“Doppler Radar”

by Caleb, KE0FOE

As we continue with our series covering JetStream, The National Weather Service’s new Online School for Weather, the topic this time is: Doppler Radar.

Doppler Radar allows meteorologists to essentially look inside thunderstorms to try to determine precipitation type and intensity, wind velocity and direction, and to identify possible rotation.

The current Doppler Radar system that the National Weather Service uses was developed in 1988. It was improved earlier this decade with the addition of dual polarization. While the pulses sent by National Weather Service Doppler Radar have an average transmitted power of around 450,000 watts, these transmissions only last a fraction of a second. In fact, when you add up all of the pulses during an entire hour, weather radar only transmits for a total of seven seconds. The remaining 59 minutes and 53 seconds are spent listening for reflected radar signals.

Despite all of this sophisticated technology, there is one thing that Doppler Radar cannot do: Radar cannot determine if rotation is reaching the ground. This is because the radar pulses are sent at an upward angle above the horizon and cannot see what’s happening on the ground several miles away. This is why trained weather spotters are very helpful. Radar can see rotation hundreds and thousands of feet above ground. However, Skywarn spotters on the ground are the ones who confirm whether or not this rotation is touching the ground and if there is indeed a tornado occurring.

There are a lot of interesting facts about Doppler Radar that you and your family can learn about on the National Weather Service’s new Online School for Weather called JetStream. Visit their website: weather.gov/jetstream