NEXRAD: Eye to the Sky
Across the United States, various groups use Doppler radar to gather information vital to our everyday lives. From weather forecasting, to military operations, to emergency management, the Next Generation Weather Radar, or NEXRAD, ensures public safety and enhances commerce.
A world-wide network of 167 NEXRAD radars provides weather coverage for the entire United States and select international locations. The formal name of the radar is the WSR-88D – which stands for “Weather Surveillance Radar 1988″—for the year the design was established—and D, for “Doppler.”
The radar network is supported by the Radar Operations Center in Norman, Oklahoma. Their job is to keep the radars running smoothly and improve radar technology and capabilities. To maintain peak performance from all radars, the Radar Operations Center help desk offers 24-hour expert assistance to radar technicians around the world. Hardware and software upgrades apply new science and increase radar productivity. The support provided by the Radar Operations Center allows the radar network to deliver continuous, reliable weather coverage to its users.
The radar collects data by sending a radio signal out to a target. The signal bounces off the target—raindrops, in this case—and returns to the radar. The returned signal conveys three important properties of the target:
First, the time it takes for the signal to bounce off the target and return determines the distance from the target to the radar unit, and thus the location of the storm.
Second, the strength of the returned signal, also known as reflectivity, is proportional to the size and number of raindrops in the storm.
* Third, the frequency of the returned signal reveals whether the winds are moving toward or away from the radar, as well as their speeds. The combination of speed and direction is called “velocity.”
The data is converted into visual images and used by the National Weather Service forecasters, the Federal Aviation Administration, and the military to provide weather support to the nation. In addition, selected visual images are made available on the web and shown on TV weather broadcasts. Radar data is also used by private companies and studied by university researchers to improve forecasts.
Forecasters use the continuous, immediate weather information provided by radar to track storms and warn the public of dangerous weather. Radar allows forecasters to see all types of weather and provide advanced warning for thunderstorms, hail, tornadoes, hurricanes, wildfires, flash floods, snow, and freezing precipitation.
A recent study proved Doppler radar helped reduce tornado deaths and injuries by nearly half, nationwide. By using Doppler radar, forecasters have increased the average tornado warning lead time to nearly thirteen minutes.
Outside of the National Weather Service, other groups use Doppler radar to collect information about the weather and the atmosphere.
The Federal Aviation Administration benefits from NEXRAD by overlaying weather radar data on air traffic control displays. This capability helps traffic flow managers safely route air traffic and reduce weather delays for travelers.
The Department of Defense uses radar data to help plan missions for land, sea, and air operations. With accurate weather information, the military is able to enhance flight safety, maximize training opportunities, and protect military assets and personnel.
Community leaders use radar to protect their citizens from nature’s destructive forces. Local emergency managers monitor storms on radar and determine their exact locations. This information is used to notify their communities of approaching danger and better coordinate emergency response. Early winter weather forecasts give snow removal crews lead time to plan and react more effectively.
Water management agencies use radar to estimate not only how much rain will fall, but where it will fall. Radar is especially useful for collecting rainfall data where there are spatial gaps between rain gauges. Improved precipitation estimates help water managers monitor and control the water supply.
Homeland security managers can now integrate wind measurements with computer models to determine the exact path of chemical and biological agents released accidentally or as a result of a terrorist attack.
Radar can also detect the density, location, and direction of biological targets like birds, insects, bats and butterflies. For instance, ornithologists use the data to study the flight and migration patterns of birds.
Private meteorological companies can provide tailored products to their customers by adding specialized features and information to NEXRAD data.
Local and national television meteorologists use NEXRAD data to keep their viewers informed of real-time weather conditions. Even if a station has its own weather radar, they will often use regional NEXRAD data to provide a broader view of the weather approaching their area.
Today’s weather radar technology and capabilities are a direct result of decades of research and development. What began as a strategic weapon in World War II has evolved into a world-class weather detection system. Continuous improvements to the radar’s hardware and software have been made since 1988. Recently, new equipment upgrades will allow better detail in the images forecasters see. The next step is dual polarization, an additional capability that allows NEXRAD radar to send and receive both horizontal and vertical pulses. This new information will give meteorologists a better idea of the structure and type of precipitation – resulting in more accurate forecasts. The research done today will continue to give us benefits for years to come.
With its eye to the sky, the NEXRAD radar provides critical information used by a variety of people for many different purposes. It is not only a vital tool for forecasting and researching weather — but for many everyday activities that impact us all.