On Feb 7, 7:18*am, "Peter" wrote:
I was viewing the BOM (Bureau of Meteorology) weather radar of Victoria
(17:00 07/02/2009) despite the fact that locals assure me that there was no
rain at the time over eastern Victoria a number radar returns indicated very
heavy rain at a number of the bush-fire sites. It appears that the radar was
detecting the smoke.
I was under the believe that weather/rain radars gave returns from rain
droplets and that smoke should give little or no return.

Any thoughts!

http://mirror.bom.gov.au/products/IDR023.loop.shtml

--
Peter *VK6YSF

http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm

Weather radars declare a weather target based the amount of signal
recieved back or reflectivity of the target. The greater the
reflectivity the heavier the weather. Typically a series of 6
thresholds are set up with the minimum threshold indicating the
minimum level of precipitation the radar will report, under normal
conditions smoke will reflect less signal than is required to meet the
first threshold. Raging brush or forest fires are not normal
conditions as they put a huge amount of particulate matter and
moisture into the air. Otherwise there is not normally anything
special about weather radars that would allow it to tell the
difference between weather and smoke. Then again new technology is
always coming along. Most modern radars produce a digital image of the
weather in memory . This image is the processed by computer to declare
targets. If there is a difference between the signature of weather and
that of smoke it may be possible that software could or has been be
developed to tell the difference, if this is the case I am not aware
of it..




Jimmie