I am discussing a system (in a scientific context) which is described with spherical polar coordinates. This has a radial coordinate r, a polar angle θ and a azimuth angle φ. A diagram can be found on the linked page.
I would like a term to describe (for example) motion in the polar direction (increasing or decreasing θ). The equivalent terms for the other two directions would be "radial" and "azimuthal". There are several possibilities:
"Polar" is the obvious choice, but this could also mean motion of the pole itself.
"Poloidal" seems to mean the correct thing, but might only refer to a toroidal, instead of a spherical, geometry.
"Poleward", but this has connotations of only being towards the nearest pole. Hence the word we are looking for is to "poleward" as "vertical" is to "upward".
"Vertical" is used by some, as the θ direction is parallel to the z-axis in the equatorial plane, and the z-axis is commonly taken to be the vertical direction. However, this is inappropriate close to the pole when the θ direction becomes horizontal.
"Latitudinal" describes the correct direction, but seems odd when not paired with "longitudinal" for azimuthal motion.
Is there another term, or is there a clear best option?