Tropical Cyclones

- genesis depends on ocean conditions

- huge removal of heat energy from ocean

- damage primarily from storm surge caused by strong winds

Geography 104 - “Physical Geography of the World’s Oceans”

High and Low Pressure Systems

warm and cold fronts

general east-west movement following jet stream

cold front usually more intense

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, 1985-2005Tracks 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

powered by the release of vast amounts of water’s latent heat (condensation)

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

hurricane intensity scaletropical depression < 38 mphtropical storm 38 – 74 mphtropical 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

http://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2007-10-06

Typhoon Krosa: 1-8 October 2007

http://earth.esa.int/ew/cyclones/Typhoon_Krosa-oct07/

-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 ChangeSST 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