THUNDER AND LIGHTNING
We have all seen tall, dark puffy clouds forming on a hot humid
afternoon. These are cumulonimbus clouds, sometimes nicknamed "thunderheads."
They can actually form any time of day when the temperature falls rapidly higher
up in the sky. These tall dark clouds are full of moisture and contain strong up
and down air currents. Cumulonimbus clouds may tower more than 50,000 feet, and
cover from just a few square miles up to two hundred square miles.
Why do thunderstorms rarely occur over open seas:
Most thunderstorms (accompanied by lightning) occur over land. They are
much rarer at sea. The requirements for developing one include, not only
unstable air mass, but also a little "push" from somewhere to initiate updrafts.
On land, these little pushes are easy enough to come by: the ground, overheated
by the Sun, increases the instability of the air mass, or a high landmass forces
the air to rise. This cannot happen over the open sea.
What is Lightning: To put it simply, lightning is
electricity. It forms in the strong up-and-down air currents inside tall dark
cumulonimbus clouds as water droplets, hail and ice crystals collide with one
another. Scientists believe that these collisions build up charges of
electricity in the cloud. The positive and negative electrical charges in the
cloud separate from one another, the negative charges dropping to the lower part
of the cloud and the positive charges staying ins the middle and upper parts.
Positive electrical charges also build upon the ground below. When the
difference in the charges becomes large enough, a flow of electricity moves from
the cloud down to the ground or from one part of the cloud to another, or from
one cloud to another cloud. In typical lightning these are down-flowing negative
charges, and when the positive charges on the ground leap upward to meet them,
the jagged downward path of the negative charges suddenly lights up with a
brilliant flash of light. Because of this, our eyes fool us into thinking that
the lightning bolt shoots down from the cloud, when in fact the lightning
travels up from the ground. In some cases, positive charges come to the ground
from severe thunderstorms or from the anvil at the very top of a thunderstorm
cloud. The whole process takes less than a millionth of a second.
Kinds of Lightning: There are words to describe different
kinds of lightning. Here are some of them:
In-Cloud Lightning: The most common type, it travels
between positive and negative charge centres within the
thunderstorm.
Cloud-to-Ground Lightning: This is lightning that
reaches from a thunderstorm cloud to the ground.
Cloud-to-Cloud
Lightning: A rare event, it is lightning that travels from one cloud to
another.
Sheet Lightning: This is lightning within a cloud that lights
up the cloud like a sheet of light.
Ribbon Lightning: This is when a
cloud-to-ground flash is blown sideways by the wind, making it appear as two
identical bolts side by side.
Bead Lightning: Also called "chain
lightning," this is when the lightning bolt appears to be broken into fragments
because of varying brightness or because parts of the bolt are covered by
clouds.
Ball Lightning: Rarely seen, this is lightning in the form of
a grapefruit-sized ball, which lasts only a few seconds.
Bolt from the
blue: A lightning bolt from a distant thunderstorm, seeming to come
out of the clear blue sky, but really from the top or edge of a thunderstorm a
few miles away.
What Puts the Thunder in the Thunderstorm: Lightning
bolts are extremely hot, with temperatures of 30,000 to 50,000 degrees F. That's
hotter than the surface of the sun. When the bolt suddenly heats the air around
it to such an extreme, the air instantly expands, sending out a vibration or
shock wave we hear as an explosion of sound. This is thunder. If you are near
the stroke of lightning you’ll hear thunder as one sharp crack. When lightning
is far away, thunder sounds more like a low rumble as the sound waves reflect
and echo off hillsides, buildings and trees. Depending on wind direction and
temperature, you may hear thunder for up to fifteen or twenty miles.
ALL IN ALL AN INCREDIBLE PHENOMENON, A SHOW OF NATURES STRENGTH
