GPS technology helpful with hurricane research

By Sonya

CHARLESTON, S.C. (WCIV) -- Global positioning systems aren't just helpful for navigation -- they also come in handy for hurricane research.

The satellite signals get bounced around in tropical systems, which give researchers an opportunity to measure and map wind speeds. This information can help meteorologists better predict the largest storms on Earth.

"The radio wave bounces off the waves," said Stephen Katzberg, a Distinguished Research Associate at the NASA Langley Research Center in Hampton, Va. "As the surface gets rougher, the reflections get more disturbed and that's what we measure."

The new technique is an inexpensive way to get even more measurements on just how much punch a storm packs.

The old technique is very accurate, but expensive costing over $700. It involves dropping roughly 20 single-use dropsondes into the storm from a Hurricane Hunter aircraft. The dropsondes are long tubes packed with various meteorological instruments that measure wind speed, pressure, humidity and temperature.

The cost limits the amount of dropsondes used and therefore the amount of data, which is why the new GPS method is so appealing. Another plus is that the Hurricane Hunters are already equipped with GPS systems.

"The reflected GPS signal system can essentially run non-stop, constantly gathering information about the wind below," said Katzberg.

With the two methods combined, the data will be much more widespread.

"The ultimate goal isn't to replace dropsondes, but rather to add a much broader view of wind speeds to the data the dropsondes provide,' said Katzberg.

The measurements are taken by GPS receiver chips located inside the plane. A computer compares signals from the satellites above with the reflections from the sea below and then calculates an approximate wind speed.

This new technique for measuring wind speed could soon be implemented on satellites too.

NASA plans to launch a system of small satellites, called the Cyclone Global Navigation Satellite System (CYGNSS) in 2016. They would measure reflected GPS satellite signals from low orbit to monitor storm wind speeds from space.

Down the road, reflections of powerful satellite broadcasts such as DirecTV and Sirius XM Radio could be used in addition to GPS.

"Those signals are extremely powerful and easy to detect," said Katzberg. "These satellites cost hundreds of millions or even billions of dollars, but our system only costs a few hundred. We're taking advantage of the expensive infrastructure that's already there."

The bottom line is that researchers want as much wind speed data as possible so they can learn more about hurricanes, which will ultimately result in a more accurate forecast.