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

[Dennis Shea]

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
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> List instructions, subscriber options, unsubscribe:
>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>
>>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20150407/4d91018a/attachment.html