Wednesday, December 21, 2011

Dual Pol Radar

Radar has come a LONG way since the 60s. The above image is from NOAA and shows some tornadic storms from 1965. Since then, we now have color radar, Doppler capabilities, and many more products that help us track flooding, tornadoes, and severe storms.

All of us are familiar with the "reflectivity" product on radar. We use this product the most.
The above image is reflectivity or what we use to show where it is raining and how hard. This is the most popular radar product and for years has been very helpful. In recent times, the resolution has become MUCH better! That means it is more precise. Another radar product you see often during tornado coverage is "Velocity" data.
Velocity data shows us which direction the wind is moving and it's magnitude. Click image to enlarge. The green is the wind coming "toward" the radar site and the red is the wind going "away" from the radar site. Many times we show "Reflectivity" with the "Velocity" data in our scope. Now let's talk about some new products as of this month!

The NWS radar in Memphis has been upgraded to be a Dual Polarization radar! This is a project that is upgrading every NWS radar in the country by the end of 2013. Memphis is one of the first batch of radars to be upgraded. This is VERY good for us. Dual Pol radar not only sends out horizontal pulses, but vertical pulses. This helps to measure "WHAT" is falling from the sky and the size.

The new data will help determine precipitation types, rainfall rates, and hail detection. At KAIT, we have upgraded our radar display systems to have access to this data and to be able to show it to you on air! With that said, I'm not sure how often we will show it yet, but it is available. Here's what some of the data looks like using the same rain in the above images from last night.
The above image is "Differential Reflectivity" or "ZDR" and essentially can tell us the precipitation type and how large the raindrops are, and hail detection. I plan on making a radar legend for this product for typical values and what can be associated with those values. With StormTRACK Doppler 8, we can click the radar data to obtain the values and make some determination of what is falling from the sky.

The above image is "Correlation Coefficient": or CC data. I plan on using this to track ducks! LOL CC shows the behavior of of the pulses horizontally and vertically between each volume. Birds are not uniform and will change often and will be easily detected. Plain ole rain wills show up in shades of pink as seen above. If there was hail or snow with big snowflakes, it would react differently and you would see some shades of blues and greens, reds and oranges.
The above image here is Differential Phase or "KDP". I believe this is going to come in handy for Flash Flood events, but we need some real time events to see exactly how this will be used. It will show where the higher concentration of particles is located.

There's still a lot of studying to be done, but I'm excited about this new data we have to use at KAIT! To my knowledge, we may be the only television station with Dual Pol data for on-air use in Arkansas at this time. I'm still checking on that.

Have a great day!


Karen H. said...

That is so awesome. Me and my family depend on KAIT8 for the weather forecast. So glad yall have so much of the newest technology to help forecast our local weather. Keep up the great work!

Anonymous said...

The new radar is awesome!!!!! Very Cool!!!!

The news in HD looks excellent!

Any word on when commericials for the news will be switched to 16:9 Aspect Ratio HD? Their still 4:3?

When will Wheel of Fortune be?