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

[Maria Gehne - NOAA Affiliate]

It should really do that, only the first year average for DJF is JF and
only the last year NDJ is ND. It doesn't really make sense to talk about
seasonal averages when you only use 2 month averages for one of the season
options. And it's not necessary to only use 2 months for DJF in the middle
of the data where you have DJFs in a row. The reason the documentation
mentions the 2 month averages for the first DJF and last NDJ average is so
that people know those values are only based on 2 months and not 3 like the
rest of the DJF and NDJ values.

You can easily test the DJF averages by computing the averages for a few
years yourself and comparing that to the result from month_to_season.

Maria

On Thu, Feb 19, 2015 at 9:18 AM, Daniel Barandiaran <dbarandiaran at gmail.com>
wrote:

> does it really do that? my reading of the documentation suggests that DJF
> is just JF for all years, and similarly NDJ is just ND.
> On Feb 19, 2015 8:30 AM, "Maria Gehne - NOAA Affiliate" <
> maria.gehne at noaa.gov> wrote:
>
>> 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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