Lightning: How does it form?
The simple definition for lightning formation is when a giant spark of electricity occurs in the atmosphere between the clouds, the air, or the ground. The technical definition for lightning formation is when a series of electrical processes take place and a charge is transferred along a discharge channel between electrical charges of the opposite sign. Always remember that lightning is the
result of build-up between two opposite charges. An example of this can be seen when you rub a balloon against your clothes and then it sticks to the wall. When you rub a balloon against your clothes the balloon will have an excess amount of electrons, otherwise known as negative charges, on the surface of the balloon. When this occurs the wall will become more positively charged. When the two objects collide, the balloon will stick to the wall because opposites attract, meaning that positive to negative charges have connected with each other. This is similar to how lightning works.
So how exactly do we get lightning? Thunderstorms carry both negative and positive charges. There are two theories to how this works. One being the convection theory and the other being the precipitation theory. The convection theory is the idea that a Thunderstorm’s updraft carries positive charges found near the ground upwards into the updraft, while a Thunderstorm’s downdraft
carries negative charges downward. The precipitation theory is the idea that the Thunderstorm’s updraft causes a collision between graupel and smaller ice crystals. Heavier particles create negative charges, while lighter particles create positive charges. This results in the charges separating. When the charges separate an electrical field is created. However, with this in mind, the air around us is a great insulator for electricity.
This means that electricity is unable to flow freely through the air. Due to this, the electrical build-up has to be pretty significant before lightning can overcome the insulated air. When this electrical build-up overcomes the insulated air we get what is known as lightning. There are four different types of lightning. That being Cloud-to-ground, In-cloud, Cloud-to-cloud, and Cloud-to-air.
Over 20% of all lightning strikes are Cloud-to-ground. Because of this, we will focus on this type of lightning formation. For Cloud-to-ground lightning strikes to occur they need a collection of charges at the base of a storm. This causes positive charges to accumulate along the ground. As the electrical field strengthens, negative charges move from the base of the storm to the ground. This is what we call a stepped leader. During this process, positive charges will also rise from the ground into the air towards the stepped leader. This is called a streamer. When both the stepped leader and streamer connect
lightning occurs. On average, lightning kills around 31 people yearly, while injuring around 279 people yearly. 90% of those who experience a direct lightning strike survive. The likelihood of you being struck by lightning during your entire time on earth is 1 to 13,000. From 2006 to 2015, the United States saw around 313 fatalities related to lightning strikes with Florida seeing the highest amount with 47 fatalities. 64% of all fatalities occurred while people were relaxing, with only 15% of fatalities occurring while people were doing their daily routines.
Since 1940, we have seen a steady decline in fatalities related to lightning as more information related to protecting yourself during a Thunderstorm has become available. With all of this in mind, you should take necessary precautions during Thunderstorms to mitigate being struck by lightning.
There are 5 different ways that you can come into contact with lightning. This being a direct lightning strike to your body, which is seen in 5% of all cases, contact voltage, which is seen in 5% of all cases, an upward streamer, which is seen in 15% of all cases, side flashes, which is seen in 35% of all cases, and ground current, which is seen in 50% of all cases. Since ground current contacts are
the most common, we will focus on how to mitigate this threat during a Thunderstorm. First and foremost, if you see lightning go indoors and stay away from electrical equipment inside the structure. Wait 30 minutes before going back outside as lightning can reach as far out as 15 miles from the main storm. If you are outside with no structures in view, avoid elevated terrain and trees. Trees are a great electrical conductor because they have sap and water components. When you reach level ground, keep your head as low as possible without laying down. Surface current could travel through your body. Make sure to crouch as low as possible to minimize the contact area you have with the ground.
About the writer: Michael Thornton is a recent Emergency Management graduate at Rose State College with a certificate in Emergency Planning & Preparedness. He has a background in meteorological studies and is a NOAA Weather-Ready Nation ambassador who works with individuals, businesses, and governments to create more disaster-resilient communities.