Note to Editors: The Hurricane Katrina image can be downloaded at http://ccar.colorado.edu/~leben/katrina_path.pdf.
An image produced by a University of Colorado at Boulder team shows the wind speeds of Hurricane Katrina increasing dramatically as it passes through the warm waters of the Gulf of Mexico's Loop Current toward the Gulf Coast in late August.
Processed at CU-Boulder's Colorado Center for Astrodynamics Research, or CCAR, the image was produced with data from four satellites that use altimeters to measure sea-surface height to an accuracy of less than one inch. The researchers extrapolated ocean temperatures from subtle height changes in the water measured by altimeters bouncing microwave pulses from the satellites to the ocean surface and back, said aerospace engineering Associate Research Professor Robert Leben of CCAR.
The sea-surface height image shows the warm Loop Current standing 20 inches to 30 inches higher than the surrounding water, said Leben.
As Katrina passed over the Loop Current, it gained a huge amount of energy from the unusually warm waters that subsequently increased its maximum winds, said Leben. The storm evolved from a Category 3 hurricane to a Category 5 hurricane in just nine hours by converting heat from the Loop Current into energy, he said.
"A hurricane is like a steam engine," said Leben. "The more heat that is put into it, the faster it is going to run. When I saw the predicted storm track over the Loop Current, I became concerned we might see a doomsday scenario."
In the Gulf of Mexico, there is a tight correlation between the sea-surface height measured by the satellites and the temperature of the waters, said Leben. "The higher the sea-surface is above the mean, the deeper the warm water underneath it," he said.
According to CCAR Director George Born, an aerospace engineering professor who works with Leben, the conditions in the Loop Current were unusual. "Ordinarily, the Loop Current does not intrude this far north and west into the Gulf," Born said. "If it had not, the storm would not have gained such intensity."
The CCAR researchers used data from the U.S./French TOPEX/Poseidon and Jason-1 satellites, as well as the U.S. Navy's Geosat Follow-On satellite and the European Space Agency's Envisat satellite. They then combined the data with hurricane wind speed and position data from the National Oceanic and Atmospheric Administration to produce the unique image, Leben said.
More than 100,000 images from the CCAR Web site, which is maintained primarily by CU-Boulder undergraduates, were downloaded last year by federal agencies, private customers and the public, said Born. The center produces daily maps of changing ocean currents around the world for governments and private businesses.
The CCAR Web site for mapping ocean currents and eddies in the Gulf of Mexico is funded primarily by NASA's Jet Propulsion Laboratory and is used by petroleum corporations as well as educators and the general public, said Leben.
Since May 2005, satellite ocean-current maps generated by CCAR have been used to support a bluefin tuna tagging program by New Zealand's Ministry of Fisheries, helping scientists locate prime tuna habitats for a tag-and-release program. The CCAR maps illuminate "cold-core" eddies where the fish congregate, helping the government better understand the relationship between sea-surface heights and the distribution and migration of the tuna, Leben said.
The group also has been providing ocean-current maps in the Gulf of Mexico to help marine-mammal researchers locate and count sperm whales. The sperm whales often congregate in nutrient-rich eddies near the edge of the Gulf's Loop Current where squid - their primary food source - are plentiful, Leben said.
Two years ago CCAR ocean-current maps helped a private oil company find a suitable towing route through the Gulf of Mexico for a submersible drilling rig used in deep water oil and gas exploration. The company avoided problematic eddy currents and took advantage of beneficial eddies, reducing transit time by 50 hours on the 400-mile journey and saving the company $650,000 in rig downtime and towing costs.
CCAR faculty and students focus on research in astrodynamics, satellite meteorology, oceanography, geodesy and terrestrial vegetation studies.