Weather MODIFICATION / Tornado Season ??

I'll start with a little more on weather radars from Newsweek.com:
"Ground Clutter, Anomalous Propagation, and Other False Echoes

Echoes from objects like buildings and hills appear in almost all radar reflectivity images. This "ground clutter" generally appears within a radius of 25 miles of the radar as a roughly circular region with a random pattern. An mathematical algorithm can be applied to the radar data to remove echoes where the echo intensity changes rapidly in an unrealistic fashion. These "No Clutter" images are available on the web site. Use these images with caution; ground clutter removal techniques can remove some real echoes, too.

Under highly stable atmospheric conditions (typically on calm, clear nights), the radar beam can be refracted almost directly into the ground at some distance from the radar, resulting in an area of intense-looking echoes. This "anomalous propagation " phenomenon (commonly known as AP) is much less common than ground clutter. Certain sites situated at low elevations on coastlines regularly detect "sea return", a phenomenon similar to ground clutter except that the echoes come from ocean waves.

Radar returns from birds, insects, and aircraft are also rather common. Echoes from migrating birds regularly appear during nighttime hours between late February and late May, and again from August through early November. Return from insects is sometimes apparent during July and August. The apparent intensity and areal coverage of these features is partly dependent on radio propagation conditions, but they usually appear within 30 miles of the radar and produce reflectivities of <30 dBZ.

However, during the peaks of the bird migration seasons, in April and early September, extensive areas of the south-central U.S. may be covered by such echoes. Finally, aircraft often appear as "point targets" far from the radar."

Regarding HAARP and composite reflectivity circular echoes and 'other technologies' at NEXRAD sites: The radar operates under operator selected 'Scan Strategies'. A couple of the strategies are available when operating the radar in Precipitation Mode and another strategy is available for operating the radar in Clear Air Mode. Each Scan Strategy has a specified number of fixed elevation angles that the radar rotates through to complete what is called a Volumn Scan. When an elevation sweep at any of the set elevation angles detects clouds or weather (when scanning in Precipitation Mode) an echo return is sent back to the radar. Three types of echo return data are processed by the Radar Data Acquisition unit, i.e., reflectivity (moment 0), radial velocity (moment 1) and spectrum width (moment 2). All three types of data can provide useful information to the Radar Meteorologist (note that level 10 spectrum width is an excellent severe thunderstorm/tornado signature). Composite reflectivity is an image created by the Radar Product Generator (RPG) software that contains all of the reflectivity returns for all of the elevation angles in a single Volume Scan with display preference given to the highest reflectivity detected over each point within the Volume Scan along all azimuths and distances (its actually a little more complex than that, but I've kept it simple for ease in understanding - I know, easy for me to say

).

Okay, with that long preamble, lets take a weather situation where there is an cyclone with thick clouds and rain at the surface and colder temperatures below freezing aloft and this weather is extensive in its horizontal coverage and is occuring over the radar site. Assume a Precipitation Mode Scan Strategy with nine elevation angles ranging from 0.5 degrees to 16 degrees. The reflectivity return from the lowest 0.5 elevation angle shows returns for light to moderate rain extending from near the radar site out to some considerable distance from the radar (remembering that because of the curvature of the earth, the distant returns are from clouds and weather that is a lot higher in the atmosphere than the returns that are very close to the radar site). At a point quite some distance from the radar at this low evevation angle there is a sudden sharp ring of higher reflectivity that forms a full circle, with lower reflectivities both inward and outward from the circle. The next higher elevation scan has an echo return that is quite similar except that because the elevation angle is higher the circle of higher reflectivity is a little closer in toward the radar site. This process will repeat with all nine elevation angles and whan the RPG develops the Composite Reflectivity product the image will have nine circles around the radar. Each of those bright reflectivity circles represents the altitude of the freezing level (or melting level) for that particular elevation angle. Melting snow causes an uncommonly high reflectivity return. The first time that we saw this at Raytheon when we were starting our radar tests we were certain that there was something wrong with the radar - until we figured out what it was.

I guess the short version of the story is that no mysterious new technology is causing erroneous circular radar returns that point toward weather modification. In fact, if such a technology was in use, it would likely interfere with the NEXRAD signal itself. A few of the NEXRAD sites are operated by Air Force Weather personnel, but most of them are National Weather Service operated sites - I've been to both AF and NWS sites and they generally all operate in the same manner. Also note that the radar will pick up a straight-line return along a specific azimuth (or two) - it picks up the sun at sunrise and sunset.

Hope that at least some of this helps.
Cheers,
ED

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