Air pollution causes rain to decrease

Dust from vehicles, factories and wood burning operations can prevent the formation of rain in arid mountainous areas, threatening important water sources, a new study shows.

Atmospheric dust can reflect sunlight back into space, causing the space below them to cool. Besides, dust can upset the process of forming clouds and rain.

Because the measurement of dust concentration has only been carried out regularly in recent times, scientists cannot specifically demonstrate their effects on rain formation. Fortunately, when a team of experts at The Hebrew University, Jerusalem (Israel), discovered that the Chinese meteorological agency had full meteorological data on a mountain range called Hua in central China. from the 50s. They chose this mountain range as a research place.

Cloud formation

Clouds form above the mountains when air is pushed upward on one side of the mountain and cooled, causing water to evaporate condensation. When the air moves down the other side of the mountain, it becomes warmer and the clouds evaporate.

Rainfall in the peaks has decreased by 20% in half a century.(Photo: Evgenidinev)

Steam forms droplets in clouds by condensing around dust particles. Water droplets collide with each other until they form larger droplets and eventually become heavy enough to fall down into rain.

Every year, only a certain amount of water evaporates into the air. Therefore, when the amount of dust in the atmosphere increases (the consequences of pollution), the amount of water condensing around each dust molecule will decrease, while the time for them to collide with each other to form big droplets more increased.

Impact of atmospheric pollution

Because the lifetime of clouds is relatively short, they evaporate as soon as they fly down the mountain, so the droplets will evaporate before they become rainy.

Rosenfeld and his colleagues figured out how to quantify the impact of dust on rain formation. According to them, the closer the vision is (due to more dust in the atmosphere), the lower the rainfall. Data from the Chinese meteorological agency showed that rainfall in the mountain range was chosen as the place where the research has decreased by 20% over the past 50 years.

Rainwater from mountains is the main source of water for rivers. When the pollution is not serious, the formation of rain will become more difficult, causing a decrease in the number of water sources for rivers and streams, Rosenfeld said.

Viet Linh