Types of Winds and Wind Belts

  • Wind is the horizontal movement of air from areas of high pressure to areas of low pressure caused by the uneven heating of earth by the sun. Winds can be characterised on the bases of their direction, deflection and, speed.
  • Wind Direction can be measured with the help of wind vane.
  • Windsock is used to show the strength and direction of the winds.
  • Anemometer is an instrument, which is used to measure wind speed.
  • Beaufort scale has 13 levels of wind strength, ranging from dead calm to Hurricane.
  • The factors that affect the direction and speed of wind are pressure gradient, Coriolis force, temperature, rotation of earth, altitude, latitude, and friction.
  • Pressure Gradient is the rate of change of atmospheric pressure between two points on earth’s surface.
  • Coriolis force is produced by the rotation of earth on its inclined axis. Due to this force, winds get deflected to right in the Northern Hemisphere and to left in the Southern Hemisphere.
  • There is an inverse relation between temperature and pressure. So, the winds always move from high pressure areas to low pressure areas.
  • Rotation of Earth affects the pressure pattern.
  • Air pressure decreases with the increase in altitude.
  • Because of the spherical shape of earth, different parts are heated differently. There is different pressure at different latitudes.
  • Friction determines the angle at which the air will flow across the isobars.
  • Winds can be classified into different types on the basis of region where they blow, and the duration of time for which they blow. Four important types of winds are planetary winds, periodic winds, local winds, and variable winds.
  • Planetary winds blow throughout the year all over the world. They are also known as permanent winds or prevailing winds because they blow in a definite direction.
  • These are of three types based on the latitudes in which they blow. These are trade winds, westerlies and polar easterlies.
  • Trade Winds blow from Sub-tropical High Pressure Belt to the Equatorial Low Pressure Belt.
  • Westerlies blow from the Sub-tropical High Pressure Belt to the Sub-Polar Low Pressure Belt.
  • Polar Easterlies blow from Polar High Pressure Belt to Sub-polar Low Pressure Belt between the latitudes 60° and the poles on both sides of the Equator.
  • Periodic winds blow in regular cycles during a particular period of day or season, land and sea breeze and monsoon winds.
  • Sea breeze and land breeze develop in coastal areas. They are caused by differential rate of heating of land and sea.
  • Monsoon winds develop due to differences in heating conditions of continent and oceans.
  • Local winds are restricted to a certain place only. They blow for a short period of time. Some of the local winds are Sirocco, Leveche, Pampero, Khamsin, Loo, Mistral, Bora, Chinook, Foehn, Berg, Nor’westers, Brickfielder, etc.
  • Variable winds are related to pressure systems. Two chief types of variable winds are cyclones, and anti-cyclones.

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  • Q1

    In which direction trade winds blow?

    Marks:1
    Answer:

    In the Northern Hemisphere, trade winds blow in north-east and in the Southern Hemisphere trade winds blow in south-east direction.

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  • Q2

    Who devised Beaufort scale and Why? State any one characteristic of this scale.

    Marks:1
    Answer:

    Sir Francis Beaufort devised this scale in 1805 to help sailors at sea.

    There are 13 levels of wind strength (0 to 12) on this scale, ranging from calm to hurricane.

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  • Q3

    What is meant by intertropical convergence zone?

    Marks:1
    Answer:

    The region of thunderstorms where the trade winds converge is called the intertropical convergence zone.

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  • Q4

    What are variable winds?

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    Answer:

    Winds that blow in different directions depending on the movement of the pressure systems are known as variable winds. They last for a few days and affect only small areas. The speed and direction of these winds vary from time to time.

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  • Q5

    What is wind?

    Marks:1
    Answer:

    Wind is the movement of air from high pressure to low pressure regions, which is caused by uneven heating of the earth.

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