Specific methods of artificial rainfall

Artificial rainfall (artificial rainfall)

1, how to make artificial rainfall

Dropping water from the sky to the ground to prevent it from running in vain is artificial rainfall, but a more scientific name is artificial precipitation enhancement, which has two methods: aerial operation and ground operation.

Aerial work is to spread catalyst in the clouds of the plane. Ground combat is to launch from the ground with anti-aircraft guns and rockets. The shell exploded in the cloud, burning the silver iodide in the shell into smoke and scattering it in the cloud. After the rocket reached the height in the cloud, the silver iodide began to ignite, and along with the rocket's flight, there was smoke all the way. Aircraft operation generally chooses stable weather to ensure safety. General anti-aircraft guns and rockets are widely used.

2. Artificial rainfall conditions

Artificial rainfall should have sufficient conditions. Generally, natural precipitation requires not only certain macro weather conditions, but also microphysical conditions in the cloud, such as: there must be large water droplets in the warm cloud above 0℃; There should be ice crystals in Leng Yun below 0℃. Without this condition, no matter how good the weather is or how good the clouds are, it won't rain. But in natural circumstances, this microphysical condition is sometimes not available; Sometimes, but not enough. The former will not produce precipitation at all; The latter has less rainfall. At this time, if artificial ice cores are planted artificially in the cloud, the process of ice water transformation will occur in the cloud, and then with the help of the natural collision process of water droplets, rainfall can be generated or increased. For example, the catalyst in the cloud plays a role, just like salted tofu, which increases the intensity of precipitation that would not have been generated.

3. Artificial rainfall is harmless to people.

The principle of artificial rainfall is to make the water droplets in cumulonimbus clouds bigger and fall down. Anti-aircraft gun artificial rainfall is to shoot a shell containing silver iodide with a large number of cumulonimbus clouds at an altitude of 4000-5000 meters. Silver iodide diffuses in the air and becomes the condensation nucleus of water droplets in the cloud, and the water droplets quickly condense around it to a certain volume and then land. When silver iodide is transported to high altitude by artillery shells, it will spread into small particles that are difficult to distinguish with the naked eye.

Compared with the huge water drops, the silver iodide rising into the sky is just a drop in the ocean. Too much will not only increase rainfall, but will "scare away" cumulonimbus clouds. Therefore, under such a disparity, people will never feel the existence of silver iodide.

In addition, the shrapnel of the shell will become less than 30 grams after high-altitude explosion, or even only two or three grams of debris will fall to the ground, and the falling areas are all no-man's land that has been tested and measured before, which will not cause harm to the human body. At the same time, artificial rainfall has a history and mature technology, so people don't have to worry about artificial rainfall.

According to the principle of cloud and precipitation physics, by sowing catalysts (salt powder, dry ice or silver iodide, etc. ) When entering the cloud, cloud droplets or ice crystals will increase to a certain extent and fall to the ground to form precipitation. Also known as artificial precipitation enhancement. Its principle is that by sowing catalyst, the microphysical process of clouds is affected, so that clouds that cannot naturally precipitation under certain conditions are stimulated to produce precipitation; It can also create clouds that can naturally precipitation, improve precipitation efficiency and increase precipitation. The methods of seeding catalyst include aircraft seeding in the cloud, anti-aircraft guns or rockets firing silver iodide shells into the cloud to explode, and ground burning silver iodide flame agent.

Because many basic problems in the process of natural precipitation and artificial catalysis are still unclear, the theory and technical methods of artificial precipitation are still in the stage of exploration and experimental research. About 80 countries and regions in the world have carried out this experiment successively, among which the United States, Australia, the former Soviet Union and China have carried out larger-scale experiments. This experiment has been carried out in some drought-prone provinces in China, and there are many successful examples. This has played a positive role in increasing precipitation and alleviating the threat of drought.

As the saying goes, "the weather is unpredictable." However, with the development of science and technology, this view has become a thing of the past. For thousands of years, mankind's desire to "sow clouds and rain" has now become a reality. The scientist who realized artificial rainfall for the first time was irving langmuir, an outstanding American physical chemist. Irving langmuir,1881131was born in Brooklyn, new york, USA. Langmuir was very interested in natural science and applied technology since he was a child. When he was young, he had a great ideal: to realize artificial rainfall and get rid of the fate of relying on the weather for food. Langmuir fully understood the farmers' thirst for rain in the dry season. Facing the farmers' eyes for rain and boundless blue sky, as a scientist, he made a rational and scientific exploration. After in-depth research, he finally figured out the mystery.

