Science

What Causes Lightning? Everything Explained

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Lightning is a discharge of electricity created by imbalances between storm clouds and the earth or inside the clouds themselves. The majority of lightning strikes within clouds.

What Causes Lightning?

In the United States, lightning is one of the most common weather-related causes of death and injury. Most people are unaware that they can be struck by lightning even if the thunderstorm’s centre is 10 miles (16 kilometres) distant and the sky is clear.

What Causes Lightning
Image: Unsplash

Lightning is merely an electrical discharge – a “spark” or “flash” as charged regions in the atmosphere briefly equalize themselves through this discharge. It is a beautiful yet deadly natural occurrence.

But what causes the atmosphere’s charged regions to form in the first place? In a nutshell, it’s when hail particles collide with smaller ice particles in a thunderstorm, causing electrons to flow from one to the other. During a collision, the smaller ice particles lose an electron and gain a positive charge, whereas the hail gains an electron and gains a negative charge.

The hail falls towards the bottom of the cloud, while the smaller ice particles concentrate at the top, due to their varied weights and interactions with the storm updraft, giving the two parts of the cloud a negative and positive charge, respectively.

Once a sufficient charge difference has built up, lightning occurs as a fast discharge of electricity to equalize the charged regions.

The polarity of a lightning strike can have an impact on how it spreads and branches in space and time. Different ‘types’ of lightning are defined by this, as well as their starting and finishing points and movement directions. Lightning can strike the ground, the air, or within clouds, however, cloud flashes are generally 5 to 10 times more common than ground flashes.

What are the different types of Lightening?

The different types of lightning are described below

1. Cloud-to-Ground (CG) Lightning

In CG lightning, a negative charge channel termed a stepped leader zigzags downward in a “forked” pattern, hence the name “forked lightning.” This stepped leader is invisible to the naked eye and descends in a nanosecond.

As it approaches the ground, the negatively charged stepped leader is drawn to a positive charge streamer that extends upward, usually through a tall object such as a tree, house, or telephone pole.

A tremendous electrical current flows when the oppositely charged leader and streamer join (which is why it’s not a good idea to stand under a tall item during a thunderstorm!). A return stroke (the very brilliant visible flash that we see as lightning) travels back into the cloud at around 60,000 miles per second, with one flash containing up to 20 return strokes.

2. Negative Cloud-to-Ground Lightning (-CG)

A downward-moving, negatively-charged stepped leader is followed by an upward-travelling return stroke in the most common CG flashes. This flash has the net effect of lowering the negative charge from the cloud to the ground. The unique downward branching of negative CG lightning strikes can be observed.

3. Positive Cloud-to-Ground Lightning (+CG)

There are times when lightning strikes negatively charged particles on the ground, and positive charges in the cloud’s upper parts overcome negative charges in the cloud’s bottom. This is when you get a positive lightning strike.

Positive lightning strikes are less common than negative lightning strikes, but they are more destructive. They must traverse longer distances, implying that they are also stronger. They also bring a lot more thunder with them.

4. Cloud-to-Air (CA) Lightning

This is a discharge that jumps from a cloud into clear air and quickly ends — in fact, CG lightning contains CA lightning via branches that stretch from the main channel into mid-air. Long, bright lightning channels extend from the sides of cumulonimbus clouds, creating the most stunning instances.

5. Ground-to-Cloud (GC) Lightning

An upward-moving leader originating from a ground object initiates a discharge between cloud and ground. On towering structures and skyscrapers, ground-to-cloud lightning strikes, also known as upward-moving lightning, are prevalent. The polarity of GC lightning can either be positive or negative.

6. Intracloud (IC) Lightning

This is the most common type of emission which refers to lightning embedded within a single storm cloud that jumps between multiple charge zones in the cloud.

Clouds illuminated by a lightning discharge are referred to as sheet lightning when the actual lightning channel is either within the clouds or below the horizon (i.e., not visible to the observer). Usually connected with IC lightning, Sheet Lightning is just any lightning that is hidden by clouds or topography except the flash of light it creates.

A similar term, heat lightning is a kind of lightning that is too far for the thunder to be heard. It is named for the fact that it is frequently seen during hot summer evenings when thunderstorms are common.

7. Cloud-to-Cloud (CC) Lightning

Lightning can travel from one cloud to another; however, this is uncommon. Long, horizontal moving lights are commonly seen on the underside of stratiform clouds and are known as spider lightning. (Not to be confused with lightning that occurs within a single cloud.)

The impact of Lightning Strike

Lightning is not only spectacular, but it is also hazardous. Every year, over 2,000 people are killed by lightning around the world.

Hundreds more survive but suffer from long-term problems such as memory loss, dizziness, weakness, numbness, and other life-altering diseases. Strikes can result in cardiac arrest and severe burns, although nine out of ten victims survive.

In a lifetime, the average American has a 1 in 5,000 chance of being hit by lightning.

The tremendous heat of lightning will evaporate the water inside a tree, causing steam that could blow the tree apart. Cars are safe havens against lightning, but not for the reason most people think. Tires conduct current, as do metal frames, which carry a charge to the ground in a harmless manner.

Many homes are grounded by rods and other devices that transfer the electricity from a lightning bolt harmlessly to the earth. Plumbing, gutters, and other components can potentially unintentionally ground a home.

Conductive electricity can shock people who touch flowing water or use a landline phone, even if the building is grounded.

When you hear thunder, the greatest thing you can do is go inside. When the thunderclaps, go indoors! Do not seek refuge under a tree. Even if lightning strikes the tree, you could be electrocuted. If you can, seek shelter; if you can’t, stay as low to the ground as possible until 30 minutes following the final thunderclap.

What Happens When Lightning Hits the Water?

If you’re swimming in the water and a rainstorm appears to be approaching, you have two options: get out and find some cover, or dive deeper. According to the US National Weather Service, a typical lightning flash has 300 million volts and 30,000 amps, which is deadly.

Rather than spreading vertically, the majority of the electrical discharge spreads horizontally. This is bad news for folks who like to float or swim near the surface of the water.

The lightning current will most likely spread across the ground. Various estimations have been made for the distance it would dissipate to the point that it would no longer be dangerous to a human.

Fish are safer than human swimmers because they move about at deeper depths. People that protrude heads or even complete bodies, like surfers or paddleboarders, maybe in more danger. You might become a target during a storm if you’re out on the open sea, comparable to standing in an open field. Lightning chooses the path with the least amount of resistance.

According to Nasa research, lightning bolts are more likely to strike land than sea, and deep ocean strikes are uncommon. The waters along the coast are more frequently affected. Seasonal risks are also different.

You should expect more strikes closer to land since that’s where the most heat, updrafts, and storms build-up, especially in the summer. That may alter in the winter, but it’s evident that there are fewer people in the sea at that time.

Lightning conductors can be installed on boats to send the charge into the sea while avoiding the most vulnerable locations, such as passenger spaces and equipment rooms.

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