WIND is simply defined as air in motion. are horizontal flows of air; windsblow from areas of high pressureto areas of low pressure (naturetries to equalise pressure)
Factors Affecting The WindsPressure Gradient ForceCoriolis EffectFriction
Strong winds alsooccur in low latitudesdue to strongerheating and steeperpressure gradients.Hurricanes andtornadoes are bothtropical phenomena.Hurricane in Florida Tornado in USAWind strengthdepends onthe differencein pressurebetween thehigh and lowpressuresystems, andthe distancebetweenthem.This is called thePRESSUREGRADIENT; it isthe spacing of theisobars whichindicates thepressure changesoccurring over agiven distance.ISOBARS are lineconnecting places ofequal pressure.
CORIOLIS EFFECTHIGHLOWTheoretical windwhich wouldresult solely frompressure gradientActual windwhich blows, asdiverted byCoriolis Force�The earth’s rotationdiverts this wind directionlaterally.This force iscalled the CORIOLISFORCE.� The Coriolis force divertswind the right in thenorthern hemisphere; tothe left in the south.� The effect is stronger athigh altitude whereground level friction is lesssignificant.HIGHIn the north, windsblow clockwise outfrom a highpressure. (In thesouth, they blowanti-clockwise).LOWIn the north, windsblow anti-clockwiseinto a low pressuresystem. In the south,they blow clockwise.
TWO GENERAL TYPES OFWINDS Local Winds Prevailing Winds Periodic Winds
Local Winds winds we frequently encounter andthese blow in any direction. produced on a local scale byprocesses of heating and cooling oflower air.
Two Categories of Local Winds Katabatic Wind a category includes local winds in hillyor mountainous regions, where on clearand clam nights, heat is rapidly lost byground radiation. This produces a layer of cold.Katabatic Wind usually felton the great ice caps ofGreenland and Antarctica
Convection Wind a category that includes landand sea breezes. land and sea breezes are limited toperiods of generally warm, clear weatherwhen regional wind flows is weak, butthey form an important element of thesummer climate along coasts.
Prevailing Winds winds that blow from the samedirection and most often travel longdistances. also known as PERMANENT WINDSor PLANETARY WINDS. it is sub divided in to the tradewinds, anti trade winds, and polarwinds.
Two factors That Affect theDirection Of PrevailingWindsUnequal heating of theearth’s surfaceEarth’s rotation
Periodic Winds are also known as seasonalwinds or monsoons. they blow from water bodies toland.
Categories of Wind Systems DOLDRUMS long known as the equatorial belt ofvariable winds and calms. this zone is located on a belt oflow pressure. it has no strongpressure gradients to induce persistentflow of wind.
TRADE WIND BELTS these winds are the result of apressure gradient thus the prevailing wind is from thenortheast and the winds aretermed northeast trade winds in the Southern hemisphere, deflectionof moving air towards leftcauses the southeast trades
WESTERLIES also known as prevailing westerly winds. in these belts, storm winds are commoncloudy days with continued precipitationare frequent. weather is highly changeable. in Southern hemisphere the westerliesgain great strength and persistence.
POLAR EASTERLIES characteristic wind systems of the Arcticand Antarctic latitudes is describedas polar easterlies. polar easterlies show anoutward spiraling flow. radial winds would spiralcounterclockwise, producing a system ofsoutheasterly winds.
WINDS OF HORSE LATITUDES long known as subtropical beltsof variable winds or horse latitude. these are not continuous belts most of the world’s great deserts liein this zone and in the adjacent trade-wind belt