Re: Seasonal data on a continuous time axis

[Steve Hankin <hankin@xxxxxxxxxxxxx>]

Hi Mark,

This analysis can be quite a lot simpler than the path you've started
down, below. No intermediate files are needed.

Bare bones:

 1. define your seasonal (climatological) axis with DEFINE AXIS
		see "yes? use climatological_axes" for "seasonal_reg"
		as one example (try SHOW AXIS seasonal_reg)
 2. define new variables regriding from your entire 3-year data set to
		the seasonal axis with gt=seasonal@mod
		and gt=seasonal@modvar (try yes? SHOW TRANSFORMS)

The "binning" used in the modulo operations is unweighted -- see index
under "Modulo Regridding" at
http://ferret.wrc.noaa.gov/Ferret/Documentation/Users_Guide/v44/ for a
complete write-up)

	Happy Ferreting - steve

=============================================================================

Mark Williams wrote:
> 
> I am working quite a bit with seasonal data, for example the months DJF for
> OLR.
> Each season is defined by, say,
> let DJF9293 = olr[t=01-dec-1992:28-feb-1993]
> let DJF9394 = olr[t=01-dec-1993:28-feb-1994]
> let DJF9495 = olr[t=01-dec-1994:28-feb-1995]
> from which means, variances etc can be readily worked out for each season.
> If I then combine each season using the save/append command the newly
> created file will have each of the 3 seasons on a continuous time axis with
> nil data for the intermediate months (Mar till Nov each year).
> If I then define a new variable using the transformations @ave or @var for
> the full 3 years ferret seems to weight the results according to the gaps
> in the data along the time axis.  What I want to do is to find a way of
> easily creating a file with the all the data along a continuous and equally
> spaced time axis so that @var etc will give the answers I am looking for.
> 
> If anyone can help it would be appreciated.
> 
> Thanks in advance.
> 
> Mark Williams
> Monash CRC for Southern Hemisphere Meteorology
> Victorian Regional office
> Bureau of Meteorology
> Melbourne
> Australia

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