[gradsusr] Precipitation Difference

[mehwish ramzan]

Dear GrADS Community,

I need help your kind help. I am trying to make a differential map between
JJA precipitation in mm/day for past and future climate using the same
climate model with same resolution but with different time periods by using
the following script;

'open rain_future.ctl'
'open rain_past.ctl'
'set display color white'
'c'

'set lon 10 100'
'set lat -20 50'
'set mpdset hires'

'set dfile 1'
'set t 1  12'
'define c1= ave(prec, t+0, time=dec2050, 12)'
'modify c1 seasonal'
'define fut= ave(c1, t=6, t=8)'

'set dfile 2'
'set t 1 12'
'define c2 = ave(prec, t+0, time=dec2005, 12)'
'modify c2 seasonal'
'define pas= ave(c2, t=6, t=8)'

'define diff = fut - pas'

'd diff'

But i receive an error message.
'' cannot contour grids--- all undefined values''....

So please tell me where i am doing wrong in the above script? Or is there
an alternate method to calculate it?


Thank you

With Best Regards,

Mehwish
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