxout contour'
'set lev 850'
'define u=ave(uwnd,t=26353,t=26712)'
'set lev 200'
'define u1=ave(uwnd,t=26353,t=26712)'
'd u1-u'
'draw title 1973-74 Average zonal DJF wind shear (m/s)'
'printim ZW_Map_DJF7374.jpeg x400 y300' 

and when I query my files this is what I get;
 
ga-> q file 1                         
File 1 : 
  Descriptor: uwndDJF_1900_2008.cdf
  Binary: uwndDJF_1900_2008.cdf
  Type = Gridded
  Xsize = 41  Ysize = 31  Zsize = 1  Tsize = 39096  Esize = 1
  Number of Variables = 1
     uwnd  1  t,z,y,x  6-hourly U-wind on Pressure Levels
ga-> q file 2
File 2 : 
  Descriptor: uwndDJF_200_1900_2008.cdf
  Binary: uwndDJF_200_1900_2008.cdf
  Type = Gridded
  Xsize = 41  Ysize = 31  Zsize = 1  Tsize = 39096  Esize = 1
  Number of Variables = 1
     uwnd  1  t,z,y,x  6-hourly U-wind on Pressure Levels
 
When I run my script I get an error message " Data Request Warning:
Request is completely outside file limits" and I don't understand why.
The areal limits are correct and I have cross-checked them and the
time-steps are 6-hourly daily wind components. May somebody assist me
please? 
 
 
Regards
Simba


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