Satellite data can improve estimates of hurricanes' punch

As Tropical Storm Noel churned off Florida's east coast in November, NASA and university scientists announced they had developed a promising new technique for estimating the intensity of tropical cyclones from space. The method could one day supplement existing techniques, assist in designing future tropical cyclone satellite-observing systems, and improve disaster preparedness and recovery efforts, say researchers.

Graeme Stephens, a Distinguished University Professor at Colorado State, is the principal investigator on CloudSat – one of the very few university-led NASA Earth Science missions. Results from CloudSat illustrate how the satellite radar, which sits 438 miles above Earth, can help the international science community improve weather and climate forecasting, says Stephens.

Accurate measurements

The technique uses NASA satellite data and cloud-top height and cloud profiling information from the CloudSat satellite. Both satellites fly in formation as part of NASA's "A-Train" of Earth-observing satellites, a system developed by scientists at NASA's Jet Propulsion Laboratory, Colorado State University, and the Massachusetts Institute of Technology.

Scientists commonly use measurements of a tropical cyclone's maximum sustained winds to define their intensity and gauge their destructive potential. The CloudSat team analyzed NASA satellite data from nine storms, calculated their peak winds, and compared the estimates with available weather data, including data from aircraft. Initial study results show the technique's estimates agreed with available weather data, and the technique appeared to work better for stronger storms.

Monitoring tropical cyclones

Meteorological satellites have been used to monitor tropical cyclones since the mid-1960s. Relating measurements of storm intensity to existing satellite data has been difficult. The primary technique used by the National Oceanic and Atmospheric Administration since the mid 1970s estimates a storm's maximum sustained winds by looking for recognizable patterns of clouds in visible and infrared satellite images and calibrating them against reconnaissance aircraft data.

Stephens said the latest results show the value of being able to look inside storms to reveal their inner structure – information unique to CloudSat. "Current hurricane intensity estimating techniques are generally effective but have higher wind speed errors than scientists would like," he said. "This new technique may reduce those error rates."

Results of the study are published in the September issue of Geoscience and Remote Sensing Letters. For more information on CloudSat, access http://cloudsat.atmos.colostate.edu.