[ncl-talk] Problems with reading and re-gridding polar stereographic grid data

[Rick Brownrigg]

I found that file online, and it does indeed have metadata about the
projection parameters.  I'm not totally sure how some of them map onto
PROJ4 parameters, but I will experiment with it and see if I can get a
reasonable result.

FWIW...
Rick


On Tue, Apr 7, 2015 at 3:31 PM, Dennis Shea <shea at ucar.edu> wrote:

> To me, this looks like GIS based data.
>
> An expert commented on on your request as follows:
> ===
> I think this could be done using PROJ4, or actually we could use
> Mohammad's NCL interface to PROJ4. I am not totally sure there is
> enough info in what she had given. We would need the center of the
> projection -- probably 90 latitude but not so clear about longitude.
> Maybe the x and y metric coordinates have a 0 point that indicates the
> projection center. It's one we would have to play with a bit to get
> working.
> ====
>
> Who created the data? Maybe they could create nc file containing the
> lat/lon arrays
>
> D.
>
> On Tue, Apr 7, 2015 at 8:51 AM, Tsai Judy <judytsaibuy at gmail.com> wrote:
>
>> Hi,
>>
>> I think the problem I have is that my Greenland bed elevation data
>> doesn't have any lat lon information just like the data set you suggest (
>> land5.input.nc ).
>>
>>
>> -----
>>     float lat(time, y1, x1) ;
>>         lat:grid_mapping = "mapping" ;
>>         lat:long_name = "Latitude" ;
>>         lat:standard_name = "latitude" ;
>>         lat:units = "degreeN" ;
>>     float lon(time, y1, x1) ;
>>         lon:grid_mapping = "mapping" ;
>>         lon:long_name = "Longitude" ;
>>         lon:standard_name = "longitude" ;
>>         lon:units = "degreeE" ;
>> -----
>>
>> And my data set only has "projection_x_coordinate(x)" and
>> "projection_y_coordinate(y)" information
>> ----
>>     float projection_x_coordinate(x) ;
>>         projection_x_coordinate:units = "kilometres" ;
>>         projection_x_coordinate:standard_name = "projection_x_coordinate"
>> ;
>>         projection_x_coordinate:long_name = "x coordinate of projection" ;
>>     float projection_y_coordinate(y) ;
>>         projection_y_coordinate:units = "kilometres" ;
>>         projection_y_coordinate:standard_name = "projection_y_coordinate"
>> ;
>>         projection_y_coordinate:long_name = "y coordinate of projection" ;
>>     float BedrockElevation(y, x) ;
>>         BedrockElevation:units = "metres" ;
>>         BedrockElevation:grid_mapping = "Polar-Stereographic" ;
>>         BedrockElevation:coordinates = "projection_x_coordinate
>> projection_y_coordinate" ;
>>         BedrockElevation:missing_value = " -9999." ;
>>         BedrockElevation:standard_name = "BedrockElevation" ;
>>         BedrockElevation:long_name = "Bedrock elevation with respect to
>> the EIGEN-GL04C geoid for Greenland. Please discuss correct acknowledgement
>> and referencing with J. Bamber before publishing any results using these
>> data." ;
>> ----
>>
>> So my question is that is there anyway I can obtain real lat/lon
>> information from "projection_x_coordinate(x)" and
>> "projection_y_coordinate(y)" with NCL in order to regird that into T31 grid?
>>
>> Thank you
>>
>>
>>
>> 2015-04-06 19:22 GMT-04:00 Dennis Shea <shea at ucar.edu>:
>>
>> Not sure if the following are related to:
>>>       "... Greenland bed elevation data set ..."
>>>
>>> See: http://www.ncl.ucar.edu/Applications/ESMF.shtml
>>>         Example 33
>>>
>>> See: http://www.ncl.ucar.edu/Applications/ice.shtml
>>>         gland section
>>>
>>> The land5.input.nc file is at
>>>
>>> www.cgd.ucar.edu/~shea/gland5.input.nc
>>>
>>> HTH
>>>
>>> On Mon, Apr 6, 2015 at 3:11 PM, Tsai Judy <judytsaibuy at gmail.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> I have a Greenland bed elevation data set (.nc file) with polar
>>>> stereographic grid and I want to re-grid that into CCSM T31 grid in order
>>>> to calculate the difference between them. However, my Greenland bed
>>>> elevation data set doesn't have the associated longitude and latitude
>>>> information (i.e lon2d and lat2d) within the nc file. It just has "
>>>> projection_x_coordinate (x)" and " projection_y_coordinate (y)." Can anyone
>>>> suggest that is there any way (or function) available in NCL that I can use
>>>> to deal with this issue?
>>>>
>>>> Thanks
>>>>
>>>> _______________________________________________
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>>>>
>>>>
>>>
>>
>
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