By Amon Samwel – Art in Tanzania internship

Environmental Advocacy Program

Lightning is the brilliant electric spark discharged into the atmosphere during a thunderstorm between clouds. The flashing of light is produced by a discharge of atmospheric electricity, which results from the discharge of atmospheric electricity within a thunderstorm cloud way up into the sky. Many small bits of ice-frozen raindrops bump into each other as they move around in the air. These collisions create an electric charge and usually occur in areas mainly concentrated with metals.

Lightning can occur any time of the year, but lightning casualties are highest during summer. July is generally the month with the most lightning, and the strikes mostly happen in the afternoon. Two-thirds of all lightning casualties occur between noon and 6 p.m.

Examples of places or countries affected by lightning are all regions of the USA: Alabama, Colorado, Florida, Georgia, Missouri, and North Carolina. Florida is considered the lightning capital of the country, with more than 2000 lightning injuries over the past 50 years.

According to the U.S. Department of Health and Human Services, they have reported some categories which are:

  • Males are five times more likely than females to be struck by lightning. Around 85% of lightning fatalities are men.
  • People aged 15-34 account for almost half of all lightning strike victims (41%). The majority (89%) of lightning deaths occur among Caucasians.
  • About one-third (32%) of lightning injuries occur indoors.

Lightning is the results of thunderstorm from a charge in the normal electrical field between the surface and the atmosphere, in fair weather the surface is negatively charged, and atmosphere is positively charged. Owning to the intense friction of air within the Cumulonimbus cloud, higher charges are built up, with positive charges in the upper portion and negative charges in the lower portion. When the potential difference becomes more pronounced, discharges [lighting] occur from the cloud to the ground, from cloud to cloud or within the same cloud.

The occurrence of lighting involves different processes as explained below;

  • The sky is filled with electric charge. In calm skies they are positive + and negative[-]charged
  • Within a thunderstorm, the electric charge is distributed differently.
  • A thunderstorm is made up of ice crystals and hailstones.
  • The ice crystal has a positive charge (+), and the hailstone has a negative charge (-).
  • The hailstone is pushed to the bottom of the thunderstorms by its downdraft.
  • During thunderstorms, the Earth’s surface becomes positively charged. Because the positive charge attracts, the negative charge at the bottom of the thunderclouds wants to link up with the positive charge of the Earth’s surface.
  • Once the negative charge at the bottom of the cloud gets large enough, a flow of negative charge rushes towards the earth’s surface. This is known as the “stepped leader,”
  • The positive charge of the Earth’s surface is attracted to this stepped leader, causing a flow of positive charge to move into the air when the stepped leader and the positive charge from the Earth meet a storm.

THUNDERSTORM

This term refers to violent convective storms accompanied by thunder and lightning, usually localized and lived. Vertical air motion, considerable humidity, and instability combine to create towering cumulonimbus clouds. It frequently occurs with storms, such as hurricanes, tornadoes, and cold fronts in mid-latitude cyclones, as well as orographic lifting.

Types of Thunderstorm

  • Orographic thunderstorms are caused by air forced up by a mountain or hillside.  
  • Air mass thunderstorms result from localized convection in an unstable air mass.
  • Frontal thunderstorms – occur along the boundaries of weather fronts (e.g. cold fronts).

 Characteristics of thunderstorms

  • Thunderstorms last for a short duration, seldom two hours
  • It consists of a down and updraft of air with electric charges and thunder.
  • It is associated with heavy precipitation or hail.
  • It is usually destructive as it can kill people and animals and destroy property.

Condition leading to the formation of thunderstorms

  • There should be a prevalence of atmospheric instability such that air updrafts can set off.
  • There should be ample atmospheric moisture for condensation to occur and maintain a storm.
  • There should be some agent to initiate convection, such as uplift over a hill or mountain.

STAGES OF THUNDERSTORM

The thunderstorm has three main stages: the cumulus stage, the mature stage, and the dissipating stage.

The cumulus stage is the first stage of the thunderstorm. It is characterised by updrafts that form the cloud formations required for cumulonimbus clouds. The continuous strong updrafts prevent precipitation from falling. This occurs when super-cooled water droplets and ice crystals coalesce, and the fall initiates a downdraft.

The mature stage: Once the storm has developed, it will enter the mature stage. Both updrafts and downdrafts dominate this stage and is the most dangerous stage. Falling precipitation is an indicator that the storm has reached the mature stage. Lighting, severe turbulence, and hail can all be encountered during this time. It is also most active at this time.

The dissipating stage is the last. Once the updrafts begin to die out, the storm is dominated by downdrafts and enters the dissipating stage. This indicates that the thunderstorm is dissipating. In this stage, downdrafts dominate, and turbulence ceases.

          THUNDERSTORM FORMATION

The action of warm air rising and cool air sinking plays a key role in the formation of severe thunderstorms. If the warm surface air is forced to rise because it is less dense than the surrounding air, this will occur. This also happens when cold air and warm air meet. The warm air is forced to rise because it is less dense, and the cold air sinks, so the warm air in the atmosphere will settle and condense slowly. 

Two of the most important ingredients for thunderstorm formation are instability and moisture. Usually, unstable air causes a disturbance in the atmosphere. Additionally, the humidity caused by warm air cooling in the atmosphere may result in precipitation—even the presence of moisture and unstable air can lead to thunderstorm formation.

The uplifting of warm and humid air forms thunderstorms. The air that is formed is forced to move upwards because it is denser. Typically, it becomes cooler and mixes humid air with water droplets, leading to precipitation or rain.

When humid air is lifted, it cools, and the moisture in the air condenses to form a cloud. So, after the warm air rises upward to the atmosphere, it usually meets the moist air or moisture that forces it to cool and become humid. This situation leads to the formation of the clouds known as cumulonimbus. Usually, these clouds are formed after the mixing of warm air containing both positive and negative charges, which, when they come into contact, lead to the occurrence of a thunderstorm.

Upon further uplifting, the clouds will extend higher. Water droplets in the clouds continue to grow in size as the clouds extend further upward, and ice crystals may form due to low temperatures. This means that the denser air rising higher in the atmosphere forces and causes the clouds known as cumulonimbus to form higher in the atmosphere. Additionally, the cool temperature in the higher atmosphere caused the water droplets to freeze into ice crystals, which were essential for the cloud’s formation.

Finally, thunderstorms are produced by the cumulonimbus cloud. Typically, cumulonimbus clouds contain two different charges: a positive charge known as a crystal and a negative charge known as hail. Once these come together, they produce a steeper light known as lightning, accompanied by a loud and powerful sound, referred to as thunder.

What should we do during the lightning and thunderstorm period?

In summary;

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