[ncl-talk] month_to_season() how does it work?

Maria Gehne - NOAA Affiliate maria.gehne at noaa.gov
Thu Feb 19 08:29:28 MST 2015

```Hi Erik,

month_to_season gives you as many seasons as you have full years in your
data. So if your data has 13 years then you will end up with 13 values for
DJF with the first one only being computed for JF in the first year. The
last december value will be ignored, because that would be the 14th season.

Does that help?

Maria

On Thu, Feb 19, 2015 at 12:56 AM, Erik Jan Schaffernicht <
eschaffe at uni-koeln.de> wrote:

> I am not sure how month_to_season() function works for   DJF   (and NDJ is
> probably similar).
>
> Say, I select "DJF"
>
> I take the years like this:
> [snip]
> iYYYY=  ind(YYYY.ge.1979 .and. YYYY.le.2003)
> slp= ifle->slp(iYYYY,:,:)   + ...   (further steps, input from ncep slp
> data.nc, and I flip some dimension to make it fitting to formal
> requirements)
> slpSeason=  month_to_season(slp, "DJF")
> [snip]
>
> What does the month_to_season() exactly do?
>
> My understanding of 'what belongs to a season' written down looks like
> this, if I group it by DJFseason:
>
> 1979-Jan and 1979-Feb
> 1979-Dec and 1980-Jan and 1980-Feb
> ...
> 2002-Dec and 2003-Jan and 2003-Feb
> 2003-Dec
>
> How does  month_to_season() process this?
> It says that DJF takes only  two months?   Does it mean only two for the
> first entry of this list, i.e. 1979-Jan 1979-Feb     but thereafter it
> takes always three, so 1979-Dec + 1980-Jan+1980-Feb, so three months in
> general except for one exception at the beginning?
> Or is it always
> 1979-Jan-Feb
> 1980-Jan-Feb
> 1981-Jan-Feb,   so December is skipped completely?  Then the "*D*JF" is
> confusing!?
>
> And what happens to the 'lonely'  2003-Dec? It has no neighbouring
> DJFmonths due to time range selection by years AD.  Is it skipped? Or is
> it: "take this month and define it as a season"?
>
>
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>
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