Tropical Cyclones - genesis depends on ocean conditions - huge removal of heat energy from ocean - damage primarily from storm surge caused by strong winds Geography “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, 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 scale tropical depression < 38 mph tropical storm 38 – 74 mph tropical cyclone (hurricane)
MODIS Image of Hurricane Katrina (28 Aug UTC)
track of hurricane Katrina
MODIS Image of hurricane Rita – 21 Sept. 2005
storm track: Hurricane Rita
storm surge – hurricane Rita 21 Sept Sept. 2005
flooding from storm surge during Katrina
Typhoon Krosa: 1-8 October 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 Reader Maps pgs Midterm on Wednesday 5 Nov 2008