What are the dangers of fog?
Fog is a weather phenomenon that occurs in autumn and winter. It is a phenomenon in which a large number of water droplets or ice crystals are suspended in the near-surface layer, making horizontal visibility less than 1 km. There are two basic conditions for the formation of fog: first, the water vapor content in the air near the ground is abundant, and second, the ground temperature is low. In winter and early spring in Beijing, because the cold air from the north and the warm and humid air from the south often meet in North China, gray weather after snow, rain and fog is very likely to occur at the intersection.
According to different causes of fog formation, it can be divided into radiation fog, advection fog, etc. Radiation fog is formed when the ground air is cooled by radiation and heat dissipation at night and reaches a state of water vapor saturation. This type of fog mostly appears at night or in the morning when it is clear, gentle, and the water vapor near the ground is relatively abundant. Advection fog is caused by the horizontal movement of air. Heavy fog is also a disastrous weather. Many road traffic, flight and shipping accidents are caused by heavy fog. At the same time, the combination of fog and pollutants in the air will cause great harm to people's health.
Fog is a "ruthless killer" of transportation. When dense fog occurs, visibility is very poor. Sometimes you can only see a few meters or tens of meters away, making the haze near the ground low and blurry vision. According to statistics, traffic accidents caused by fog and other bad weather on highways account for about 1/4 of the total accidents; for aviation, for the safety of passengers, airports must be closed in heavy fog. According to historical statistics, domestic flights cannot take off and land normally due to fog, accounting for 78.9%, and foreign flights accounting for 57%. River shipping is also deeply "poisoned" by fog.
Due to the high humidity, heavy fog can easily destroy the porcelain insulation of high-voltage transmission lines, causing frequent pollution flashovers, cracking of the power grid, and large-scale power outages. In the past ten years, "pollution flashovers" caused by heavy fog have occurred in North China and Northeast China, power grids have collapsed, and large-scale power outages have seriously affected people's production and life.
Fog also has a negative impact on agricultural production. Long-term heavy fog blocks sunlight, hinders the respiration and photosynthesis of crops, reduces the reserves of carbohydrates in crops, and crops become weak. Ultraviolet rays from sunlight are reduced by fog droplets, making crops susceptible to pests and diseases. In foggy areas, insufficient sunlight exposure will cause delayed flowering and poor growth of crops, thereby affecting or reducing product quality and yield.
In recent years, due to climate warming, rising temperatures, increased water vapor content in the atmosphere, and increased pollutants in the atmosphere caused by human activities, the number of condensation nuclei that cause water vapor to condense has increased, so the fog Frequency and intensity of occurrence tend to increase. Fog droplets that permeate the air often carry bacteria and viruses, affect the spread of urban pollutants, and even increase the toxicity of substances such as sulfur dioxide. Therefore, people should go out less often in foggy weather, not to mention exercising in foggy weather, to avoid breathing more harmful substances in the fog and causing harm to health.
Like other weather phenomena, fog is not without its faults. The natural beauty shaped by fog has become an important tourism resource. Fog can also purify the air. After a heavy fog, you will feel that the air becomes fresher. This is because the smoke particles and dust in the air are removed and dissipated by the fog droplets, just like the air with impurities is washed away after rain and snow, making the air purified. The air is purified.