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vertices order in curvilinear grid according to CF-conventions.

Added by Lars Buntemeyer about 2 years ago

Hello, I have a more or less general question concerning the order of vertices (lon_vertices, lat_vertices) and how this is handled in cdo (cmor, remapcon, etc..). I hope i can explain myself clearly! I recognized, e.g., that if i cmorize data and let the cmor operator add those vertices for me, i get the first vertex in the "top left" ordered counterclockwise. However, it seems that CF-conventions require the frist vertex at the lower left (e.g., see also here: https://cfconventions.org/cf-conventions/cf-conventions.html#cell-boundaries). I created a short notebook with some plots to make my case (https://nbviewer.org/github/larsbuntemeyer/notebooks/blob/main/vertices-order.ipynb). The problem is with other CF-compliant tools that require cell boundaries relying on CF-conventions. I mostly use CORDEX datasets and i recognized that many models start with vertices at the top left. Maybe i misinterpret the CF-convention?

Thanks a lot!
Lars


Replies (1)

RE: vertices order in curvilinear grid according to CF-conventions. - Added by Uwe Schulzweida about 2 years ago

Hello Lars,

The position of the cell vertices does not matter in CDO. It is important that the cell vertices are ordered counterclockwise, because some algorithms (like remapcon) need this.

Regards,
Uwe

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