South Atlantic High is a semipermanentpressure high centered at about25°S,15°W, in theAtlantic Ocean. It is also called theSt. Helena High,Saint Helena island being the only land in the area. It can stretch thousands of miles across the South Atlantic.[1][2] This does not mean that the position and the intensity of this anticyclone are permanent, but just that there is an anticyclone on the maps describing the average monthly pressure. This area of high pressure is part of the great subtropical belt ofanticyclones called thesubtropical ridge.
In theHorse latitudes, generally in the region between 30 and 35 degrees of north and south latitude, there are more or less permanent highs. This is the subsiding part ofHadley cells. Indeed, near the equator, where theCoriolis force is quite weak, a direct circulation of air is established. In the lower levels of the atmosphere, the difference in temperature between the equator and the northerly warmer regions gives rise to theIntertropical Convergence Zone where the warmer air rises because of convergence and relatively lower density. Subsequently, this air spreads north and south and cools at higher altitude and descends further north and south.[1]
This system greatly affects sailing because the associated winds are generally not strong and sailing vessels have to go far north or south of the centre of the high pressure region depending on the direction of travel to find winds that are favourable in strength and direction.[3]
The anticyclonic circulation produces a dry climate, contributing to the aridity of theNamib andKalahari deserts, but its influence does not stop there: the South Atlantic High brings warm weather from the east coast of South America to Africa in summer as it carries tropical air to its southern flank.[1] On its northern flank, where the winds are easterly trade winds, there is the intertropical convergence zone that controls theAfrican monsoon and the rainy season inthe Guianas.[4]
circulation de Hadley.
| Concepts | |||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Anticyclone |
| ||||||||||||||||||||||||||||||||||||||||||||||
| Cyclone |
| ||||||||||||||||||||||||||||||||||||||||||||||
