Hi Guillermo,
this is to be handled by my CDS colleagues.
Why do need to exact grid point location
Are you really sure that you want to handle the native grid. We usually recommend to handle the data interpolated on a regular lat-lon grid. From mars, the closest lat-lon grid would be 0.36x0.36 (add grid=0.36/0.36, in the mars request)
and then the data would be evenly spaced, starting from the northern most latitude (90 if you have not specified a sub area in the mars request), at 0 longitude (all this is specified in the grid headers) and unrolling eastwards by step of 0.36
(i.e. 0,90; 0.36,90;...) until you reach the point just before it wraps around to the 0 meridian (90, 360-0.36), then in goes to the next latitude below (90-0.36) and so on
Again, I am not in the data support team. I can answer question on the wave modelling aspect, but for specific question on how to handle the data, please request help from the CDS support team
ECMWF support simple grib tool (Ask the CDS team, or search for GRIB tools). the following will dump all the longitudes and latitudes of grib file my_data:
grib_dump -d -p distinctLongitudes,distinctLatitudes my_data
Not super useful, but it all depends what you want to do. Ask my colleagues
Jean