It's the same intensity as the one we spotted in Tennessee last week when the "Russian booster" came streaking over. Anybody in the military out there have an idea what's up?

http://weather.yahoo.com/graphics/radar/US_loop.html

http://weather.yahoo.com/graphics/radar/Southwest_US_loop.html

-- @ (@@@.@), September 05, 1999

Answers

Gawd,

a------do you have any idea what time it is?

I certainly hope you are on the west coast or make that hawaii!

-- David Butts (dciinc@aol.com), September 05, 1999.

Will you artbellies *please* Get A Grip?

Radar image artifacts are as old as radar itself.

What next? Y2K-shaped crop circles?

-- Ron Schwarz (rs@clubvb.com.delete.this), September 05, 1999.

Schwarzkopf,

How come your so-called "artifacts" don't happen at all the radar stations, just once in a while they originate from military bases?

-- @ (@@@.@), September 05, 1999.

@,

The radar circles show up centered around military bases because that's where most of the new doppler weather radars are located. The new radars require a "clear zone" around the antenna which the older radars didn't call for.

Uncle Sam decided to put the new radars on the bases to save buying lots of land for the National Weather Service. Instead the "other" user of the new doppler radars, the DOD wa picked to host the radars on unpopulated areas of military bases. A very few of the new radars sites are at non-military, low population locations, like airports.

The circle effect is a function of what's commonly referred to as the "inversion layer". It's actually an interaction of a sidelobe of the radar beam being reflected back to the antenna from the E or F layers of the atmosphere. A good companion effect would be local radio reception getting better for far-off stations about the time the "radar circles" are present at long ranges. It's the same basic effect.

As far as sidelobe images go. It's a good sign that weather-wise things are so slow at the weather station that the radar operators have turned the reciever gain full-up to try and find some precipitation nearby and there is none.

FWIW, The opposite effect in an aircraft using radar is what's called "the altitude line". That's where a sidelobe signal is picked- up from directly below the aircraft. It appears as a line across the scope at the range mark which matches your altitude; such as flying at 40,000 ft above ground level will give you an altitude line at about 7.5 miles.

WW

-- Wildweasel (vtmldm@epix.net), September 05, 1999.