Full text reading of artificial rainfall

Definition of technical terms of industrial precipitation

Chinese name: artificial precipitation English name: artificial deposition；; Rainmaking nickname: definition of artificial rainfall 1: means of artificially promoting cloud precipitation. Discipline: atmospheric science (first-class discipline); Definition 2 of atmospheric physics (two disciplines): precipitation caused by artificial methods (such as dropping precipitation enhancers such as dry ice, silver iodide, urea, sodium chloride and calcium chloride). Discipline: electric power (first-class discipline); General Theory (two disciplines) Definition 3: Means of artificially promoting cloud precipitation. Discipline: resource science and technology (first-class discipline); Climate Resources Science (two disciplines) This content is approved and published by the National Committee for the Examination and Approval of Scientific and Technological Terminology.

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Artificial rainfall is to choose the right time according to the physical characteristics of different clouds, and to spread dry ice, silver iodide, salt powder and other catalysts into the clouds by planes and rockets to make the clouds precipitation or increase precipitation, so as to alleviate or alleviate farmland drought, increase irrigation water or reservoir water supply capacity, or increase power generation. The earliest experiment of artificial rainfall in China was in 1958. This summer, Jilin Province suffered a drought that had not happened in 60 years, and artificial rainfall was successful. 1987, artificial rainfall played an important role in extinguishing the great forest fire in Daxinganling.

catalogue

abstract

Principle and method of Leng Yun catalysis

Warm cloud catalysis

Kinetic catalysis

Analog numerical value

Effect test

Development history

Invent a short story

Development situation

philology

Dry ice, a common artificial rainfall agent

iodide of silver

Overview of high cost

Principle and method of Leng Yun catalysis

Warm cloud catalysis

Kinetic catalysis

Analog numerical value

Effect test

Development history

Invent a short story

Development situation

philology

Ordinary artificial rainfall agent

Dry ice silver iodide is expensive to edit. Overview of this paragraph

According to the principle of cloud and precipitation physics, cloud droplets or ice crystals are added to artificial precipitation by sowing catalysts (salt powder, dry ice or silver iodide, etc.). ) into the cloud.

To some extent, it falls to the ground to form precipitation, which is also called artificial precipitation enhancement. 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. This is the most common experiment in weather modification. Under certain conditions, the microphysical process of artificially influencing clouds can stimulate clouds that can't naturally precipitation, and can also make those clouds that have more water supply and can often naturally precipitation, improve precipitation efficiency and increase precipitation. However, cloud energy that can't naturally precipitation can supply less water, so the economic value of artificial catalysis is limited.

Principles and methods of editing this paragraph

Leng Yun catalysis

Ice crystal concentration plays an important role in the process of cold cloud precipitation below 0℃. According to the measured data and theoretical estimation of precipitation particle concentration, precipitation efficiency will be higher only when the ice crystal concentration reaches 1/L or higher. For natural clouds with low precipitation efficiency due to insufficient ice crystal concentration, if ice catalyst is sown in the supercooled part, the ice crystal concentration can be increased. Each gram of dry ice or silver iodide can produce more than 10 12 ice crystals. If you use a few hundred grams, the concentration of ice crystals in the clouds of dozens of cubic kilometers can reach 10/ liter. These artificial ice crystals grow rapidly through the Bergeron process, which promotes the cold cloud precipitation process and increases precipitation. Statistical analysis of some rigorous experiments shows that Leng Yun catalysis can increase precipitation 10 ~ 20%. If the concentration of artificial ice crystals is large, the average scale of snow crystals will be small, and it will take a long time to fall from the clouds to the ground. Under the action of airflow, they will fall further downwind, changing the distribution of precipitation. artificial rainfall

