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Broadcast Dual Polarization Radar

In the fall of 2004, the first Broadcast Dual Polarization Radar in the world went online. WHNT in Huntsville Alabama teamed up with the University of Alabama in Huntsville to turn a decommissioned radar into a revolutionary Dual Pol Doppler radar to be used for education, research, and broadcasting. Baron Services stepped in to install this first of its kind radar.

WHNT and UAH call their radar ARMOR, or Advanced Radar for Meteorological and Operational Research. Before it became what it is today, it was a WSR-74C system. The system was first used in 1977 and was upgraded to a Doppler in 1991. In order to refurbish this radar to become one of the most powerful radar systems available, Baron Services provided a ingest computer, C-Band transmitter, and radome. In spring of 2005, Baron Services upgraded ARMOR with a 350 kW solid-state transmitter.

“The past year and a half has been a slow learning curve, and we are still learning how to interpret the information,” WHNT Chief Meteorologist Dan Satterfield said. “But the potential is incredible.” Satterfield went on to say he believes Dual Pol could potentially fix the problems that current radars have.

What makes this radar different from current radars is that Dual Polarization uses two different echoes, vertical and horizontal. The radar sends beams with pulses, one in waves that move up and down and another wave that moves side to side, making detection of precipitation much easier. For instance, during a rain or storm event, Dual Pol can infer how big the particles falling from the sky are. Particle size gives several pieces of information: the type and amount of precipitation and any debris that may be in the storm. The system is even sensitive enough to study wind patterns before a storm develops.

This was most recently put to the test during a hailstorm that moved through Huntsville in early April. “We were actually able to help the weather service by seeing the hail in the storm before it hit the ground. The algorithms are great for detecting hail,” Satterfield said.

Because this radar technology is so new, very few people in the country are familiar with it, causing WHNT and UAH to learn as they go. However, Dr. Walt Peterson at UAH believes over the next 3 years, Dual Polarization Radars will become the standard. Currently, they are using the radar on campus to research hydrology, cloud physics, storm electrification, initiation of clouds in the boundary layer, and even bird migration patterns. Scientists are implementing algorithms in real time and providing that information to WHNT and the National Weather Service.

“One of the most amazing things I have learned with Dual Pol, is the speed at which rainfall can fall in the southeast,” Peterson said. “We can go from weak echoes to pouring rain in 3 to 4 minutes. It’s phenomenal to watch.” The next major research study for UAH scientists is learning about the boundary between rain and snow. They are designing a completely new algorithm to distinguish the difference and produce better forecasts.