Analysis on the causes of thunderstorm

In summer, direct sunlight makes the water on the ground evaporate faster than in winter, spring and autumn. The air close to the ground can receive more water vapor because of its high temperature, which leads to the decrease of air density, the lightening of air and the rising of the lightened air. With the increase of altitude, the temperature will gradually drop (0.6 degrees per 100 meters), and the air will gradually cool down. When the air is cool, it can't hold the original abundant water vapor. Some water vapor will condense into small water droplets, and the sky will be cloudy. So, why don't these little drops fall down quickly and turn into rain? This is because the water droplets are too small, and the rising hot air lifts them up and pushes the suspended water droplets higher and higher. Clouds are getting bigger and higher. This kind of cloud is called cumulonimbus cloud in meteorology, and its bottom is about 1000 meters above the ground.

When the small water droplets in the cumulonimbus cloud constantly collide and merge into larger water droplets, they begin to fall, while the hot air rising from the ground keeps rushing upwards, and the friction between them is charged. The rising airflow is positively charged and the falling water droplets are negatively charged. With the passage of time, a large number of positive charges have accumulated at the top of cumulonimbus clouds, while many negative charges have accumulated at the bottom. Due to the negative charge at the bottom of cumulonimbus clouds, the ground is also positively charged.

The water droplets in the cloud merge and increase until the rising hot air can't hold it, and then fall straight from the cloud. The hot air at the lower level was drenched by rain and suddenly became cold. Instead of rushing up, it turned to the ground. At this point, the charge in the air began to discharge, accompanied by thunderous thunder. Because lightning travels at a speed of 300,000 km/s and thunder travels at a speed of 33 1 m/s, people first see lightning and then hear thunder. Sometimes the thunder drags on for a long time, which is caused by the thunder reflected back and forth from clouds, peaks and ground.