Rename particle position attributes from (lon, lat, depth) to (x,y,z)

[fluidnumericsJoe]

What version of Parcels are you running?

v4

Is your feature request related to a problem?

Parent models don't always define positions on globe/spherical coordinates. Hard-setting the names of the particle positions to .lon, .lat, and .depth implies that this is indeed the norm. Many high resolution regional simulation use cartesian coordinates and users of these kinds of models often just use x y and z .

Describe the solution you'd like

I would propose that particles use attributes x y and z as the names for the particle position attributes (rather than lon, lat, and depth). This would also mean that the increments in position be recorded as dx, dy, dz.

The interpretation of the meaning of the generic x y and z is in the hands (minds?) of the parcels user and in the units aligned with each dimension (degrees longitude/latitude for spherical coordinates or meters for cartesian).

Describe alternatives you've considered

No response

Additional context

No response

[VeckoTheGecko]

You're right that we also need the metadata to be updated.

Parcels/src/parcels/_core/particle.py

Lines 138 to 152 in 9be378b

	Variable(
	"z",
	dtype=spatial_dtype,
	attrs={"standard_name": "vertical coordinate", "units": "m", "positive": "down"},
	),
	Variable(
	"lat",
	dtype=spatial_dtype,
	attrs={"standard_name": "latitude", "units": "degrees_north", "axis": "Y"},
	),
	Variable(
	"lon",
	dtype=spatial_dtype,
	attrs={"standard_name": "longitude", "units": "degrees_east", "axis": "X"},
	),

idk what if the metadata is updated in the case of a flat mesh or if it stays degrees. We should probably update this metadata to be a constant like inherit from model or something