Dual-Pol Upgrades Expected to be Beneficial

When severe weather approaches, there’s one tool meteorologists everywhere depend on to give out an accurate explanation of what is currently going on, as well as what may happen – radar. Up until now, the radars used by the National Weather Service offices as well as television stations have gotten the job done. But there have been some complaints.

“The biggest problem with past and current Doppler radars has been trying to differentiate between different types of precipitation,” said Dave Freeman, chief meteorologist at KSNW-TV in Wichita, Kan. “For instance, sometimes it can be difficult to tell the difference between a very heavy rain echo or maybe just a hail core on radar. But it looks like dual-pol will help fix that.”

Freeman is referring to the dual-polarization (dual-pol) radar upgrade being installed across the United States. This upgrade is expected to give meteorologists better, more accurate information about what kind of precipitation is falling in an area, as well as help with tornado detection. The difference between dual-pol radars and conventional ones are in the way each transmits and receives the data.

Dual-Pol

Picture showing the difference between conventional, dual-pol radar. Picture courtesy of NWS Wichita.

“A conventional Doppler radar transmits and receives a beam that moves in a horizontal motion,” said Robb Lawson, a meteorologist with the National Weather Service office in Wichita, Kan. “But a dual-pol radar sends and receives beams that are moving both in a horizontal direction and a vertical direction.”

The additional vertical component to the radar beam can tell the meteorologist the shape and size of the precipitation particles that are suspended in the storm clouds. While also being able to predict how much precipitation will fall, this upgrade can help lead to better distribution of flash flood warnings, severe thunderstorm warnings and tornado warnings.

“If there were to be a rain-wrapped tornado, it’d be hard to see with the older Doppler radars,” Lawson said. “There would just be too much rain in between the radar and tornado for the radar to see it. But adding this horizontal component will vastly help in our ability to penetrate through the rain and see inside the storm better.”

This is welcome relief in the Great Plains region where tornadic activity is most common. Norman, Okla. and Wichita, Kan. were the first and third radar sites to be upgraded to dual-pol, respectively. Upgrades to dual-pol for all National Weather Service radar sites are expected to be complete by May 2013. That’s not a moment too soon for Freeman.

“We didn’t really get to reap the benefits of the dual-pol upgrade last year due to the severe drought we experienced,” Freeman said. “I look forward to using dual-pol. Its perks and benefits mean I’ll be able to get better information out to the public more quickly and possibly save more lives.”

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