Our directory of things of interest

University Directory

New methods of measuring storms result in the discovery of vast 'megaflashes'

New methods of measuring storms result in the discovery of vast 'megaflashes'
17 Sep
2020
Advances in space-based lightning mapping have allowed scientists to measure flash extent and duration over broader ranges. The development has led to the discovery of 'megaflashes' – vast electrical surges that discharge over long distances and durations

Residents of Cordoba, Argentina, and Porto Alegre in southern Brazil, often see the sky ripple with dramatic storms. Some of these illuminate the sky with such stunning electrical force, that the term ‘megaflash’ has arisen – the rare phenomenon of single lightning flashes traveling hundreds of kilometres.

The World Meteorological Organization recently confirmed that on 31 October 2018, a single flash covering a horizontal distance of 709 kilometres across southern Brazil – equivalent to the distance between London and the border of Switzerland – set a new record for the longest reported distance of a single lightning flash. The megaflash more than doubled the previous record of 321 kilometres, which occurred on 20 June 2007 across the US state of Oklahoma.

Records for the greatest duration for a single lightning flash have also been extended: on 4 March 2019, a megaflash occurred for 16.73 seconds over northern Argentina.

Most lightning is formed when warm air is pushed upward during storms. As the water droplets in the warm air meet ice crystals in the cold air above they bump together and move apart, resulting in static electrical charges in the clouds. Over time, the bottom of the cloud gains a higher negative charge, which seeks to link up with the ground’s positive charge. As a flow of negative charges rush toward the Earth and positive charges flow upward, a strong electric current occurs – the bolt.

Stay connected with the Geographical newsletter!
signup buttonIn these turbulent times, we’re committed to telling expansive stories from across the globe, highlighting the everyday lives of normal but extraordinary people. Stay informed and engaged with Geographical.

Get Geographical’s latest news delivered straight to your inbox every Friday!

Megaflashes have some unique characteristics, however: ‘In storms, negative charge is often equalised to the positive charge of the ground, but in megaflashes, the equalisation happens with positive charges at the tops of other clouds,’ explains Randall Cerveny, professor of geographical sciences at Arizona State University and World Meteorological Organization’s rapporteur of weather and climate extremes. ‘Their cloud-to-cloud equalisation allows megaflashes to cover broad distances and to discharge for long durations.’

Some thunderstorms, termed ‘mesoscale convective systems’ (MCSs) provide the optimal conditions for megaflashes: ‘These storms are created by massive surface heating, rather than by frontal uplift, like the storms common in the UK. These hot-air based MCSs form in large open plains, like the plains of Argentina and southern Brazil,’ says Cerveny.

Before these recent record-breakers were detected, lightning was monitored using on-the-ground geolocation. However, advances in space-based lightning mapping have allowed scientists to measure flash extent and duration over broader ranges, allowing them to detect new extremes. ‘We are literally rewriting the definition of “lightning”,’ says Cerveny, who is passionate about the value of this monitoring. ‘Lightning has great importance to our basic understanding of the science of the atmosphere. As meteorologists learn more about how our atmosphere works, our ability to predict weather events improves. Knowledge of extremes helps engineers to design better planes and buildings. The records also draw attention to basic lightning human safety practices.’

While engineers, meteorologists and climatologists will be fascinated by the implications of ‘megaflashes’ for advancing knowledge in atmospheric science, Cerveny relates to the more elemental stirrings that lightning incites. ‘I’m told that announcements of these extremes draws the youngest generation of meteorologists into the field. It draws attention to the excitement of atmospheric science.’

Cerveny thinks that space-based lightning mapping technology will be increasingly important to detect the effects of climate change: ‘It’s like measuring a child’s growth by marking their height on a door. If you only have one measurement, you can’t say whether or not the child is growing. The more that we monitor climate and weather, in particular extreme events, the clearer picture emerges as to how our climate is changing.’

SUBSCRIBE TO OUR MONTHLY PRINT MAGAZINE!
Subscribe to Geographical today for just £38 a year. Our monthly print magazine is packed full of cutting-edge stories and stunning photography, perfect for anyone fascinated by the world, its landscapes, people and cultures. From climate change and the environment, to scientific developments and global health, we cover a huge range of topics that span the globe. Plus, every issue includes book recommendations, infographics, maps and more!

Related items

NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in NATURE...

Wildlife

James Wallace, Chief Executive of Beaver Trust, shares an unlikely…

Wildlife

The winners of the most hotly anticipated photography competition have…

Polar

Artist and geographer Nick Jones was appointed artist in residence…

Oceans

Photojournalist Tommy Trenchard joins a research expedition to the Saya…

Climate

So far, carbon offsets have focused mostly on tree-planting. But…

Oceans

Marine scientists are often too few and too underfunded to…

Wildlife

Indigenous marmosets are under threat from released pets and forest fragmentation

Wildlife

A rare encounter with a leopard in the mountains of…

Oceans

The Saildrone Surveyor, a type of uncrewed autonomous vehicle, has…

Climate

Australia has the highest per-capita use of rooftop solar power…

Wildlife

Ecoacoustics – a way to listen in closely to the…

Wildlife

Ash dieback is set to transform the British landscape. Robert…

Geophoto

Photographer Patrick Wack documents documents changes in the Chinese province 

Climate

A growing tide of legal action is increasing pressure on…

Wildlife

Classifying a group of organisms as a separate species has…

Geophoto

Artist Sarah Gillespie used the historic mezzotint technique for her…

Geophoto

The winners of the 2021 competition of Earth Photo have…

Climate

As climate change dysregulates weather patterns, cases of pest explosions…

Polar

Arctic nations are gearing up to exploit the region’s abundant natural…