Temperature conditions of Leng Yun catalysis: The effect of artificial precipitation enhancement is closely related to the natural conditions of clouds. As far as Leng Yun catalysis is concerned, the temperature condition in the cloud is very important. As far as the whole cloud is concerned, the cloud top temperature is generally the lowest, which is often used as a parameter to estimate the concentration of natural ice crystals in the cloud. When the cloud top temperature is low enough, a large number of ice crystals often form in the clouds. At this point, by manually adding ice crystals, the effect is not significant. On the other hand, if the cloud top temperature is too high, the ice-forming ability of silver iodide and other catalysts is too low, which is not conducive to artificial catalysis. Therefore, when Leng Yun catalytic method is used to increase precipitation, cloud top temperature should not be too high or too low. The statistical analysis of some experimental results of artificial precipitation enhancement in topographic clouds and cumulus clouds shows that the effect of artificial precipitation enhancement is obvious when the cloud top temperature is at-10 ~-25℃, and this optimal temperature range is called cloud seeding temperature window. In view of the complexity of precipitation process, it is necessary to study the most favorable temperature conditions or other conditions in various clouds when using different catalytic technologies.

Warm cloud catalysis

In warm clouds with temperature higher than 0℃, precipitation is mainly produced in the process of cloud droplet collision. The bigger the cloud droplets are, the faster they collide and grow. The calculation shows that when the radius of cloud droplets exceeds 0.04 mm, they can quickly collide and grow into raindrops. In the natural cloud with insufficient concentration of large cloud droplets, sowing a large number of water droplets with radius greater than 0.04 mm can promote the precipitation process. The calculation shows that millions of large cloud droplets can be formed per gram of water, and several tons of water are needed to catalyze 10 cubic kilometers of clouds. If particles or solution drops of hygroscopic substances with a certain size are sown in the cloud, they can absorb the water in the cloud and quickly grow into large cloud drops, so the amount of catalyst needed is less than one tenth of that of water. In addition to sowing clouds, some people in France and the Soviet Union also tried to heat the ground to cause artificial updraft, trying to stimulate or increase precipitation under certain meteorological conditions. Some people in the United States imagine using asphalt or carbon black to absorb solar radiation, raise the local air temperature and promote the development of clouds to increase precipitation. Some people in China have studied the influence of explosion on precipitation. The research of these artificial precipitation enhancement methods is still in the exploratory stage.

Kinetic catalysis

Leng Yun catalyzes the production of a large number of ice crystals in clouds, and the latent heat released will change the macro-dynamic process of cumulus clouds and increase precipitation. This is a progress of artificial precipitation enhancement experiment in 1960s. The velocity of updraft in cumulus clouds is mainly determined by the buoyancy generated by the temperature difference between inside and outside the clouds. There are a lot of supercooled water droplets in the exuberant cumulus. When a large number of ice-forming catalysts are sown in this cloud, supercooled water droplets can freeze and release latent heat, and water vapor also releases latent heat when it condenses on the surface of ice particles. It is estimated that these two kinds of latent heat are enough to raise the local temperature in the cloud by about 0.5℃, thus increasing buoyancy, promoting the rising speed of some cumulus clouds, expanding the clouds and prolonging their life. In this way, the total amount of water entering the cloud will increase, and the precipitation will also increase. Although the catalyst used in kinetic catalysis is the same as that used in general Leng Yun catalysis, the emphasis is different, and the amount of catalyst used in kinetic catalysis must be greatly increased to be effective. Cumulus kinetic catalysis was tried as early as 1950s, but the well-designed cumulus kinetic catalysis experiment didn't begin until 1963. J Simpson's random experiment in Florida, USA, showed that the cumulus cloud top increased by 65438 0.6 km on average, and the average rainfall increased by 65438 0.7 times. He pointed out that the increase of cloud top after catalysis is closely related to atmospheric stratification (see atmospheric static stability). Other countries and regions have done similar experiments, but the results are different. A random experiment of dynamic catalytic cumulus population was conducted in the whole region, and the preliminary results showed that it had the effect of precipitation enhancement. artificial rainfall

Edit the simulation value of this paragraph.

