How is hail formed and what is its principle?

The water on the local surface is evaporated by the sun, and then rises into the air, and a large amount of water vapor condenses into clouds. At this time, the relative humidity is 100%, and it will liquefy when it meets cold air. Taking the dust in the air as the condensation nucleus, raindrops (tropical rain) or ice crystals (mid-latitude rain) are formed, which are getting bigger and bigger. When the temperature drops to a certain extent, the water vapor in the air is supersaturated.

So it rained. If you encounter cold air without condensation nuclei, water vapor will condense into ice or snow, which is snow. If the temperature drops sharply, it will form a bigger ice mass, which is hail.

Extended data

From the perspective of regional natural disaster system theory, hail disaster is a disaster formed by the interaction of hail disaster-prone environment, disaster-causing factors and affected bodies. Hail and rainstorm are both strong convective weather processes, often accompanied by terrain constraints, so heavy rain and terrain have become the main factors that breed hail disasters.

The intensity and regional differentiation of hail disaster first depend on the characteristics of hail. Judging from the regional distribution of hail in China, the hail high-value area presents the characteristics of one area and two zones: the first area refers to the hail-prone area on the Qinghai-Tibet Plateau; These two belts refer to the southern hail belt and the northern hail belt. The former is mainly distributed in the Yunnan-Guizhou Plateau at an altitude of1000 ~ 2000m, extending eastward to the junction of Xiangxi and Sichuan and Hubei, while the latter is connected with the Inner Mongolia Plateau from the northern part of the Qinghai-Tibet Plateau via Qilian Mountain and Liupanshan Mountain.

Compared with the regional differentiation of hail disasters (hail) in China, the regional differentiation of hail disasters has an obvious trend of expanding eastward, southward and westward, with the following three obvious differences. First, from a large area, the hail disaster-prone area and the highest frequency area are completely different. The former is densely populated in the middle and lower reaches of North China-Yangtze River, while the latter is sparsely populated in Qinghai-Tibet Plateau.

Secondly, there are two hail disaster-prone areas, but the former is located further east than the latter, especially in the east, forming a north-south hail disaster area. Thirdly, the hail-prone areas are all located in the hail-prone areas, which are distributed in a lump.

It can be seen that the regional differentiation of hail disasters in China is deeply influenced by the scope of human activities, showing the spatial pattern characteristics of more central and eastern regions and less western regions. From the comparison of regional hail and hail disaster spatial differentiation, it is only a natural process, and the change of the nature of the affected body makes the hail disaster high-value area not necessarily a disaster high-value area.

Although the affected body is not the direct driving force of the disaster, it makes the hail disaster relatively expand or shrink.

Baidu Encyclopedia _ Hail (Weather Phenomenon)