N

W E

v(Direction of deflection)

S

Illustration of Eastward deflectionof North bound winds in the Northern Hemisphere

As seen from an inertial frame (space), when the air moves north to a higher latitude it retains its tangentialvelocity from lower latitudes due to inertia. There areno shear forces in air to change the tangential velocity.The ground at higher latitudes has smaller tangentialvelocity.This excess of air tangential velocity over thatof the ground below is perceived on the earth as an eastward component of the wind.

'E airmass O R E E airmass Oa 2 v

O

Northward motion is Deflected Eastwards

Northern Hemisphere Southern Hemisphere

Southward motion is deflected Westwards

Northward motion is deflected to the West

Southward motionis deflected East

The lower halves of the loopsare surface winds with directionas shown.

(Source: Kaufmann W., 1996 Universe, W.H.Freeman and Co. New York.)

Global Winds and their directions

Ferrel Cell

Hadley Cell

Polar Cell

Unnamed Hurricane during ‘Halloween Storm’ of October 1991 (http://www.ncdc.noaa.gov/ol/satellite/satelliteseye/ hurricanes/unnamed91/unnamed91.html)

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