Re: [CF-metadata] How to represent "6-hourly diurnal monthly means" in CF ?
Thanks, Jonathan. On 2/21/2012 11:18 AM, Jonathan Gregory wrote: Dear John 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." It doesn't matter in the instantaneous case, but it does matter for statistics that apply to the whole cell, like means and accumulations, such as precipitation:cell_methods="time: sum within days time: mean over days"; If the sums were for 24-hour intervals, the bounds might be climatology_bounds="2008-08-01T00:00Z", "2008-09-01T00:00Z", Here, the time of day is the same (00:00Z) at both ends. That means it applies to full days. That's what the bit quoted is talking about. However, this doesn't arise in your six-hourly case. Best wishes Jonathan ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
Re: [CF-metadata] How to represent "6-hourly diurnal monthly means" in CF ?
On 2/21/2012 7:48 AM, Jim Biard wrote: 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. You might be right, Im trying to get clarification on this. Thanks for your comments. John 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@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.bi...@noaa.gov 828-271-4900 ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.c
[CF-metadata] How to represent "6-hourly diurnal monthly means" in CF ?
Dear John > 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." It doesn't matter in the instantaneous case, but it does matter for statistics that apply to the whole cell, like means and accumulations, such as > precipitation:cell_methods="time: sum within days time: mean over days"; If the sums were for 24-hour intervals, the bounds might be > climatology_bounds="2008-08-01T00:00Z", "2008-09-01T00:00Z", Here, the time of day is the same (00:00Z) at both ends. That means it applies to full days. That's what the bit quoted is talking about. However, this doesn't arise in your six-hourly case. Best wishes Jonathan ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
Re: [CF-metadata] How to represent "6-hourly diurnal monthly means" in CF ?
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@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.bi...@noaa.gov 828-271-4900 ___ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
[CF-metadata] How to represent "6-hourly diurnal monthly means" in CF ?
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@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata