For info, I spoke briefly to Ning Wang about this. He can talk to NCEP
software people he works with, but this isn't his highest priority, and
this may take some time.
I wonder if there is a more formal route for a request-for-change that we
could follow to get this change made officially. Bob, any experience with
this?
On Wed, Jan 28, 2015 at 5:21 PM, Bob Lipschutz - NOAA Affiliate <
robert.c.lipschutz@xxxxxxxx> wrote:
> Hi John. Thanks for the ping. No, I don't have access to other sample GRIB
> files with this property. The only progress we've made is that we had an
> exchange with a fellow in the NCEP marine modeling group (EMC/MMAB) who
> said this about their sea ice products:
>
> The 1/8th degree grid never went to production. I'm amazed that there was
>> a table entry for it. The high resolution ice grids in production are
>> number 171, 172, 173 -- northern hemisphere, southern hemisphere, global,
>> respectively. The hemispheric grids are 1/30 bedient, and global is 1/12th
>> degree.
>
>
> This leads me to believe that the scanMode setting in the grid 174
> definition is in error, and that 174 probably had never really been used
> until we came along. We need to talk to the maintainers of the NCEP tables,
> and see if we can get it corrected.
>
> Thanks again for your support on this!
>
> -Bob
>
>
> On Wed, Jan 28, 2015 at 11:52 PM, John Caron <caron@xxxxxxxx> wrote:
>
>> Hi Bob:
>>
>> Any word from NCEP on this issue? Or sample files that already use
>> scanmode 64?
>>
>> John
>>
>> On Wed, Jan 14, 2015 at 10:30 AM, Bob Lipschutz - NOAA Affiliate <
>> robert.c.lipschutz@xxxxxxxx> wrote:
>>
>>> John,
>>>
>>> Thanks for looking at this. Sorry, I don't have any particular
>>> recommendation here. The grid specification does seem odd and inconsistent
>>> with other domains with scanMode=64 that give south-to-north corner
>>> coordinates. It's also inconsistent with the similar 1/12th degree '173'
>>> grid, which has scanMode=0 and north-to-south corners. We will check with
>>> NCEP to see if there's an error in the table, but it's not a new entry and
>>> ostensibly used by someone out there (it's described as a Sea Ice grid)...
>>>
>>> Thanks again,
>>>
>>> -Bob
>>>
>>> On Wed, Jan 14, 2015 at 1:14 AM, Bonny Strong - NOAA Affiliate <
>>> bonny.strong@xxxxxxxx> wrote:
>>>
>>>> John, I don't have Bob's expertise, but I know that during discussions
>>>> here at GSD trying to figure this out, one developer gave his opinion that
>>>> the lats of the first and last point were unrelated related to the scan
>>>> direction. Bob may wish to add to that tomorrow.
>>>>
>>>> Bonny
>>>>
>>>> On Tue, Jan 13, 2015 at 6:07 PM, John Caron <caron@xxxxxxxx> wrote:
>>>>
>>>>> Hi Bob:
>>>>>
>>>>> Thanks for reporting this problem. Im looking at it now. Do you have
>>>>> any idea how these various parameters interact? They have first lat in
>>>>> north, last lat in south, but a positive Dj. Then with scanMode 64, they
>>>>> say "Points of first row or column scan in the +j (+y) direction". Seems
>>>>> overspecified with the possibility of inconsistent results. Im looking
>>>>> though my data samples now to see if I can detect if there is are
>>>>> problems,
>>>>> but im not exactly sure what combinations should be legal. Any thoughts?
>>>>>
>>>>> heres my dump on your record:
>>>>>
>>>>> 47: La1 -
>>>>> latitude of first grid point == 89938000
>>>>> 56: La2 -
>>>>> latitude of last grid point == -89938000
>>>>> 68:
>>>>> Dj - j direction increment == 125000
>>>>> 72:
>>>>> Scanning mode == 64
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Jan 12, 2015 at 4:02 PM, Bob Lipschutz - NOAA Affiliate <
>>>>> Robert.C.Lipschutz@xxxxxxxx> wrote:
>>>>>
>>>>>>
>>>>>> Java NetCDF Folks,
>>>>>>
>>>>>> We have recently begun generating global 1/8 degree GRIB files
>>>>>> using NCEP's grid 174 definition (
>>>>>> http://www.nco.ncep.noaa.gov/pmb/docs/on388/tableb.html#GRID174).
