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
>>>
>>
>>
>
