text| Xiao Shanqing
Edit| Xiao Shanqing
●—≺ What are supercooled water droplets ≻—●
Rain-seeding techniques have been widely used over the past few decades, especially in arid and semi-arid regions. In artificial rainfall technology, the use of supercooled water droplets to achieve artificial rainfall is a classic method. Subcooled water drop technology not only increases precipitation, but also extends precipitation time and rainfall area.
Supercooled water droplets refer to the phenomenon of water droplets with a temperature below 0 degrees Celsius, but still in a liquid state. Normally, water solidifies into ice below 0 degrees Celsius, but under certain conditions, water can continue to remain liquid. The reason for this phenomenon is that the movement of molecules in the water is restricted, resulting in a super-cooling state.
Supercooled water droplets are common in nature, such as at high altitudes, in the polar regions and on rainy days in winter. But supercooled water droplets can also cause some problems, such as ice on the surface of the aircraft in aviation, affecting safe flight; Road ice will also form on traffic roads, increasing the danger of driving
The formation and stability of supercooled water droplets are related to the interaction between water molecules. Under certain conditions, the interaction between water molecules will make water molecules less likely to crystallize below 0 degrees Celsius, forming water droplets in an ultra-cooled state.
However, supercooled water droplets are not permanently stable, and they eventually solidify into ice crystals. This is usually due to external factors, such as tiny particles, bubbles or mechanical shocks, which provide a starting point for water molecules to form ice crystals. Once there is an ice crystal nucleus in the water droplet, the supercooled water droplet will quickly solidify into ice crystals.
Supercooled water droplets have a wide range of applications in scientific research and industrial production. For example, in cloud physics research, supercooled water droplets are important precursors to the formation of ice crystals in clouds, which play an important role in understanding clouds and climate change. In the biomedical field, subcooled water droplets can be used to preserve cells and tissues, as well as to prepare pure biological macromolecules. In addition, subcooled water droplets can also be used to prepare high-quality alloys and nanomaterials, as well as to study air pollution and environmental pollution.
Unlike ordinary water droplets, the moisture inside the supercooled water droplets does not freeze, but is in a supercooled state. When supercooled water droplets encounter a core material, such as sodium chloride or dry ice, they quickly freeze to form crystals. This phenomenon, known as condensation nucleation, is one of the key steps in the formation of artificial rainfall.
●—≺ Causes of supercooled water droplet formation ≻—●
The formation of supercooled water droplets is mainly related to the physical properties of water. Normally, water gradually solidifies into ice below 0 degrees Celsius, which is due to the interaction between water molecules that cause water molecules to be arranged in order and form a crystal structure. However, in some cases, water can be cooled below 0 degrees Celsius while still remaining in a liquid state, which is called the ultra-cooled state.
The supercooled state is formed mainly because the interaction between water molecules is limited and the crystal structure cannot be formed. This restriction can come from the presence of tiny particles or other tiny substances in the air, which can provide some physical or chemical surface on which water molecules can interact instead of arranging freely. This limitation can also come from the motion properties of the water molecules themselves, such as the supercooling state of the water molecules due to the limitation of centrifugal forces under high-speed rotation or strong magnetic fields.
Once water droplets in an ultra-cooled state have formed, they can remain liquid for hours or days, depending on factors such as water purity, temperature, humidity, and conditions in the surrounding environment. However, once water droplets are subjected to mechanical or chemical disturbances, such as tiny particles or air bubbles, or external factors such as vibrations and impacts, they can quickly crystallize into ice.
The formation of supercooled water droplets is also related to the dynamic behavior of water molecules. There is an interaction force between water molecules that allows water molecules to form clusters of water molecules as they approach the freezing point. The number of molecules in these water clusters is small, usually only a few dozen to hundreds, and their size depends on factors such as the strength of the interaction between water molecules, the purity of the water, temperature and pressure.
As the temperature decreases, the size and number of water clusters will gradually increase, until they reach a certain size, these water clusters will begin to form a solid structure, forming ice crystals. However, in some cases, the size and number of water clusters can increase near freezing without forming ice crystals, a phenomenon known as supercooled water droplets.
The formation of supercooled water droplets is a relatively complex process that is affected by many factors, such as temperature, pressure, purity, air pressure, air humidity, and other factors. Studying the formation mechanism and properties of supercooled water droplets has important scientific significance for understanding the dynamic behavior of water, cloud physics, climate change and other fields.
