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From: "Brian E. Doty" <doty@COLA.IGES.ORG>
Subject:      Re: plotting question
To: GRADSUSR@LIST.CINECA.IT
Status: RO

Seasonal averages can be done in two steps:

First creat a 12 month seasonal average, and save it
as a defined variable:

    set lon 0 360
    set lat -90 90
    set z 1
    set t 1 12
    define ozave = ave(ozone,t+0,t=144,12)

Now 'ozave' contains the seasonal mean for each month (the above assumes
the data starts with January).

Then, to display a seasonal mean -- for example, DJF:

   display (ozave(t=12)+ozave(t=1)+ozave(t=2))/3

or if you want to account for the lengths of the months (note that ave
does not do this by default when averaging monthly data):

   display (ozave(t=12)*31+ozave(t=1)*31+ozave(t=2)*28)/90

...Brian