Mathematical and physical equations are used to describe and calculate cloud precipitation process and artificial catalysis process, and numerical calculation method is used to simulate the artificial influence process of various catalysis technologies under different conditions, and the principle, technology and effect of catalysis are studied. Because of the natural variability of clouds and precipitation, the research period of field experiments is very long and the cost is very high. A strictly designed experiment (some catalytic procedures, technologies, etc.) usually takes several years. ) to evaluate its effect. If we want to compare the effects of different catalytic technologies and choose the best experimental design, it will take longer. Therefore, it is very important to provide a basis for practical experiments and theoretical research through numerical simulation. Simpson used cumulus numerical simulation to calculate the development height of natural clouds in 1960s, and assumed that dynamic catalysis made water droplets in clouds freeze at a higher temperature than natural processes, releasing latent heat, thus calculating the development height of cumulus after catalysis. The measured results of the test are quite consistent with the model calculation. This provides a scientific basis for the principle of kinetic catalysis and the selection of experimental clouds. With the popularization of computer, many countries have carried out many numerical simulations on various artificial precipitation enhancement experiments. Although they greatly simplify the actual process and have limitations in different aspects, combining with field experiments can shorten the test period of evaluating the effect of artificial precipitation enhancement, thus becoming an important part of experimental research on artificial precipitation enhancement. land

Edit this paragraph effect test

Generally, the artificial precipitation enhancement method can only play a role when the natural clouds have already fallen or are close to falling. Because of the natural variability of precipitation, it is difficult to evaluate the effect of artificial precipitation enhancement. The precipitation increased by artificial catalysis is the difference between the actual precipitation after catalysis and the natural precipitation without catalysis. The actual precipitation can be measured, but whether the natural precipitation can be correctly evaluated is the key to the effect test. In the case of insufficient understanding of the physical laws of precipitation, we mainly rely on statistical methods to evaluate the natural possible precipitation. In the initial statistical test methods, regression statistics are mostly used, and an area near the artificially catalyzed target area is selected as the control, and the regression equation of precipitation in the target area and the control area is established with historical data. Substituting the precipitation in the contrast area in the artificial precipitation enhancement experiment into the regression equation, the natural possible precipitation in the target area can be obtained, and then comparing it with the measured precipitation in the target area, the effect of artificial precipitation enhancement can be evaluated. Using this method to carry out the same experiment, selecting historical data from different comparison areas or different years for comparison, the results may be quite different, so the reliability of this method is not high. It is generally believed that random testing can avoid subjective bias and get a statistically credible evaluation. Random test is to divide the test opportunities (test units) suitable for artificial precipitation into two groups according to random rules (such as lottery): one group is catalytic observation, and the other group is only observation without catalysis for comparison. When there are enough test units, the natural conditions of the two groups of test units randomly determined should have only a very small systematic difference, and the systematic difference of the measured precipitation in the two groups of tests can be attributed to the result of artificial catalysis. Judging the catalytic effect, there is the possibility of success and failure. When judging that catalysis is effective but actually ineffective, this possibility is often expressed by the level of significance. The smaller the significance level, the higher the confidence of judging the catalytic effectiveness. In the experiment of artificial precipitation enhancement, the significance level is generally required to be less than 5%, that is, the reliability is greater than 95%. The effect of artificial precipitation enhancement is restricted by cloud and other conditions. It may have a significant positive effect under one condition and may be ineffective or even negative under another. Statistics generally do not consider conditions, and the analysis results are often not significant. When the test units are divided into several categories according to a certain index, sometimes more significant results can be obtained. For example, Leng Yun catalytic test, according to cloud top temperature classification, statistics show that it has a significant effect in a certain temperature range. artificial rainfall

From the research of artificial precipitation enhancement, it is not enough to evaluate the rainfall increase only, and it is necessary to have an exact understanding of each link of the whole physical process. For example, whether the catalyst has reached a certain concentration in a designated part of the cloud, and whether the concentration of ice crystals or large droplets has increased significantly. Observing and counting the changes of these macro and micro characteristics can analyze the effect of artificial catalysis from the physical process. This observation experiment is called the physical experiment of artificial precipitation enhancement effect. For example, in the Leng Yun experiment, it was observed that the concentration of ice crystals increased and the supercooled water droplets decreased after catalysis, indicating that artificial catalysis played a role in the microphysical process of clouds. It is generally believed that the scientific experiment of artificial precipitation enhancement must be carried out for a long time in strict accordance with the predetermined design according to the statistical requirements, and at the same time, the natural precipitation process and artificial catalysis process should be carefully detected and simulated on the spot, so that the experiment can have a solid physical foundation and statistical credibility. Because of the importance of water resources to the national economy, artificial precipitation enhancement experiment, as a potential means to develop water resources, has been widely valued. About 80 countries and regions in the world have carried out this experiment, among which the scale of experiments in the United States, Australia, China and the Soviet Union is relatively large. After 1958, ice-forming catalysts such as dry ice or silver iodide were spread into large-scale layered clouds by plane in northern provinces of China in an attempt to increase precipitation in winter and spring; China's southern provinces also use airplanes or anti-aircraft guns to scatter catalysts such as salt powder or silver iodide into cumulus clouds to increase precipitation during the summer drought. However, many basic problems in natural precipitation and artificial catalysis are still unclear, and there are still many difficulties in testing the effect of artificial precipitation.

