Paul,
What you are doing is essentially perfect. Ferret is complaining, but
Ferret complains about a lot of things that are correct. It assumes too
much.
There is one imperfection in your example: describing your upper bounds
as inclusive. CF upper bounds are always exclusive, so your upper bounds
should be 1960-01-01 00:00:00.0 and 1961-01-01 00:00:00.0. Your days
since 1955-01-01 00:00:00.0 upper bound values in your example are
correctly exclusive, so this isn't a "real" problem here, but I've found
that thinking about the upper bounds the wrong way can lead to
strangeness down the road, so I thought I'd point it out.
Your example also raises a question in my mind, so I'll throw an
off-track thought at you just for fun. Is there a driving reason why you
are choosing midnight on July 2 for some intervals and noon on July 2
for others? I know that is the exact midpoint in each case, but my
tendency would be to pick either midnight or noon and use that
consistently. More specifically, I would pick YYYY-07-02 12:00:00.0 for
all my time variable values. That's just me, but doing this is both
valid (in particular since you have bounds that makes the input range
clear) and places the value unambiguously on the same day in each year.
This is more of a style issue, so don't feel compelled to change
anything unless you feel like it.
Grace and peace,
Jim
On 3/11/15 8:24 PM, Durack, Paul J. wrote:
Hi folks,
I¹m generating a file which contains annual pentadal averaged data - so
effectively a 5-year running mean saved with an annual time step. The file
looks like:
---
dimensions:
time = UNLIMITED ; // (56 currently)
bound = 2 ;
level = 26 ;
latitude = 180 ;
longitude = 360 ;
variables:
float time(time) ;
time:bounds = "bounds_time" ;
time:units = "days since 1955-1-1 0:0:0.0" ;
time:long_name = "time" ;
time:standard_name = "time" ;
time:calendar = "gregorian" ;
time:axis = "T" ;
float bounds_time(time, bound) ;
...
data:
time = 913, 1278.5, 1644, 2009, 2374, 2739.5, 3105, 3470, 3835, 4200.5,
4566, 4931, 5296, 5661.5, 6027, 6392, 6757, 7122.5, 7488, 7853, 8218,
8583.5, 8949, 9314, 9679, 10044.5, 10410, 10775, 11140, 11505.5, 11871,
12236, 12601, 12966.5, 13332, 13697, 14062, 14427.5, 14793, 15158,
15523,
15888.5, 16254, 16619, 16984, 17349.5, 17715, 18080, 18445, 18810.5,
19176, 19541, 19906, 20271.5, 20637, 21002 ;
bounds_time =
0, 1826,
365, 2192,
731, 2557,
1096, 2922,
...
---
I¹m wondering what the most CF-like way of creating these bounds?
Currently the bounds are specified as:
Index 1:2
1955-1-1 0:0:0.0 -> 1959-12-31 12:59:59.0
1956-1-1 0:0:0.0 -> 1960-12-31 12:59:59.0
And time values as above:
Index 1:2
1957-7-2 0:0:0.0
1958-7-2 12:0:0.0
When I try and load the file using Ferret, this throws a warning.. Which
makes me think I¹m not doing things correctly:
Ferret v6.93
yes? use file.nc
*** NOTE: Axis definition error on axis: time. Bounds describe cells that
overlap one another
*** NOTE: Error in bounds "bounds_time" or bounds do not enclose point on
axis time
*** NOTE: Substituting coordinate midpoints
Are there any tips for me regarding this, I wasn¹t able to find anything
clear (at least to me) in the v1.7.2 Draft CF document.
Cheers,
P
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NOAA's National Climatic Data Center <http://ncdc.noaa.gov/>
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