It turns out that the water vapor on the ground is a "cloud" when it rises and condenses when it meets cold. The tiny freezing point in the cloud is only about 0.0 1 mm in diameter and can be suspended in the air for a long time. Small ice crystals can be formed when they meet some impurity particles (called ice cores). Once the ice crystals appear, water vapor will quickly condense on the surface of the ice crystals, making small ice crystals grow into snowflakes, and many snowflakes stick together to become snowflakes. When the snow is big enough, it will fall from the sky, which is snowfall. If a snowflake collides with a cloud drop during falling, and the cloud drop condenses on the snowflake, this opaque ice hockey is called hail. If the snowflake falls to a warm area with a temperature higher than 0℃, it will melt into water droplets and start to rain. However, clouds do not necessarily rain. This is because the ice cores in the cloud are not rich and the number of ice crystals is too small. At that time, there was a popular view among the people that raindrops were made of dust particles as "ice". If it rains, there must be dust particles in the air besides water vapor. This popular view seriously restricts people's experiments and research on artificial rainfall. Because it is difficult to raise all the dust on cloudy days. Langmuir is a rigorous and pragmatic scientist. He was then the deputy director of the research laboratory of General Electric Company in Schenectady, new york. There are artificial clouds in his laboratory, which are water vapor filled in the refrigerator. Langmuir tried his best to make the water vapor in the refrigerator the same as that in the atmosphere before it rained. He also kept adjusting the temperature and adding all kinds of dust to carry out experiments.

1946 One day in July, the sun was shining and the heat was unbearable. Langmuir was conducting an experiment nervously. Suddenly, the refrigerator stopped cooling because of some equipment failures, and the temperature in the refrigerator could not be lowered. He decided to use dry ice to cool down. The gasification heat of solid carbon dioxide is very high, which is 87.2 calories/g at -60℃. Under normal pressure, it can be quickly converted into gas, absorb environmental heat and refrigerate, which can reduce the environmental temperature to about -78℃. When he just put some dry ice into the freezer, a wonderful picture appeared: small ice particles danced and circled in the freezer, rain and snow fell from the floor, the whole freezer was chilly, and artificial clouds turned into ice and snow. Langmuir analyzed this phenomenon and realized that dust is not an absolutely necessary condition for rainfall. Dry ice has a unique function of condensing water vapor, that is, ice crystals or ice cores in the cloud are used as "seeds". The temperature drop is also one of the important factors that water vapor turns into rain. He constantly adjusted the amount of dry ice and changed the temperature, and found that artificial rainfall was possible as long as the temperature dropped below MINUS 40℃. The dry ice cloud method developed by Langmuir is a breakthrough in the study of artificial rainfall, and it has got rid of the shackles of old ideas. Interestingly, this breakthrough invention was made in the refrigerator in hot summer. Langmuir is determined to apply the dry ice cloud method to the practice of artificial rainfall. Although 1946 is a 66-year-old man, he is still burning with enthusiasm for exploring the mysteries of nature like a young man. /kloc-one day in 0/946, under the command of Langmuir, a plane took off and flew over the sea of clouds. The experimenter scattered 207 kilograms of dry ice into the sea of clouds, just like a farmer sowing seeds in a wheat field. After 30 minutes, a strong wind suddenly blew and rain poured down on the earth. The first artificial rainfall experiment was successful.

Langmuir initiated a new era of artificial rainfall. According to the theory of ice crystal nucleation in supercooled clouds, scientists also found that silver iodide (AgI) can be used as a "seed" for artificial rainfall. And in terms of effect, silver iodide is better than dry ice. Silver iodide can be scattered on the ground and floated into the clouds in the air under the action of updraft, which is simpler and easier than dry ice rainfall.

As a new type of meteorological weapon, "artificial rainfall" plays an important role in the war. During the US-Vietnam War, the "Ho Chi Minh Trail" from Cambodia to Vietnam was busy with traffic, and foreign war materials supporting the Vietnamese people in their resistance to the US imperialist aggressors were continuously sent to the front through this unique passage. However, there are often heavy rains and floods, which will damage bridges and dams. A large number of transport vehicles are struggling on muddy mountain roads, and the traffic is greatly affected, which is as destructive as bombing. Start crossing

Fang knew nothing about this sudden rainstorm. Later, after many investigations, it was learned that this was a secret meteorological operation that President Johnson personally approved and implemented for six years, that is, the United States carried out "artificial rainfall" on that road.

The significance of "unpredictable weather" lies not only in "artificial rainfall", but also in inspiring people to control the weather reasonably. Langmuir also studied this. He hopes to nip it in the bud by manual control before storm warning. This idea is not only reasonable, but also feasible, and has been widely used now.