Edit the development process of this paragraph.

Pray for rain to the sky as early as ancient times, our ancestors fantasized about mastering the ability to call the wind and call the rain. Primitive people who slash and burn kneel in the red-hot sun to pray for rain; Wizards try their best to beg for rain, sometimes dancing with masks, and sometimes singing with their throats open; They often sacrifice the souls of cattle, sheep and animals to invisible gods, and sometimes even to the living. Wizards use reed pipes to blow water droplets into the air, hoping that this symbolic raindrop will bring abundant rain. Indians in America hang dead snake bodies on fences for rain, while orientals dance dragons and westerners pray. But the relentless drought has withered their hopes again and again. Later, the pattern of begging for rain was constantly refurbished. Someone shot, someone exploded, and someone ignited chemicals. I think the smoke of this compound may attract rain. There are also some lucky people among these rain-seekers, and accidental coincidence makes their spells famous for a while. In American history, there was once a man who prayed for rain. His opportunity was very timely, and he was "effective" several times, but he was self-defeating and almost died. At that time, the rainfall in southern California reached 5 1cm, and the land was swallowed up by the flood, causing countless human and animal casualties and millions of dollars in losses. Ignorant villagers complained bitterly and accused the rain seekers of using magic to cause great disaster.

Edit the short story of this invention.

