|Notes: Cloud data thanks to National Weather Service/Aviation Weather Center; blue overlay dots are WWLLN Lightning; Red circles are WWLLN receivers; Red line is the terminator.|
University of Washington in Seattle operating a network of lightning location sensors at VLF (3-30 kHz). Most ground-based observations in the VLF band are dominated by impulsive signals from lightning discharges called "sferics". Significant radiated electromagnetic power exists from a few hertz to several hundred megahertz, with the bulk of the energy radiated at VLF.
With our network of sferic sensors we are producing regular maps of lightning activity over the entire Earth. Our map showing the entire world uses coloured spots to indicate lightning strokes (red stars inside an open circle are active WWLLN lightning sensor locations). Click on the map for explanation.
The WWLLN Management Team, lead by Prof Robert Holzworth of the University of Washington produced these data and images with the cooperation of the universities and institutes which host the stations. Wideband VLF spectrograms from all WWLLN stations are available at this link . We currently have over 80 sensors around the globe to detect sferic activity in the VLF band.
We welcome offers of hosting a new WWLLN sensor to add to the list above. All hosts receive all the world-wide data for their own research on monthly CDs. In return, each host provides the computer and meets any local expenses like power, Internet, and maintenance. However, do not think that a sensor on your own campus is going to give you lightning location data on its own. Only the whole network does that.
Each lightning stroke location requires the time of group arrival (TOGA) from a least 5 WWLLN sensors. These sensors may be several thousand km distant from the stroke. The geographical arrangement of the sensors is important: a lightning stroke which is enclosed by sensors is much more accurately located than one which is not so enclosed. Clearly a uniform spacing of sensors around the Earth is the ideal. Since the Earth is round, there are no edges: every lightning stroke is surrounded by sensors, but not necessarily by the sensors which sense it. Typically only about 15 to 30% of strokes detected by one sensor are detected by 5 or more. These strokes are usually the stronger ones. Recent research indicates our detection efficiency for strokes about 30 kA is approximately 30% globally.
To cover the whole world by sensors spaced uniformly about 1000 km apart would require roughly 500 sensors. If spaced 3000 km apart, we would need “only” around 50 to 60 sensors. Presently we have 40 WWLLN sensors, and we are in the process of expanding to 60 sensors within the next year or two.
More information on the World Wide Lightning Location network (WWLLN) is available from our publication list
WWLLN Monthly CDs containing all stroke locations over the whole world for 1 month. These are mailed to subscribers each month, or they may opt to download the data weekly. Archival data are available for sale from August 15, 2004 to the present. Our site hosts receive a free monthly subscription.
WWLLN Data are available via internet with cadence every 10 minutes for research purposes from the University of Washington, or with a cadence of as fast as every minute (i.e. in realtime) from our commercial reseller. Contact Prof. Holzworth for more info.
for all questions relating to WWLLN: Prof Robert Holzworth, Earth and Space Sciences, University of Washington email@example.com
Webpage maintained by:
Craig J Rodger (University of Otago)
Robert Holzworth (University of Washington)