Inmeteorologyaridgeorbarometric ridgeis an elongated area of relatively high atmospheric pressure compared to the surrounding environment, without being a closed circulation.[1]It is associated with an area of maximumanticycloniccurvature of wind flow. The ridge originates in the center of ananticycloneand sandwiched between twolow-pressure areas,and thelocusof the maximum curvature is called theridge line.This phenomenon is the opposite of atrough.
Description
editRidges can be represented in two ways:
- On surfaceweather maps,the pressureisobarsform contours where the maximum pressure is found along the axis of the ridge.
- In upper-air maps,geopotential heightisohypsesform similar contours where the maximum defines the ridge.
Related weather
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Given the direction of the winds around an anticyclonic circulation and the fact that weather systems move from west to east:[2]
- 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 thenegative vorticity advectionzone ahead of the upper-level ridge.[2]The vertical downward air motion then gives a divergence of the winds near the surface. Thesubsidenceof the air causes a warming in the column compared to the previous environment and therefore a drying of it because itsrelative humiditydecreases, which has the effect of clearing the sky.[2]
Subtropical ridge
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An important atmospheric ridge is thesubtropical ridge.It is a series of ridges near thehorse latitudecharacterized 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.[3][4]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 steertropical cyclonesand themonsoon.[5]
Ridge blocking
editBlocksinmeteorologyare large-scale patterns in theatmospheric pressurefield that are nearly stationary, effectively "blocking" or redirecting migratorycyclones.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).[6]Upper ridges are often associated with such blocks, particularly inOmega blocks.[6]
References
edit- ^American Meteorological Society."Ridge".AMS Glossary.RetrievedAugust 2,2019.
- ^abcMétéo-France."Dorsale".Glossaire(in French). Archived fromthe originalon 2021-10-10.RetrievedAugust 2,2019.
- ^Robert Tardif (2002).Fog characteristics.Archived2011-05-20 at theWayback MachineUniversity Corporation for Atmospheric Research.Retrieved on 2007-02-11.
- ^Myanmar government (2007).Haze.Archived2008-02-24 at theWayback MachineRetrieved on 2007-02-11.
- ^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.
- ^ab"The Omega Block".theweatherprediction.com.Retrieved27 July2019.