In an anticyclone, the atmospheric pressure is higher than the pressure of the surrounding air.
An anticyclone is an atmospheric phenomenon that, in the northern hemisphere, represents a zone of high pressure with the wind circulating in the same direction as clockwise , while in the southern hemisphere the opposite occurs. The anticyclone generally causes clear, stable weather without rain.
In an anticyclone, the atmospheric pressure is higher than the pressure of the surrounding air. The air in the anticyclone moves downward from the upper layers of the atmosphere towards the earth's surface. This phenomenon, called subsidence, makes it difficult for clouds to form, contributing to good weather .
Types of anticyclone
The descent of air can be due to different reasons. When the movement is produced by a process of advection in the elevated area, we speak of a dynamic anticyclone . The weather , in these cases, is hot and dry, with a strong presence of the sun.
If the air mass descends because it is at a lower temperature than its surroundings, it is a thermal anticyclone . The descent of the air increases atmospheric pressure and the temperature falls more sharply in low areas. The weather thus becomes cold, although dry and sunny.
The progress of an anticyclonic circulation is called anticyclogenesis . The opposite process, on the other hand, is called cyclogenesis (the circulation is cyclonic in the atmosphere ).
Sailing is affected by anticyclones.
Its impact on navigation
Sailing is one of the activities most affected by anticyclones, as they cause a lack of wind and force sailors to move considerably further north or south to take advantage of the wind direction, depending on their destinations.
Between 30 and 35 degrees south and north latitude, which we could call subtropical latitudes , it is normal to find anticyclones that appear to remain in the same region. This is the area where the Hadley cell descends, an atmospheric circulation pattern that gives rise to the easterly winds and trade winds in tropical areas.
In fact, in areas close to the equator, where the Coriolis effect is not strong (which is observed when a body moves relative to a reference system that is in full rotation), the air presents a direct circulation.
The heat is less at lower levels of the atmosphere, and this temperature characteristic opens the doors to what is known as the intertropical convergence zone , in which Archimedes' principle (belongs to the field of physics, and proposes that a body at rest, totally or partially submerged in a fluid, suffers a vertical thrust with a weight equal to the mass of the displacement, that is, the volume of fluid displaced) and convergence (the collision of two horizontal air flows) are the causes of the elevation suffered by the warmer air.
South Atlantic Anticyclone
The South Atlantic anticyclone is located in a subtropical zone in the southern Atlantic Ocean, and is also known as the Saint Helena anticyclone . It is important to note that its position is not permanent, nor is its intensity, but rather an anticyclone usually appears in a fairly defined area on weather charts used to describe the average monthly pressure.
The approximate coordinates are 25°S 15°W, and a wide expanse of high atmospheric pressure is usually observed there. The two names given to this anticyclone correspond to its proximity to the island of Saint Helena , the only land area present in the vicinity, and to the fact that it is located in the Atlantic Ocean .