ROSSBY WAVE

in meteorology, large symmetrical undulation that develops in a jet stream's axis of flow and separates cold, polar air from warm, tropical air. These waves are named for Carl-Gustaf Arvid Rossby, who first identified them and explained their movement. Rossby waves are formed when polar air moves toward the Equator while tropical air is moving poleward. Because of the temperature difference between the Equator and the poles due to differences in the amounts of solar radiation received, heat tends to flow from low to high latitudes; this is accomplished, in part, by these air movements. The tropical air carries heat poleward, and the polar air absorbs heat as it moves toward the Equator. When the waves become very pronounced, masses of cold and warm air enclosed in the loops are detached, and these become the low-pressure cells (cyclones) and high-pressure cells (anticyclones) that are important in producing the climate of the middle latitudes.