Extracting point data from EURO-CORDEX rotated pole grid using WGS 84 coordinates

Added by Damian Badora about 2 months ago

Hi everyone,

I am working with EURO-CORDEX NetCDF files (specifically SMHI-RCA4 model, EUR-11 domain). These files use a rotated pole grid system.

I want to extract a time series for a specific weather station: Puławy (Lat: 51.4162o N, Lon: 21.9723o E, WGS 84).

My question is: Can I use the WGS 84 coordinates directly with the remapnn operator, or do I need to manually transform the station coordinates to the rotated grid before calling CDO?

I am currently planning to use:
cdo -outputtab,date,value -remapnn,lon=21.97_lat=51.41 input_file.nc > output.txt

Does CDO automatically handle the coordinate transformation between the geographical WGS 84 input and the rotated pole definition found in the NetCDF attributes? Also, is remapnn the recommended approach for single-point extraction on rotated grids, or should I use remapbil? Version CDO 2.4.

Thank you for your help!

Replies (3)

RE: Extracting point data from EURO-CORDEX rotated pole grid using WGS 84 coordinates - Added by Uwe Schulzweida about 2 months ago

Hi Damian,

Yes, CDO automatically handles the coordinate transformation, and remapnn is the recommended approach for single point extraction.

Cheers,
Uwe

RE: Extracting point data from EURO-CORDEX rotated pole grid using WGS 84 coordinates - Added by Damian Badora about 2 months ago

Hi Uwe,

tkanks for your answer.

I have one more question. Was it like this in every version of CDO, or did you have to perform the transformation yourself before? I am asking because I downloaded data a few years ago and I think I did it a little differently when it came to the coordinates of a single station in WGS 84. I think I had to fit those coordinates into the grid first. I think it was CDO version 1.7.

Cheers,
Damian

RE: Extracting point data from EURO-CORDEX rotated pole grid using WGS 84 coordinates - Added by Uwe Schulzweida about 2 months ago

This has worked unchanged since at least cdo version 1.6.9.
Of course, this only works if cdo automatically recognises the rotated grid. The grid section of ‘cdo sinfon’ should look something like this:

   Grid coordinates :
     1 : projection               : points=62992 (254x248)
                          mapping : rotated_latitude_longitude
                             rlon : -30.44 to 25.22 by 0.22 [degrees]
                             rlat : -25.72 to 28.62 by 0.22 [degrees]

(1-3/3)

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