Sferics - 'Listen' to lightning

Posted by: spud

Sferics - 'Listen' to lightning - 07/06/2019 11:03

This may interest someone.

Lightning produces a radio signal as well as light.

A sferic (sometimes also spelled "spheric") is an electromagnetic impulse that occurs as a result of natural atmospheric lightning discharges.

Sferics propagate from their lightning source for enormous distances in the right conditions (best at night due to the changes in the radio reflectivity of the ionosphere after sunset.

By night you can ‘listen’ to lightning easily over a thousand kilometres away depending on radio clarity with the myriad amounts of interference caused by TV’s, LED lights, monitors etc etc etc...

This will give an idea of what you are listening for https://www.youtube.com/watch?v=9c5ZLX7x8D8

From SE QLD I easily receive lightning at night from anywhere in the Tasman Sea associated with autumn/winter lows plus through SE Asia, PNG etc.

By day it is less but still can be easily heard several hundred kilometres away.

You only need an AM band radio (tune to the bottom of the band ie 522 kilohertz khz (preferred) or 531 etc.

Better still, an old multiband radio with a Low Wave Band ie 30-300 kHz (radio band below AM) is best with mid range frequencies good.

This http://en.blitzortung.org/live_lightning_maps.php?map=20 is handy. Only shows ground strikes mostly but is near real-time to see what you are hearing.

If interference is ridiculous I use a directional loop antenna on an old radio connected to the external antenna and ground terminals to ‘null’ out some interference sources such as the pole hung internet cables.

Failing that you can tune to the bottom of AM in your car and get away from interference..

Hope this helps add a different meteorological interest and offset a smidge of storm deficit syndrome for someone.
Posted by: ozthunder

Re: Sferics - 'Listen' to lightning - 07/06/2019 14:46

Every Aussie storm chaser tunes to AM522. The USA ones have loads of data instead.
Posted by: retired weather man

Re: Sferics - 'Listen' to lightning - 07/06/2019 16:04

SFERICS was the name for the lightning detection system BoM used up to about 1980. There were 2 systems...the northern one consisted of Cloncurry, Townsville, Charleville, Brisbane.

The southern system was Port Hedland, Perth, Laverton ( Vic ), plus I think Alice Springs.

I only worked on the northern one.

The system operated thus.... Each station had two ground based aerials aligned North/South and East/West. The receiver was indoors tuned to a Long Wave frequency. A CRT showed the direction of the flash on a 360 deg inscribed screen. Distant flashes were long and narrow, closer flashes were fatter, overhead flashes were circular around the centre of the screen.

The old Brisbane Airport office was the control centre for the northern system. The 4 offices were all hooked up by a PMG phone link on long distance call rates for 3 minutes, between 4 and 6 times daily depending on the season.

At the control office the operator ( also connected to the other 4 offices by headset ) stood before a large cork board map of Australia and surrounding oceans. Each of the 4 stations had its own wire and pin ( different colours for each station ). When a flash occurred the Brisbane radar officer would call " NOW ", and each station in turn would call the direction of the flash seen on its CRT. Brisbane might say 340, then Charleville 040, Cloncurry 160, Townsville 220 ( very rough figures ). The control officer at the map pin board would use each station's pin and wire and pinpoint the flash. My rough example given would be in the Emerald area.

After 3 minutes the control officer would allocate lat/long to each flash and send the results out in a code by teleprinter for other stations to plot.

These were the early ways of detecting TC development in the Coral Sea before satellites and TS in the remote area outside the rudimentary radar coverage of those days.
Posted by: spud

Re: Sferics - 'Listen' to lightning - 07/06/2019 17:36

RWM I believe an old sferic unit is in the Caloundra Air Museum
Posted by: Knot

Re: Sferics - 'Listen' to lightning - 07/06/2019 17:39

Nice post RWM.
Posted by: retired weather man

Re: Sferics - 'Listen' to lightning - 08/06/2019 08:41

I might add the aerial arrays were inside large low to ground wooden structures and were 5 star accommodation for the local snakes as we found out each time maintenance was needed.
Posted by: Foehn Correspondent

Re: Sferics - 'Listen' to lightning - 08/06/2019 11:37

Very interesting post RWM.