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Geography 104 - “Physical Geography of the World’s Oceans”
Tropical Cyclones
- genesis depends on ocean conditions
- huge removal of heat energy from ocean
- damage primarily from storm surge caused by strong winds
High and Low Pressure Systems
warm and cold fronts
cold front usually more intense
general east-west movement following jet stream
largest most intense storm systems are not fronts, but huge
rotating masses of low pressure known as tropical cyclones
paths taken by hurricanes, cyclones, and typhoons
(following trade winds in east to west direction)
Tracks of all tropical cyclones, 1985-2005
Source: Wikipedia
hurricane Katrina (2005)
“The energy in a single hurricane is greater than that generated by
all energy sources in the United States over the last 20 years.”
Essentials of Oceanography Textbook
hurricane structure
hurricane process:
1. low pressure system
2. moisture from ocean
3. warm moist air rises
4. heat from condensation
5. warm air rises further
6. surface pressure lowers
7. go to 2.
typical diameter < ~100 miles
powered by the release of vast amounts of water’s latent heat (condensation)
hurricane intensity scale
tropical depression < 38 mph
tropical storm 38 – 74 mph
tropical cyclone (hurricane)
MODIS Image of Hurricane Katrina
(28 Aug 2005 - 1700 UTC)
track of hurricane Katrina
MODIS Image of hurricane Rita – 21 Sept. 2005
storm track: Hurricane Rita
storm surge –
hurricane Rita
21 Sept. 2005
26 Sept. 2005
flooding from storm surge during Katrina
Typhoon Krosa: 1-8 October 2007
http://earth.esa.int/ew/cyclones/Typhoon_Krosa-oct07/
http://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2007-10-06
-18 killed on Taiwan
- China evacuates 1.4 million in Zhejiang
and Fujian provinces
Sea Surface Temperature (SST) Anomaly and
Atlantic Tropical Cyclone Counts (Mann & Emanuel, 2006)
- SST and Atlantic hurricanes on the recent increase due to climate change
Atlantic Hurricane Tracks 2005 and 1933 (Landsea, 2007)
- increased Atlantic hurricane frequency from new observational technologies
Number of Atlantic tropical cyclones that struck land versus number that
stayed over the open ocean. The solid line is the 1900–2006 long-term
mean of 9.2 per year. (Landsea, 2007)
Percentage of all reported Atlantic tropical cyclones that struck land. (Landsea, 2007)
QuikSCAT Satellite – a microwave radar for
measuring surface winds
Quickscat launch – 19 June 1999
wind speed from Quickscat (ascending pass)
wind speed from Quickscat (descending pass)
Hurricanes Strongly Mix the Upper Ocean
SST Change
Hurricane Francis (2004); ocean profiles before and after
- huge removal of heat from the ocean
Readings (Ocean and Atmosphere):
Text Chapter 8 (pgs 138 – 163)
Reader pgs. 51 - 61
Reader Maps pgs 200 - 204
Midterm on Wednesday 5 Nov 2008