GKites: Wind Origins
Apr 3, Global Winds: Trade Winds, Westerlies and Polar Easterlies. Shares. Share. Share The trade winds meet at the doldrums. You can visualize. The cold polar easterlies meet the warm prevailing westerlies in this zone, and because of the extreme differences in pressure, dramatic weather conditions. Prevailing winds are winds that blow predominantly from an individual direction over a The westerlies or the prevailing westerlies are the prevailing winds in the The polar easterlies (also known as Polar Hadley cells) are the dry, cold.
Strong updraftsdowndrafts and eddies develop as the air flows over hills and down valleys. Wind direction changes due to the contour of the land. If there is a pass in the mountain range, winds will rush through the pass with considerable speed due to the Bernoulli principle that describes an inverse relationship between speed and pressure. The airflow can remain turbulent and erratic for some distance downwind into the flatter countryside. These conditions are dangerous to ascending and descending airplanes.
At night, the sides of the hills cool through radiation of the heat. The air along the hills becomes cooler and denser, blowing down into the valley, drawn by gravity. This is known a katabatic wind or mountain breeze.
Polar easterlies - Wikipedia
If the slopes are covered with ice and snow, the katabatic wind will blow during the day, carrying the cold dense air into the warmer, barren valleys. The slopes of hills not covered by snow will be warmed during the day. The air that comes in contact with the warmed slopes becomes warmer and less dense and flows uphill. This is known as an anabatic wind or valley breeze.
Orographic liftPrecipitation types meteorologyand United States rainfall climatology Orographic precipitation occurs on the windward side of mountains and is caused by the rising air motion of a large-scale flow of moist air across the mountain ridge, resulting in adiabatic cooling and condensation.
In mountainous parts of the world subjected to consistent winds for example, the trade windsa more moist climate usually prevails on the windward side of a mountain than on the leeward or downwind side.
Moisture is removed by orographic lift, leaving drier air see katabatic wind on the descending and generally warming, leeward side where a rain shadow is observed. DuneErosionand Insect Insects are swept along by the prevailing winds, while birds follow their own course. Because of this, wind barrier strips have been developed to minimize this type of erosion.
This is called the Coriolis force, and is caused by the rotation of the earth. Imagine yourself in a fixed position in space, looking down at the earth. You would observe that the wind moving from the equator to the north pole was traveling in a straight line, with the earth's rotating surface moving beneath it. Now place yourself at a location on the earth's surface and observe the wind again. The wind would appear to be curving to the right. The earth rotates on its axis at the rate of miles per hour at the equator.
The speed decreases with increasing latitude until it is virtually zero at the poles. This is because the latitude circles grow smaller. Place an object on the equator and allow 24 hours to go by. When the object returns, it will have traveled more than 24, miles - in other words, to travel that distance in 24 hours its linear speed was mph. Now place the object at 60 degrees north and let it make its circle. In 24 hours it will travel about 12, miles at mph.
Global Winds: Trade Winds, Westerlies and Polar Easterlies
At the north pole the linear speed would be zero because there would be no distance traveled. As an object such as a piece of wind, or a rocket starts to move in a straight path from the equator to the north pole, its eastward speed the earth rotates from west to east will be mph.
As it travels northward, its eastward movement will be faster than the eastward movement of the surface of the earth at higher latitudes.
It will run ahead of any object at higher latitudes, and appear to an earth based observer to be curving to the right. Similarly, if the object traveled from the north pole to the equator it would have no eastward movement, and would fall behind a lower latitude object whose eastward movement would be faster. To an earth based observer the curve would again appear to be to the right of the direction of motion.
Why is it, then, that in the southern hemisphere this apparent motion is reversed - that is, the Coriolis deflection is to the left? Imagine yourself once again in space.
This time you are hovering just above the north pole.C5-Pressure Belts,Permanent Winds upsc ias-Coriolis Force, Easterlies,Westerlies,Doldrums
When you look down at the rotation of the earth you see it moving counterclockwise. Now relocate yourself to just above the south pole. When you glance down, the earth is rotating clockwise. 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. 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 what stormy region do the westerlies and polar easterlies converge
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.