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[THREDDS #WDE-773911]: Fwd: Accessing NCAR FNL data via THREDDS server
- Subject: [THREDDS #WDE-773911]: Fwd: Accessing NCAR FNL data via THREDDS server
- Date: Thu, 06 Oct 2016 09:58:26 -0600
Ashwin,
Unfortunately, this is expected behavior. GRIB files are just collections of
GRIB messages, which are horizontal, 2D slices of the gridded model fields; the
order of these messages within a file depends on the order in which they arrive
from over the network. Also different fields within the GRIB output can be on
different sets of time coordinates (such as different forecast periods), causes
the need to have multiple time dimensions within the GRIB dataset. Combined,
this leads to multiple, arbitrary time coordinate variables. Thus, depending on
where the first message for a certain field is within the file results in a the
different numbered time field.
There is a solution, though. Every variable has an attribute called
"coordinates" that lists the names of all the coordinate variables that pertain
for a given variable. For instance, if I look at the "Temperature_isobaric"
variable on the dataset you linked, I see:
coordinates: reftime time isobaric3 lat lon
So (today at least), the relevant coordinate information would be contained in
the "time" variable. So to insulate your code against the changes to this name,
instead of hard-coding the name of the time variable, you need to pull it out
of the coordinates attribute.
If you're using Python, there's an example of how we handle that in this
Jupyter notebook:
https://github.com/Unidata/notebook-gallery/blob/master/notebooks/500mb_Vorticity_Advection.ipynb
I hope this helps,
Ryan
> http://rda.ucar.edu/thredds/dodsC/aggregations/g/ds084.1/1/TP.html
>
> On Thu, Oct 6, 2016 at 5:31 PM, ashwinD12 . <address@hidden> wrote:
>
> > You can see the bug for yourself - today the GFS OPeNDAP page shows time
> > as the coordinate variable of Temperature_Isobaric. Yesterday it was
> > showing time3. So when you have scripts that use time3 they get broken.
> >
Ticket Details
===================
Ticket ID: WDE-773911
Department: Support THREDDS
Priority: Normal
Status: Closed
===================
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