hours to global atmospheric circulations caused by the differential heating of the Equator and the poles and the Earth's rotation. Winds are often referred This glossary of meteorology is a list of terms and concepts relevant to meteorology and atmospheric science, their sub-disciplines, and related fields. atmospheric circulation The global-scale movement of air masses within the Earth's atmosphere. All meteorological phenomena are consequences of the atmospheric circulation, which manifests as a network of both latitudinal and longitudinal "cells" of convective activity; together with ocean circulation, these cells are the primary means by which thermal energy from the Sun is distributed across the Earth's surface. wind The bulk movement of air within the Earth's atmosphere. Wind occurs on a wide range of scales, from very strong thunderstorm flows lasting tens of minutes to milder local breezes lasting a few hours to global atmospheric circulations caused by the differential heating of the Equator and the poles and the Earth's rotation. Winds are often referred to by their strength and direction; the many types of wind are classified according to their spatial… atmospheric circulation The global-scale movement of air masses within the Earth's atmosphere. All meteorological phenomena are consequences of the atmospheric circulation, which manifests as a network of both latitudinal and longitudinal "cells" of convective activity; together with ocean circulation, these cells are the primary means by which thermal energy from the Sun is distributed across the Earth's surface. atmospheric sounding A measurement of the vertical distribution of physical properties through an atmospheric column, usually including pressure, atmospheric tide A global-scale periodic oscillation of the Earth's atmosphere caused by gravitational and thermal influences from the Sun and the Moon, analogous to oceanic tides. cell 1. Any atmospheric circulation feature that is more or less closed, occurring at any of number of scales, including massive latitudinally oriented circulations such as Hadley cells; mesoscale motions that characterize cellular convection and cause the formation of cellular clouds; and storm cells formed by updraft and/or downdraft loops within a thunderstorm. 2. In weather radar, a local maximum in radar reflectivity that undergoes a life cycle of growth and decay, and which often displays an identifiable structure in radar returns. Cells in ordinary convective thunderstorms typically last 20 to 30 minutes, but may form longer-lasting multicell storms or supercells. electrometeor Any visible or audible indicator of atmospheric electricity, including all types of lightning discharges, thunder, and aurorae. meridional circulation The component of the large-scale atmospheric general circulation that is oriented parallel to a meridian or line of longitude, and thus shows large north–south movement. monsoon 1. An abrupt seasonal wind reversal accompanied by corresponding changes in precipitation. 2. Any seasonal change in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea. In this context, the term is often used to refer specifically to the rainy phase of such a pattern, and in some places colloquially (and less correctly) to any locally very heavy but short-term rainfall. prevailing winds The predominant winds encountered at a particular point or region of the Earth's surface, identified by their source and direction. Though wind speed and direction can vary widely for a given location at a given time, the prevailing winds represent the primary trend in the characteristics of local winds averaged over a long period of time. They are influenced both by global patterns of atmospheric air movements and by local topography. radar winds Atmospheric motion detected by using radar to track a target attached to a radiosonde, or by Doppler radar. ridge Also wedge. An elongated region of relatively high atmospheric pressure, almost always associated with an area of maximum anticyclonic curvature of wind flow. Ridges may exist at the surface or aloft or both; they may contain the closed circulation of a distinct high-pressure area, and a high may have one or more distinct ridges. Under certain conditions, ridges may alternate with troughs in a high-amplitude pattern. tropical cyclone Variously hurricane, typhoon, tropical storm, cyclonic storm, or simply cyclone. A very large, rapidly rotating storm system characterized by a low-pressure center surrounded by a closed low-level atmospheric circulation, strong winds, and continuous spiral bands of thunderstorms that produce heavy rain. Tropical cyclones develop almost exclusively over and derive their strength from warm tropical seas. The strongest systems can last for more than a week, span more than 1,600 km (1,000 mi) in diameter, and cause significant damage to coastal regions with powerful winds, storm surges, and concentrated precipitation that leads to flooding. Depending on its location and strength, a tropical cyclone may be referred to by different names and categorized within a variety of classes. wind The bulk movement of air within the Earth's atmosphere. Wind occurs on a wide range of scales, from very strong thunderstorm flows lasting tens of minutes to milder local breezes lasting a few hours to global atmospheric circulations caused by the differential heating of the Equator and the poles and the Earth's rotation. Winds are often referred to by their strength and direction; the many types of wind are classified according to their spatial scale, their speed, the types of forces that cause them, the regions in which they occur, and their effects. wind shear Sometimes used interchangeably with wind gradient. Any difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal.