John,
Is this actually climatology data? If it were climatology data, it
would usually be the average for a given hour, day, or whatever, where
the average is taken over a decade or so. I think you may just need to
apply regular bounds.
Grace and peace,
Jim
On 2/20/2012 12:27 PM, John Caron wrote:
> Im working with NOAA's CFSR dataset, reading it into the CDM, which
> essentially means converting GRIB into CF/netCDF.
>
> ref:
> http://nomads.ncdc.noaa.gov/data.php#cfs-reanal-data
> http://dss.ucar.edu/datasets/ds093.2/
>
> from NCAR's DSS page:
>
> "CFSR monthly atmospheric, oceanic and land surface output products
> are available as 6-hourly diurnal monthly means (00Z, 06Z, 12Z, and 18Z)"
>
> If I understand this correctly, the monthly mean data is as follows:
>
> for each month:
> for each day of the month:
> compute separate averages of the data at the 0,6,12, and 18Z
> time coordinate.
>
> So one ends up with 4 time coordinates per month, and the data
> represents the average for that month at that time. The time
> coordinate is not a real calendar date, for example for the month
> 2008-08, the time coordinate is not really
>
> 2008-08-01T00:00:00.000Z
> 2008-08-01T06:00:00.000Z
> 2008-08-01T12:00:00.000Z
> 2008-08-01T18:00:00.000Z
>
> but more like:
>
> 2008-08-*T00:00:00.000Z
> 2008-08-*T06:00:00.000Z
> 2008-08-*T12:00:00.000Z
> 2008-08-*T18:00:00.000Z
>
> where the * indicates an average over the days in that month.
>
> From
>
> http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#climatological-statistics
>
> It appears that CF would represent this as:
> dimensions:
> time=4;
> nv=2;
>
> variables:
> float temperature(time,lat,lon);
> temperature:long_name="surface air temperature";
> temperature:cell_methods="time: point within days time: mean over days";
> temperature:units="K";
>
> double time(time);
> time:climatology="climatology_bounds";
> time:units="days since 2008-01-01";
>
> double climatology_bounds(time,nv);
>
> data:
> time="2008-08-01T00:00Z","2008-08-01T06:00Z","2008-08-01T12:00Z","2008-08-01T18:00Z" ;
>
> climatology_bounds="2008-08-01T00:00Z", "2008-08-31T00:00Z",
> "2008-08-01T06:00Z", "2008-08-31T06:00Z",
> "2008-08-01T12:00Z", "2008-08-31T12:00Z",
> "2008-08-01T18:00Z", "2008-08-31T18:00Z" ;
> Using "point within days" because we have an instantaneous quantity.
>
> However, im not sure what this sentence in 7.4 means: "When
> considering intervals within days, if the earlier time of day is equal
> to the later time of day, then the method is applied to a full 24 hour
> day."
>
>
> Another case is when the data are on time intervals, for example
> "Total Precipitation Accumulation". In this case, the original data
> are on time intervals which i represent as (start,end) dates:
>
> 2008-08-01T00:00:00.000Z, 2008-08-01T00:00:06.000Z
> 2008-08-01T06:00:00.000Z, 2008-08-01T00:00:12.000Z
> 2008-08-01T12:00:00.000Z, 2008-08-01T00:00:18.000Z
> 2008-08-01T18:00:00.000Z, 2008-08-01T00:00:24.000Z
> 2008-08-02T00:00:00.000Z, 2008-08-02T00:00:06.000Z
> 2008-08-02T06:00:00.000Z, 2008-08-02T00:00:12.000Z
> 2008-08-02T12:00:00.000Z, 2008-08-02T00:00:18.000Z
> 2008-08-02T18:00:00.000Z, 2008-08-02T00:00:24.000Z
> 2008-08-03T00:00:00.000Z, 2008-08-03T00:00:06.000Z
> ...
>
> which are are averaged over days, giving 4 averages for each month,
> which i denote as:
>
> 2008-08-*T00:00:00.000Z, 2008-08-*T00:00:06.000Z
> 2008-08-*T06:00:00.000Z, 2008-08-*T00:00:12.000Z
> 2008-08-*T12:00:00.000Z, 2008-08-*T00:00:18.000Z
> 2008-08-*T18:00:00.000Z, 2008-08-*T00:00:24.000Z
>
> So perhaps this is:
> dimensions:
> time=4;
> nv=2;
>
> variables:
> float precipitation(time,lat,lon);
> precipitation:long_name="surface air temperature";
> precipitation:cell_methods="time: sum within days time: mean over days";
> precipitation:units="K";
>
> double time(time);
> time:climatology="climatology_bounds";
> time:units="days since 2008-01-01";
>
> double climatology_bounds(time,nv);
>
> data:
> time="2008-08-01T03:00Z","2008-08-01T09:00Z","2008-08-01T15:00Z","2008-08-01T21:00Z" ;
>
> climatology_bounds="2008-08-01T00:00Z", "2008-08-31T06:00Z",
> "2008-08-01T06:00Z", "2008-08-31T12:00Z",
> "2008-08-01T12:00Z", "2008-08-31T18:00Z",
> "2008-08-01T18:00Z", "2008-08-31T24:00Z" ;
> ??
>
>
>
>
> thanks for any insights,
> John
>
>
>
>
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
--
Jim Biard
Government Contractor, STG Inc.
Remote Sensing and Applications Division (RSAD)
National Climatic Data Center
151 Patton Ave.
Asheville, NC 28801-5001
jim.biard at noaa.gov
828-271-4900
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachments/20120221/5a646b7f/attachment-0001.html>
Received on Tue Feb 21 2012 - 07:48:40 GMT
