Beginning September 12 and ending this week, the Portland NWS Forecast Office has been upgrading it’s WSR-88D radar to a dual polarization radar.
This is the latest technology available to weather forecast offices and boasts better precip estimations and better size estimation of precip droplets. It also will improved detection of flash flood situations, false echoes, precip type, and severe thunderstorm signatures. While research is still being done on Dual-pol technology, it is clear with already 14 additional products possible through the new system, that a lot could be possible.
What’s the difference? Regular radar sends a pulse of energy out away from the radar dome. The beam heads out until it hits something, and then bounces back. The result is what is called a radar signatures. If the beam hits something, that could mean a rain drop, a cloud drop, bugs, ice, etc. As the radar beam rotates and sends more and more pulses of energy, we get a clearer picture of the pattern of signatures. That helps us tell whether we’re detecting clouds, rain, or false echoes. (For example we get a signature on the radar, but the sky is clear. It’s obviously not rain, but could be another phenomenon that the pulse can’t differentiate.) The current radar that most office use, the single-pol, sends out a horizontal radio wave.
A dual-pol radar is different in that it sends a horizontal wave and a vertical wave to more accurately measure the signature coming back from the beam. That’s why the dual-pol system will better display what type of signatures we’re detecting. It will help tell the difference between a deep, intense thunderstorm, or a thin layered band of rain. It will help us eliminate fall echoes caused by bugs, birds, or other interference.
Want more information? Check out the NWS Radar page.