Describe the Characteristics of the Following Winds I. Prevailing Winds Ii. Seasonal Winds Iii. Cyclones Iv. Local Winds in Terms of Their Origin/Source, Features and Their Effects on the Climate.

Topics: Tropical cyclone, Wind, Monsoon Pages: 11 (4316 words) Published: January 18, 2011
Wind is caused by differences in atmospheric pressure created, in large part, by the unequal heating of the earth's surface by the sun. Air moves from a region of higher pressure to one of lower pressure and this movement is wind. Any difference in pressure will cause wind, but the greater the difference the stronger the wind. The direction that wind takes is influenced by the rotation of the earth. On a non-rotating earth wind would move in a straight path from a high- to a low-pressure area. It is deflected from this path—to the right in the Northern Hemisphere and to the left in the Southern—by the turning of the earth on its axis. Prevailing winds are winds that blow predominantly from a single general direction over a particular point on the Earth's surface. The dominant winds are the trends in direction of wind with the highest speed over a particular point on the Earth's surface. A region's prevailing and dominant winds are often affected by global patterns of movement in the Earth's atmosphere. In general, easterly flow exists at low and high latitudes globally. In the mid-latitudes, westerly winds are the rule and their strength is at the mercy of the polar cyclone. In areas where winds tend to be light, the sea breeze/land breeze cycle is the most important to the prevailing wind; in areas which have variable terrain, mountain and valley breezes dominate the wind pattern. Highly elevated surfaces can induce a thermal low, which then augments the environmental wind flow. As part of the Hadley cell circulation, surface air flows toward the equator while the flow aloft is towards the poles. A low-pressure area of calm, light variable winds near the equator is known as the doldrums, equatorial trough, intertropical front, or the Intertropical Convergence Zone. When located within a monsoon region, this zone of low pressure and wind convergence is also known as the monsoon trough. Around 30° in both hemispheres air begins to descend toward the surface in subtropical high-pressure belts known as subtropical ridges. The sinking air is relatively dry because as it descends, the temperature increases but the absolute humidity remains constant, which lowers the relative humidity of the air mass. This air mass is dry and subsident, or sinking through the troposphere, and sometimes reaches the ground. When this warm, dry air reaches the surface it is known as a superior air mass. The superior air normally resides over the top of maritime tropical air masses over oceans, forming a warmer and drier layer over the more moderate maritime tropical air mass below. When the temperature increases with height, it is known as a temperature inversion. When it occurs within a trade wind regime, it is known as a trade wind inversion. The surface air that flows from these subtropical high-pressure belts toward the Equator is deflected toward the west in both hemispheres by the Coriolis Effect. These winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. Because winds are named for the direction from which the wind is blowing, these winds are called the northeast trade winds in the Northern Hemisphere and the southeast trade winds in the Southern Hemisphere. The Trade Winds meet at the doldrums. As they blow across tropical regions, air masses heat up over lower latitudes due to more direct sunlight. Those that develop over land (continental) are drier and hotter than those that develop over oceans (maritime), and travel northward on the western periphery of the subtropical ridge. Maritime tropical air masses are sometimes referred to as trade air masses. The one region of the Earth which has an absence of trade winds is the north Indian Ocean. Clouds which form above regions within trade wind regimes are typically composed of cumulus which extend no more than 4 kilometres (13,000 ft) in height, and are capped from being taller by the trade wind inversion. Trade winds...
Continue Reading

Please join StudyMode to read the full document

You May Also Find These Documents Helpful

  • Essay about The Wind
  • wind Essay
  • wind power Essay
  • Essay on Wind Chill
  • wind Essay
  • Essay about The Wind
  • Wind : Essay
  • Essay about Wind

Become a StudyMode Member

Sign Up - It's Free