meridional

Meridional means relating to a meridian or to the north-south direction. It derives from Latin meridionalis, from meridies meaning noon or midday, and ultimately from the sense that the meridian is the line along which the sun reaches its highest point.

In geography and cartography, meridional describes features aligned with or defined by meridians, which are lines of longitude running from the north to the south pole. A meridian is a half great circle connecting the poles and defined by a longitude value. The term appears in phrases such as meridional distance, meridional section, or meridional direction.

In meteorology and climatology, meridional describes north-south components of movement or transport, in contrast to zonal (east-west). Meridional circulation patterns carry heat or atmospheric mass northward or southward and can influence weather systems.

In astronomy, the local meridian is the great circle passing through the celestial poles and the zenith; objects crossing it are said to transit the meridian. In this sense, meridional relates to observations and coordinates tied to the celestial meridian.

See also meridian, longitude, zonal, north-south.