[gradsusr] Detrending seasonal data

James T. Potemra jimp at hawaii.edu
Tue Mar 15 15:04:42 EDT 2011


First, you need to compute the seasonal mean using "ave", then convert 
this to a seasonal variable (repeats over time), then just subtract it.  
For example, if you have 10 years of monthly mean data (t=1 to 120):

* compute the seasonal mean
'set t 1 12'
'define aveolr = ave(olr,t+0,t=120,12)'

* modify this new variable to be the same t-length as the data
'set t 1 120'
'modify aveolr seasonal'

* subtract the seasonal cycle from the original variable
'd olr-aveolr'

Or something like that....


Jason Snyder wrote:
> To Whom it May Concern,
> does anyone know how to go about detrending a set of OLR data varies 
> seasonally.  I would like to eliminate any seasonal trends from it.  
> How do I go about doing this using a GrADS function/script?
> Thanks,
> Jason
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