Category: Education/Science >> Science and Technology
Question description:
Our teacher wants to ask us, urgently!!!
Analysis:
Calling the wind and calling the rain is not just a dream, the weather can also be determined by people
Calling the wind and the rain has always been the "patent" of the gods in myths and legends. With the advancement of science and technology, human beings seem to have peeked into the "Book of Heaven", gradually mastered the "secret" of making wind and rain, and began to learn to "point and control" the sky.
Artificial fog elimination: from heavy fog to bright sunshine
Since heavy fog is not conducive to the diffusion of pollutants, it not only reduces the environmental quality of urban areas, but also causes high humidity and carbon-containing Pollutants and other environments degrade the insulation performance of the air, causing pollution flashovers and short circuits between high-voltage lines, resulting in large-scale failures of transmission lines. In order to minimize the impact of heavy fog on human activities, meteorological experts have come up with various methods of "eliminating fog". For warm fog with temperatures above 0°C, heating methods are often used or helicopters or jet engines are used to stir the airflow to reduce the concentration of fog droplets; in addition, hygroscopic agents such as calcium chloride, salt powder, and urea can also be spread to form large droplets. And sink. For cold fog below 0℃, you can spray liquid carbon dioxide, propane, liquid nitrogen and other refrigerants to generate ice crystals, or introduce artificial ice crystals of silver iodide to freeze the water vapor in the fog, allowing the fog to turn into "snow" and fall. fog elimination purpose.
Artificial rainfall enhancement: aircraft, balloons, generators, anti-aircraft guns and rockets are used together
There are two conditions for the formation of precipitation. One is that there must be sufficient water vapor in the clouds; It is necessary to have an appropriate number of condensation nuclei. Therefore, the method of artificial rainfall is to introduce artificial condensation nuclei into the clouds. Generally, the catalyst is sent into the cloud by means of airplanes, rockets, anti-aircraft guns, balloons, and burning silver iodide on the ground in the updraft area. Planes generally fly to an altitude of about 6,000 meters to pierce the clouds and spread catalysts. Rockets and anti-aircraft guns directly bombard appropriate parts of thunderclouds, and the warheads are loaded with silver iodide and sent into the clouds. A silver iodide flame bomb is hung under the balloon, which rises into the clouds and burns above the freezing level, releasing the catalyst. For warm clouds with a temperature above zero, hygroscopic substances such as salt powder, urea, calcium chloride, etc. are generally used to turn the water vapor in the cloud into large water droplets and fall into rain. For cold clouds with temperatures below zero, artificial crystal nuclei such as silver iodide are sown, or dry ice, liquid nitrogen, etc. are sown to increase the number of ice crystals in the cold clouds and improve precipitation efficiency.
Artificial hail prevention: Do everything possible to prevent hail from "growing up"
When hailstones as big as eggs or even basketballs hit the ground from the sky, facilities are destroyed and livestock are killed in the blink of an eye. , personnel were injured, and the degree of damage was no less than a "saturation aerial bombing". Therefore, how to nip hail in the "cradle" before it hits the ground has always been an urgent issue facing meteorologists.
When water vapor in clouds hits condensation nuclei, it will form water droplets that fall. If they encounter low temperature layers and updrafts, the water droplets will freeze and be lifted up into the clouds. If it falls again and encounters low temperatures and updrafts, it will freeze again and be sent up into the clouds again. Repeatedly, the hailstone will "grow bigger and bigger" until finally the updraft can no longer bear its weight, and it will fall to the ground. According to experts from the Beijing Weather Modification Office, catalysts are also the main force in artificial hail prevention. When anti-aircraft guns concentrate and quickly deliver a large amount of silver iodide and other catalysts into the clouds, a large number of condensation nuclei will be formed in the clouds. In this way, clouds that were originally prone to large hailstones due to too few condensation nuclei will not be easy to "grow" due to the sudden appearance of a large number of condensation nuclei. When the diameter of hail is less than 5 mm, it will not cause harm to the ground. Once we find that a cloud has "the wrong momentum", we will "retaliate against it", "strike first to gain the upper hand", use anti-aircraft artillery to "saturate" it, and turn the hail into "small grains of salt" Fall meekly.
Artificial rain suppression: rain in advance or hold back
The principle of rain suppression is actually the same as artificial rainfall. It just makes the rain that is supposed to fall in areas that need shelter be advanced. Just down. Generally speaking, it is about 50 kilometers upwind of the area that needs to be protected from rain. "Once we find which cloud is going to rain, use artificial rainfall to let the rain fall in advance." In this way, the area that needs rain protection will naturally That is to say, the sky is clear and clear. In addition, meteorological experts can also launch a large number of catalysts into the clouds to prevent the raindrops in the clouds from growing too large, and wait until the clouds pass through the rain shelter area before it rains. This can also play the role of artificial rain elimination.
The biggest difficulty faced by artificial rain elimination technology is to ensure the accuracy of artificial rain elimination. Otherwise, artificial rain suppression is likely to fail. (Sheyu is excerpted from "China Science and Technology News")