How do rain and snow form, and what are the meteorological processes and principles involved? Precipitation forms when water vapor condenses or ice crystals grow in clouds. We will learn how rain and snow are formed through various principles, including the ice crystal process and the collision-merger process.
How does precipitation, such as rain or snow, form? Clouds form when water vapor in the air condenses into tiny water droplets or ice crystals suspended in the air. Precipitation occurs when these water droplets or ice crystals grow inside the clouds.
Cloud formation begins with the condensation or sublimation of water vapor in the atmosphere. At this point, cloud particles are very small, about 0.01 mm in diameter, and do not evaporate easily. As cloud particles collide and merge, they gradually grow larger and fall to the ground in the form of precipitation. The form of precipitation is determined by various meteorological conditions such as temperature, air flow, and atmospheric pressure. In temperate or polar regions, ice crystals grow and produce precipitation. When the temperature in clouds is between 0°C and -40°C, supercooled water droplets and ice crystals coexist in clouds. Supercooled water droplets are small water droplets in the atmosphere that exist in a liquid state without freezing even at temperatures below 0°C (32°F). However, below 0°C, the saturation vapor pressure of supercooled water droplets is greater than the saturation vapor pressure of ice crystals. Therefore, supercooled water droplets evaporate and become water vapor, which then migrates to ice crystals. The migrated water vapor adheres to the ice crystals, and the ice crystals gradually grow in size. This process is called “crystallization”. When these large ice crystals fall to the ground, they become snow, and when they melt on the way down, they become rain. Artificial rain is also created by using the process of ice crystal formation. When silver iodide is sprayed into clouds, it helps to create ice crystals, which grow through the ice crystal formation process and become snow or rain.
On the other hand, in the tropics, ice crystals do not exist when the temperature in the clouds is above 0°C. Therefore, precipitation in the tropics is produced by a different process than the process of ice crystal formation. There are water droplets of different sizes in the clouds, and relatively large water droplets collide with and merge with smaller water droplets as they fall. At this time, the updrafts in the clouds cause large water droplets to stay in the clouds longer, causing them to collide repeatedly with smaller water droplets. As a result, the larger water droplets fall and collide with other water droplets, repeating the process of merging. This process is called “collision-merger”. When millions of water droplets merge through the collision-merger process, they become raindrops and fall to the ground. The cloud seeding process is also used to artificially induce precipitation by spraying materials that absorb moisture in the air, such as salt particles or water droplets, into the air to increase the size of the droplets in the cloud.
Precipitation plays an important role in the Earth’s water cycle. Precipitation maintains moisture on the Earth’s surface, which is essential for the balance of the ecosystem. In addition, precipitation replenishes groundwater resources, is used as water for agriculture and industry, and plays an important role in preventing natural disasters. For example, when it rains, it washes dust and pollutants out of the atmosphere, improving air quality, and adequate precipitation helps alleviate drought. On the other hand, excessive precipitation can cause flooding, which requires proper forecasting and management.
Thus, precipitation is formed by various weather conditions and processes and has a significant impact on our lives and the environment. Scientists study these processes to improve the accuracy of weather forecasts, develop artificial precipitation technology, and help prevent natural disasters. Understanding the formation of precipitation and its effects is very important for responding to climate change and sustainable environmental management.
