Dictionary:

zonal

  (zō'nəl)

1. Of or associated with a zone.
2. Divided into zones.
3. Geology. Of or relating to soil characterized by well-developed horizons, reflecting the type of vegetation the soil supports and the climate to which it is exposed.

Referring to phenomena occurring in bands roughly parallel with lines of latitude.

The adjective has 2 meanings:

Meaning #1: relating to or of the nature of a zone
  Synonym: zonary
  Pertains to noun: zone (meaning #3)

Meaning #2: associated with or divided into zones
  Antonym: azonal (meaning #1)