Transcript tropical_cyclones

Tropical Cyclones
Earth’s most destructive storms
Also Known As
• Atlantic Ocean : Hurricane
• Pacific Ocean : Typhoon
• Indian Ocean: Cyclone
Driving Energy Contrast
• Warm sea surface vs. cool, dry troposphere
Necessary Conditions
• Warm sea surface
• Latitude > 10° N or S
• Low wind shear
Coriolis Force on Earth
Earth rotates to the East
Trajectories
deflect right
in N
hemisphere
Source: Strahler and Strahler, Introducing Physical Geography, 2005.
Rotation of the Earth
• Rotates West to East
(counterclockwise as
seen from above North
pole)
• poles on axis; equator
farthest from axis
Source: Earth and Moon Viewer,
Copyright © 1989 by Jef Poskanzer.
Coriolis Force on Earth
What happens in the Southern Hemisphere?
Trajectories
deflect left
in S
hemisphere
Source: Strahler and Strahler, Introducing Physical Geography, 2005.
Cyclonic Storms on Earth
Hurricane Ike, September 12, 2008
NASA Earth Observatory
Southern Hemisphere Cyclones
Cyclone Monty, NW Australia, March 2, 2004
Both Hemispheres
NASA Earth Observatory, September 3, 2008
Overall Progression
• Thunderstorm cluster forms
• Convectional uplift causes low pressure
• Inrushing air diverted by Coriolis effect;
winds circle
• Inrushing air picks up water vapor; energy
released by condensation
Structure
• Cyclonic rotation
• Strong radial pressure gradient
• Winds increase, pressure decreases
toward center
• Spiral rain bands
• Highest clouds, winds at eye wall
• Calm, clear eye
Damaging Features
• High winds
• Heavy rains
• Storm surge