What do you mean by foggy days? What's the difference between haze and fog?

In many areas of 1, fog and haze are combined as disastrous weather phenomena for early warning and forecasting, which are collectively called "haze weather". Mostly in cities.

2 Difference between fog and haze: When haze occurs, the relative humidity is not large, but it is saturated (if there are a large number of condensation nuclei, the relative humidity may not reach 100%, which may lead to saturation). Generally speaking, when the relative humidity is less than 80%, the visibility deterioration caused by atmospheric turbidity is caused by haze, and when the relative humidity is more than 90%, the visibility deterioration caused by atmospheric turbidity is caused by fog. When the relative humidity is between 80% and 90%, the deterioration of visibility caused by blurred vision is caused by the mixture of haze and fog, but its main component is haze. The thickness of haze is relatively thick, which can reach about 1-3 km. Unlike fog and clouds, there is no obvious boundary between haze and clear sky, and the distribution of haze particles is relatively uniform and the scale of haze particles is relatively small. From 0.00 1 micron to 10 micron, the average diameter is about 1-2 micron, and no floating particles can be seen by naked eyes. Because the smog is composed of dust, sulfuric acid, nitric acid and other particles, the longer the scattering wavelength, the more the light ratio, so the smog looks yellow or orange-gray.

Fog is an aerosol system composed of a large number of tiny water droplets or ice crystals suspended in the air near the ground, and it is the product of water vapor condensation (or condensation) in the air near the ground. The existence of fog will reduce air transparency and worsen visibility. If the horizontal visibility of the target drops below 1000 meters, the weather phenomenon of water vapor condensation (or condensation) suspended in the air near the ground is called fog. The phenomenon that the horizontal visibility of the target is 1000- 10000 meters is called light fog or mist. When fog is formed, the atmospheric humidity should be saturated (if a large number of condensation nuclei exist, the relative humidity may not reach 100%). In terms of its physical essence, fog and clouds are both condensation of water vapor in the air. So fog becomes a cloud when it rises from the ground, and it is called fog when it falls to the ground or moves to a high mountain. Generally, the thickness of fog is relatively small, and the thickness of common radiation fog is about tens of meters to 100 meters. Fog, like clouds, has obvious boundary with clear sky area, and the concentration distribution of fog drops is uneven. The scale of fog drops is relatively large, ranging from a few microns to 100 micron, with an average diameter of about 65438. Droplets floating in the air are visible to the naked eye. Because the light scattered by fog composed of liquid water or ice crystals has little to do with wavelength, the fog looks milky white or bluish white.

Haze weather hazards: In the past, meteorological departments often used PM 10 as an indicator to monitor air pollution, and PM2.5 can be directly inhaled into the lungs by the human body. Because of its strong penetration, it is more harmful than PM 10. PM2.5 "ultrafine dust" mainly comes from motor vehicle exhaust dust, fuel dust, sulfate, cooking fume dust, building cement dust, coal dust and nitrate, and is an important part of harmful fine particles in smog.

Meteorologists and medical experts believe that smog weather caused by fine particles is even more harmful to human health than sandstorms. Particles with a particle size larger than 10 micron will be blocked outside the human nose; Particles with a particle size of 2.5 microns to 10 microns can enter the upper respiratory tract, but some of them can be excreted through sputum and blocked by villi inside the nasal cavity, which is relatively harmless to human health; However, fine particles with a particle size less than 2.5 microns are not easily blocked. When inhaled into the human body, it will directly enter the bronchus, interfere with the gas exchange in the lungs, and cause diseases including asthma, bronchitis and cardiovascular diseases.

Dust entering alveoli can be quickly absorbed, directly enters the blood circulation without liver detoxification, and is distributed all over the body, which impairs the ability of hemoglobin to transport oxygen. It may have serious consequences for patients with anemia and blood circulation disorders. For example, it will aggravate respiratory diseases and even cause heart diseases such as congestive heart failure. These particles can also enter the blood through bronchi and alveoli, and harmful gases and heavy metals are dissolved in the blood, which is more harmful to human health. The physiological structure of human body determines that it has no ability to filter and block PM2.5, but the harm of PM2.5 to human health has gradually exposed its horrible side with the progress of medical technology.

In EU countries, PM2.5 has reduced people's average life expectancy by 8.6 months. PM2.5 can also be a carrier of viruses and bacteria, which is helpful for the spread of respiratory infectious diseases. At present, the major developed countries in the world and Japan, Thailand and India in Asia have listed PM2.5 in the air quality standard.

Fog has always been called a "killer", and pollutants such as industrial waste gas, automobile exhaust, dust in the air, bacteria and viruses in the air are attached to these water droplets. In daily life and travel, these substances will have an impact on the human respiratory tract, easily causing acute upper respiratory tract infection (cold), acute tracheobronchitis, pneumonia and asthma attacks, and inducing or aggravating chronic bronchitis. According to experts' analysis, toxic substances in the atmosphere adsorbed by PM2.5 are absorbed by the human body after entering the respiratory tract, and the impact on the body is all-round. Fog is composed of invisible water droplets, while haze is composed of invisible particles and flying dust, which is very harmful to health.

In the past 30 years, the public smoking rate in China has been declining, but the prevalence of lung cancer has increased by more than four times. At present, it is generally believed that this may be related to the increase in haze days. Many people compare the smog weather to the "smoking room" of nature. Not only foggy days with very low visibility will have an impact on human health, but also foggy days and cloudy days will have the same problem. Hazy days also have a serious impact on cardiovascular and cerebrovascular diseases, which will hinder normal blood circulation, lead to cardiovascular diseases, hypertension, coronary heart disease, cerebral hemorrhage, and may also induce angina pectoris, myocardial infarction and heart failure. And cause pulmonary heart disease in chronic bronchitis. thank you