Scheduled Downtime
On Friday 21 April 2023 @ 5pm MT, this website will be down for maintenance and expected to return online the morning of 24 April 2023 at the latest

How can I know which interpolation method was used

This post was from a previous version of the WRF&MPAS-A Support Forum. New replies have been disabled and if you have follow up questions related to this post, then please start a new thread from the forum home page.


New member
is there a way to know which interpolation method was really used (in geogrid or metgrid) for each grid point ?

In the tutorial "wps_advanced", a slide shows this kind of information. I wonder how it was obtained, since the information (number of the interpolation method) is not present in the geogrid or metgrid output files. Is there a means to output this information?
You can always find the interpolation option in GEOGRID.TBL.ARW (for static data) and METGRID.TBL.ARW (for forcing data).
Yes these options can be output as global attributes. It is not our priority to add these information to output. but users are always welcome to modify the codes too output whatever they need.
The figures in question (slides 32 and 35 of the Advance WPS tutorial presentation) were produced using a modified version of the metgrid code some years back. Unfortunately, this modified metgrid code wasn't saved, and isn't available as part of any release of the WPS.

In case you'd like to determine which interpolation method is used for each grid cell (and for each field), you could begin in the interp_met_field routine, which is invoked to interpolate each field to the WRF grid. That routine calls the interp_to_latlon routine for each WRF grid point Finally, interp_to_latlon calls the recursive interp_sequence routine, which attempts to apply a list of possible interpolation methods, returning after a method has been successfully applied.

By suitably adding additional arguments to interp_to_latlon and interp_sequence, it should be possible to get the informtion you're looking for.
And then, could this interpolation method be used with the current version of the program, or is there no possibility/no point in doing so?