In an anticyclone, the atmospheric pressure is higher than the surrounding air pressure.
An anticyclone is an atmospheric phenomenon that represents, in the northern hemisphere, an area of high pressure with the wind circulating in the same direction as clockwise , while in the southern hemisphere the opposite occurs. The anticyclone generally makes the weather clear, stable and without rain.
In an anticyclone, thus, the atmospheric pressure is higher than the pressure of the surrounding air. The air found in the anticyclone makes a downward movement from the highest strata 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 an advection process in the elevated area, it is called 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 the environment, it is a thermal anticyclone . The descent of the air increases the atmospheric pressure and the temperature falls more intensely in the low areas. The weather, thus, becomes cold, although dry and sunny.
The progress of an anticyclonic circulation is called anticyclogenesis . The opposite process, however, 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 that is most affected by anticyclones, since they cause a lack of wind and force sailors to move considerably away to the north or south, to take advantage of the direction of the wind, according to their destinations.
Between 30 and 35 degrees of south and north latitude, what we could call the subtropical latitudes , it is normal to find anticyclones of apparent permanence in the same region. This is the part where the Hadley cell descends, an atmospheric circulation pattern that gives rise to easterlies 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 with respect to a reference system that is in full rotation), the air presents a direct circulation.
The heat is lower in the lower levels of the atmosphere, and this temperature characteristic opens the doors to what is known as the intertropical convergence zone , in which the 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 displaced volume of fluid) and convergence (the collision of two air flows). horizontal) They are the causes of the rise that the hottest air suffers.
South Atlantic Anticyclone
The South Atlantic anticyclone is located in a subtropical zone located 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 in a fairly defined area an anticyclone usually appears on the meteorological 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 seen there. The two names given to this anticyclone respond to its proximity to the island of Saint Helena , the only area of land present in the vicinity, and to the fact that it is located in the Atlantic Ocean .