Why are there thunderstorms?

Thunderstorm is a bad weather phenomenon caused by extremely unstable air. It often carries strong winds, heavy rains, lightning, lightning strikes, and even hail or tornadoes, so it can often cause disasters.

Thunderstorms can be roughly divided into two types, one is frontal thunderstorm and the other is air mass thunderstorm. It starts to increase in March every year and reaches its peak in July and August. Thunderstorms from March to June are mostly frontal thunderstorms, and from July to September are mostly air mass thunderstorms.

The birth of Thunderstorm;

The life of a single thunderstorm cloud (cumulonimbus cloud) is very short, usually only one or two hours, and the period can be divided into three stages: development stage, maturity stage and dissipation stage (Figure 1 1). In the first stage, an updraft is formed, sending warm and humid air into the air. When the rising air gets cold, the water vapor in it begins to condense and turn into clouds. As the airflow continues to rise, the clouds will accumulate higher and higher and go straight to the colder altitude. The water droplets in the clouds are getting bigger and heavier. Some are frozen into snow or hail, and some raindrops are getting bigger and bigger until they can no longer support the updraft. Downward flow, which comes when it rains or before it rains, will cause cool gusts, which means a thunderstorm is coming.

Turbulent airflow will generate static electricity in thunderstorm clouds, and the reason is not completely clear at present, partly because of the friction and decomposition of water droplets. The positive charge is at the top of the cloud, and the negative charge attracts the positive charge on the ground below. As an insulator between the cloud and the ground, air prevents bipolar charges from finding a balanced current in a short time. Lightning occurs when the voltage formed by the charges at the two poles is large enough to break through the insulated air. In some thunderstorms, the electrostatic voltage can reach several million volts. Lightning will happen in a cloud, or between two clouds, or from top to bottom, or from bottom to top between clouds and the ground. Worldwide, the average number of lightning strikes the earth is about 100 times per second.

Most lightning strikes twice in a row. The first lightning strike is called "pilot lightning strike", which is an invisible charged air.

Lead, straight down to the ground. This charged air is like a wire, which establishes a guide for the second firing current. At the moment when the leader approached the ground, a "counterattack" current jumped up along the guide road, followed by visible lightning and audible thunder, which was the second blow.

This backflow has a power core, surrounded by a circle of hot air like a tube, which will glow, expand and explode, that is, thunder. Lightning was seen almost immediately when the explosion occurred, but thunder always arrived later, because the speed of sound (about 340 meters per second) was slower than the speed of light (300,000 kilometers per second).

Lightning makes the unbalanced potential in thunderstorm clouds tend to balance. Similarly, the downward flow caused by rain makes the temperature of hot air and cold air tend to be equal. When the ground cools down, the hot air no longer rises, so the weather often clears up quickly after a short thunderstorm in summer. References:

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