Climatology for Kerala PSC: Types of WindJuly 1, 2022 2022-07-01 13:59
Climatology for Kerala PSC: Types of Wind
Climatology for Kerala PSC: Types of Wind
Winds can be broadly divided into three types.
1. Permanent winds
2. Seasonal winds
3. Local winds
● The trade winds, westerlies and easterlies are the permanent winds.
● These blow constantly throughout the year in a particular direction between high pressure belt to low Pressure belts.
● Winds blowing from the subtropical high pressure belts towards the equatorial low pressure belt are called Trade winds.
● The word ‘trade’ has been derived from a Latin word, ‘tread’, which means constant direction.
● The monsoons are also part of the planetary wind system but of a different nature.
● These trade winds blow from the north-east direction in the northern hemisphere and from the south-east in the southern hemisphere.
● The trade winds from both hemispheres converge at the Inter Tropical convergence Zone (ITCZ).
● Trade winds have contrasting properties in different parts.
● In their areas of origin, they are descending and stable. Hence the poleward parts are dry.
● As the trade wind approaches the equator, they become more humid and warmer and their instability produces copious rainfall.
● The Westerlies are the winds blowing from the subtropical high-pressure belts towards the subpolar low-pressure belts.
● They blow from the south west in the northern hemisphere and from the north- west in the southern hemisphere.
● The poleward boundary of the westerlies is highly fluctuating and there are many seasonal and short fluctuations.
● Westerlies carry much west to east moving temperate cyclones with them.
● Roaring forties, furious fifties and shrieking sixties are dreaded terms for navigators.
● The Polar Easterlies or Polar winds blow from the polar high pressure to the subpolar low-pressure areas. In the northern hemisphere, their direction is from the north-east.
● In the southern hemisphere they blow from the south-east.
● These winds change their direction in different seasons.
● The pattern of wind circulation is modified in different seasons due to the shifting of regions of maximum heating, pressure and wind belts.
● The most pronounced effect of such a shift is noticed in the monsoons, especially over southeast Asia.
● The surface winds which change their directions with changing seasons in Indian Ocean are called monsoon winds.
● These winds blow from sea to land in summer and from land to sea in winter. This is because of differential heating of land and water.
● These winds originate in the belt of trade winds lying between the Tropic of Cancer and the Tropic of Capricorn. These winds are common in South and South-East Asia.
● These blow only during a particular period of the day or year in a small area.
● Differences in the heating and cooling of earth surfaces and the cycles that develop daily or annually can create several common, local or regional winds.
Land and Sea Breezes
● The land and sea absorb and transfer heat differently.
● During the day the land heats up faster and becomes warmer than the sea. Therefore, a low pressure is created over the land and a relatively high pressure over sea.
● Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze.
● In the night the reversal of conduction takes place. The land loses heat faster and is cooler than the sea.
● The pressure gradient is from the land to the sea and hence land breeze results
Mountain and Valley Winds
● In mountainous regions, during the day the slopes get heated up and as a result the air moves upslope and to fill the resulting gap. The flow of air from the valley blows up the valley is known as the valley breeze.
● During the night the slopes get cooled and the dense air descends into the valley as the mountain wind.
● The cool air of the high plateaus and ice fields draining into the valley is called katabatic wind.
● Another type of warm wind occurs on the leeward side of the mountain ranges. The moisture in these winds, while crossing the mountain ranges condense and precipitate.
● When it descends down the leeward side of the slope the dry air gets warmed up by an adiabatic process. This dry air may melt the snow in a short time.
Foeh or Chinook
● It is the most well-known hot wind in the middle latitude.
● It occurs on the lee side of a mountain range and causes extremely rapid evaporation of snow or soil moisture.
● The warm and moist air ascends the slope and causes rainfall.
● The wind helps in removing snow from grazing ground and also the early ripening of the grapes.
● It is a hot, dry, suffocating wind or whirlwind which blows during the spring and the summer in the Sahara and Arabian desert.
● It carries dense masses of sand thereby reducing the visibility.
● This cold wind flows in the winter from higher land and snow-capped mountains to the north onto the Mediterranean Coast of France
● It is a dry wind with high velocity.
● It is the hot north-easterly wind experienced in the Tarim Basin of Sinkiang.
● The sand blown by the Karaburan cause major changes in the course of desert rivers