Expect artificial rainfall in the high temperature? It turns out that you can’t just make it rain whenever you want…

Who doesn't want a sudden rainstorm every summer? But God is not always so kind, and the sun is always shining brightly.

When the sun is blazing, people will inevitably think of artificial rainfall. What conditions are needed for artificial rainfall under high temperatures? In fact, it is not possible to make rainfall just because you want it!

Artificial rainfall

Although artificial rainfall is man-made, it is closely related to natural rain.

Rain in nature is formed when moisture in the air evaporates into the clouds, where it forms water droplets and falls due to the combined effects of pressure and temperature.

Artificial rainfall is also known as artificial rain-inducing. Its main operating principle is to add some necessary substances for rainfall into the clouds according to natural rainfall conditions.

These substances will accelerate the condensation of water droplets in the clouds, or increase the number of water droplets, making the rain fall more and faster.

Artificial rainfall work needs to be subdivided. The clouds in the sky are divided into warm clouds and cold clouds. Different catalysts are used for different clouds.

In warm clouds, due to the relatively high temperature, it is more suitable to spread urea, salt powder and other hygroscopic particles.

Precipitation from warm clouds is mainly caused by the condensation and collision of cloud droplets. When the radius of cloud droplets exceeds 0.04 mm, they can quickly collide and become rain.

Schematic diagram of artificial rainfall

At this time, it is only necessary to spread water droplets with a radius larger than 0.04 mm to quickly form rainfall.

Data studies have shown that one gram of water can form millions of cloud droplets. Based on this, it can be inferred that several tons of water are needed to promote rainfall in 10 cubic kilometers of clouds.

If hygroscopic particles are released into the clouds, a small amount of particles can save a lot of water and make the rainfall process easier.

There are not enough ice crystals in the cold cloud layer, so ice nuclei need to be artificially introduced to create the conditions for rainfall, which is called cold cloud catalysis.

Rainfall is inseparable from ice crystals in the clouds

Studies have found that when the concentration of ice crystals reaches 1 to 100 per liter, the efficiency of precipitation will also increase.

Therefore, in cold clouds, professionals spread materials such as dry ice to lower the temperature of the cloud top, increase the activation concentration of ice nuclei, and promote the clouds to fully produce natural rainfall.

At this time, there must be friends who cannot understand, human technology is so advanced, why can't we make artificial rain whenever we want?

Conditions for artificial rainfall

Artificial rainfall is just like its nickname - artificial rain-inducing. All artificial means only have a promoting effect. Whether it can really rain depends on whether God provides clouds.

Clouds are a necessary condition for rainfall. So far, humans do not have the mature technology to create clouds in the sky that can provide precipitation.

Therefore, for a cloudless sky, even if experts want to make it rain, they are powerless.

And having clouds is not enough. Artificial rainfall is carried out when the clouds are close to precipitation or have already precipitated. As a potential means of developing water resources, it utilizes accumulative clouds to increase their precipitation and thus conserve water well during the rainy season.

Cumulonimbus

For example, during a drought, after a long period of rainfall, there is not much rain and the drought starts again.

At this time, the water-increasing nature of artificial rainfall becomes particularly important. It will increase the allocation of rainwater in the dry season and help alleviate the severity of drought.

At the same time, in some hydroelectric power stations, due to the low rainfall in winter and the low electricity generated by the water flow, people will increase the water flow in the river through artificial rainfall.

The Three Gorges Hydropower Station is the largest in the world

In this way, the water flow in the middle and upper reaches will increase, so that the riverbed in the downstream will not be cut off due to lack of water, or the silt in the river channel will not accumulate after the dry season.

In cold cloud catalysis, unique cloud conditions are also required.

Generally speaking, the lower the temperature of the clouds, the higher the degree of natural activation of the ice nuclei in the cloud top. If we want to achieve a good ice crystal induction effect artificially, the cloud top temperature must reach between minus 4°C and minus 10°C.

