Dual-Polarization Radar: Why you'll be safer in severe weather
Thu, 21 Mar 2013 21:45:50 GMT —
A series of upgrades to the National Weather Service's Doppler radar network will be complete in our area soon...and the updates are significant.
Mainly in that the radars that cover the WNWO viewing area, (KIWX in North Webster, Indiana, KDTX in White Lake, Michigan, and KCLE in Cleveland, Ohio), will all be dual-polarization radars.
CLE and IWX are already complete...and DTX should be wrapped up in the coming days.
The dual-polarization upgrade is the most significant update to the nation's radar network since it was installed in the early 90s...and it will give those of us in the weather biz the ability to better identify all types of severe weather...and even more accurately monitor winter weather.
So what's "dual-pol" and why is it such a big deal.
Prior to the upgrade, the radars sent out only horizontally oriented radar pulses. While the picture was still good...it was, essentially, one dimensional. This made it impossible to accurately determine if the returns were coming from rain, hail or snow.
The new dual-pol sets send out pulses that are oriented both horizontally and vertically. With proper processing, the returned signals provide a much more accurate picture of what the radar is hitting. This makes it possible to "see" rain, snow, hail...even precipitations types that fall somewhere in-between.
Not only is type readily identified...so is size, giving forecasters better abilities in determining where flash flooding is likely to take place.
In addition to identifying the type and size of individual "hydrometeors", (read raindrops), it can also differentiate between drops and debris suspended in the air.
This is critical to helping identify when and where a tornado is first forming...or already tracking.
Horizontally oriented radars relied on radar "signatures" or "shapes" of radar returns to identify where a tornado might be.
With dual-pol radars, we have the ability to identify things in the air that aren't rain or hail...and that's important.
As radar beams travel away from the radar site they travel, for our purposes here, in a straight line. And since Mother Earth is not flat, the earth and beam get farther apart as that distance from the site increases.
That means most radar based tornado warnings are based on radar data where the radar beam is thousands of feet above the ground at the location where the warning is issued for. It's this fact that contributes to the high incidence of unverified warnings.
With dual-pol radar, the accuracy rate for those radar based warnings will definitely improve...as will the exact placement of tornados when warnings are issued.
This will especially be important for night-time tornadoes...when eyeballs aren't there to see what, exactly, is happening on the ground.
The bottom line is that the hardware and subsequent software updates and upgrades will improve accuracy to a point we haven't seen before.
That means you'll be safer in the next big storm...and for me, as a taxpayer and a Meteorologist, that's money well spent.
You can see pictures from an installation here.
And a rather "campy" video that hits the major points here.