Why is the air in Guangzhou gray and foggy? It's been like this since the Asian Games. What is the reason? Is there any way to improve it?

Haze is also called atmospheric brown cloud. In the ground meteorological observation standard of China Meteorological Bureau, the definition of smog is: "A large number of extremely fine dry dust particles float evenly in the air, which makes the air with horizontal visibility less than 10 km generally turbid, making bright objects in the distance slightly yellow and red, and making darker objects slightly blue." At present, there are four areas with serious smog in some parts of China: Huanghuaihai area, Yangtze River basin, Sichuan basin and Pearl River Delta.

2. The difference between fog and haze

Fog is an aerosol system, a natural phenomenon consisting of a large number of tiny water droplets or ice crystals suspended in the air near the ground, and the visibility is reduced to below 1 km. Generally speaking, the difference between fog and haze mainly lies in the size of water content: fog with water content above 90% and haze with water content below 80%. Between 80% and 90%, it is a mixture of fog and haze, but the main component is haze. In terms of visibility, if the horizontal visibility of the target is reduced to less than 1 km, it is fog; The horizontal visibility is between 1 km and1km, which is called light fog or haze; The horizontal visibility is less than 10 km, which is caused by dust particles, that is, haze or ash haze. In addition, there are some visible "differences" between haze and fog: the thickness of fog is only tens of meters to 200 meters, while haze is 1 km to 3 kilometers; The colors of fog are milky white and bluish white, while haze is yellow and orange gray. The boundary of fog is clear, and it may be clear in Wan Li after passing through the "fog area", but the boundary between haze and surrounding environment is not obvious.

3. The causes of haze

As a natural phenomenon, smog has three factors. First, the phenomenon of static wind in the horizontal direction has increased. In recent years, with the rapid development of urban construction, buildings are built higher and higher, which increases the friction coefficient of the ground and weakens the airflow when passing through the urban area. The increase of static wind phenomenon is not conducive to the diffusion and dilution of atmospheric pollutants to the periphery of urban areas, and it is easy to accumulate high-concentration pollution in urban areas. The second is the phenomenon of vertical inversion. The inversion layer is like a pot cover over a city, which causes the inversion phenomenon that the temperature at high altitude is higher than that at low altitude. Under normal climatic conditions, pollutants diffuse from low altitude with high temperature to high altitude with low temperature and are gradually discharged into the atmosphere. Under the inversion phenomenon, the low-altitude temperature is lower, which leads to the retention of pollutants and cannot be discharged in time. The third is the increase of suspended particulate matter. In recent years, with the development of industry, the increase of motor vehicles, the discharge of pollutants and the increase of suspended solids in the city have directly led to the decrease of visibility and made the whole city look gray.

4. Hazards of smoke

First, it affects health. The composition of smog is very complex, including hundreds of atmospheric particles. Among them, aerosol particles with a diameter less than 10 micron are harmful to human health, such as mineral particles, sea salt, sulfate, nitrate and organic aerosol particles. Can directly enter and adhere to the upper and lower respiratory tract and lung lobe of human body. Because most atmospheric aerosols in smog can be inhaled by human respiratory tract, especially submicron particles will be deposited in upper respiratory tract, lower respiratory tract and alveoli respectively, causing diseases such as rhinitis and bronchitis, and long-term exposure to this environment will also induce lung cancer. In addition, because ultraviolet rays in sunlight are the only way for human body to synthesize vitamin D, the weakening of ultraviolet radiation directly leads to the high incidence of rickets in children. In addition, ultraviolet light is the main weapon to kill atmospheric microorganisms such as bacteria and viruses in nature. Hazy weather leads to the weakening of ultraviolet rays in the surface layer, which is easy to enhance the activity of infectious bacteria in the air and increase infectious diseases. Second, it affects mental health. Whether the gray weather is easy to make people feel pessimistic, if it is not adjusted in time, it will easily get out of control. The third is to affect traffic safety. When there is haze weather, outdoor visibility is low, pollution continues, traffic jams and accidents occur frequently. The fourth is to affect the regional climate. Regional extreme weather events occur frequently and meteorological disasters occur one after another. What is even more worrying is that smog has also accelerated the early arrival of photochemical smog pollution in cities. Photochemical smog is a kind of light blue smog. Automobile exhaust and factory exhaust contain a lot of nitrogen oxides and hydrocarbons. These gases will undergo photochemical reactions under the action of sunlight and ultraviolet rays, resulting in photochemical smog. Its main components are a series of oxidants, such as ozone, aldehydes and ketones. It is very toxic and has a strong stimulating effect on the human body. In severe cases, people will have difficulty breathing, decreased vision, hand and foot convulsions and other phenomena.

