NASA monitors lightning inside hurricanes
According to a new study from NASA, it is possible to forecast a storm's intensity by monitoring the lightning strikes near a hurricane's eye. And it can be done weeks before the storm arrives with the help of 'highly-sensitive sensors located thousands of miles from the storm.' Today, the Pacific Lightning Detection Network (PacNet) is based on a network of four lightning location sensors in the central north Pacific. The detectors have been installed in Dutch Harbor (Alaska), Kwajalein Atoll (Marshall Islands), Lihue and Kona (both in Hawaii). More sensors should be installed in Kiritimati (Christmas Island, Kiribati)and in Japan, Korea, and Australia.
Here is an example of how NASA is using these lightning sensors. Two years ago, on September 21, 2005, one of the Tropical Rainfall Measuring Missions (TRMM)'s Microwave Imager (TMI) collected data as the satellite passed over the center of Hurricane Rita and lightning strike locations (circles). "The left image indicates the temperature of the ice particles; the right image indicates the concentration of ice particles in the hurricane eyewall. Ice is important for charge separation in the clouds needed to produce lightning." (Credit:NASA). You can see related images on this page and on the main NASA's Hurricane web page.
Here is how NASA describes how it is possible to forecast a storm's intensity by monitoring lightning strikes. "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. If the ensuing updrafts are strong enough, they can cause the separation of charge that produces lightning. The tight correlation between the rate of lightning strikes, the amount of rainfall and the heat released in the eyewall of a storm allows the lightning rate data to be useful in computer models that forecast hurricane track and intensity."
As said the lead author of this study, Kirt Squires, a recent graduate of the meteorology program at the University of Hawaii in Honolulu, "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. What’s really compelling about the new sensors is their increased sensitivity to pick up lightning's electromagnetic signal over 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 is essential to improving the way meteorologists can look at a growing storm to judge just how harsh it will be."
Here is a link to the PacNet web page which provides tons on information, including pictures and maps. "The goal of the network is to monitor the location of electrical activity associated with thunderstorms. These thunderstorms represent a threat to ocean shipping and airborne carriers and are beyond the range of weather radar. The network also promises to give insight into the intensification of tropical cyclones and flash flood events. Additionally the lightning detectors provide ground truth for a NASA satellite based instrument and a data stream for ingest into global weather prediction models."
Finally, here is a link to the NASA's TRMM Microwave Imager web page. [This] "is a passive microwave sensor designed to provide quantitative rainfall information over a wide swath under the TRMM satellite. By carefully measuring the minute amounts of microwave energy emitted by the Earth and its atmosphere, TMI is able to quantify the water vapor, the cloud water, and the rainfall intensity in the atmosphere. It is a relatively small instrument that consumes little power. This, combined with the wide swath and the good, quantitative information regarding rainfall make TMI the 'workhorse' of the rain-measuring package on Tropical Rainfall Measuring Mission."
Sources: Gretchen Cook-Anderson, NASA's Goddard Space Flight Center, via EurekAlert!, September 6, 2007; and various websites
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