New lightning sensors warn of hurricane's power from far awayUniversity of Hawaiʻi at Mānoa
School of Ocean and Earth Sciences and Technology
The groundbreaking study, to appear in an upcoming issue of the American Meteorological Society's Monthly Weather Review, uses data from a growing network of new long-range lightning sensors, a NASA satellite, and aircraft-based instruments to explore the effect eyewall lightning outbreaks had on the intensity of two of the most severe Atlantic storms on record before they made landfall - category-five hurricanes Katrina and Rita.
"There are very few observing systems that offer a broad view of a storm over the open ocean where hurricanes tend to build or lose strength," said study co-author Steven Businger, a senior professor of meteorology at the University of Hawaii in Honolulu. "What's really compelling about the new PacNet sensors is their increased sensitivity to pick up lightning's electromagnetic signal over the water from such a long distance. As a result, we can see thunderstorm activity over the ocean from thousands of miles away for the first time. This development provides a new way for meteorologists to look at a growing storm and to alert us about just how harsh it will be."
As explained by Businger, when water condenses from vapor into a cloud droplet, "latent" or hidden heat is released, which in turn builds updrafts - air moving upwards in a cloud. Latent heat provides the energy that fuels hurricanes. These updrafts, if they are strong enough, cause the separation of charge that produces lightning. Thus, there is a relationship between the rate of lightning strikes, the amount of rainfall, and the heat released in the eyewall of a storm. This fact allows the lightning rate data to be used in computer models that forecast hurricane track and intensity.
"Hurricane forecasters and researchers are very interested in developing methods that allow a continuous examination of the structural growth of the eyewall within hurricanes," said lead author Kirt Squires, a recent graduate of the meteorology program at the University of Hawaii. "We know that the intensity of lightning outbreaks near the storm's epicenter directly relates to the heat energy released in the storm. The relationship between the lightning activity and the storm's energy source means it's crucial for us study and pick apart the evolution of the lightning."
At the core of Businger and Squires' research are data from two devastating 2005 hurricanes, Katrina and Rita. The researchers specifically combined data from NASA's Tropical Rainfall Measuring Mission satellite, with data from instruments onboard the National Oceanic and Atmospheric Administration's P-3 "hurricane hunter" aircraft that fly through the hurricanes, and with data from the enhanced sensor capability of the NASA-co-funded PacNet sensor network.
Though Businger acknowledges that more research is needed, results from this study show that the growth and density of lightning strikes in a hurricane's eyewall provide important insight into the inner workings of the most powerful storms on Earth, information that may help save lives in future through improved hurricane forecasts.
Release by Gretchen Cook-Anderson, NASA Goddard Space Flight Center 301-879-9200. For information about NASA and agency programs on the web, visit http://www.nasa.gov.
For Interviews contact:
Steven Businger, Department of Meteorology, School of Ocean & Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI Phone: (808) 956-3163, firstname.lastname@example.org
Kirt Squires, Department of Meteorology, School of Ocean & Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI Phone: (631) 365-9256, email@example.com
The Morphology of Eyewall Lightning Outbreaks in Two Category Five Hurricanes - Monthly Weather Review; Volume TBA
For more information, visit: http://www.nasa.gov/centers/goddard/news/topstory/2007/lightning_hurricane.html