5. How to deal with smog

First of all, a smog index forecast and a smog weather early warning mechanism should be established. Set up ground-based optical observation points in cities to monitor aerosol optical thickness with satellite remote sensing data; At the same time, set up horizontal visibility observation stations and vertical visibility observation stations in the surrounding areas of the city to carry out horizontal visibility and vertical visibility observation and directly provide public services for smog weather; Carry out atmospheric boundary layer detection, regularly grasp the relationship between boundary layer characteristics such as inversion and haze weather, understand the influence of industrialization and urbanization on atmospheric boundary layer structure, improve the accuracy of haze weather forecast, and improve the ability of haze weather monitoring and prevention; Strengthen solar radiation monitoring and assess the impact of atmospheric smog on agricultural production and climate change. Only by combining the establishment of a smog weather forecast system with the establishment of a dynamic pollution control system and a decision-making system to control the emission of pollution sources can we effectively deal with smog. Judging from the current situation, urbanization and industrialization are the main factors causing smog, and a meteorological feature of smog weather is that there is an air stagnation area in its area. Some developed countries abroad try to solve the harm of smog by dynamically adjusting social production under different meteorological conditions, the essence of which is to adjust the total amount of pollution sources. For example, in the United States, once the air stagnation zone is detected in a certain area, the industrial gas emission in that area will be controlled, and when the atmospheric conditions are good and the air diffusion ability is strong, it can be fully discharged. Secondly, strict measures should be taken to limit automobile exhaust emissions and industrial gas emissions in order to eliminate or reduce the harm of smog to cities. At the same time, smog prevention should be considered as a whole among urban agglomerations. As a regional climate disaster phenomenon, only through regional cooperation can we achieve the best governance effect. Finally, in urban planning, we should pay attention to the study of the sinking distance between the urban updraft and the suburbs, and arrange the heavily polluted industrial enterprises outside the sinking distance to prevent the pollutants discharged by these factories from flowing from the near ground to the urban area; Satellites should also be built outside the circulation of urban heat islands to avoid mutual pollution. It is necessary to fully consider the diffusion conditions of the atmosphere and reserve air passages. Increase urban green space, so that urban green space can exert environmental benefits such as smoking, dust removal, air filtration and beautifying the environment, thus purifying urban atmosphere and improving urban air quality. Attention should be paid to exercise in this kind of haze weather: haze weather is easy to stimulate the human respiratory and circulatory system, especially in the morning when the human blood concentration is high and the body stretching function is poor. At this time, exercise is easy to sprain the body and induce myocardial infarction and pulmonary heart disease. Generally speaking, regardless of special weather systems such as cold air, typhoon, front and shear line, the air quality is the best and the visibility is the highest in the evening 17 ~ 19. Therefore, the daily exercise time should be set at night 17 to 19. In addition, the amount of exercise and intensity should be moderately reduced in foggy weather, and places with more trees and grass are better choices. Generally speaking, visibility less than 10 km is a haze phenomenon, 5 to 8 km is a moderate haze phenomenon, 3 to 5 km is a severe haze phenomenon, and less than 3 km is a serious haze phenomenon.

6. Matters needing attention in foggy days

Drink more water and stop doing morning exercises. Medical experts remind the public that smog weather will affect their health and they should drink more soup. People who have the habit of doing morning exercises had better stop doing morning exercises, or choose to do outdoor exercises in the afternoon and evening. Drink more soup to keep indoor ventilation 1. After work or holidays, you can take more time to walk and exercise outdoors with fresh air; 2. Drink plenty of water to keep the respiratory tract moist. In addition, dry weather is easy for bacteria to gather, so keep indoor ventilation; 3. Soup making is also a magic weapon for "drought resistance". Lily, soft-shelled turtle, fish and other materials can be used to cook some soup for nourishing yin and moistening lung. 4. Try to wear a mask when going out (once or more).

7. National standard for haze determination

On June, 2065438 1 day, the Haze (Haze) observation and forecast Grade issued by China Meteorological Bureau was officially implemented. Haze, a weather process similar to fog, will be accurately distinguished. In the observation and forecast scale of haze (haze), the standard of haze is specified in detail, that is, when the visibility is less than 10 km and the relative humidity is less than 95%, the visual distance obstacle caused by weather phenomena such as precipitation, sandstorm, sand blowing, floating dust, smoke, snow blowing and blizzard can be ruled out, and it can be judged as haze. Before this standard appeared, the difference between fog and haze was not very clear. Pu Ming, director of the Science and Technology Department of Sichuan Meteorological Bureau, said that smog contains more dust and fog is mainly water vapor, which is slightly different in humidity and visibility. The national standard also stipulates four main atmospheric components that cause smog (aerosol mass concentration with diameter less than 2.5μm, aerosol mass concentration with diameter less than 1μm, aerosol scattering coefficient and aerosol absorption coefficient). As long as one of the sufficient indicators exceeds the standard, even if the visibility is greater than 10 km, it is still smog. The smog forecast level is divided into four levels: mild, mild, moderate and severe.