USING NOAA RADAR "GROUND CLUTTER" TO PREDICT FM TROPO???

[Jay Walker]

This is probably old news for you veterans of tropo on this board. It's been a long while since I've been serious about DXing and as I fall back into the hobby I've been looking at ways to improve my "tool box".

It could be my imagination, yet I seem to notice a correlation between the amount of Radar "Ground Clutter" and Tropo openings here in the DFW area. The higher the amount of "clutter" the better the tropo opening. As the ground clutter patterns began to overlap, the spread and coverage seems to improve. This is using 2m and FM broadcast as my reference signals. I've also noticed that I can reasonably predict the tropo direction and coverage area with the various clutter patterns using the NOAA displays as well.

The ground clutter prediction method appears to work about 90% of the time. When I compare times of high "clutter" events with this Tropo link

http://aprs.mountainlake.k12.mn.us/

I find that it pretty much mirrors the activity indicated on reported tropo openings.

Tropo is a regular event here in DFW due to the proximity to the Gulf Coast and front passages from the west to the east. In fact it's almost a daily event in the early AM hours before the the layer burns off.

Anybody else ever seen this unscientific correlation using NOAA Ground Clutter?? Just thinking outside of the proverbial box..
Thanks
Jay Walker

 

[K6JHU]

The weather radar is using a frequency approximately 20 times (if my arithmetic is right) higher than the FM frequency of interest. The reflected waveform can tell you if a front is coming in which may indicate an affect on propagation. However, ground clutter is due to beam angle and that is adjustable. When the weather bureau wants to look far out the beam is adjusted closer to the horizontal (more ground clutter). When there is something close the beam is tilted up (less ground clutter). So it could be that the weather bureau is looking at something further away on a cleer day (more chance of tropo) and something closer on a lousy day (less chance of tropo) and steering the beam accordingly. I see that looking at the local weather radar here. Correlation is not causality.

 

[Lawppy]

It does happen. But i'm not enough in the know to tell you exactly what causes it. However, I have noticed that on evenings, overnights and early mornings where ground clutter is present on the radar I tend to have better luck particularly with shorter-haul enhancement, which is almost always limited to 100 miles, but with those stations in like locals.

 

[rbrucecarter5]

The only time I saw a correlation was the Columbia disaster. Radar came alive with debris, and yes, it did bring in skip. My heart wasn't into DX'ing. I quit after a couple of minutes. People had died.

 

[tomservo]

The NWS can adjust the beam angle but the product we see on the consumer site is at the same level every time. The base reflectivity is at 0.5° and doesn't change. The composite product does show results higher up in the scan but not separated out. As I understand it, under normal operations the radar makes scans at each pre-determined level, then starts over at the bottom, which is the only layer we see on the public site. The levels in the clean air mode are at 0.5, 1.5, 2.4, 3.4 and 4.3 degrees. In precip mode it goes up to something like 19.5° with more levels scanned.

I think during clean air mode the radar scans more slowly and is more sensitive to objects, so what you're seeing is not necessarily ground clutter but air "pollution". So maybe there's something to using radar to predict tropo after all. Heavy clutter does seem to coincide with near field tropo down here on the coast, too.

 

[Jay Walker]

When I compare the NOAA site with the near real-time Tropo link I posted previously I have noticed a correlation between the "density" of clutter displayed on NOAA and Tropo activity....

[http://aprs.mountainlake.k12.mn.us/]

I understand that NOAA radar is not "VHF", however I do know that Tropo does occur through low micro-wave frequencies. There were/are several civilian tropo-scatter systems that operated on around 2Ghz for long haul high bandwidth applications in the days before satellite that provide 99.9% reliability on paths in the 300km range. Usually the average downtime on those links were around 3 minutes in a given month. Of course the antenna gain figures were between 40 and 60 dBi (!!!) on each end of the circuit with transmitter power in the range of 1 to 10kw (not ERP, TPO)


I brought this to the table to see if others had observed the correlation.
Hopefully this is something beyond "smoke and mirrors" as it would be neat to be able check NOAA and then fire-up the Yaesu on 2m SSB and point and shoot for DX or light up the Denon and twist the yagi around for a taste of FM DX. To further add to the fun, I've also noticed the correlation between frontal boundaries and tropo.

;D ;D
Or it could be just a coincidence...
;D ;D

73
Jay Walker

 

[Jay Walker]

The only time I saw a correlation was the Columbia disaster. Radar came alive with debris, and yes, it did bring in skip. My heart wasn't into DX'ing. I quit after a couple of minutes. People had died.

I remember spending a lot of time on HF listening to down-range and recovery operations...It was a very bad day.

Regarding the enhanced propagation effects because of the tragedy...

Your observation makes sense as the ionization of the debris entering the atmosphere is similar to the meteor scatter comms we know and love. I use high speed CW to make contacts during the short duration "pings" from the Ionization trails left in the wake of a good shower event such as Perseid Meteor Showers that occur every August... It also makes for good FM Dxing "IF" the Ionization Trails are of long duration. Of course a means of recording is an absolute must...