Wednesday, June 18, 2008
High-Speed Storm Radars to Track Tornadoes, Fend Off Tragedy
When tornadoes start killing Boy Scouts, the world pays attention. But even as a deadly EF-4 tornado whipped through Little Sioux, Iowa, with 145-mph-plus winds last Wednesday night, federal climate scientists and a group of university researchers were in the early phases of testing high-tech replacements for an aging Doppler radar system. Twisters across the United States in 2008 are headed for a record-setting pace (February's 148 nearly doubled a 37-year-old record); however, by 2013 a new network of satellites could be triangulating microfrequencies from the sky to Wi-Fi for real-time reactions to dangerously shape-shifting weather patterns.
America's current system for detecting tornadoes—about 120 Next Generation Radar, or NEXRAD, devices tracking a storm's direction and velocity—has been the backbone of weather prediction since the early 1990s, but experts say it is deeply flawed. The radars are tilted upward from the Earth half a degree, which may not seem like much—until you factor in the curvature of the Earth. By the time you get 40 or 50 miles out, radar beams are more than one-half mile high, therefore missing the bottom third of the troposphere where severe weather often begins to form. And at 5 to 6 minutes for a complete area scan, NEXRAD simply remains too slow.
The Collaborative Adaptive Sensing of the Atmosphere (CASA) network aims to address both problems, with short-range-satellites targeting the bottom of a storm and refreshing much more often—as in every minute. "CASA radars are gap-filling radars," explains Harold Brooks, a research meteorolgist at the National Oceanic and Atmospheric Administration (NOAA), which is developing the system with four schools across the country. "While the main NEXRAD radars give a really good view of the storm aloft, CASA radars could be set up to probe that area where the NEXRAD radars don't see."
This new rig borrows technology from the U.S. Navy, which for years has been using a similar system to track vessels on the seas. CASA radars, however, will be installed just a few miles away from each other on rooftops, cell towers and other existing infrastructure. The first testbed is a network of four nodes in the middle of Tornado Alley in southwestern Oklahoma; other early sites include Houston and Mayaguez, Puerto Rico. CASA officials expects to see at least quasi-operational CASA networks within the next five years to address some well-known gaps in the NEXRAD system, and widespread deployment within the next 15 years.
Aiming for nearby clouds, CASA's low-power nodes send out 10-watt microwave frequencies, which then bounce back before being sent to a processing unit in the bottom of the node over a gigabit Ethernet connection. The information is wirelessly transmitted to a central location over a 2-megabit-per-second DS3 connection. Here, data from all the nodes is collected and run through weather-predicting algorithms, which are growing more sophisticated as this new data is made available—and as new threats speed up research.
The high-speed-transmission approach, dubbed Distributed Collaborative Adaptive Sensing (DCAS), can respond to quickly changing weather conditions in real time. Based on faster and more comprehensive data collection, DCAS processing can refocus the CASA radars on a particularly interesting part of a storm (like an area that looks like it might develop a tornado) without losing track of an entire storm cell. "The system is continuously diagnosing the atmosphere and reallocating resources using wireless Internet as a backbone," says David McLaughlin, an engineering professor from the University of Massachusetts at Amherst who directs the CASA team. "At the core, this is a system that is able to focus the resources where and when the need is greatest. We can keep track of evolving hotspots—rotations and things like that—as nature spins them up."
Even with next-generation satellites and other storm-tracking technology in place, human know-how at the eye of the storm will always trump prevention research—and the Iowa Boy Scouts are only the most recent case study in disaster preparedness gone mostly right but still frighteningly sour. Brenda Philips, director of industry, government and end-user partnerships for the CASA team at UMass, is working with emergency responders, sociologists, human factors engineers and others to figure out how the massive data-gathering abilities of the CASA system can be fine-tuned to help would-be survivors take their own action.
"People want to know the tornado is going down their street," she says. "That's what makes people respond to warnings." Under the current NEXRAD Doppler system, a warning could be statewide, leading to false alarms for most of its residents. While the CASA rig and its corresponding data algorithms probably won't be able to predict the exact path of a tornado, they will combine to shrink the warning zone. And even shrinking those locations by a partial form factor could help save more of those at the heart of the storm. Someday, it could even allow isolated campers like the fallen Boy Scouts enough time to drive to underground shelter.