posted 04-05-2001 09:45 PM            

I wish that I could help you out more than I am able to. The fact is, the radar that I work with in an air-to-air mode does not display raw data like a weather radar does. Instead, software decodes the raw data and has a sophisticated method for picking legitimate targets out from the background clutter. In turn, my radar screen will be a lot less cluttered than the picture on a Nexrad terminal.

In an air-to-ground mode, however, the radar will display raw data. I don't use it very often at all in training. I do know that it is very sensitive, though, and it is labor intensive to work the gain control so you get a picture that is viewable. I suspect that the "blobs' have something to do with this as well. For those that don't know, when the Weather Channel shows a radar sumary of the entire continental United States, it combines data from of all the Nexrad sites across the country. The "blobs" that show up are all right on top of Nexrad sites. So, I think that your explanation is the most feasible, 3T3L1.

Along the same lines, I also think that the "donut holes" probably have something to do with the system filtering out ground clutter out to a certain range.

O.K., on to the more strange of the anomalies. I looked pretty hard at your maps, and I can't say what the "rays" are. I've seen what jamming can do to a search radar, and sometimes it looks similar to what is on the maps in your post. However, I'm not saying that it is jamming, though. As sensitive and tempermental as the radar I work with is, I know that there are many things (environmental and man made) that can really screw a radar picture up.

I did notice something curious about your last map. I noticed that the three "ray" sites in southern California, Las Vegas, and Utah all seem to point to a relatively small spot north of Las Vegas. With the mystery and secrecy behind the military areas in southern Nevada, one might infer that there was something out there that was causing that. I don't think that it was a UFO or anything, but a test of some type may have caused some interference with the radar sites.

Well, I hope that I've helped. Dirk may be able to help you out more since he probably flies with a weather radar.

Good luck!

posted 04-05-2001 09:59 PM            

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About Doppler Radar

You may notice that on days when the weather is pretty nice, the radar is covered with large blobs of gray, blue and green weather patterns that can often obscure the entire screen. This is called "anomalous propagation," better known as ground clutter. It is a pattern of radar echoes from fixed ground targets. When the weather is nice, the radar is switched to "clear air mode." This is a highly sensitive mode that actually allows the radar to detect things that are much smaller than a raindrop. It also picks up flocks of birds and even swarms of insects. This pattern can increase in periods of high humidity, haze and fog. During rain or snow, the antenna will be elevated and will greatly reduce the extent of the ground clutter. This mode is very useful in tracking shifting winds that can eventually lead to a developing thunderstorm.

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