A ridge or barometric ridge is a term in

meteorology Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did no ...

describing an elongated area of relatively high atmospheric pressure compared to the surrounding environment, without being a closed circulation. It is associated with an area of maximum anticyclonic curvature of wind flow. The ridge originates in the center of an

anticyclone An anticyclone is a weather phenomenon defined as a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere as viewed from ...

and sandwiched between two low-pressure areas, and the locus of the maximum curvature is called the ''ridge line''. This phenomenon is the opposite of a trough.

Description

Ridges can be represented in two ways: * On surface

weather map A weather map, also known as synoptic weather chart, displays various meteorological features across a particular area at a particular point in time and has various symbols which all have specific meanings. Such maps have been in use since the mi ...

s, the pressure isobars form contours where the maximum pressure is found along the axis of the ridge. * In upper-air maps,

geopotential height Geopotential height or geopotential altitude is a vertical coordinate referenced to Earth's mean sea level, an adjustment to geometric height (altitude above mean sea level) that accounts for the variation of gravity with latitude and altitude. ...

isohypses form similar contours where the maximum defines the ridge.

Related weather

Given the direction of the winds around an anticyclonic circulation and the fact that weather systems move from west to east: *ahead of an upper-ridge, the airflow that comes from the polar regions and brings cold air. *behind the upper-ridge line, the flow that comes from the equator and brings mild air. Surface ridges, just like highs, generate fair weather because they develop under wind convergence in the negative vorticity advection zone ahead of the upper-level ridge. The vertical downward air motion then gives a divergence of the winds near the surface. The subsidence of the air causes a warming in the column compared to the previous environment and therefore a drying of it because its

relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

decreases, which has the effect of clearing the sky.

Subtropical ridge

An important atmospheric ridge is the

subtropical ridge The horse latitudes are the latitudes about 30 degrees north and south of the Equator. They are characterized by sunny skies, calm winds, and very little precipitation. They are also known as subtropical ridges, or highs. It is a high-press ...

. It is a series of ridges near the horse latitude characterized by mostly calm winds, which act to reduce air quality under its axis by causing fog overnight, and haze during daylight hours as a result of the stable atmosphere found near its location. The air descending from the upper troposphere flows out from its center at surface level toward the upper and lower latitudes of each hemisphere, creating both the trade winds and the westerlies. It helps steer

tropical cyclone A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Dep ...

s and the

monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...

.C.-P. Chang, Yongsheng Zhang, and Tim Li (1999)
Interannual and Interdecadal Variations of the East Asian Summer Monsoon and Tropical Pacific SSTs. Part I: Roles of the Subtropical Ridge.
Journal of Climate: pp. 4310–4325. Retrieved on 2007-02-11.

Ridge blocking

Blocks in

are large-scale patterns in the atmospheric pressure field that are nearly stationary, effectively "blocking" or redirecting migratory cyclones. These blocks can remain in place for several days or even weeks, causing the areas affected by them to have the same kind of weather for an extended period of time (e.g. precipitation for some areas, clear skies for others). Upper ridges are often associated with such blocks, particularly in '' Omega blocks''.

References

{{Reflist Atmospheric dynamics Atmospheric circulation Synoptic meteorology and weather