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ICSE-IX-Geography

14: Atmospheric Pressure and Winds

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    Section : I
    Short Answer Questions
  • Qstn #1
    Define the following terms :
    (a) Pressure Gradient
    (b) Winds
    (c) Coriolis force.
    (d) Altitude
    (d) Monsoons.
    Ans : (a) Pressure Gradient — It is the rate of change of atmospheric pressure between two points on the earth’s surface.
    (b) Winds — Horizontal movements of the air from high pressure to low pressure areas are called winds.
    (c) Coriolis force — This force is created by the rotation of the earth as the winds in different belts deflect towards right in Northern hemisphere and to the left in Southern hemisphere.
    (d) Altitude — The pressure also decrease with increasing altitude at the rate of 100 millibars in every 1000 metres of height gained.
    (d) Monsoons — are the periodic seasonal winds blowing in the regions of South East Asia and Northern Australia. The word monsoon is derived from the Arabic word ‘Mausim’ meaning ‘Season’, on account of deeply affecting the seasons of the particular region.
  • Qstn #2
    Name the four main pressure belts of the earth.
    Ans :
    1. Equatorial low pressure belt
    2. Sub-tropical high pressure belt
    3. Circum-polar low pressure belt
    4. Polar high pressure areas.
  • Qstn #3
    What is Circum-polar Low Pressure Belt ?
    Ans : It is the belt of low pressure belt between 60°N - 70°N and 60° S - 70° S.
  • Qstn #4
    How does Coriolis Force vary latitudinally ?
    Ans : In the northern hemisphere the winds deflect towards right and in Southern hemisphere deflect towards left due to the effect of the rotation of the earth, e.g. the trade winds take the Southwest direction in place of southern direction in northern tropical belt and in southern tropical belt these winds take northwest direction in place of northern direction.
  • Qstn #5
    Name the three chief types of wind.
    Ans : Three chief types of winds are Trade winds, Westerlies, and Polar winds.
  • Qstn #6
    What are periodic winds ?
    Ans : Periodic winds blow at regular intervals or in regular cycles. They are winds that result from localised differences in pressure and temperature. For example, land and sea breezes and the seasonal winds.
  • Qstn #7
    What are local winds ? Name any two local winds.
    Ans : The local winds blow in certain places and these are warm and cold according to the area from which they blow. Example: Foehn winds blow descending on the slopes of the Alps and makes the temperature ideal for grapes due to its warm effect. In the same way Chinook winds blowing and coming down from the Rockies mountains in North America helps to increase the temperature and are beneficial to keep grasslands ice free and warms the ranches, so good for animal rearing.
  • Qstn #8
    Name two types of variable winds ? Why are they so called ?
    Ans : Variable winds change their direction and force from place to place due to changing the pressure system. These blow for a short time or for a few days. These are cyclones and anticyclones. These are the circular winds with low pressure and high pressure in the centre respectively.
  • Qstn #9
    Why are cyclones frequent in summer in the tropical region ?
    Ans : In summer in the tropical region due to die shifting of Doldrums, the low pressure region is strongly originate between 8° and 20° N and S. They mainly originate in China sea and surrounding area. In Bangla Desh, these are known as ‘Kal Baisakhi’ rneaning ‘Time of Death’ and cause heavy calamities and destruction. These are known as ‘hurricanes’ in North America, ‘Typhoons’ in China,‘willywillies’ in Australia.
  • Qstn #10
    Mention any two differences between Tropical Cyclones and Temperature Cyclones.
    Ans :
    Tropical Cyclones Temperature Cyclones
    Tropical cyclones are produced mainly over the sea. Temperate cyclones are produced both on land and on sea.
    They generally originate in the tropical region between 8° and 20°N and S. They originate in the mid latitudinal region between 35° latitude and 65° latitude.
  • Qstn #11
    How are cyclones named differently in different parts of the world ?
    Ans : The name of the cyclones is different in different parts of the world on the basis of the local languages.
    Examples: hurricanes in America, typhoons in China and Japan, meaning the destructive horrible cyclonic winds.
  • Qstn #12
    What are two chief characteristics of anticyclones ?
    Ans : Two chief characteristics are that these provide clear weather and the winds blowing from the centre towards outside in clockwise direction.
  • Qstn #13
    Why are the summer monsoons known as South-West Monsoons in the Indian subcontinent ?
    Ans : Due to the low pressure created in the Northern Indian subcontinent and high pressure centre located in the Indian ocean, the Monsoons start to blow from the ocean to the Indian landmass taking a direction from southwest to northeast in summer seasons.
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