Natural Phenomenon : Upward Lightning

Natural Phenomenon : Upward Lightning

‘Lightning can form at the ground and travel upward’

LIGHTNING

What is lightning?

Lightning is a giant spark of electricity in the atmosphere between clouds, the air, or the ground. In the early stages of development, air acts as an insulator between the positive and negative charges in the cloud and between the cloud and the ground. When the opposite charges builds up enough, this insulating capacity of the air breaks down and there is a rapid discharge of electricity that we know as lightning. The flash of lightning temporarily equalizes the charged regions in the atmosphere until the opposite charges build up again.

What causes lightning?

The creation of lightning is a complicated process. We generally know what conditions are needed to produce lightning, but there is still debate about exactly how a cloud builds up electrical charges, and how lightning forms. Precipitation and convection theories both attempt to explain the electrical structure within clouds.

Precipitation theorists suppose that different sized raindrops, hail, and graupel get their positive or negative charge as they collide, with the heavier particles carrying negative charge to the lower part of the cloud.

Convection theorists believe that updrafts transport positive charges found near the ground upward through the cloud while downdrafts carry negative charges downward.

UPWARD LIGHTNING

Everyone knows that thunder and lightning always come together, but a very rare occurrence in thunderstorms is upward lightning. Tom A. Warner had been researching and filming lightning for years when he realized he had witnessed this phenomenon many times without knowing it. Out of almost 800 flashes captured on film, Tom noticed that 41 of them were actually flashing upward.

Warner studied the upward lightning flashes and came to several conclusions. He found that upward lightning is most likely to occur when a “normal” lightning flash takes place nearby. The first flash creates an electrical field change that causes a positive leader flash to “climb” upward.

The flashes can even “start” from a tall building or tower rather than the sky. Warner found that the shape of the tower or building is integral to enhancing the existing electric field and creating an upward lightning flash. He further determined that upward lightning would not be possible without the proximity of tall structures. Further research showed that during a snowstorm, upward leader flashes can be initiated by tall buildings without the presence of a “normal” lightning flash.

During winter snow storms, Tom's research also shows that tall objects can initiate upward leaders without preceding triggering flashes.These findings are very important because there are a lot of tall structures being built, especially wind turbines. These structures are experiencing lightning currents from upward lightning at a much higher rate than they might experience from normal downward lightning, even up to 100 times more often. Therefore, there is a much greater chance for damage. Also, it is unclear what global atmospheric impacts (i.e. atmospheric chemistry) if any, may result from the increase in lightning (specifically upward lightning) due to man-made tall objects.