<P> In meteorology, the polar front is the boundary between the polar cell and the Ferrel cell in each hemisphere . At this boundary a sharp gradient in temperature occurs between these two air masses, each at very different temperatures . </P> <P> The polar front arises as a result of cold polar air meeting warm tropical air . It is a stationary front as the air masses are not moving against each other . Off the coast of eastern North America, especially in winter, there is a sharp temperature gradient between the snow - covered land and the warm offshore currents . </P>

Diagram of a polar front depression for both northern and southern hemisphere