This sea surface height map of the Gulf of Mexico, with the Florida
peninsula on the right and the Texas-Mexico Gulf Coast on the left,
is based on altimeter data from four satellites including NASA’s
Topex/Poseidon and Jason. Red indicates a strong circulation of
much warmer waters, which can feed energy to a hurricane. This area
stands 35 to 60 centimeters (about 13 to 23 inches) higher than the
surrounding waters of the Gulf. The actual track of a hurricane is primarily
dependent upon steering winds, which are forecasted through the use of
atmospheric models. However, the interaction of the hurricane with the
upper ocean is the primary source of energy for the storm. Hurricane
intensity is therefore greatly affected by the upper ocean temperature
structure and can exhibit explosive growth over warm ocean currents and
eddies. Eddies are currents of water that run contrary to the direction of
the main current. According to the forecasted track through the Gulf of
Mexico, Hurricane Rita will continue crossing the warm waters of a Gulf of
Mexico circulation feature called the Loop Current and then pass near a
warm-water eddy called the Eddy Vortex, located in the north central Gulf,
south of Louisiana.
The Jason satellite carries a dual-frequency radar altimeter. This
instrument beams microwave pulses-at 13.6 and 5.3 Gigahertz,
respectively-downward toward the Earth. To determine the ocean's height,
the instrument precisely measures the time it takes for the microwave
pulses to bounce off the surface and return to the spacecraft. This
measure, multiplied by the speed of light, gives the range from the
satellite to the ocean surface.
The joint U.S.-French Topex/Poseidon mission is managed by the JPL for
NASA's Earth Science Enterprise, NASA Headquarters, Washington, D.C. JPL
is a division of the California Institute of Technology in Pasadena.
Research on Earth's oceans using Jason and other space-based capabilities
is conducted by NASA's Earth Science Enterprise to better understand and
protect our home planet. For more information on Topex/Poseidon, see
http://topex-www.jpl.nasa.gov.)