●—≺ Principles of artificial rainfall ≻—●
The principle of using supercooled water droplets to achieve artificial rainfall is to artificially generate a large number of supercooled water droplets, so that they combine with the water vapor in the cloud to form cloud droplets, thereby promoting cloud condensation and rainfall.
The process of achieving artificial rainfall is generally divided into the following steps: select suitable clouds: artificial rainfall needs to select suitable clouds, generally choose clouds with a cloud base height of 2000-4500 meters, a cloud thickness greater than 2000 meters, and a cloud base temperature below -5 °C.
Dispensing of supercoolant: Dosing of subcooler is a key step in the generation of supercooled water droplets. Generally, in the form of gas or aerosol, the supercoolant is sprayed into the cloud, so that the water vapor in the cloud condenses into supercooled water droplets.
Formation of cloud droplets: After the supercoolant is applied, the supercooled water droplets combine with the water vapor in the cloud to form cloud droplets, and the cloud droplets collide with each other and gradually increase to form rainfall nuclei.
Promote rainfall: After the formation of rainfall core, it is necessary to promote rainfall through the action of air flow under certain meteorological conditions. When the cloud droplets increase to a certain extent, they form water droplets large enough to start rainfall. It should be noted that the implementation of artificial rain technology needs to consider factors such as local meteorological conditions, rainfall effects and environmental impacts. Therefore, detailed meteorological analysis and evaluation are required prior to implementation to ensure the safety and effectiveness of cloud-seeding techniques.
Can increase precipitation: With supercooled water drop technology, the number of ice crystals in the cloud can be increased, thereby increasing precipitation. Precipitation time can be extended: With supercooled water droplet technology, the formation time of ice crystals in the cloud can be extended, thereby extending the precipitation time. Rainfall area can be extended: With supercooled water droplet technology, water droplets in the cloud can be promoted to freeze and form crystals, thereby increasing the rainfall area.
Subcooled water droplet technology also has the following shortcomings: limited by environmental conditions: Supercooled water droplet technology requires certain environmental conditions to effectively achieve artificial rainfall, such as cloud height, temperature and humidity. Safety concerns: Subcooled water droplet technology requires the use of chemicals as condensation nucleating agents that can pose potential risks to the environment and human health. May affect rainfall quality: Supercooled water droplet technology may have certain effects on the quality of rainfall, such as rainfall intensity and uneven distribution.
●—≺ Application of subcooled water drop technology ≻—●
Subcooled water droplet technology has been widely used in arid and semi-arid regions. In China, for example, subcooled water droplet technology has been applied to arid regions such as Inner Mongolia, Xinjiang and Gansu to increase rainfall and alleviate drought. In addition, subcooled water droplet technology can also be used in areas such as snow disaster control and agricultural irrigation.
Subcooled water droplet technology has applications in many fields. Here are some common applications:
Cryopreservation: Subcooled water droplet technology can be used for cryopreservation, such as freezing embryos, cells, tissues, etc. Ultra-cold water drop technology slows down the metabolic rate of cells and tissues, thereby extending their survival time and making them better preserved.
Biomedical research: Subcooled water droplet technology can be used for biomedical research, such as cell freezing, freeze-drying, etc. These techniques can help researchers better preserve and process biological samples for more accurate experiments and studies.
Food processing: Subcooled water drop technology can be used in food processing, such as frozen fish, shrimp and other aquatic products. These technologies can maintain the freshness and taste of food and extend its shelf life.
Physicochemical research: Subcooled water droplet technology can be used for physicochemical studies, such as studying the properties and behavior of ultracold water droplets. These studies can contribute to a better understanding of the physicochemical properties and kinetic behavior of water, as well as their application in both natural and artificial environments.
Advanced weather forecasting technology and cloud-based physical models are used to optimize rainfall scenarios to improve efficiency and rainfall quality. Subcooled water drop technology is an important science and technology, with the continuous development and improvement of science and technology, its application scope will continue to expand and deepen.
Subcooled droplet technology has been widely used in arid and semi-arid regions to increase rainfall and mitigate drought. In the future, there is still a lot of room for development and application of subcooled water droplet technology, which can improve the efficiency and rainfall quality through new materials as condensation nucleating agents and optimizing artificial rainfall schemes.