What are the forms of precipitation?

Precipitation can be divided into the following types according to its shape:

Rain: Droplet-like liquid precipitation. If there are conditions in the water cloud (cloud body composed of liquid water droplets) to make the cloud droplets grow into raindrops, and the raindrops have a certain speed of falling, then it is rain or Mao Mao rain that falls. Ice crystals or snowflakes falling from ice cloud (clouds composed of ice crystals) and mixed clouds (clouds composed of water droplets and ice crystals) fall into the gas layer above 0℃, and also fall to the ground as raindrops after melting.

Rain is divided into light rain, moderate rain, heavy rain, heavy rain and heavy rain according to its intensity. Long-term continuous rainfall, heavy rain and heavy rain cause a lot of precipitation in a short time, resulting in huge surface runoff, flooding low-lying areas, or flooding rivers, flooding large areas of land, causing crops to be flooded, agricultural production to fail, and bringing huge losses to the country. This is so-called flood weather. In China, there is often a situation of "waterlogging in the south and drought in the north" or "waterlogging in the north and drought in the south". If the Meiyu period in Central China lasts for a long time and there is much precipitation, the Yangtze River basin will be flooded, while the North China and Northeast China will be dry and short of water. The best measure to combat drought and waterlogging is to vigorously build water conservancy projects. Such as the construction of large, medium and small reservoirs, soil and water conservation forests and farmland shelterbelts. Many areas in China have made remarkable achievements in this regard.

Snow: It is all kinds of solid precipitation composed of ice crystals. Snowflakes have many shapes, such as star, cylinder and flake. But the basic shape is hexagonal. Why are snowflakes mostly hexagonal and have so many patterns? This is because ice molecules are mostly hexagonal, so snowflakes are mostly hexagonal. The diversity of snowflake shapes is closely related to the water vapor conditions when it is formed. Because the saturated water vapor pressure on the surface, edge and corner of hexagonal ice crystals is different, the corner is the largest, the edge is the second and the surface is the smallest. When the sudden vapor pressure is only greater than the plane saturated vapor pressure, the vapor only condenses on the surface, forming columnar snowflakes; When the sudden water vapor pressure is greater than the saturated water vapor pressure at the edge, water vapor condenses on the edge and surface, forming flake snowflakes; When the sudden water vapor pressure is greater than the saturated water vapor pressure on the corner, water vapor condenses on the edges, surfaces and corners, forming dendritic or star-shaped snowflakes.

According to the intensity of precipitation, snow can be divided into light snow, medium snow and heavy snow. Sleet is melted snow or precipitation in which snow and rain fall at the same time.

Hail: it is ice cubes with different surface shapes, with a diameter of 5~50 mm, and some are larger. The center of the hail is an opaque ice core, surrounded by several layers of transparent and opaque ice shells. Hail weather is a serious agricultural disaster. Although it appeared in a small area for a short time, it was fierce and strong, often accompanied by violent storms, and hail fell on the stems, leaves and fruits of crops, causing great mechanical damage. Severe hail will cause devastating damage to crops at flowering and mature stages, ranging from reduced production to no grain harvest.

Hail mostly occurs in late spring and early summer when the four seasons alternate. At present, there are two methods of artificial hail suppression, namely catalytic method and explosion method. The principle of catalytic method is the same as that of artificial rainfall. A large number of silver iodide particles or salt powder are added to the hail cloud, which destroys the formation process of hail and makes the water in the cloud disperse and condense into small hail or water droplets to avoid serious harm. Many places in China have gained some experience and achievements in artificial hail suppression.

Artificial rainfall: With the development of agricultural production, how to effectively artificially influence local weather and prevent the occurrence of unfavorable agricultural weather has become an urgent problem to be solved. During the period of 1958, China successfully conducted a large-scale artificial precipitation enhancement experiment with dry ice as catalyst in Jilin Province, and since then, the artificial precipitation enhancement experiment has been widely carried out throughout the country. In recent years, due to the rapid development of science and technology, new technologies have been continuously introduced, and great progress has been made in the macro-and micro-structure detection of clouds, fog and precipitation, as well as catalytic methods and technologies, and effect testing.

There are two main principles of artificial rainfall. On the one hand, the cloud is composed of tiny water droplets, and the volume of cloud droplets increases by 654.38+0.0000 times to become raindrops of ordinary size. In order to make cloud droplets grow up quickly, it is necessary to form some ice crystals or large cloud droplets in the cloud first, but this does not often happen in nature, so in many cases there are clouds without precipitation. Therefore, it is necessary to sow the catalyst into the cloud artificially, so that some ice crystals or large cloud droplets are produced in the cloud, and the cloud droplets quickly grow into raindrops and land. There are many kinds of catalysts used. Dry ice or silver iodide is often used to "sow" clouds below 0℃, which is called Leng Yun catalysis. For clouds above 0℃, salt powder or calcium chloride is often used to introduce large cloud droplets, which is called warm cloud catalysis. On the other hand, the precipitation in the cloud is generally proportional to the volume of the cloud, so a large number of supercooled water droplets on the upper part of the cloud are seeded and crystallized, and at the same time the potential is released, which leads to the development of updraft in the cloud, increasing the volume and life of the cloud, thus increasing the precipitation of the cloud. At present, although a large number of artificial precipitation enhancement experiments have been carried out on the ground, aircraft seeding catalyst is still the main way of artificial precipitation enhancement experiments.

Artificial rainfall has played a certain role in alleviating drought in some areas and contributed to agricultural production. However, the best measure to combat drought is to build water conservancy and build soil and water conservation forests and farmland protection forests.