How GPS Technology Is Used for Hurricane Tracking
Over the last five years, major advances in global positioning system (GPS) technology have allowed it to become a bigger part of meteorology, especially when it comes to tracking hurricanes. In the recent hurricanes that battered the United States and Caribbean islands (Harvey, Irma, Maria), scientists used GPS to track the path and severity of the storms.
The signals from GPS satellites bounce around in a unique way during storms, which allows scientists to calculate the wind speeds, allowing them to predict that kind of damage the storms are capable of committing and where they are most likely to hit and cause significant issues.
GPS satellites, while in orbit, send constant beam radio signals to the ground that reveal the location of the satellite and when that message was sent. These satellites are then used as reference points for GPS receivers as they calculate their position.
Radio waves bounce off many types of surfaces, similar to how beams of light reflect off shiny metal, water and mirrors. In fact, scientists estimate that about 60 percent of all radio signals sent by GPS satellites reflect off large bodies of water and back into the sky. The way this bounce occurs, however, is not as predictable as the direction in which light will reflect off a mirror, because the surface of the ocean is neither calm nor flat. The larger the waves, the larger the corresponding variance in how those signals bounce.
As these GPS signals bounce off waves, the surface of the water scatters the signal in many different directions. Scientists can analyze this resulting distortion to determine how rough the waters are, and therefore how strong the wind is currently blowing.
An evolution of storm tracking
So how exactly are scientists tracking important hurricane-related measurements with GPS systems?
Previously, scientists would measure and track wind speeds of a hurricane by dropping large tubes packed with scientific instruments directly into storms. These tubes are referred to as “dropsondes.” They get attached to small parachutes and tossed from airplanes, gathering storm data as they fall. The devices inside measure humidity, barometric pressure and temperature, as well as wind speed. The National Oceanic and Atmospheric Administration (NOAA) uses about 20 of these for each storm it tracks.
While this method is somewhat effective, it is costly and ultimately limited in the information it provides. New GPS-based methods would allow scientists to get a much broader look at the storm and its wind speeds at much lower cost. Instead, GPS receiver chips would be placed inside aircraft. A computer would then compare the radio waves coming from satellites, measuring the reflected signals from the sea below and then calculating an approximate wind speed. This method involves much less guesswork than dropsondes.
The downside is that dropsonde measurements, while not as easy to get, are currently significantly more precise. The GPS method also cannot be used over land, as it requires the large bodies of water to reflect radio signals.
For more information about how GPS technology is evolving for storm tracking purposes, contact our GPS tracking service at GPS Technologies today.
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