Hail is also called "hail", commonly known as hail and "bully", and it is called "Lengzi" in some areas (such as Xuzhou and Gansu), which is the most common in summer or at the turn of spring and summer. It is some ice particles as small as mung beans and soybeans and as big as chestnuts and eggs.

The water on the local surface is evaporated by sunlight and then rises into the air. A lot of water vapor condenses into clouds. The relative humidity at this time is 100%. When it meets cold air, it will liquefy, and the dust in the air will form raindrops (tropical rain) or ice crystals (mid-latitude rain), and it will become bigger and bigger. When the temperature drops to a certain extent, the water vapor in the air will be supersaturated, so it will rain.

Except Guangdong, Hunan, Hubei, Fujian, Jiangxi and other places, our country suffers from hail disasters in different degrees every year. Especially in the mountainous and hilly areas in the north, the terrain is complex, the weather is changeable and there are many hail, which is very harmful to agriculture. Heavy hail destroyed crops and houses, injured people and killed livestock. Extraordinary hail is bigger than grapefruit, which will kill people, destroy a large area of farmland and trees, and destroy buildings and vehicles. It has powerful lethality. Hail disaster is one of the most serious disasters in China.

Formation condition

In the hail cloud, the strong updraft carries many large and small water droplets and ice crystals, some of which fuse with ice crystals and freeze into larger ice particles. These particles and supercooled water droplets are transported by the updraft to the water content accumulation area, which can become the hail core. The initial growth core of these hailstones has good growth conditions in the water content accumulation area.

After the hail enters the growth area with the updraft, it collides with supercooled water droplets in the area with large water volume and low temperature, and grows into a transparent ice layer, and then enters the low temperature area with small water volume, where it is mainly composed of ice crystals, snowflakes and a small amount of supercooled water droplets, and the hail adheres to them and freezes to form an opaque ice layer.

At this time, the hail has grown up and the updraft there is weak. When it can't support the growing hail, the hail will fall in the updraft and continue to grow through the fusion of ice crystals, snowflakes and water droplets in autumn. When it falls to a higher temperature area, the supercooled water droplets that hit it will form a transparent ice layer.

At this time, if it falls into another stronger updraft area, the hail will rise again and repeat the above growth process. In this way, hail grows in transparent layer and opaque layer; Due to the differences in growth time and water content, the thickness and other characteristics of each layer are also different. Finally, when the updraft couldn't support the hail, it fell from the clouds and became the hail we saw. ?

Extended data

Hail suppression measures

China is one of the countries with early artificial hail suppression. Due to the serious hail disaster in China, the hail suppression work has received the attention and support of the government. Many provinces have established long-term experimental fields, conducted rigorous experiments and achieved many valuable scientific research results. Artificial hail suppression is carried out to make it develop in the direction people expect and achieve the purpose of disaster reduction. Commonly used methods are:

1, use rockets, anti-aircraft guns or planes to directly send catalysts such as silver iodide, lead iodide and dry ice to the cloud;

2. On the ground, silver iodide, lead iodide, dry ice and other catalysts are sent into the free atmosphere before the formation of cumulonimbus clouds, so that the hail embryo of these substances increases in the hail cloud and the hail becomes smaller;

3. Launching rockets and anti-aircraft guns at hail clouds on the ground, or launching rockets and bombs at hail clouds on airplanes, so as to disrupt the water transport to hail clouds;

4. Sprinkle condensation nuclei on warm clouds with rockets and anti-aircraft guns to make the clouds form precipitation, so as to reduce the water in the clouds; In the cold cloud, some ice cores are scattered to inhibit the growth of hail embryos.

Baidu Encyclopedia-Hail (Weather Phenomenon)

Baidu Encyclopedia-Hail (Natural Disaster)