General information on
Worldwide, more than 1,600 thunderstorms take place at the same time. These natural events manifest themselves in the form of lightning and thunder as a result of electrical discharges. The two most frequent types of thunderstorms are:
Air-mass thunderstormsAir-mass thunderstorms can be a result of temperature changes in different air masses. Heat thunderstorms in the summer are a typical example of this type of thunderstorm. In this process, heated air moves up quickly and causes large temperature differences in the clouds. In the winter, the process is exactly the opposite. Here, the thunderstorm is often triggered by polar air at high altitudes. Air-mass thunderstorms are geographically limited.
Multicell (cluster) stormsMulticell storms are a result of air displacements, e.g. due to moving cold fronts. The approaching masses of cold air force existing masses of warm air to rise. Multicell storms can reach great dimensions.
Almost all thunderstorms are accompanied by lightning and thunder as well as heavy rain, hail or strong winds that can even reach gale force. In the summer months, thunderstorms are much more frequent than in the winter.
How do thunderstorms form?
Due to the strong up and down winds in thunderclouds, sleet and ice crystals rub against each other and thus cause powerful electrical charges.
The strong up winds cause the light ice crystals to enter higher areas of the cloud and there to increasingly build up positive charges. The lower part of the cloud, which contains sleet and water droplets, is charged negatively. High potential differences result in electrical discharges, i.e. lightning.
The discharge lasts less than a few microseconds (µs). One microsecond is one millionth of a second (1/1.000.000). The channel of lightning is only a few centimeters wide.
Thunderbolts can reach a temperature of up to 30,000 degrees Celsius, which is five times the temperature of the sun’s surface. The current strength of a thunderbolt can reach more than 200,000 amperes. The voltage is estimated to be several million volts.
It is assumed that the earth is hit by lightning strikes up to 30 million times every day!
What types of lightning strikes are there?
In the majority of cases, cloud-to-cloud lightning results in discharges between clouds, also known as intra-cloud lightning. A distinction is made between positive and negative cloud-to-cloud lightning. It depends on which part of the cloud the lightning strike is originating from.
The cloud-to-ground lightning strike moves from the cloud towards the ground. Negative cloud-to-ground lightning is the most frequent form of lightning. In this process, the branches of the stepped leader move from the negatively charged area of the cloud towards the positively charged surface of the ground.
Ground-to-cloud lightning works in exactly the opposite way. Here, the stepped leader moves from the surface of the ground towards the clouds. Depending on the polarity of the surface, a distinction is made between positive and negative lightning.
Distance of the thunderstorm
It is very easy to calculate the distance between yourself and a thunderstorm. Thunder moves with the speed of light, i.e. approximately 330 meters per second. This means the thunder requires about three seconds for a distance of one kilometer.
3 seconds = 1 kilometer
Count the seconds between seeing the flash of a lightning bolt and hearing the roll of the thunder and divide the result by 3 to learn the distance of the thunderstorm in kilometers.
Example: Hearing the thunder after 12 seconds
means that the thunderstorm is approximately 4 kilometers away.
Where does the thunder come from?
Air that heats up will expand. Lightning heats up the air in the fraction of a second, just like an explosion. This creates a shock wave which breaks the sound barrier and hence is faster than the speed of sound of 1,235 km/h. When this happens, a loud rumble can be heard - the roll of thunder.
When noticing the roll of thunder, there is often a huge distance between the observer and the thunderstorm. This is a result of the echoes that develop between the clouds and the ground and overlap before the thunder can be heard.
The sound of the thunder is an indication of the distance. A deep rumbling sound can be heard when the thunder is further away. If the lightning is close, it is more like a metallic whooshing sound. Counting the seconds between seeing the flash of a lightning bolt and hearing the roll of the thunder allows you to easily figure out how far away the thunderstorm is.
The word “thunder” is derived from the Latin word “tonare” and means thudding, cracking, and grumbling.
The history of thunderstorms
At all times, lightning was always an important symbol for many peoples. It symbolized great strength and untamed energy and was often associated with the power of gods. The most powerful ancient gods were those that had the power of lightning. Lightning strikes in connection with heavy thunderstorms were considered as divine punishment and expression of the anger of Jupiter (Romans), Thor/Donar (Teutons) or Zeus (Greeks).
The fact that lightning is a natural phenomenon in the form of electrical discharge and not sent by gods was not proven by the American scientist Benjamin Franklin before 1752. At that time he assumed that lightning strikes are nothing else than grand-scale sparks. He supposedly installed corresponding systems and even performed experiments with kites.
The lightning bolts kept their secrets for a long time and it was not until the modern times that they were discovered. Until today, lightning bolts and their characteristics and effects are still subject to examination.
Discovery of the lightning conductor
1706 - 1790
The use of the word “Gewitter” in our language
Meaning: swearword, cry of irritation
“Like greased lightning”
“Like a flash”, “Like a bat out of hell”
Meaning: exclamation of astonishment
“Did it hit you?”
Meaning: to have a sudden ingenious/witty idea
Meaning: appalled, shocked, upset
“A bolt from the blue”
Meaning: surprised, unprepared
Surge protection means safety for devices and systems. In the event of a lightning strike, it prevents damages to electrical devices. There is high-quality surge protection technology for all types of applications.
There is no need to be afraid of thunderstorms.
But there are a few things to be considered to not put yourself in danger unnecessarily:
During thunderstorms, do not take a swim in open-air pools or lakes and do not take a walk in open fields or ride your bicycle! You should also take a break from outdoor sports activities like soccer, tennis or golf and seek protection in closed rooms or cars.
When there is no suitable emergency shelter, try to find a hollow. Sit down and put your feet closely together.
Stay away from trees of any kind as their height not only presents an excellent target for lightning strikes, they might also explosively burst apart when struck by lightning and thus present an additional source of risk due to flying tree branches, etc.
There are also ways to protect your home against damages caused by lightning strikes and surge voltages. Phoenix Contact offers a comprehensive product range to protect your electronic devices such as TV, computer, hifi-systems and the entire building automation.