What are trade winds
The trade winds were extremely important in the centuries from the XV due to their great influence on sailing, and even today there are many who dare to put their sails in their favor. These are winds that occur between the equator and the tropics, blowing from the Northern hemisphere and also from the South, being in the well-known Intertropical Convergence Zone.
The trade winds are wind currents that blow almost constantly during the summer of the Northern Hemisphere and more irregular in the winter. Its effect occurs between the equator and the tropics , approximately up to 30º latitude both North and South. They are moderate force winds, with an average speed of about 20 km / h.
Due to their non-destructive force and their marked constancy in the summer months, historically they have had great importance, since they allowed the existence of important maritime trade routes and, in addition, they were also responsible for making it possible to cross the Atlantic to reach America on a sailboat. The first to establish a detailed map that included both the trade winds and the monsoons was Edmund Halley, who published it in 1686, in a study that he produced with data from English commercial sailors.
The trade winds blow from NE (Northeast) to SW (Southwest) in the upper part of the planet, the Northern hemisphere, and from SE (Southeast) to NW (Northwest) in the lower part of the Earth, that is, in the southern hemisphere. Its oblique direction is due to the Coriolis effect , which causes the Earth’s rotation to affect moving objects and modify their movement differently depending on the hemisphere they are in.
The origin of the trade winds is found in how the sun’s rays heat different parts of the planet in different ways. This is the process of the formation of the trade winds summarized:
- As the influence of solar rays is much greater when they impact fully, that is, perpendicularly, the Earth’s equator receives a greater amount of heat, a circumstance to which it owes its warmer climate. With regard to trade winds, when the sun’s heat falls on the lands and waters of the equatorial zone, this heat ends up returning to the surface air in quantity, so it overheats. This air, when heated, expands and loses density, becoming lighter and rising.
- As the hot air rises , a vacuum is created that is filled by the colder airs in the tropics.
- In turn, the hot air that has risen near the equator is moving towards 30º latitude, regardless of the hemisphere in which it is located.
- By the time it reaches this point, much of that air has cooled enough to drop back down to a surface height, giving rise to the closed circuit known as the Hadley cell .
- However, not all the air cools down again. A part heats up again and circulates towards the Ferrel cell , which is located between 30º and 60º of latitude, continuing its way towards the poles.
- The Coriolis effect is what causes these winds to blow not perpendicularly but obliquely, as well as their senses in the two hemispheres to be partially reversed.
Furthermore, the point where the trade winds of the two hemispheres meet, or rather the small area between them, is called ITCZ, Intertropical Convergence Zone . This area is of great importance for sailors, as it has low pressures and large upward air flows. In it intermittent torrential rains are common and its exact location constantly changes with the evolution of the air masses.
The trade winds are produced, as we have mentioned, throughout the territory that encompasses the area between the equator and 30º latitude, both North and South . This affects a large number of countries.
There are trade winds in the Canaries , which are partly responsible for the climate of these Spanish islands. In winter they make themselves felt with little force thanks to the stabilizing influence of the Azores anticyclone. Its location near the Tropic of Cancer and its geographical peculiarities give it its subtropical climate of dry summers, similar to the Mediterranean despite the distance.
They also have an important influence in countries such as Venezuela, Chile, Colombia, Ecuador or Costa Rica , all from tropical areas and with complex climates that cause the trade winds to blow in them with marked differences depending on the specific geographical area and the season of the year.
Keep in mind that although the trade winds and monsoons are closely related, they are far from the same and should not be confused. The trade winds are moderate and fairly constant force winds, while the monsoons are winds with heavy seasonal storms that discharge enormous amounts of precipitation.