How to "call the wind and call the rain"

The Journey to the West told many stories about calling the shots. For example, the king of the senses called for wind and rain overnight, making it cold and frozen, freezing the Tongtian River; The miracle of betting on the rain with the river dragon. The most interesting story is that four Tang Priests and apprentices went to the Western Heaven to learn Buddhist scriptures, passing through the "East Chiguo", and they were encountering the local "long drought and no rain" and the land was cracked. In order to subdue the demons, the Monkey King went to heaven to beg for rain. With the cooperation of the gods such as Dragon King, Lei Gong, Feng Po and Yun Tong, he pointed his golden cudgel to the sky a few times, and suddenly the clouds rolled and the thunderstorm blew, and the mulberry fields turned into the sea and the waves rolled on the land, which saved the local emergency caused by drought.

In the past, science was not developed, and people didn't know the origin of rain. In dry years, people wanted, hoped and begged for rain. When the wish can't come true, we can only ask God to worship Buddha, build a dragon king and pray for the blessing of the gods. And created many beautiful fantasies.

as the saying goes, "the weather is unpredictable". In ancient times, the changeable weather was really unpredictable, and of course, it was impossible to call the shots and control the weather.

with the development of science, people gradually master the ins and outs of rain and the law of its formation. There is no cloud in the sky and it doesn't rain, because clouds are the precursor of rain, and rain falls from clouds. The sun shines on the land and the ocean, and water is evaporated into water vapor and enters the atmosphere, and when it condenses, it forms fine water droplets. Clouds are generally "warm clouds" composed of suspended and polymerized water droplets, with the temperature above ℃, and the other is "Leng Yun" composed of relatively cold water droplets and small ice crystals, with the temperature below ℃. There are more warm clouds in summer and more in Leng Yun in winter. When the temperature in the cold cloud is below -2℃, the small ice crystals suck the water vapor evaporated from nearby water droplets, and their volume increases. They "travel" up and down in the clouds and collide with each other. The rising airflow can't hold the ice crystals, so they fall from the sky. This is the snowflake. If in the process of falling, through the transformation of ice water, rainfall is formed.

Now, people's beautiful fantasies and hopes for thousands of years have come true.

There was an interesting story: On a winter night in 1773, the Royal Ballroom in Petersburg, Russia, was dancing wildly. Hundreds of candles were lit in the hall, and the doors and windows were closed. Because the hall was as warm as spring, the air gradually became very stuffy. Several women fainted to the ground, some people used their quick wits to break the glass on the window, and cold air poured in ... So, people danced with ecstasy again. Suddenly, people were surprised to find that snowflakes were floating in the hall. At first, some people thought that snow floated in from the window, but when they looked outside, the sky was full of stars. In this regard, people have been puzzled.

more than a century has passed, and meteorologists have solved the mystery. It turns out that hundreds of candles in the hall emit a lot of smoke and carbon dioxide after burning, and many couples also emit a lot of water vapor and carbon dioxide when breathing. When cold air suddenly poured into the hall, the temperature suddenly dropped, and the water vapor condensed on the smoke, thus forming a snow-floating miracle.

In p>193, Dutch scientist Viyralt conducted an experiment of artificial rainfall. He carried 1.5 tons of dry ice fragments at an altitude of 2,5 meters by plane and scattered them in the clouds 2 meters away from the plane. Four planes were also dispatched to monitor under the clouds, and it was found that abundant rain fell within 8 square kilometers.

the experiment was successful. However, Viyralt did not know the principle of rain. In 1933, Swede Becky learned through continuous research that there were ice crystals and supercooled water droplets in the cold cloud at the same time. Because the saturated water vapor pressure of ice crystals was lower than that of supercooled water droplets, water vapor would condense directly on the ice crystals. As long as there are enough ice crystals in the cloud, after "ice water conversion", rainfall can be formed. Later, someone put forward and developed the theory of warm cloud rainfall.

Since then, people's rainfall experiments have been carried out all over the world.

since 193s, China has conducted many experiments on artificial rainfall, snowfall and hail suppression, and achieved great results.

In the summer of p>1958, Leilin City and its surrounding areas suffered a drought that had not happened for decades. The rainfall in July was only 2 mm, and the storage capacity of Songhua Lake was greatly reduced due to the long drought. The dry land, withered crops, drinking water for people and livestock and industrial electricity are all seriously threatened. Therefore, China began the first artificial rainfall experiment.

When the plane crossed the clouds and scattered the rain catalyst-dry ice on the cumulus clouds, a miracle appeared: the clouds rolled, the clouds became thicker, and soon the wind increased, and showers fell from the sky. From August to mid-September, the plane flew 22 sorties and sprinkled 1 tons of dry ice, which basically eliminated the drought.

from 197 to 1972, the artificial rainfall experiment was carried out at Xin' anjiang Hydropower Station in Zhejiang Province, which was estimated to increase the storage capacity of the reservoir by 9-1.5 billion cubic meters and generate electricity by 19-24 million kWh. In 1971, Zhexi Reservoir in Hunan Province carried out artificial rainfall by plane, with 29 sorties, which made the average rainfall in the reservoir area 77 mm, an increase of 3-5% over the same period of the previous year. Raising the water level of the reservoir by 7 meters can generate 63 million kwh of electricity. In 1972, forest fires in some areas of Heilongjiang were very serious. Artificial rainfall and other measures were taken to finally put out the fires.

People throw dry ice into the clouds, and dry ice absorbs the surrounding heat, which will make Leng Yun colder, and there are more and more ice crystals in the clouds. Silver iodide can condense water droplets and water vapor into ice crystals at -4℃. In warm clouds, the catalyst for sowing is generally "salt powder". Because salt powder is a kind of condensation nucleus with strong hygroscopicity, when it is scattered in the cloud, the surrounding water vapor will quickly attach to salt particles and become larger water droplets; Salt powder can also promote cloud disturbance, vertical convection and temperature change, thus accelerating rainfall.

The success of the experiment of artificial rainfall has not only made great contributions to overcoming drought and extinguishing fires, but also paved the way for controlling the weather and transforming the climate.

from 1969 to 1975, the artificial rainfall method made great achievements, one of which was that thousands of hectares of desert in Israel were turned into cultivated land by artificial rainfall.

People use urea treated with capsules to spread into the fog layer, which can absorb the surrounding water vapor and increase its volume. When it falls, it swallows small water droplets along the way and finally falls into rain.

Today, the weather still affects human beings to varying degrees. However, the experiment of artificial rainfall has made great achievements. In addition to spreading these catalysts by plane, people can also use shells, rockets or balloons on the ground to send the catalysts to the clouds, which can artificially eliminate hail, restrain thunderstorms and lightning, or weaken typhoon wind.