meridional circulation

(meteorology) An atmospheric circulation in a vertical plane oriented along a meridian; it consists, therefore, of the vertical and the meridional (north or south) components of motion only.
(oceanography) The exchange of water masses between northern and southern oceanic regions.

In meteorology, air flowing longitudinally, across the parallels of latitude. Meridional flow occurs in atmospheric cells and results in part from changes in temperature along lines of longitude.