Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Distorted GPS signals reveal hurricane wind speeds

16.07.2013
By pinpointing locations on Earth from space, GPS systems have long shown drivers the shortest route home and guided airline pilots across oceans.

Now, by figuring out how messed up GPS satellite signals get when bouncing around in a storm, researchers have found a way to do something completely different with GPS: measure and map the wind speeds of hurricanes.


An Air Force pilot performs a pre-flight inspection of a "Hurricane Hunter" aircraft. Similar aircraft have begun measuring GPS signals bouncing off the ocean surface to determine wind speed. Photo by Manuel Martinez.

Improved wind speed measurements could help meteorologists better predict the severity of storms and where they might be headed, said Stephen Katzberg, a Distinguished Research Associate at the NASA Langley Research Center in Hampton, Va., and a leader in the development of the new GPS technique. On a global scale, experts hope to use the new measurement method to better understand how storms form and what guides their behavior.

The new technique could inexpensively provide a much more extensive view of a storm’s wind speeds than currently possible, its developers say. Test flights on storm-hunting airplanes of the National Oceanic and Atmospheric Administration (NOAA) – nicknamed Hurricane Hunters –demonstrate that the system provides valuable information at little additional cost, according to Katzberg and his colleagues.

An article describing the scientists’ methods and findings has been accepted for publication in Radio Science, a journal of the American Geophysical Union.

GPS ricochet

Hovering thousands of miles above Earth, GPS satellites constantly beam radio waves toward the ground carrying information about both the position of the satellite and the time the message was sent out. These radio waves can reflect off a surface similar to the way visible light reflects off a mirror.

When a radio wave from a GPS satellite strikes the surface of a body of water, such as the ocean, about 60 percent of the signal reflects back toward the sky, Katzberg said. Unlike a mirror, however, the surface of the ocean is rarely calm and flat. Wind blowing over a body of water generates heaving waves.

"Imagine you blow on a hot bowl of soup," he explained. "The harder you blow, the bigger the 'waves' are in the bowl." When a GPS signal strikes a wave, the rough surface distorts the reflection by scattering the signals in various directions.

"The radio wave bounces off the waves," said Katzberg. "As the surface gets rougher, the reflections get more disturbed and that’s what we measure."

The new method of calculating wind speeds is the fruit of years of fine-tuning by scientists from NASA and NOAA, Katzberg added. In operation, the measurements are taken by GPS receiver chips, similar to those found in smartphones, located inside the aircraft. A computer compares signals coming directly from satellites above with the reflections from the sea below and calculates an approximate wind speed with better than 5 meters per second (about 11 miles per hour) accuracy. The wind speed of a mid-range, Category 3 hurricane, for comparison, is about 55 meters per second (123 miles per hour).

Drops in the ocean

In order to measure hurricane wind speeds using the standard method, scientists drop a 16-inch-long tube packed with scientific instruments called a dropsonde. These dropsondes are attached to small parachutes and jettisoned from airplanes, gathering information during their descent. Each device measures pressure, humidity and temperature in addition to wind speed. A typical Hurricane Hunter mission uses about 20 single-use dropsondes, each costing around $750.

Dropsondes provide 10 times more precise wind speed measurements than the new GPS method can, so far. Their accuracy is about 0.5 meters per second (1.1 miles per hour).

But, since the dropsondes are so expensive, their releases are spread out around and in storms. This distance means meteorologists need to use some guesswork to fill in the gaps. According to Katzberg, the reflected GPS signal system can essentially run non-stop, constantly gathering information about the wind below. 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.

"You were already going to have these GPS systems onboard, so why not get additional information about the environment around you," said Katzberg.

Since the method requires large bodies of water to work, the system can’t be used over land. Also, in cases where the ocean’s surface is choppy without any wind, such as the eye of a storm, Katzberg says other tools would need to be used instead to get an accurate measurement.

Satellite radio

Although the new measurement technique is being tested on planes, it may get implemented on satellites, according to Katzberg. In 2016, NASA plans to launch a system of small satellites, called the Cyclone Global Navigation Satellite System (CYGNSS), to measure reflected GPS satellite signals from low orbit to monitor storm wind speeds from space.

And, looking further into the future, reflections of powerful satellite broadcasts from 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."

Notes for Journalists

Journalists and public information officers (PIOs) of educational and scientific institutions who have registered with AGU can download a PDF copy of this accepted article by clicking on this link: http://onlinelibrary.wiley.com/doi/10.1002/rds.20042/abstract

Or, you may order a copy of the final paper by emailing your request to Thomas Sumner at tsumner@agu.org. Please provide your name, the name of your publication, and your phone number.

Neither the paper nor this press release are under embargo.

Title:
"The use of reflected gps signals to retrieve ocean surface wind speeds in tropical cyclones"
Authors:
Stephen J. KatzbergNASA Langley Research Center, Hampton, Virginia, USA;Jason DunionUniversity of Miami/CIMAS – NOAA/AOML/Hurricane Research Division, Miami, Florida, USA;George G. GanoeNASA Langley Research Center, Hampton, Virginia, USA.

Contact information for the coauthor:

Stephen Katzberg, Email: Stephen.J.Katzberg@nasa.gov, Phone: +1 (803) 516-6068

Thomas Sumner | American Geophysical Union
Further information:
http://www.agu.org

More articles from Earth Sciences:

nachricht Predicting eruptions using satellites and math
28.06.2017 | Frontiers

nachricht NASA sees quick development of Hurricane Dora
27.06.2017 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Supersensitive through quantum entanglement

28.06.2017 | Physics and Astronomy

X-ray photoelectron spectroscopy under real ambient pressure conditions

28.06.2017 | Physics and Astronomy

Mice provide insight into genetics of autism spectrum disorders

28.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>