What are the catalysts for artificial rain augmentation
Did you know. Salt has many uses, besides being edible, it is also one of the main catalysts for artificial rain enhancement.
So, at this moment, will you come up with an idea: go to the kitchen and grab a handful of salt, to the clouds in the air a sprinkle, can achieve the purpose of rain?
Actually, no. Generally speaking, the diameter of a grain of table salt is about 0.1 millimeters, or about 100 microns. This is very small for most foods. But for the water vapor in the air, a grain of table salt is a huge head, because in clouds where no rain is formed, the size of water vapor molecules is generally only 5-10 microns. Throwing a handful of salt grains into the clouds is like throwing a lead balloon at a marshmallow. Due to gravity, the salt grains have reached the standard of descent and will fall straight down through the clouds. So you can imagine that when the operator throws a handful of salt into the clouds in an airplane, the salt particles will drift down and the clouds will still be the same.
So how does salt work to increase rain on clouds?
Salt is mainly used in warm clouds to increase rain. When warm clouds naturally precipitate, the diameter of the cloud droplets generally has to reach more than 100 microns before they can beat the updraft and form raindrops falling towards the ground. When the water vapor in warm clouds is very abundant, the diameter of water vapor particles is generally only 5 microns to 10 microns, these particles are freely suspended in the air, because they are very light, and will not fall down. If you seize the opportunity to sow salt powder in the cloud, because of the arrival of salt powder, water vapor particles will be united in one place, until the diameter of the water vapor particles grows to dozens of microns, but still continue to collide and merge with the surrounding small droplets to overcome the updraft into raindrops down.
Therefore, salt as a hygroscopic agent to increase rain is a fact, but also really have years. Just to increase rain, we must first give the salt particles to do a good job of “thinning” work. Early to the warm clouds to increase the rain of salt particles, after physical methods of grinding, until its diameter is small to about 30 microns. But because the size is still on the large side, when the salt powder into the cloud, the rain effect is not very good.
After repeated practice, a chemical method is now used to produce salt particles (potassium chloride and sodium chloride) of less than 1 micron by combustion reactions between substances. These salt particles, being tiny, are well suited as playmates for the water vapor in the clouds, into which they are sent, where they are able to bond with the water vapor molecules, absorbing moisture, colliding, and growing in size in the process. It has been experimentally proven that the smaller the diameter of the salt grains, the more rainwater is produced by sowing the same volume of salt powder.
In practice, it is more common to use artificial methods to increase rain on cold clouds. In layman’s terms, this is done by using a catalyst to make the ice crystals in the cloud grow larger and larger, and then settle and melt into rain. The catalysts for cold clouds to increase rain include ice-forming agents (e.g., silver iodide) and refrigerants (e.g., dry ice, liquid carbon dioxide, liquid nitrogen, etc.) that can cause the temperature to plummet.
To summarize, AIW catalysts are divided into three categories: ice-forming agents, refrigerants and hygroscopic agents.
Ice-forming agent: It is mainly used for cold cloud catalyzing operations at -6℃~-20℃. Silver iodide is one of the most commonly used ice-forming agents, and its crystal structure is similar to that of ice crystals, which makes it an expert in creating ice crystals. Tiny particles of silver iodide are mainly obtained through chemical methods, in the silhouette aircraft, the staff put a certain proportion of chemical composition and accelerant ignition, when the temperature reaches more than 2000 ℃, the generated silver iodide instant gasification, in the air in the cold and rapid sublimation, tiny silver iodide particles immediately into the cloud layer into the working condition to participate in ice formation. Generally speaking, each gram of silver iodide can be divided into 1013 to 1014 silver iodide particles.
Cooling agent: It is used for 0℃~-6℃ convective cloud or stratiform cloud catalytic operation, and there are members such as dry ice, liquid nitrogen and propane. Dry ice is solid carbon dioxide, its sublimation temperature is -78.5 ℃, temperature increase directly from the solid sublimation into a gaseous state, 1 gram of dry ice can produce tens of billions of ice crystals, is a refrigeration can do. The boiling point of liquid nitrogen is -195.8℃, the boiling point of propane is -80℃, and its working principle is similar to that of dry ice.
Moisture absorber: Used for warm cloud catalytic operation above 0℃. There are members such as sodium chloride (table salt), calcium chloride, ammonium nitrate, urea, etc. 1 gram of table salt can catalyze tens of millions of raindrop embryos.
In terms of weight, 1 gram of catalyst can catalyze anywhere from a thousand to tens of billions of ice nuclei or raindrop embryos and ice crystals, so only a small amount of catalyst is needed for each operation to complete the task efficiently.
In terms of composition, for example, the cooling agents dry ice and liquid nitrogen, after participating in the completion of the rain enhancement mission, vaporize into carbon dioxide and nitrogen – both of which are constituent members of air. Another example is the hygroscopic agents salt and urea, which originally come from nature and return to nature after the completion of rain enhancement. So they are all ecologically safe catalysts and certainly do not pollute the environment.
Another example is the use of
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