It was not until 1948 that people really discovered the scientific method of artificial rainfall. This year, Vincent Schaefer, a scientist of the American General Electric Company, discovered the key of artificial rainfall unexpectedly in an experiment after a long-term exploration, and solved the problem that has not been solved for thousands of years, becoming a story in the history of science. With the progress of science and technology, people gradually understand the ins and outs of rain. Water vapor rises from the water surface of oceans and lakes, becomes part of the air, and then forms clouds, from which rain or snowflakes fall. However, how water vapor condenses into raindrops has long been unclear. Later, John Atkin proved that water vapor gathered around fine particles such as dust to form water droplets or ice crystals. These dust particles are so tiny that the naked eye can't detect them at all, but without them, even if there is enough water vapor in the air, it is impossible to form a drop of rain. During World War II, General Electric Company hired Dr. Alvin Langemuir to study the problem of airplane wings freezing when crossing clouds. Young Fu Xie is Dr. Langemuir's assistant. After accepting the task, they set off for New Hampshire in the northeast of the United States, where the peaks are covered with snow all year round, snowstorms are frequent and the wind is cold. Schaefer and Langmuir work in the cold air in the mountains all day. They gradually discovered a strange phenomenon: although the temperature is often below zero degrees Celsius, there are no ice crystals in the clouds around them and under their feet. This strange phenomenon remains deeply in Fu Xie's mind. After the war, Schaff made a small machine that could produce cold and wet air, which was very similar to the air in the clouds in the mountains of New Hampshire. Fu Xie speculated that the failure to form ice crystals in cold air may be due to the lack of crystallization centers mentioned by Aitkin. Fu Xie took a deep breath into his small machine, then began to cool, and then put a little powder into the cold air, such as flour and powdered sugar. Fu Xie experimented patiently for several months, throwing all kinds of powders he could think of into the machine, but none of them could form the condensation center of snowflakes or raindrops. 1948 One morning in July, it was very hot. Fu Xie continued to patiently throw various powders into the cold air again and again, but there was still no result. At this time, a friend of Fu Xie invited him to dinner. Fu Xie is exhausted and would like to have a rest. Before he left, he covered the refrigerator with his mouth up, so that the heavy cold air would sink to the bottom and could not escape. Fu Xie hurried through lunch, still thinking about the cold air in the machine. He went back to the refrigerator and saw that the thermometer had risen above freezing point, which made him feel a little annoyed. For months, he was so absorbed in his experiment that he didn't notice that summer was coming unconsciously. Fu Xie thinks that if you do freezing experiments in hot weather, you should be more careful in the future. What about today's experiment? He closed the lid tightly and waited patiently for the refrigerator to cool the air again. Fu Xie stared at the falling mercury column, worried, and turned to find some dry ice, which he wanted to use to speed up the air cooling process. Fu Xie opened the lid of the refrigerator and threw the dry ice with white steam in. At this time, he took a deep breath into the refrigerator. Suddenly, he felt a silver light flashing in front of him. In a beam of golden sunshine that shot into the refrigerator, he saw countless glittering silver crystals rolling. Fu Xie immediately understood that this was the ice crystal he dreamed of. After numerous failures, he succeeded with an occasional wave of his hand. Fu Xie quickly called an assistant. He took a deep breath into the refrigerator and then threw a handful of dry ice. At this time, a small ice crystal with brilliant silver light appeared immediately, and it slowly fell down, as if a beautiful white fluff-artificial snow experiment was successful. Fu Xie thought, if you can make snowflakes in the laboratory, why not try them in the clouds in the field? He decided to install a device for injecting dry ice on the plane and try it in the sky. 1 1 On a cold day in June, Shav and Langmuir saw a cloud on the horizon. Shaf immediately boarded the plane. He knew it might take a long time to find a cloud suitable for spreading dry ice. This is a huge gray cloud filled with water vapor. Fu Xie chose the right time and started the machine. Dry ice fell into the clouds like a dragged ribbon. Halfway through, dry ice lowered the surrounding temperature and even put out the engine of the plane. Fu Xie used his quick wits and immediately threw all the remaining dry ice into the clouds below from the cabin window. Dr. Langemuir, who was waiting on the ground, looked up at the white snowflakes floating from the clouds and was extremely excited. Fu Xie turned blue with cold when he got off the plane. Langemuir ran to meet him with joy and shouted happily, "You have created a miracle in history!" " Fu Xie's experiment has indeed turned a new page in the history of human influence on the weather. Since then, scientists' planes have often flown over pastures, fields and mountains. They poured dry ice into the clouds and let the crystal raindrops moisten the roots of thirsty plants. After Fu Xie discovered that artificial rainfall could be formed by freezing, he stopped looking for substances that could form the center of water droplets. However, Bernard vonnegut, another young scientist at GE, was not satisfied with Schaefer's conclusion. Just as young Fu Xie is interested in exploring the unknown, he believes that Aitkin's conclusion that there are particles in the center of raindrops is well founded. He looked up a lot of information, hoping to find a chemical substance whose volume and shape are suitable for forming the center of water droplets or ice crystals. Vonnegut finally chose silver iodide. He used the extremely fine powder obtained after burning, hoping to spread in the clouds and form snowflakes. Vonnegut used a ground transmitter to shoot iodine into the clouds and waited patiently. But nothing happened. Vonnegut was puzzled and went to consult a chemist. They soon discovered why the silver iodide used in vonnegut was not pure enough. He quickly put on new silver iodide, and after shooting at the clouds, white snow flowers floated down one after another. Once used, silver iodide precipitation enhancer has been widely used than dry ice. Because silver iodide can be easily launched from the ground to the cloud with a simple device, it is not as troublesome as using dry ice. It is sometimes dangerous to use dry ice. Several times, huge ice cubes of dry ice fell straight to the roof, leaving a big hole, causing a panic. In the face of success, the most conservative people also admit that modern artificial rainfall is a great progress in controlling the weather. Today, it is no longer a myth that it will rain in Yun Geng. The inventions of Fu Xie and vonnegut brought good news to people suffering from drought. Their diligent observation, diligent thinking and persistent spirit of exploration will also be praised for a long time.

