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| Radar 'interference' issue (March...) [SEC=UNCLASSIFIED] From : XXXXX-bom.gov.au> Subject : Radar 'interference' issue (March...) [SEC=UNCLASSIFIED] To : Colin Andrews Wed Aug 25 2010 7:18:09 PM 1 attachment Colin Further to your messages of earlier this year... The attached document explains the various radar image problems the Bureau was encountering... I thought you might be interested. Trevor The Australian Bureau of Meteorology. |
Attachment from BOM
Radar Anomalous Propagation
Pyrocumulus and fire detection using radar Weather Radar will reflect from ash and other debris
carried aloft by a fire, it also detects other natural phenomena such as insect swarms and flocks of
birds if they are present in the radar beam.
The radar image below would also include raindrops that form in the pyrocumulus cloud above the
fires. These clouds develop into thunderstorms generating lightening that causes additional fires and
strong micro busts (downdrafts) that make the fire more behaviour even more erratic.
For more information about radar images go to:
http://www.bom.gov.au/weather/radar/about/radarfaq.shtml
Radar Anomalous Propagation
Pyrocumulus and fire detection using radar Weather Radar will reflect from ash and other debris
carried aloft by a fire, it also detects other natural phenomena such as insect swarms and flocks of
birds if they are present in the radar beam.
The radar image below would also include raindrops that form in the pyrocumulus cloud above the
fires. These clouds develop into thunderstorms generating lightening that causes additional fires and
strong micro busts (downdrafts) that make the fire more behaviour even more erratic.
For more information about radar images go to:
http://www.bom.gov.au/weather/radar/about/radarfaq.shtml
Donut Rings around radar
The donut echo pattern is termed anomalous propagation and is caused by a faulty radar setting to
do with range normalisation. To achieve a display range to 512km the radar is required to sweep
three times at a slightly lower elevation at each step to accommodate for the curvature of the earth.
This ensures the beam is approximately the same height above the surface out to a distance of
512km. This adjustment is termed range normalisation. If the radar receiver setting is too sensitive
at one of the elevation settings a donut pattern results from background noise from the returned
signal. The problem is rectified by a technician reducing the sensitivity for the affected elevation
setting.
For more information about radar images go to:
http://www.bom.gov.au/weather/radar/about/radarfaq.shtml
The donut echo pattern is termed anomalous propagation and is caused by a faulty radar setting to
do with range normalisation. To achieve a display range to 512km the radar is required to sweep
three times at a slightly lower elevation at each step to accommodate for the curvature of the earth.
This ensures the beam is approximately the same height above the surface out to a distance of
512km. This adjustment is termed range normalisation. If the radar receiver setting is too sensitive
at one of the elevation settings a donut pattern results from background noise from the returned
signal. The problem is rectified by a technician reducing the sensitivity for the affected elevation
setting.
For more information about radar images go to:
http://www.bom.gov.au/weather/radar/about/radarfaq.shtml
Radial echoes
The radial echo pattern is termed anomalous propagation. The line echo radiating toward the south
east from the Melbourne Airport radar toward Bass Straight results from interference from another
radio source that is unknown. The other source could possibly be microwave communication or a
reflection from a city building. The radar beam passes over the city to the area where the echo is
displayed.
For more information about radar images go to:
http://www.bom.gov.au/weather/radar/about/radarfaq.shtml
The radial echo pattern is termed anomalous propagation. The line echo radiating toward the south
east from the Melbourne Airport radar toward Bass Straight results from interference from another
radio source that is unknown. The other source could possibly be microwave communication or a
reflection from a city building. The radar beam passes over the city to the area where the echo is
displayed.
For more information about radar images go to:
http://www.bom.gov.au/weather/radar/about/radarfaq.shtml
Spiral echoes
The spiral echo pattern is termed anomalous propagation. This type of interference pattern is caused
by a nearby radar transmitting on the same frequency. In the Melbourne case below a weather radar
operating at the Bureau’s Training Centre at Broadmeadows as a back up radar for the composite
radar map was affected when another radar being used for training purposes at the Broadmeadows
site was switched on. The offending radar was switched off once the problem was apparent and the
spiral pattern disappeared. Normally the situation would not arise, however the Melbourne radar
located at Laverton had a major component fault and was not operational at the time. The backup
radar at Melbourne Airport was being used in operational mode and one of the training radars at
Broadmeadows was switched on as a backup.
For more information about radar images go to:
http://www.bom.gov.au/weather/radar/about/radarfaq.shtml
The spiral echo pattern is termed anomalous propagation. This type of interference pattern is caused
by a nearby radar transmitting on the same frequency. In the Melbourne case below a weather radar
operating at the Bureau’s Training Centre at Broadmeadows as a back up radar for the composite
radar map was affected when another radar being used for training purposes at the Broadmeadows
site was switched on. The offending radar was switched off once the problem was apparent and the
spiral pattern disappeared. Normally the situation would not arise, however the Melbourne radar
located at Laverton had a major component fault and was not operational at the time. The backup
radar at Melbourne Airport was being used in operational mode and one of the training radars at
Broadmeadows was switched on as a backup.
For more information about radar images go to:
http://www.bom.gov.au/weather/radar/about/radarfaq.shtml
| ========================================= The Whole Mystery Has Not Been Answered Thanks to numerous observers across Australia here are more strange effects seen between July 8, 2010 and August 18, 2010 which includes two new effects not seen before i.e. A yellow 'Sun Burst' design and what must surely be some kind of interference with the geostationary satellite positioned south of the continent, huge white arcs stretching across the northern third of the continent. With regards the latter, when the national weather loop video is played the satellite shows very short duration interference blips. When these are captured as frame grabs they translate into what was seen on the national weather system. These are not referred to in the BOM explanation above, which attempts to account only for the radar images. By Colin Andrews August 28, 2010 |
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| Townsville - August 13, 2010 Yello Sun Burst not seen before. Copyright BOM |
| Third of Australia - July 24, 2010 Not seen before or covered in BOM report. |
NOT SEEN BEFORE
| The following images have been observed in recent weeks - my thanks to observers in Australia for regular input. |
Access to the whole research of this topic HERE
| The Australian Weather Radar Mystery Resolved ? By Colin Andrews |
| The Australian Bureau of Meteorology sent the following explanation to me this week - but read on to see new observations below. My special thanks to so many observers in Australia especially Conchita |