page_title: Anticyclone
section_title: Subtropical ridge
hierarchical_section_title: Anticyclone / History / Subtropical ridge
caption_attribution_description: English: Water vapor imagery depiction of the subtropical ridge National Climatic Data Center's GIBBS satellite archive ftp://eclipse.ncdc.noaa.gov/pub/isccp/b1/.D2790P/images/2000/258/Img-2000-09-14-12-GOE-10-WV.jpg
context_page_description: An anticyclone is a weather phenomenon defined by the United States of America's National Weather Service's glossary as "a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere". Effects of surface-based anticyclones include clearing skies as well as cooler, drier air. Fog can also form overnight within a region of higher pressure. Mid-tropospheric systems, such as the subtropical ridge, deflect tropical cyclones around their periphery and cause a temperature inversion inhibiting free convection near their center, building up surface-based haze under their base. Anticyclones aloft can form within warm core lows such as tropical cyclones, due to descending cool air from the backside of upper troughs such as polar highs, or from large scale sinking such as the subtropical ridge.
  The evolution of an anticyclone depends upon variables such as its size, intensity, and extent of moist convection, as well as the Coriolis force.
context_section_description: Heating of the earth near the equator forces upward motion and convection along the monsoon trough or intertropical convergence zone.  The divergence over the near-equatorial trough leads to air rising and moving away from the equator aloft.  As air moves towards the mid-latitudes, it cools and sinks leading to subsidence near the 30° parallel of both hemispheres.  This circulation known as the Hadley cell forms the subtropical ridge.  Many of the world's deserts are caused by these climatological high-pressure areas.  Because these anticyclones strengthen with height, they are known as warm core ridges.
caption: The subtropical ridge shows up as a large area of black (dryness) on this water vapor satellite image from September 2000.
exif: {}