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Re: 360 day years
Hi Thijs,
The quick solution is is to "associate" your model time axis with a corresponding
Gregorian time axis for purposes of plotting. The details:
The spacing of points in time on your days-360 time axis would be correctly
represented by
DEFINE AXIS/T=15-FEB-1900:15-FEB-2000:90/units=days t360_seasons
But this leads to the problem you are seeing -- as illustrated by this look at
the "Feb" season each year, which "drifts" about 5 days per year
yes? show axis/l=1:20:4 t360_seasons
name axis # pts start end
T360_SEASONS TIME 407 r 15-FEB-1900 02-MAR-2000
T0 = 01-JAN-1900
L T BOX_SIZE TIME_STEP (DAYS)
1> 15-FEB-1900 00:00:00 90 45
5> 10-FEB-1901 00:00:00 90 405
9> 05-FEB-1902 00:00:00 90 765
13> 31-JAN-1903 00:00:00 90 1125
17> 26-JAN-1904 00:00:00 90 1485
Now, a Gregorian seasonal time axis with 4 equal-length seasons could be defined
with
yes? DEFINE AXIS/T=15-FEB-1900:15-FEB-2000:`365.2485/4,prec=9`/units=days tGreg_seasons
and has no long term "drift" problems:
yes? show axis/l=1:200:`4*10` tGreg_seasons
name axis # pts start end
TGREG_SEASONS TIME 401 r 15-FEB-1900 15-FEB-2000
T0 = 01-JAN-1900
L T BOX_SIZE TIME_STEP (DAYS)
1> 15-FEB-1900 00:00:00 91.31213 45
41> 15-FEB-1910 11:38:27 91.31213 3697.485
81> 15-FEB-1920 23:16:54 91.31213 7349.97
121> 15-FEB-1930 10:55:22 91.31213 11002.46
161> 15-FEB-1940 22:33:49 91.31213 14654.94
(A more exact time axis is explained in
http://ferret.wrc.noaa.gov/Ferret/Documentation/Users_Guide/v50/partII.html#V5.0_DEFINE AXIS$/EDGES)
If you have a variable, MY_VAR, defined on a time axis like t360_seasons you can
make a nice plot of it using
yes? PLOT MY_VAR[GT=tGreg_seasons@ASN]
where the "@ASN" denotes regridding by association.
Note that we are working on more automated solutions to this problem for future
versions of Ferret.
Thanks for your question.
- steve
================================================
Thijs van Reenen wrote:
> Hello,
>
> My model produces seasonal output, each season (jfm, amj, ...) lasting for 90
> days. I would like to Ferret to use the 360-day model year so that the
> time-references on the plots will correspond to the model months.
>
> How can I achieve this?
>
> Thanks!
> --
> ____________________________________________________________
> | |
> | Name : Thijs van Reenen |_
> | Adress : Royal Netherlands Meteorological Institute (KNMI) | |
> | P.O. Box 201, 3730 AE De Bilt, The Netherlands | |
> | Tel : +31 30 2206366 | |
> | Fax : +31 30 2202570 | |
> | Email : reenenv@knmi.nl | |
> | URL : www.knmi.nl/~reenenv/ | |
> |____________________________________________________________| |
> |____________________________________________________________|
--
| NOAA/PMEL | ph. (206) 526-6080
Steve Hankin | 7600 Sand Point Way NE | FAX (206) 526-6744
| Seattle, WA 98115-0070 | hankin@pmel.noaa.gov
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