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Earth Sense: Better weather radar is on horizon
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Spirits were high but clouds hung low during graduation ceremonies on the Brenau campus a week ago. Commenting on the light rain that was falling, Brenau President Ed Schrader said, jokingly, “according to the weather radar on my computer, these rain clouds don’t exist.”

He was right, of course. The National Weather Service radar showed clear sky. Even though weather observation technology has improved tremendously in the last few decades, our aging Doppler systems are showing their limitations.

Doppler was a giant leap forward from the old Plan Position Indicator radar used until late in the 20th century. In the past, we could only see what was there. It was the equivalent at taking a flash photo of the clouds at night.

With Doppler systems, wind speed and direction are detected, similar to shooting a movie of the sky. But radar depends on the reflection of the signal from the clouds. When they are thin, and raindrops are very small, you can get wet without anything showing up on the radar screen. 

Another shortcoming of current Doppler systems is that they don’t distinguish between rain, snow and hail. According to the National Oceanic and Atmospheric Administration, it’ll be another few years until new technology is ready for everyday use.

The first innovation will be a switch to polarimetric radar. Instead of shooting a horizontal beam at the sky and capturing “just clouds,” the polarimetric kind sends additional waves which oscillate vertically. Simply put, they paint a three-dimensional picture of the storm, which captures factors such as the shape and size of the rain drops. 

That’s important because a rainstorm with gazillions of small drops can put more water on the ground than one with large but fewer drops. But on the old radar, bigger drops show up as more “severe.” 

Another innovation to look forward to within a decade is phased array radar. This antenna type, currently being tested in Alaska and at Cape Cod, looks like a nightmarishly big, 10-story high boom box out of some juvenile’s car. It operates silently, though, amplifying the radar beam with a complex system that’s much more powerful and sensitive than what we have right now.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.

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