Named after the French Scientist Gaspard Gustave CoriolisBecause of the Earth’s rotation, free moving objects …• deflected to the right

in the Northern Hemisphere• to the left in the

Southern Hemisphere• Depends on an

object’s speed—higher speed means stronger Coriolis Force.

The Coriolis Force

H

L1007

1009

1011

1013

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Pressure (mb)

• A pressure gradient causes wind to blow straight from High P to Low P and accelerate as it goes

North Latitude

Equator

Just a Pressure Gradient

H

L1007

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1011

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Pressure (mb)

• Wind doesn’t blow straight from High to Low … curves to the right of straight line.

North Latitude

Equator

Pressure, Coriolis Force, Friction

Rotation of Earth

• H and L don’t last forever without energy source … why?

Atmospheric Circulation on Slowly Rotating Earth

Actual flow around pressure systems are never this regular .

Cyclonic Flow Anticyclonic Flow

Curved Flow around High and Low

Around a surface low pressure center, net inward transport of air causes a convergence … air rises in the center.

Cyclones and Anti–Cyclones

Around a surface high pressure center, net outward transport of air causes a divergence … air falls in the center.

Anticyclones : high pressures with nearly circular isobars. • Air descends toward surface due to convergence aloft. • As air nears surface it is forced outward (divergence). • Coriolis effect bends air to the right of its path creating a clockwise rotation.• Under an anticyclone, air is descending, forming an area of higher pressure at the surface. • Cloud formation is inhibited, so the weather is usually settled with only small amounts of cloud cover.

Anti–Cyclones

Cyclones: Low pressures that exhibit nearly circular isobars. • As air enters low pressure from all directions, Coriolis effect bends wind direction to the right of its path. • This creates counterclockwise rotation around the low and convergence near the center. • As air collides near center it is forced aloft where divergence takes air away from the center. • Upper-level divergence maintains low pressure. • Rising air cools,condenses helps cloud formation, so weather associated with cyclone is cloudy and wet.

Cyclone

Solid rotation typifies the terrestrial planets: Every part of the object takes exactly the same time to complete one rotation.

Differential rotation typifies Jupiter: Particles at different locations in the fluid take different lengths of time to complete one rotation.