>>>>>>
>>>>>> Following that definition, we are setting the value of scanMode to
>>>>>> 64, which
>>>>>> per GRIB2 Table 3.4 indicates "points scan in the +j direction", and
>>>>>> so filling
>>>>>> the data arrays from south to north. However, the java-netCDF package
>>>>>> (v4.5)
>>>>>> does not seem to handle the scanMode flag properly, and consequently
>>>>>> our
>>>>>> grids appear flipped on display. Meanwhile, I understand that NCL
>>>>>> does handle
>>>>>> the data mapping correctly, from which we conclude that java-netCDF
>>>>>> is has a
>>>>>> problem with this grid definition.
>>>>>>
>>>>>> As a work-around, we will set scanMode to 0 and write from north to
>>>>>> south,
>>>>>> which will fix the problem for us. But, we'd also hope to have the
>>>>>> tools work
>>>>>> correctly, too so that we can use the NCEP's grid as specified --
>>>>>> which
>>>>>> admittedly is strange in that it list the corner lons from north to
>>>>>> south.
>>>>>>
>>>>>> I've posted a sample GRIB2 file and resulting flipped image here:
>>>>>>
>>>>>> ftp://aftp.fsl.noaa.gov/divisions/its/bob/grid174_scanmode_64_example.grb2
>>>>>> ftp://aftp.fsl.noaa.gov/divisions/its/bob/flipped_174grid.jpg
>>>>>>
>>>>>> FWIW, here is the output from the (v4.3) Grib2Dump utility on that
>>>>>> data file:
>>>>>>
>>>>>> Header : GRIB2
>>>>>> Discipline : 0 Meteorological
>>>>>> products
>>>>>> GRIB Edition : 2
>>>>>> GRIB length : 2808735
>>>>>> Originating Center : 59 The NOAA Forecast
>>>>>> Systems Laboratory
>>>>>> Originating Sub-Center : 0
>>>>>> Significance of Reference Time : 1 Start of forecast
>>>>>> Reference Time : 2015-01-08T00:00:00Z
>>>>>> Product Status : 0 Operational products
>>>>>> Product Type : 1 Forecast products
>>>>>> Number of data points : 4147200
>>>>>> Grid Name : 0 Latitude_Longitude
>>>>>> Grid Shape: 0 Earth spherical
>>>>>> with radius = 6,367,470 m
>>>>>> Number of points along parallel: 2880
>>>>>> Number of points along meridian: 1440
>>>>>> Basic angle : 0
>>>>>> Subdivisions of basic angle: 0
>>>>>> Latitude of first grid point : 89.938
>>>>>> Longitude of first grid point : 0.062
>>>>>> Resolution & Component flags : 48
>>>>>> Winds : True
>>>>>> Latitude of last grid point : -89.938
>>>>>> Longitude of last grid point : 359.938
>>>>>> i direction increment : 0.125
>>>>>> j direction increment : 0.125
>>>>>> Grid Units : degrees
>>>>>> Scanning mode : 64
>>>>>> Product Definition : 0 Analysis/forecast
>>>>>> at horizontal level/layer at a point in time
>>>>>> Parameter Category : 0 Temperature
>>>>>> Parameter Name : 0 Temperature
>>>>>> Parameter Units : K
>>>>>> Generating Process Type : 2 Forecast
>>>>>> ForecastTime : 240
>>>>>> First Surface Type : 1 Ground or water
>>>>>> surface
>>>>>> First Surface value : 0.0
>>>>>> Second Surface Type : 255 Missing
>>>>>> Second Surface value : 0.0
>>>>>>
>>>>>> Thanks for any insights on this issue!
>>>>>>
>>>>>> Bob Lipschutz
>>>>>> NOAA/ESRL/Global Systems Division
>>>>>> IT Services/Data Services Group
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> netcdf-java mailing list
>>>>>> netcdf-java@xxxxxxxxxxxxxxxx
>>>>>> For list information or to unsubscribe, visit:
>>>>>> http://www.unidata.ucar.edu/mailing_lists/
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Bonny Strong
>>>> NOAA Affiliate
>>>> 303 497-3936
>>>>
>>>
>>>
>>
>
--
Bonny Strong
NOAA Affiliate
303 497-3936
