• ITVI.USA
    15,605.240
    -1.200
    0%
  • OTRI.USA
    23.180
    0.400
    1.8%
  • OTVI.USA
    15,606.030
    0.730
    0%
  • TLT.USA
    2.790
    0.010
    0.4%
  • TSTOPVRPM.ATLPHL
    3.390
    -0.060
    -1.7%
  • TSTOPVRPM.CHIATL
    2.840
    -0.080
    -2.7%
  • TSTOPVRPM.DALLAX
    1.510
    -0.070
    -4.4%
  • TSTOPVRPM.LAXDAL
    3.290
    0.080
    2.5%
  • TSTOPVRPM.PHLCHI
    1.980
    -0.060
    -2.9%
  • TSTOPVRPM.LAXSEA
    3.900
    0.100
    2.6%
  • WAIT.USA
    124.000
    -3.000
    -2.4%
  • ITVI.USA
    15,605.240
    -1.200
    0%
  • OTRI.USA
    23.180
    0.400
    1.8%
  • OTVI.USA
    15,606.030
    0.730
    0%
  • TLT.USA
    2.790
    0.010
    0.4%
  • TSTOPVRPM.ATLPHL
    3.390
    -0.060
    -1.7%
  • TSTOPVRPM.CHIATL
    2.840
    -0.080
    -2.7%
  • TSTOPVRPM.DALLAX
    1.510
    -0.070
    -4.4%
  • TSTOPVRPM.LAXDAL
    3.290
    0.080
    2.5%
  • TSTOPVRPM.PHLCHI
    1.980
    -0.060
    -2.9%
  • TSTOPVRPM.LAXSEA
    3.900
    0.100
    2.6%
  • WAIT.USA
    124.000
    -3.000
    -2.4%
AskWavesInsightsNewsWeather and Critical Events

What is Doppler radar?

AskWaves explores how Doppler radar has improved weather forecasting since 1988

In a nutshell, Doppler radar is a specialized tracking system that uses the Doppler effect (Doppler shift) to determine the location and velocity of storms and precipitation.

Now, let’s crack open that shell and get to the nuts and bolts of how it came to be and how it works.

Doppler vs. conventional radar

Doppler radar has been one of the most important technological advances in hazardous weather prediction over the past 30-plus years. Forecasters using Doppler radar can issue more timely and accurate hazardous weather information than ever before.


U.S. Weather Bureau’s first experimental Doppler weather radar unit, obtained from the U.S. Navy in the 1950s. (Photo: NOAA)

Conventional radar provides information about the location and intensity of precipitation associated with a storm, while Doppler radar adds the capability to discern air motions within a storm. This helps meteorologists detect near-ground wind shears, which are dangerous to aircraft. Doppler radar technology also enables meteorologists to forecast the location and severity of weather with greater accuracy, which has resulted in improved public safety.

How Doppler radar works

The radar dome, which many people say looks like a big soccer ball or volleyball, protects a 28-foot-wide antenna. The antenna is made up of a transmitter and a receiver. The transmitter samples the environment by sending out a pulse of energy that reflects off objects (like raindrops) and scatters the energy pulse in all directions. Part of the energy reflects back to the antenna and is measured by the receiver.

The returned energy is then processed into three types of base data: reflectivity, velocity and spectrum width. Reflectivity is calculated from the fraction of signal that is reflected back to the radar. Velocity is calculated by measuring the Doppler shift from one pulse to the next to determine the speed with which the object is moving toward or away from the radar. Spectrum width is calculated based on how much variation there is in velocity readings in a given area.

Additionally, a host of derived products are computed from the base data. These include precipitation estimates, as well as severe weather parameters like tornadoes, hail and heavy rain. During a potentially hazardous weather event, many of these products will be examined by a forecaster to make decisions on issuing warnings.

The radar does not sample the entire atmosphere at once. Rather, the antenna makes a 360-degree rotation pointed at a particular elevation angle, then changes elevation and completes another rotation. The number and selection of elevation angles, along with the speed of the antenna’s rotation, varies based on the weather conditions.

During calm conditions, the antenna rotates slowly, completing a scan of five slices in 10 minutes. During active weather conditions, the antenna rotates faster, completing a scan of up to 14 elevation slices in 4.5 minutes. This rapid scan is crucial during developing severe weather as conditions can change by the minute.

History of Doppler radar

Doppler radar and severe storms research were joined in the early 1960s when the National Severe Storms Project began in Kansas City, and continue to this day at the National Severe Storms Laboratory (NSSL) in Norman, Oklahoma. The Union City, Oklahoma, tornado in May 1973 marked the beginning of NSSL intercept teams using research Doppler radars to collect measurements from severe thunderstorms.


WSR-88D (Doppler radar) imagery of Moore, Oklahoma, tornadic supercell, May 3, 1999. The National Weather Service rated the storm an EF5 based on storm damage. (Image: NOAA)

In the 1980s, the push to get Doppler radars into warning operations became well-organized as the NEXRAD (NEXt generation weather RADar) program formed. The first operational Doppler radar, the WSR-88D (Weather Surveillance Radar-88Doppler), was installed near Norman in 1988.

In the early to mid-1990s, a national network of over 100 WSR-88D Doppler radar sites was built as part of the modernization of the National Weather Service. Today, about 160 Doppler radars dot the U.S. landscape. In recent years, these radars have been retrofitted with dual-polarization technology, firing beams aligned both horizontally and vertically. Computer programs measure the differences between the vertical and horizontal wave returns to better detect different kinds of precipitation — small raindrops, large drops, hail and snow — and other echo returns like chaff, wildfire smoke, bats, birds, insects and airborne tornado debris.

Click here for more FreightWaves articles by Nick Austin.

You might also like:

NOAA uses drones for first time to see remote tornado damage

Logistics groups ready to help during potentially busy hurricane season

Trucker a Highway Angel for helping couple after spinout

Nick Austin, Director of Weather Analytics and Senior Meteorologist

In his nearly 20 years of weather forecasting experience, Nick worked on air at WBBJ-TV and WRCB-TV, including time spent doing weather analysis and field reporting. He received his Bachelor of Science in Meteorology from Florida State University as well as a Bachelor of Science in Management from Georgia Institute of Technology. Nick is also a member of the American Meteorological Society and National Weather Association. As a member of the weather team at WBBJ-TV in Jackson, Tennessee, Nick was nominated for a Mid-South Emmy for live coverage of a major tornado outbreak in 2008. As part of the weather team at WRCB-TV in Chattanooga, Tennessee, Nick shared the Chattanooga Times-Free Press Best of the Best award for “Best Weather Team” for eight consecutive years. Nick earned his National Weather Association Broadcasting Seal in 2005.

Leave a Reply

Your email address will not be published. Required fields are marked *

We are glad you’re enjoying the content

Sign up for a free FreightWaves account today for unlimited access to all of our latest content

By signing in for the first time, I give consent for FreightWaves to send me event updates and news. I can unsubscribe from these emails at any time. For more information please see our Privacy Policy.