(The same phenomenon occurs in the Southern Hemisphere). Some of In the tropic circulation cell, the northeast trade winds are produced. Instead of one large circulation between the poles and the equator, there are three circulations. There are two main forces which affect the movement of air in the upper levels. in the northern hemisphere, if you stand with your back to the wind, low .. degrees latitude - 2 factors contribute to subsidence: porkostournaments.info-level flow moves the doldrums" - the tradewinds from both hemispheres that meet near equator in . You would observe that the wind moving from the equator to the north pole was traveling in a convergence, for it is here that the trade winds of both hemispheres meet. There are other jet streams, such as the one around 30 degrees, but.
This explains why the apparent curve is to the right in the northern hemisphere and to the left in the southern. In fact, as we continue to study wind motion, we'll see that each hemisphere is a mirror image of the other. Now one more imaginary placement of yourself.
If you straddled the equator you would see neither clockwise or counterclockwise movement. Because of this, the Coriolis force is not in effect at the equator. General Wind Patterns Local wind patterns are the result of pressure differences in the immediate area: But there are global patterns that we can observe as well.
Let's start by following movement in the northern hemisphere. Hot air rises from the equator, creates a low pressure area, and flows towards the north pole.
GKites: Wind Origins
The upper wind flow is deflected to the right by the Coriolis effect, which causes it to pile up and move from west to east. The piled up air cools, creating a high pressure area, and sinks; and as it accumulates on the surface it flows towards both the equator and north pole. The air moving toward the equator is influenced by the Coriolis effect and moves from the northeast, and because of its direction is called the northeast trade winds.
Wind is classified according to the direction from which it is blowing. The poleward moving air also moves to the right and is called the prevailing westerlies. The third wind belt develops as cold polar air sinks and moves south, is deflected to the right, and is therefore called the polar easterlies.
The same air pattern occurs in the latitudes of the southern hemisphere, except that the deflection of the wind is to the left rather than right. In the southern hemisphere the trades are called the southeast trade winds. Roughly speaking, trade winds occupy the area between 0 the equator and 30 degrees latitude; prevailing westerlies the area between 30 and 60 degrees; and polar easterlies the region between 60 and 90 degrees the pole.
The zones that separate these three major wind belts are also identified. Near the equator is a region called the doldrums, literally meaning "stagnation or listlessness".
The area was given this name by 16th century English merchant sailors, who found themselves trapped by lack of a "trade" wind to carry them onward to the next port of call. A more explanatory, if less colorful, name is the intertropical convergence, for it is here that the trade winds of both hemispheres meet.
It is known for its extremely low pressure, frequent thunderstorms, and very calm wind. At about 30 degrees is a high pressure area where the trades and westerlies diverge and go toward the equator and pole, respectively.
Intertropical Convergence Zone
Like the doldrums, it is an area with little wind; unlike the doldrums, there are no cloud formations, just blue skies and warm temperatures. The sailors gave this region a graphic name, the horse latitudes. The origin of the name varies: In any event, ships tried to avoid this zone and its lack of wind. The third zone lies at about 60 degrees latitude, and is called the polar front.
Its location varies with the seasons, since the polar front moves south in winter and north in the summer. The cold polar easterlies meet the warm prevailing westerlies in this zone, and because of the extreme differences in pressure, dramatic weather conditions occur.
Jet Streams With the development of high flying aircraft, an additional wind pattern was discovered. The jet stream is a band of fast moving, high altitude air.
Global Winds: Trade Winds, Westerlies and Polar Easterlies
Friction from the earth's surface slows down air movement, but at higher altitudes friction has no effect and air travels faster. Another factor contributing to jet streams is pressure gradient. Recall that pressure gradient is the difference between areas of pressure, and the greater the difference the faster the wind speed.
Above the polar front, where cold polar easterlies meet warm prevailing westerlies, the polar jet stream exists. This band of turbulent air moves about erratically, changing in width from 25 to miles. Wind speed, which is generally westerly, can exceed mph. Pilots traveling west to east try to hitch a ride on the polar jet to reduce their flight time, but aircraft moving east to west would be delayed by encountering the jet stream. There are other jet streams, such as the one around 30 degrees, but because of the greater and constant pressure gradient the polar jet is the best known.
To sum up at this point: Convected energy from the earth's surface rises upward and becomes wind as it begins to move horizontally.
This movement is caused primarily by pressure gradient force, as high pressure air moves toward low pressure areas. Curvature of the wind is caused by the rotation of the earth and is called the Coriolis effect.
Intertropical Convergence Zone - Wikipedia
In the area from the equator to 30 degrees a large circular overturning of air occurs as warm low pressure air rises, moves poleward, cools, and returns to the surface. Region of the oceans around 30 degrees latitude where winds are light and unpredictable. Rapidly moving band of air in the upper atmosphere.
Relatively permanent front formed at the junction of the Ferrell and polar Hadley cells. Relatively constant wind patterns that blow toward the equator at about 30 degrees latitude.
The Coriolis effect The air flows in these three circulation belts or cells do not move in a straight north to south or south to north route. Instead, the air flows seem to move east to west or west to east.
This effect was first identified by the French mathematician Gaspard-Gustave de Coriolis — in Coriolis observed that, because of the spinning of the planet, any moving object above Earth's surface tends to drift sideways from its course of motion.
In the Northern Hemisphere, this movement is to the right of the course of motion. In the Southern Hemisphere, it is to the left. As a result, surface winds in Hadley cells—both in the equatorial and polar regions—blow from the northeast to the southwest in the Northern Hemisphere and from the southeast to the northwest in the Southern Hemisphere. Surface winds in Ferrell cells tend to blow in the opposite direction: Variations and wind patterns The conditions of the wind cells described above are for general models.
In the real world, actual wind patterns are far more complex. Many elements play a part in disrupting these patterns from their normal course, as described by Hadley and Ferrell.
Since the Sun does not always shine directly over the equator, air masses in that area are not heated equally. While some masses in a cell may be heated quickly, creating a strong flow upward, others may not receive as much solar energy, resulting in a much weaker flow. Unevenness in the surface of the planet also affects the movement of air masses in a cell.
A mass moving across a uniform region, such as an ocean, may be undisturbed. Once it moves over a region with many variations, such as a mountainous area, it may become highly disturbed. Doppler radar used to measure the speed and direction of local winds. Reproduced by permission of National Oceanic Atmospheric Administration. The jet streams Inan especially dramatic type of atmospheric air movement was discovered: These permanent air currents are located at altitudes of 30, to 45, feet 11 to 13 kilometers and generally move with speeds ranging from about 35 to 75 miles 55 to kilometers per hour.
It is not uncommon, however, for the speed of jet streams to be as high as miles kilometers per hour. These narrow tubes of air, which usually travel west to east, are created by the great temperature and pressure differences between air masses. There are four major jet streams, two in each hemisphere. Polar jet streams, formed along the polar front between the Ferrell and polar Hadley cells, move between 30 degrees and 70 degrees latitude.
The other jet streams move between 20 degrees and 50 degrees latitude.
- Atmospheric circulation
Jet streams do not move in straight lines, but in a wavelike manner.