Global wind patterns
This zone of low pressure separates the westerlies from a third wind belt in Where the polar easterlies meet warm air from the westerlies. Areas where prevailing winds meet are called convergence zones. wind zones : polar easterlies, westerlies, horse latitudes, trade winds, and. subpolar low. region were polar easterlies and westerlies meet. polar front pressure zone where cold polar air is subsiding and spreading equator ward.
Similarly, when you blow up a balloon you create a high pressure area because you compress the air and increase its density within the balloon.Chapter 5 - Trades to Poles (part 9)
When the balloon is punctured the air rushes outward to the lower pressure. In both examples air moves from higher to lower pressure, and the greater the difference the faster the air travels. Global Winds Once the air has begun to move surplus heat to the poles and surplus cold to the equator another force comes into play.
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. 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. When you look down at the rotation of the earth you see it moving counterclockwise.
Global Winds: Trade Winds, Westerlies and Polar Easterlies
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. The globe is encircled by six major wind belts, three in each hemisphere.
From pole to equator, they are the polar easterlies, the westerlies, and the trade winds. All six belts move north in the northern summer and south in the northern winter.
Each belt occupies about 30 degrees of latitude, that is, one third of the way from the pole to the equator. At about the latitude of Norway and northward degreesthe Polar easterlies blow irregularly from the east and north.
Between the polar easterlies and the westerlies is the polar front. At about the latitude of Western Europe and the U.
This causes most weather in the United States to move from west to east. Where the Westerlies meet the trade winds at about 30 degrees Jacksonville, Florida is the Horse latitudesalso Variables of Cancer, Subtropical High, or Subtropical ridge. This is a region of high pressure, dry air, and variable winds, and is associated with deserts over land.
South of about 30 degrees the northern or northeast trade winds blow mostly from the northeast toward the equator.
These were the sailor's favorite winds, since the weather was warm, and the winds usually blew steadily in an advantageous direction.
Columbus used these to sail to the Caribbean.
Global winds and polar easterlies by jimmie hawkins on Prezi
At about the equator is Intertropical Convergence Zone or doldrumsa region of light and irregular wind broken by occasional thunderstorms and squalls.
The width and exact location of the doldrums is hard to predict. Sailing ships are sometimes becalmed here for many days waiting for a proper wind. In the southern hemisphere the belts are reversed.
Global wind patterns
The southeast trade winds blow from the southeast toward the equator. 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.
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.