Edit the development status of this paragraph.

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. artificial rainfall

Edit this bibliography.

Mei Sen, translated by Lasger: Cloud Physics, Science Press, Beijing, 1978. (B.J. Mei Sen, Physics of Cloud, Oxford University Press, London, 197 1. Hess, Editor of Weather and Climate Change, John Wiley & Sons Company, new york, 1974.

Edit this common artificial rainfall agent.

dry ice

Dry ice is the concentrated solid state of carbon dioxide. The temperature of dry ice is -78.5 degrees Celsius, so it is very useful to keep objects in a frozen or low temperature state. Dry ice can quickly freeze objects, reduce the temperature, and can be equipped with isolation gloves. Dry ice is widely used in many aspects. When dry ice is heated, it is directly sublimated from solid to gas and directly converted into gas, so the process of becoming liquid is omitted, so its phase change will not produce liquid, so it is called "dry ice". To change carbon dioxide into liquid, it is necessary to raise the pressure to 5. 1 atm, before liquid carbon dioxide can appear. dry ice

Artificial rainmaking: Dry ice is sprinkled on the cloud by plane, and the small water droplets in the cloud will freeze into many small ice crystals, so that more water vapor will condense on it, become raindrops and fall to the ground. Cloud making: Because the temperature of dry ice is very low, the sublimated low-temperature carbon dioxide gas can condense water vapor in the air into small water droplets, so white smoke appears, so dry ice is often used to make special effects like clouds in stage performances. Refrigerant: Because carbon dioxide is heavier than air, the sublimated dry ice can still be coated on the frozen articles, which can maintain a good freezing effect, especially for articles that need special air freezing.

iodide of silver

Silver iodide is a compound of iodine and silver. It is yellow powder (558 degrees ~), which decomposes when exposed to light and absorbs a lot of heat. Gray first and then black, insoluble in water and ammonia. It is used as a crystal nucleus for photography and artificial rainfall.

Editing this paragraph is expensive.

At present, there are two main methods of artificial precipitation enhancement. One is to use aircraft to spread coolant such as dry ice into the cloud, which makes the temperature in the cloud drop significantly, and the tiny water droplets and ice crystals increase rapidly, forcing them to drop and form precipitation. The other is to use rockets and shells to shoot chemicals into the sky, bombarding clouds to produce powerful shock waves, so that cloud droplets collide with each other and merge into raindrops to land. launch

The cost of the two methods of precipitation enhancement is different, so the choice of rocket bombardment is mainly based on cost saving, because the cost of a plane broadcast is as high as several million yuan. According to the preliminary budget of the first artificial precipitation enhancement in Shanghai, the implementation of artificial precipitation enhancement needs 4.7 million yuan, of which 400,000 yuan is needed for the catalyst directly acting on the clouds. Of course, this pending budget includes not only hardware expenses such as aircraft rental fees and broadcasting equipment, but also dozens of items such as ground monitoring fees and human resources fees. A rocket for artificial precipitation enhancement is worth about 4,000 yuan, and a rocket for artificial precipitation enhancement is worth about 200,000 yuan. Rockets belong to various arms, and transportation, escort, storage and launch costs are not small expenses. There are still so many staff members who have to work silently behind the scenes, launching sounding balloons every time, and analyzing and processing data. These indirect inputs are not easy to calculate and unclear. A weather modification worksheet in Jiangsu Province shows that from 2000 to 2004, Jiangsu Province launched 872 rockets, increasing rainfall by 654.38+75 million cubic meters. Among them, 106 pieces were launched in 2004, increasing rainfall 1. 1 100 million cubic meters. Artificial precipitation enhancement also needs GPS positioning system and other equipment, so the cost is relatively expensive, but the input-output ratio is still relatively cost-effective. According to internationally recognized statistical data, the input-output ratio of artificial precipitation enhancement is generally above 1: 5, which can reach 1: 30 in relatively high areas. Moreover, artificial precipitation enhancement has obvious economic, social and ecological benefits, whether it is to alleviate power shortage or to fight drought and reduce disasters.