Circle of latitude Circle of latitude A circle of latitude on Earth is an abstract east–west circle connecting all locations around Earth (ignoring elevation) at a given latitude. Circles of latitude are often called parallels because they are parallel to each other; that is, any two circles are always the same distance apart. A location's position along a circle of latitude is given by its longitude. Circles of latitude are unlike circles of longitude, which are all great circles with the centre of Earth in the middle, as the circles of latitude get smaller as the distance from the Equator increases. Their length
Equivalent latitude Equivalent latitude In differential geometry, the equivalent latitude is a Lagrangian coordinate . It is often used in atmospheric science, particularly in the study of stratospheric dynamics. Each isoline in a map of equivalent latitude follows the flow velocity and encloses the same area as the latitude line of equivalent value, hence "equivalent latitude." Equivalent latitude is calculated from potential vorticity, from passive tracer simulations and from actual measurements of atmospheric tracers such as ozone. The calculation of equivalent latitude involves creating a monotonic mapping between the values of equivalent latitude and the tracer it is based upon: higher values