Cloud Circles on radar.
As you know a great deal of speculation and rumour surrounds the subject of cloud
circles. These have been highlighted by radar across the USA and Canada in the last
18 months or so.
I have made many inquiries within the Meteorological Service in the UK (Dept of
MOD-British Government) and here in the USA through a number of Meteorological
organisations. In the USA it has been impossible to reach an actual human being -
all attempts are either ignored or referred to machines.
I have been successful with detailed and very useful discussion with scientists working
for the British Government. It seems most likely that these strange patterns are a
radar artefact. It has been confirmed by the MOD that the cloud circles are also
appearing in the UK but that they have no reason to believe that they are meteorological
in nature.
For information here is a reply from an expert at the UK Met. office:
Colin,
Your email has been passed onto me for reply.
I have looked at the sample image and my guess would be that this and similar patterns do
not have a meteorological origin. There can be several causes of geometric ring or spoke
patterns:-
a) If there is an unexpected increase in the amount of electrical noise in the radar system. This noise tends to 'break through' at a particular range because the effective gain is higher at long range to compensate for the inverse square fall off in the signal. Having said that, the smaller 'holes' in your sample image at extreme range dont fit this.
b) when the engineers are checking or calibrating the radar, they may inject artificial signals into the system but forget to turn off the data supply to the outside world. This can result in ring patterns.
c) Interference from other radars or
noise sources can produce spoke patterns. - particularly when two radars which are close
together in frequency are pointing at each other.
The UK weather radar network also suffers from similar artefacts to some extent (maybe one
or two incidents per month on average)
Malcolm Kitchen,
Meteorological Office
MOD-UK