Convert lat/lon coordinates to a coordinate array

NetCDF assumes the grid is rectangular, so it stores latitude by row and longitude by column. We are potentially handling irregular coordinate grids here, so we need to be able to covert to lat/lon for each grid cell.

coord_array(lat, lon)

Arguments

lat	Latitude coordinate array for the full rectangular grid
lon	Longitude coordinate array for the full rectangular grid

Value

Matrix [ngrid x 2], latitude in the first column, longitude in the second.