Wind does not cross the isobars at right angles, but is deflected by the Earth’s rotating surface . Coriolis Effect appears to deflect winds to the right of their path of motion in the Northern Hemisphere, and to the lef of their path of motion in the Southern Hemisphere. The deflection is to the right of their path of motion, because of the counterclockwise rotation of the Northern Hemisphere, and to the lef of their path of motion, because of the clockwise rotation of the Southern Hemisphere.
The Coriolis Effect describes how Earth’s rotation steers winds and surface ocean currents . Coriolis Effect causes freely moving objects to appear to move to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The objects themselves are actually moving straight , but the Earth is rotating beneath them, so they seem to bend or curve . That's why it is incorrect to call Coriolis a force. It is not forcing anything to happen!
Magnitude of the Deflecting (Coriolis) Effect is dependent on latitude: a) Maximum deflection at the Poles. b) Deflection is zero at the Equator. c) Strongest deflection at the poles and eventually becomes non- existent at the equator. d) Earth’s rotational speed 1) 0 kmph at the Poles 2) 1675 kmph at the Equator
Linear Velocity of Rotation This varies dramatically with latitude: 1) Equator = 24,902 miles (40,075 km) long Therefore rotational velocity at the Equator must be 1041 mph (1675 kmph) to cover that distance in one day . 2) 60 0 = 12,451 miles (20,038 km) long Therefore rotational velocity at 60 0 must be only 521 mph (838 kmph) to cover that distance in one day . 3) 90 0 = 0 miles (0 km) long Therefore rotational velocity at the poles is 0 mph (0 kmph).
East- West Deflection Amount of deflection varies by latitude: a) deflection is greater at 60 0 latitude than at 40 0 latitude b) defection is greater at 40 0 latitude than at 20 0 latitude c) no deflection of air flow occurs at the Equator
Wind Speed and the Coriolis Effect The amount of Coriolis deflection increases with wind speed . (Faster winds cover a greater distance than do slower winds in the same time period.) Coriolis Effect does not affect small scale motions that cover insignificant distances and very short time periods. Coriolis Effect does not increase or decrease wind speed. Coriolis Effect It is not a “real” force, but rather the effect of Earth’s rotation on a moving body . The Earth moves or rotates under the wind , making it appear to deviate from a straight line . Deviation from a straight line appears to happen , because the Earth is rotating under the wind.
Coriolis Effect – Summary 1) It is always directed at right angles to the direction of airflow. 2) It affects only wind direction , not wind speed. 3) It is affected by wind speed – The stronger the wind, the greater the deflecting force. (It increases with wind speed.) 4) It is dependent upon latitude . It is strongest at the poles and weakens Equatorward, becoming non-existent at the Equator .
- Fall '16
- Mark Smith
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