Lightning Is A Random, Chaotic And Dangerous Fact Of
Nature
At any given moment, there are 1,800 thunderstorms in
progress somewhere on the earth. This amounts to 16 million
storms each year! Scientists that study lightning have a
better understanding today of the process that produces
lightning, but there is still more to learn about the role of
solar flares on the upper atmosphere, the earth's
electromagnetic field, and ice in storms. We know the cloud
conditions needed to produce lightning, but cannot forecast
the location or time of the next stroke of lightning. There
are lightning detection systems in the United States and they
monitor an average of 25 million strokes of lightning from the
cloud to ground every year!
Lightning has been seen in volcanic eruptions, extremely
intense forest fires, surface nuclear detonations, heavy
snowstorms, and in large hurricanes, however, it is most often
seen in thunderstorms. A thunderstorm forms in air that has
three components: moisture, instability and something such as
a cold front to cause the air to rise. Continued rising
motions within the storm may build the cloud to a height of
35,000 to 60,000 feet (6 to 10 miles) above sea level.
Temperatures higher in the atmosphere are colder; ice forms in
the higher parts of the cloud.
Ice In The Cloud Is Critical To The Lightning Process
Ice in a cloud seems to be a key element in the development
of lightning. Storms that fail to produce quantities of ice
may also fail to produce lightning. In a storm, the ice
particles vary in size from small ice crystals to larger
hailstones, but in the rising and sinking motions within the
storm there are a lot of collisions between the particles.
This causes a separation of electrical charges. Positively
charged ice crystals rise to the top of the thunderstorm, and
negatively charged ice particles and hailstones drop to the
middle and lower parts of the storm. Enormous charge
differences (electrical differential) develops.
How Lightning Develops Between The Cloud And The Ground
A moving thunderstorm gathers another pool of positively
charged particles along the ground that travel with the storm.
As the differences in charges continue to increase, positively
charged particles rise up taller objects such as trees,
houses, and telephone poles. Have you ever been under a storm
and had your hair stand up? Yes, the particles also can move
up you! This is one of nature's warning signs that says you
are in the wrong place, and you may be a lightning target!
The negatively charged area in the storm will send out a
charge toward the ground called a stepped leader. It is
invisible to the human eye, and moves in steps in less than a
second toward the ground. When it gets close to the ground, it
is attracted by all these positively charged objects, and a
channel develops. You see the electrical transfer in this
channel as lightning. There may be several return strokes of
electricity within the established channel that you will see
as flickering lightning.
Thunder
The lightning channel heats rapidly to 30,000 degrees. The
rapid expansion of heated air causes the thunder. Since light
travels faster than sound in the atmosphere, the sound will be
heard after the lightning. If you see lightning and hear
thunder at the same time, that lightning is in your
neighborhood!
Negative Lightning And Positive Lightning
Not all lightning forms in the negatively charged area low
in the thunderstorm cloud. Some lightning originates in the
cirrus anvil at the top of the thunderstorm. This area carries
a large positive charge. Lightning from this area is called
positive lightning. This type is particularly dangerous for
several reasons. It frequently strikes away from the rain
core, either ahead or behind the thunderstorm. It can strike
as far as 5 or 10 miles from the storm, in areas that most
people do not consider to be a lightning risk area. The other
problem with positive lightning is it typically has a longer
duration, so fires are more easily ignited. Positive lightning
usually carries a high peak electrical current, which
increases the lightning risk to an individual.
