(Click image to enlarge) Photographed over Darwin, Australia © Jason Smith (see it in the gallery)
Lightning forms in the thunderous belly of a Cumulonimbus storm cloud. It is the sudden and enormous movement of electric charge within the cloud or to its surroundings. The huge cloud tends to develop negative charge towards its base and positive charge towards its summit. This appears to be caused by the collision between the large hail stones and smaller ice particles being blown around within the chaotic body of the cloud. When they collide, the larger hail seems to pick up some negative charge from the smaller particles. Being heavier, the hail is not blown upwards as easily by all the vertical currents of air in the cloud so the negative charge tends to build up around its base, the positive charge towards its summit.
As this distribution of charge increases, it becomes more and more unstable. Suddenly, a massive rush of electricity – the lightning bolt – redistributes the charge. Thunder is the explosive expansion of the air which is heated extremely fast as it conducts the electricity.
There are a number of different types of lightning, many of which are being demonstrated by the flamboyant thundercloud shown above. ‘Sheet lightning’ is when a bolt is hidden by the body of the cloud, so that the whole cloud appears to light up as the light passes through it. ‘Forked lightning’ tends to be classified in terms of where it travels: ‘Cloud-to-ground’ (just visible at the bottom left corner of the photograph); ‘Cloud-to-cloud’ (at the top right); ‘Cloud-to-air’ (top centre); and ‘in cloud’ (which is what is causing the sheet lightning at the centre of the image).
On the whole, clouds are the more subtle manifestations of the weather. Theirs is usually an understated beauty, which is why it is so often overlooked. No wonder, then, they want to show off every once in a while with such explosive, heart-stopping fireworks.
Current Cloud of the Month:
Crepuscular Rays (Jan 09)
Previous Clouds of the Month:
Valley Fog (December 08)
Cloud Shadows (November 08)
Contrails (October 08)
Mamma (September 08)
Kármán Vortex (August 08)
The Summertime Halo (July 08)
The Nor’west Arch (June 08)
Microbursts (May 08)
Irridescent Clouds (April 08)
Northern Lights – Aurora Borealis (March 08)
Ice halos (February 08)
Lightning (January 08)
Roll Cloud (December 07)
Banner Cloud (November 07)
Stratocumulus (October 07)
The Unclassified Cloud (September 07)
Alexander’s Dark Band (August 07)
Fumulus Snail (July 07)
Distrail (June 07)
Altocumulus undulatus (May 07)
Cumulonimbus capillatus (April 07)
Lacunosus (March 07)
Horseshoe Vortex Cloud (February 07)
Jet-Stream Cirrus (Janurary 07)
Altostratus/Altocumulus/Altowhateveritis (December 06)
Anti-Crepuscular Rays (November 06)
Stratocumulus (October 06)
Altocumulus (September ’06)
The Kelvin-Helmholtz Wave Cloud (August ’06)
The ‘Brocken Spectre’ (July ’06)
‘Whale’s Mouth’ (June ’06)
Noctilucent (May ’06)
Cirrus (April ’06)
Cap Cloud (March ’06)
Fallstreak Holes (February ’06)
Nacreous (January ’06)
Cirrostratus (December ’05)
Tuba (November ’05)
Virga (October ’05)
Cirrocumulus (September ’05)
Altostratus (August ’05)
Cumulus (July ’05)
Mamma (June ’05)
Pileus (May ’05)
Lenticularis (April ’05)
Stratus (March ’05)
Cumulonimbus (February ’05)
Contrails (January ’05)
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go to our Photograph Submissions
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