NOAA Maps Where Hurricanes Meet Ocean Heat

Tropical cyclones may feed and grow stronger on ocean heat, and a new Google Earth application based on satellite altimetry observations shows where they may find it. The application maps the heat contained in the upper portion of the ocean that can fuel storms--what scientists call the "Tropical Cyclone Heat Potential" of the global ocean. It also shows the path and intensity of tropical cyclones as they travel over the ocean surface. The application is updated daily. "We have known for some time that thermal structure of the upper ocean plays a role in the development and intensification of tropical cyclones," says Gustavo Goni, director of the Physical Oceanography Division at NOAA's Atlantic Oceanographic and Meteorological Laboratory in Miami, FL. "And, there have been a number of instances when tropical storms suddenly intensified as they passed over warm ocean features." Goni and his colleagues Francis Bringas and Pedro DiNezio of the University of Miami and Joaquin Trinanes of the University of Santiago de Compostela in Spain created the Google Earth Tropical Cyclone Heat Potential application as a research tool to study the ocean heat-hurricane connection.
The application maps the heat stored in the ocean's upper boundary layer --where the ocean meets the atmosphere. Warmed by the sun, this layer differs in temperature and density from deeper waters below.

To calculate the heat potential of each location across the globe, Goni and his colleagues start with altimeter measurements of sea surface height from the Jason-1, Jason-2 and Envisat satellites. "In most areas of the ocean there is a clear statistical relation between sea surface height and ocean heat content," says Goni, "but this relation varies from region to region. Therefore, we surveyed the ocean every 1 degree by 1 degree, to determine how best to translate sea surface height measurements into heat content." The storm track data they use come from the National Hurricane Center.

"While we developed this application for research, a number of organizations use this or similar products to help in their forecasts of storm intensity," says Goni. These include the U.S. Navy's Joint Typhoon Warning Center and weather agencies and research laboratories in Australia, France, India and Taiwan. The National Hurricane Center uses similar calculations for intensity forecasts in the North Atlantic, Caribbean Sea and the Gulf of Mexico, according to Goni. "Their needs and approach are different from ours," he says. "For operational use, they have other requirements, among which are a strict static production system that is available 24/7. On the other hand, our needs and interests allow us to regularly change our processing methodologies. We do get a lot of feedback from our users that has been extremely useful and encouraging and that allows us to constantly and quickly introduce improvements to our system for research studies." For more information and a link to the Google Earth Tropical Cyclone Heat Potential application, see http://www.aoml.noaa.gov/phod/cyclone/data/.