windy in the modern dictionary is synonymous with impermanence, changeability.But the trade winds this statement is completely split.In contrast to the breezes, the monsoon season and the more wind, the weather caused by cyclones, they are constant.How are the trade winds are blowing, and why a certain direction?Whence in our language this word - "Passat"?Is it really the constant winds and where they are located?On this and many other things you learn from this article.
meaning of the word "trade winds»
In the days of sailing ships the wind was of paramount importance for navigation.When he blew always exactly in the same direction, one could hope for a favorable outcome of the dangerous journey.And so the wind Spanish sailors dubbed «viento de pasade» - favors the movement.The Germans and the Dutch have included the word "Pasadena" in its marine navigational vocabulary terms (Passat and passaat).And in the era of Peter the Great is the name penetrated into the Russian language.Although our high
as the image of the trade winds
carry out a little experiment.Put on a few drops of the ball.Now tighten it as whirligig.Look closely at the drops.Those, which are closer to the axis of rotation remain motionless and arranged on the sides "whirligig" flowed in the reverse direction.Now imagine that the ball - the planet.She turns from west to east.The movement formed opposing winds.When the point is situated close to the poles, one day it does a smaller circle than the one which is on the equator.Therefore, the speed of its movement about the axis slowly.By friction with the atmosphere in these polar latitudes, there is no air currents.Now it is clear that the trade winds - a steady winds of the tropics.In fact, there is so-called equatorial band of calm.
direction of the trade winds
dropwise on the ball is not difficult to trace, they spread out in the direction opposite to the rotation.This is called the Coriolis force.But to say that the trade winds - a wind blowing from east to west, it would be wrong.In practice, in the Northern Hemisphere air masses deviate from their main vector to the south.The same thing happens only in a mirror image on the other side of the equator.That is, in the Southern Hemisphere trade winds blow from the southeast to the northwest.
Why equator so attractive for air masses?In the tropics, as is well known, established a permanent area of high pressure.And at the equator, on the contrary, low.If we answer the child's question, where does the wind, it shall present a capital naturalistic truth.Wind - the movement of air masses from the layers with a high pressure region to the lower.Peripherals tropics in science is called - "Horse latitudes."From there, the trade winds are blowing at a gallop in the "calm strip" over the equator.
speed constant winds
So we realized the area of distribution of trade winds.They are formed in both hemispheres of the Earth at latitude 25-30 ° and fade near the calm zone somewhere at 6 degrees.The French believe that the trade winds - it's the "right winds» (vents alizes), very convenient for the movement under sail.Their speed is low, but constant (five to six meters per second, it is sometimes as high as 15 m / s).However, the power of the air mass is so great that they form a trade-wind flow.Born in regions with hot and dry climate, the wind contribute to the development of deserts like the Kalahari and Namib Atacama.
These they permanent?
trade winds over the continent faced with local winds, sometimes changing its speed and direction.For example, in the Indian Ocean, because of the special configuration of the coast of South-East Asia and the climatic characteristics, the trade winds become during the monsoon season.As we know, they are blowing from the cool summer sea toward the heated land, and in winter - on the contrary.However, the assertion that the trade winds - the winds of this tropical latitudes, is not quite true.In the Atlantic, for example, in the Northern Hemisphere they blow in winter and spring in the range 5-27 ° N, and in the summer and autumn 10-30 ° NThis is a strange phenomenon in the XVIII century gave scientific explanation Gadlo John, British astronomer.The strip of calm is not on the equator and moving behind the sun.Thus, to the date when our star is at the zenith of the Tropic of Cancer, the trade winds shifted to the north, and in the winter - to the south.Constant wind and unequal in strength.Passat southern hemisphere is more powerful.He almost never encounters obstacles in the form of land.There it forms a so-called "roaring" forties.
trade winds and tropical cyclones
To understand the mechanics of the formation of typhoons, it is necessary to understand that each hemisphere blow two constant wind.All that we have described above, refers to the so-called lower trade winds.But the air is known to be cooled by climbing to a height (an average of one degree every one hundred meters of rise).Warm the lighter weight and move upwards.Cold air has a tendency to fall down.Thus, in the upper atmosphere there opposing trade winds.It winds in the Northern Hemisphere from the southwest, and below the equator - from the northwest.Temperature inversion in the trade winds sometimes change stable direction of the two layers.There is a zigzag winding warm, saturated with moisture and cold air masses.In some cases, tropical cyclones are gaining strength hurricane.All the same vector direction inherent in the trade winds, carries them to the west, where they bring down their destructive effect on coastal areas.