Understand how lightning is formed within a thunderstorm and the different stages involved in development. Learn about different types of lightning in thunderstorms and some not associated with storms.
What Is Lightning?
Have you ever seen lightning, then counted until you heard the thunder to see how far away a storm is? This is not just a game for children to play. It’s actually a very real way to estimate the distance. Lightning travels at the speed of light, but thunder travels at the much slower speed of sound. So, a five-second delay between lightning and thunder means that a storm is about one mile away.
This is actually very hand information, because lightning is quite a danger to humans. There are over 8.5 million lightning bolts a day that are 100,000 times the power we use in our houses, so it is a very real danger when thunderstorms are around.But what exactly is lightning and how is it formed? Lightning is a very quick electrical discharge that occurs between a cloud and the ground, between two clouds, or within a cloud. It can be seen as a bright flash and is followed by the sound of thunder. Lightning is usually associated with thunderstorms.
To understand how lightning forms in a storm, you must first understand how a thunderstorm develops.
A thunderstorm is a localized storm that has lightning and thunder and is short-lived. In the beginning of a storm’s development, air rises in updrafts above the freezing level in the atmosphere. The water droplets in the cloud freeze, get heavier, and begin to fall, creating a downdraft. The droplets leave the bottom of the storm as heavy precipitation. This is the part of the storm when severe weather can occur.
During this stage, both updrafts and downdrafts occur, which are what start the development of lightning. So this stage is when lightning and thunder may occur. Eventually, the updraft stops and only the downdraft remains. The storm weakens and finally ends.
Lightning is a bit of a mystery because the exact way electricity develops in a storm is not very well understood by scientists.
But what we do know is that the way a thunderstorm develops causes electrical charges to be separated. This is known as charge separation. The updraft of air in a storm carries positively charged water droplets with it. The downdraft of precipitation carries negatively charged water drops downward to the bottom of the cloud.
The negative charges on the bottom attract positive charges on Earth’s surface, directly below the thunderstorm. The difference in charges on the bottom of the cloud and on the ground grow stronger and stronger until there must finally be a release. A finger of negative electricity, known as a leader, shoots down from the cloud searching for a way to meet the positive charges on the ground. Usually, the leader can’t make a connection the first time, so this happens repeatedly until a finger of positive electricity shoots up from the ground to meet the leader. Once this occurs, a conduit or tunnel for electricity to pass from cloud to the ground opens up.
This is when the lightning stroke occurs and a surge of electricity strikes downward and is visible for us to see. This may happen several times in rapid succession until all negative charges are gone from the bottom of the cloud. These are known as flashes and they happen so quickly that we can’t see each individual stroke. Instead, the lightning appears to flicker.
Categories and Types of Lightning
The kind of lightning just discussed is called cloud-to-ground. It only makes up about 20% of lightning in a storm, but it is the most destructive.
Some other categories of lightning that occur within a storm are intra-cloud lightning within the same cloud and cloud-to-cloud, between two clouds. The separation of the charges in the same cloud or different clouds forms lightning and storms in the same way as cloud-to-ground, only the discharge doesn’t go to the ground.There are also other more unique types of lightning that occur in storms. Forked lightning happens with the leader breaks into several branches, making the lightning look like a fork. Sheet lightning is a bolt within a cloud that can’t be seen by itself and instead lights up the whole cloud. Heat lightning happens when the cloud is so far away that we can only see a flash and not see a bolt or hear thunder.
Ribbon lightning forms when strong wind accompanies the storm, causing a very wide lightning bolt to form. Types of lightning that occur in very high altitudes at the top of storms are called sprites and they look like giant red jellyfish. Also, blue jets form when charged particles are thrown from the top of a storm and they look like fountains.Many other types of lightning also occur and not all are caused by the formation of a thunderstorm, but all are caused by the same basic mechanism as lightning in a thunderstorm.
For example, St. Elmo’s fire is a type of lightning. It occurs around ship masts or airplane wings. The wing of a plane may become negatively charged. If it passes through a positively charged cloud and the charges are strong enough, a discharge of electricity can occur. It appears as a blue glow and has a buzzing sound.
Ball lightning appears as a spherical electrically charged ball of air about the size of a basketball, but its formation is not completely understood. Air discharge lightning develops in very dry climates. Lightning can even occur in a volcanic eruption. The different sized particles of ash in the eruption, accompanied by friction, cause positive and negative charges to develop, which can lead to lightning.
Lightning is a strong and fast discharge of electricity from a thunderstorm to the ground or within the cloud. A thunderstorm is a localized storm that has lightning and thunder and is short-lived, and it develops in stages.
During a thunderstorm, negative charges are brought to the bottom of the cloud and this is known as charge separation, which leads to lightning. As lightning forms, a finger of negative charges shoots down from the cloud, known as a leader. The leader opens up a tunnel from the cloud to the ground and a lightning stroke occurs, where a surge of electricity strikes downward that is visible to us. This may happen several times in rapid succession and appears to us as flashes or flickering. There are specific categories of lightning associated with storms:
- blue jets
Also, there are many other types of lightning that are not associated with storms:
- St. Elmo’s fire
- ball lightning
- air discharge lightning