Armor Images

James Paul and I went over to UAH today and spent some time with Dr. Walt Peterson.

Walt is a Senior Research Scientist who has been with us from day one on ARMOR. (Advanced Radar for Operations and Research) He has extensive experience with Dual Polarimetric radars (something VERY FEW meteorologists can say)

We looked at some images of the Feb 21st hail event. I am going to attach some images from the archived data to today's Blog.

The first image is a range height scan taking a cross section of a cell near Athens. You can see an intense echo through the middle. This is a line of very high reflectivity. Out in the plains this would almost certainly be hail but around here in the warm humid atmosphere..It is sometimes just heavy rain.

This is where dual pol. data can be very helpful.

The next image is the same view but we are looking at differential reflectivity. This is basically comparing the vertically polarized pulse with the horizontally polarized pulse.

Since rain drops are shaped kind of like smashed hamburger buns when
they fall, (didn't know that, did ya!) and they will reflect the horizontal and vertical pulses differently.

Thus you will have a high differential reflectivity (ZDR) in rain.

Hail on the other hand tumbles as it falls and appears to the radar to be mainly spherical. This causes the ZDR to drop to lower levels.

In the second image you are looking at ZDR and the white is the low ZDR: indicative of a mix of rain and ice particles (hail included).

You can clearly see the ice in the upper part of the storm and if you look closely near the bottom at the 20km range you can see indications of ice near the surface as well. We had many reports of hail from this storm. (A warning was issued).

Thought you who read this Blog might like to see this..I showed it on air at 10 pm but time did not allow for the more detailed explanation above.

We are learning a lot about the use of dual. Pol. data. Many other meteorologists will need to learn it soon as well because the NWS plans to upgrade all the NEXRADS to Dual Pol. in a few years.

For now we are the only TV weather department in the world running a dual polar. radar. (The link above is to our partners at UAH..they have a great web site with more Armor info)


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