By Candace Stuart
Small Times Senior Writer
JUNE 12, 2001 — While today’s severe weather monitoring technology is good, it could be better with a few upgrades and alterations, according to the designers of a key part of today’s tracking system. And Terrence Hock, an engineer at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., already is working on those improvements.
Hock and James Franklin, a hurricane specialist at the National Hurricane Center in Miami, designed a dropsonde system that has been used since 1997 to study hurricanes as they develop over oceans. The dropsondes contain MEMS, microsystems and Global Positioning System devices to measure temperature, humidity, pressure and wind speed.
Meteorologists plug those measurements into computer models to predict the path and intensity of hurricanes, nor’easters and other violent storms. The dropsondes are standard equipment for the U.S. Air Force and the National Oceanic and Atmospheric Association, which oversees the National Weather Service and NCAR. Defense and meteorological agencies in Canada, the United Kingdom, France, Germany and Japan also rely on the dropsondes for their weather studies.
But the system has two limitations, Hock and Franklin say. In order to keep costs at $500 to $600 per dropsonde – the price tag of the previous but far less accurate system – they had to use a “codeless” GPS that can handle only simple functions. And the aircraft that deploy the dropsondes can’t fly high enough to get above really big hurricanes. Instead, they fly through them at about 10,000 to 20,000 feet, leaving the climate above uncharted.
On Aug. 1, Hock will test what he hopes will be the next advancement in dropsondes. He has repackaged the launching system that normally is housed inside surveillance aircraft into a pod that can be attached to the belly of a one-man jet. The jet will be capable of soaring above hurricane peaks.
“The key to this system is it will be automated,” Hock said.
That added capability will help meteorologists like Franklin understand hurricanes and hurricane behavior even better. While the bottom layer of a hurricane concerns meteorologists because it is the section that affects people, they believe it is the climate conditions at the top and sides that most affect the hurricane itself.
“I’m really looking at what the hurricane’s environment is,” Franklin said. “A hurricane is like a cork in a stream. Wherever the stream goes, the cork will go. By looking at all three dimensions, we can determine that.”
Hock also will test a new GPS receiver this summer to get more reliable readings on wind speed. The dropsonde’s current receiver is a relatively simple unit that uses GPS satellite radio signals to track Doppler frequencies, which show the relative motion of the dropsonde and GPS satellites.
The more accurate GPS receivers track signals from at least three of the available 24 satellites to determine latitude and longitude. Receivers that track four or more satellites can lock in on altitude, too. Once position is defined, a GPS can calculate speed and other conditions.
The codeless GPS system has limited capabilities to begin with, and becomes even less reliable when it is being tossed around in the strongest hurricanes, the researchers said. “The hardware in the GPS receiver doesn’t keep up with all that jerking around,” Franklin said.
They expect the more sophisticated system will work in the roughest conditions, and provide more detailed information. But cost is sure to rise.
“The performance will be better, but it will be more expensive,” Hock said.
Eventually, Hock would like to see his dropsonde system strapped to the underside of a variety of aircraft — from military to cargo and even passenger planes – as they follow their usual flight patterns over oceans. It would be a cost-efficient way for meteorologists to learn about what brews over those vast waters, he said.
“But that’s years and years and years away,” he said, because those carriers and the federal agencies that oversee them would have to be convinced of the program’s safety and usefulness. “There’s a lot of issues that have to be dealt with.”
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CONTACT THE AUTHOR:
Candace Stuart at [email protected] or call 734-994-1106, ext. 233.