Episode 49: Do People Think Radar is Useful?

Hype of the Week: 
 Castle and Minh are joined by Michelle Saunders to talk about the Doppler weather radar and its perceived usefulness among members of the public.

Michelle Saunders, PhD Candidate at the University of South Florida
Michelle Saunders, PhD Candidate at the University of South Florida

Weather Radar Basics 

What is a Doppler weather radar?   (Source: Jeff Duda)
  • The weather radar you see on your local TV news program, The Weather Channel, or other news channel is Doppler radar. Doppler radar emits beams (pulses) of microwave energy from a transmitter into the atmosphere. When these beams collide with objects in the atmosphere such as raindrops, hailstones, snowflakes, cloud droplets, birds, insects, dust particles, trees, and even the ground, some of the energy bounces back towards the radar. A receiver on the radar then collects the reflected energy and displays it in different ways. ​
  • For an online tour of an National Weather Service Doppler weather radar (the one pictured to the right), click here!
Central Illinois Doppler Radar - www.weather.gov/ilx
What is base reflectivity?  (Source: Jeff Duda)
  • Base reflectivity is a radar product (pictured left) that displays the amount of power returned to the radar after it has reflected off particles in the atmosphere.
  • The actual amount of energy returned is not displayed. What is displayed is a term called reflectivity (hence why this product is named base reflectivity), and is measured in decibels (dBZ). A decibel is a measure of the energy transmitted by a wave, or a measure of the amplitude of a wave.
  • ​Usually, greens and yellows indicate lighter rain/snow while oranges, reds, and pinks indicate heavy rain/snow. 
What is base velocity?  (Source: Jeff Duda)
  • Base velocity is a radar product (pictured right) that displays the average wind speed (and in some sense, the direction, hence velocity) of particles that are detected by the radar.
  • Since radar only sends pulses of energy in one direction per pulse, the wind speed detected is necessarily a speed in the direction of the beam. An individual Doppler radar cannot measure or calculate wind in more than one dimension. However, two Doppler radars that are not in the same location can. It is important for you to know that when you are looking at a display of base velocity, you are looking at the wind speed either directly towards or directly away from the radar. ​
  • This means the wind direction is away from the radar when values are positive and towards the radar when values are negative. This is commonly marked with a green color for velocities towards the radar and red for velocities away from the radar. Usually, the most interesting areas are those where red and green colors meet, especially if the values are large where they meet.
Source: West Texas Mesonet
Source: Shutterstock
Want to learn more about Doppler weather radar?

Article Spotlight

Usefulness of the United States National Weather Service Radar Display as Rated by Website Users 
By: Michelle Saunders, Kevin Ash, and Jennifer Collins 

Key findings from the paper:
  • Geographically, the NWS website radar map display was most useful to those living in the southeastern and south-central United States, and least useful to those living in the northwestern United States.
  • The three most significant variables, relating to radar usefulness, were related to credibility of the NWS as a source of weather information.
    • ​Specifically, respondents who were more likely to take action based on information they received from the NWS were likely to rate the NWS radar map display as more useful.
  • The frequency of visiting the weather.gov website also corresponded to higher usefulness rating of the NWS radar map display.

To read the paper yourself, click here!
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