Principles and methods of artificial rainfall

Artificial rainfall means that according to the physical characteristics of different clouds, choose the right time, use aircraft and rockets to spread dry ice, silver iodide, salt powder and other catalysts into the clouds to make the cloud precipitation or increase precipitation, in order to relieve or alleviate farmland drought, increase reservoir irrigation or water supply capacity, or increase power generation, and so on. Let's take a look at the principles and methods of artificial rainfall.

The principle of artificial rainfall

Artificial rainfall uses the principles of cloud and precipitation physics to make cloud droplets or ice crystals increase to a certain extent and fall to the ground to form precipitation by spreading rain agents (salt powder, dry ice or silver iodide, etc.) into the clouds. The microphysical process of artificially affecting clouds can not only excite the clouds that can not be precipitated naturally under certain conditions, but also improve the precipitation efficiency and increase the precipitation of those clouds with more water supply and often natural precipitation. However, clouds that can not precipitate naturally can supply less water, so the economic value of artificial catalysis is limited.

Conditions of artificial rainfall

There are two conditions for the formation of precipitation, one is that there should be sufficient water vapor in the cloud, and the other is that there should be more condensation nodules. Therefore, the method of artificial rainfall is to introduce artificial nodule into the cloud. Generally, the catalysts are sent into the cloud by means of aircraft, rockets, anti-aircraft guns, balloons and the burning of silver iodide on the ground in the rising air flow zone. For warm clouds with temperatures above zero, hygroscopic substances such as salt powder, urea and calcium chloride are generally used to turn water vapor into water droplets and fall into rain. For cold clouds with temperatures below zero, artificial crystal nuclei such as silver iodide or dry ice and liquid nitrogen are seeded to increase the number of ice crystals in cold clouds and improve precipitation efficiency.

The method of artificial rainfall

The method of artificial rainfall is to send the catalyst into the cloud by means of aircraft, rockets, anti-aircraft guns, balloons and burning silver iodide on the ground in the rising air flow area. Aircraft usually fly to an altitude of about 6000 meters to sow catalysts through the clouds. Rockets and antiaircraft guns directly bombarded the appropriate part of the thunderstorm cloud, and the warhead loaded silver iodide into the cloud. The silver iodide flame bomb is hung under the balloon and burns above zero in the cloud to release the catalyst.

The harm of artificial rainfall

At present, artificial rainfall in China mainly uses two kinds of catalysts, one is dry ice, which cools the surrounding air layer to minus dozens of degrees Celsius during vaporization, thus causing water droplets to condense. The second category is silver iodide, which is first-class in making rain. Dry ice is actually carbon dioxide, and silver iodide, as a chemical, has very low toxicity. In addition, the efficiency of silver iodide to make ice crystals is very high, usually a cumulus cloud only needs to sow more than ten grams or dozens of grams can work, the amount is so low that it is almost negligible, so it will not cause any pollution.