How did the haze weather come from?

Haze: In windless weather, it is often seen in cities that smog rises to a certain height, then floats horizontally and diffuses in all directions, and the whole field of vision soon becomes blurred. With the coming of smoke, the weather is gloomy and the sun is dim, which makes people breathless, and at the same time, they will smell unpleasant smells such as coal smoke. People with poor physical resistance will have chest tightness, cough, sore throat, vomiting, difficulty breathing and other symptoms. When we stand high in the suburbs and look at the city, we will find a layer of mist hanging over the city like a big pot cover.

With the deterioration of air quality, cloudy days are increasing and the harm is increasing. Recently, many areas in China have incorporated the smog weather phenomenon into the fog as an early warning and forecast of disastrous weather. Collectively referred to as "haze weather". In fact, fog and haze are completely different to some extent. For example, when fog appears, the air is humid; When smog occurs, the air is relatively dry and the relative humidity of the air is usually below 60%. The reason is that a large number of extremely fine dust particles, smoke particles and salt particles float in the air evenly, so that the air with effective horizontal visibility less than 10KM is mixed together. The symbol is "∞". The diurnal variation of haze is generally not obvious. When the air mass changes little and is stable, it lasts for a long time, sometimes exceeding 10 days. Due to weather phenomena such as haze, light fog, sandstorm, sand blowing, floating dust and smoke, the effective horizontal visibility is less than 10KM due to a large number of extremely fine dust particles or smoke particles floating in the air. Sometimes it is difficult for meteorological professionals to tell the difference. It is necessary to comprehensively analyze and judge the weather background, sky conditions, air humidity, color and smell, satellite monitoring and other factors to draw a correct conclusion. The weather phenomena of fog and haze can sometimes be converted to each other.