Beyond this temperature range, the effect of artificial catalysis will be greatly weakened, and a huge amount of cost will be invested with minimal benefits.

The higher the temperature, the fewer cold clouds there are in the sky that can produce rainfall, so experts need to start with the warm clouds.

However, warm clouds do not appear just because they appear. For many areas in our country, the sky is cloudless even in hot weather.

Even if there are thick clouds, they are just ordinary cumulus clouds that do not meet the conditions. In some big cities with serious pollution, it is easy to see these meaningless cumulus clouds.

The original intention of increasing rainfall is for water resources, and objectively it cannot promote temperature reduction.

Moreover, it was originally scheduled to rain in the area, so if one simply wanted to rely on rain for cooling, artificial rainfall would inevitably seem a bit redundant.

Why can’t we lower it whenever we want?

First of all, the cost of artificial rainfall is not low. Even though it is just launching rockets loaded with special materials on the ground, or spreading them by airplane, its cost can reach as much as one million yuan.

It is written in the artificial rainfall plan implemented in Shanghai that the budget cost of artificial rainfall once is about 4.7 million yuan, and the use of catalyst alone is 200,000 yuan.

This one isn’t cheap!

The budget costs are numerous and diverse, including labor costs, aircraft rental fees, raw material costs, etc. There are dozens of items on the list.

The cost of a rocket used for artificial rainfall increase is between 2,000 and 4,000 RMB. The rocket is not expensive, but the launch pad is not cheap, with a cost of 200,000 RMB.

The costs of cloud detection before launching rockets, and the transportation, storage, and escort of rockets are all costs of artificial rainfall.

Finally, indirect investments such as data analysis and feedback, tracking and monitoring using the GPS positioning system, and evaluation of rainfall effects make the already expensive costs difficult to budget.

A rainfall report for Jiangsu Province showed that 872 rainfall rockets were fired across the province between 2000 and 2004.

The cost of the rockets alone is around 3 million yuan.

However, the benefits brought by artificial rainfall are still quite obvious. In four years, a total of 1.75 billion cubic meters of rainfall was added. Calculated at 3 yuan per cubic meter, the benefits created reached more than 5 billion yuan.

It can be seen that artificial rainfall is not as simple as people imagine. It does not mean that it will rain at any time, but if it really rains, the benefits can still be considerable.

Secondly, there is a complete ecosystem in the surrounding areas of human society or in the wild.

Everything in the ecosystem has adapted to the local climate. They have evolved unique physical characteristics to cope with drought, which fade away when the rainy season comes.

If artificial rainfall is used, a large amount of rain will fall to the ground, causing plants or animals to mistakenly believe that the rainy season has arrived, causing them to lose their original drought resistance measures.

When the artificial rainfall ended, the ground returned to drought, and the animals and plants that could not adapt to the environment eventually died.

The natural ecosystem is closely linked, and the disappearance of a species is likely to lead to the collapse of the entire ecological chain. Just like the butterfly effect, "a butterfly flapping its wings in the Pacific Ocean may bring a hurricane to the United States."

This kind of impact is not so serious in the city, but if it happens in the wild, the consequences will be unimaginable.

In every artificial rainfall report, there will be an ecological survey report on the surrounding area of ​​the rainfall to ensure that the rainfall will not damage the ecology, or has the ability to "compensate" the ecological environment.

Especially in wild areas, relevant departments are very strict in reviewing reports.

Sometimes it’s not that people don’t want it to rain, but that the review report simply cannot pass.

In ancient my country, people used witchcraft to pray for rain, and some people knelt on the ground to pray to the gods. Some people even offered sacrifices such as cattle and sheep to the gods to pray for abundant rain. All of these seem too fantastic, but it is not difficult to see that our ancestors longed for rain.

With the advancement of human technology, the dream once engraved on parchment has finally become a reality. I believe that in the future, technology can lead humans to become better.

Source: Cosmic Decoding