Fog and haze could have been two phenomena, the main difference lies in their humidity. But the boundaries between the two are blurred.
Fog itself is a natural weather phenomenon, even if there is no man-made pollution, fog still occur. Fog frequency of occurrence depends on geography, climate and other natural factors. However, this does not mean that the frequency of occurrence of fog and pollution do not have any relationship. Particulate pollutants, especially hygroscopic particles to form fog provides a wealth of condensation nuclei, there will be conducive to the occurrence of fog.
In the city, the same as another and fog will reduce visibility weather, haze, more and more frequently, mainly due to human emissions of particulate pollutants. PM2.5 haze is an important indicator of this phenomenon. According to the definition on meteorology, a large number of very fine haze of aerosol particles and other dry evenly floating in the air, so that the horizontal visibility is less than 10 km air widespread cloudiness.
Therefore, when the visibility is very low, it may affect both dry aerosols (ie haze contribution), may also have droplet impact (ie fog contribution).
But China is becoming more frequent fog and haze days, haze and fog can switch roles in a single day, it should be said about the air pollution levels. 2013 A study Chinese Academy of Meteorological Sciences and other institutions pointed out that in many parts of China, adverse weather conditions and natural serious air pollution has become "vicious circle", resulting in fog and haze persists. People often think that in the past the "fog just a natural phenomenon," but this study pointed out that China today fog and haze are not completely natural phenomenon.
Researchers believe that the haze problem has to cover the whole country. China will study the haze is divided into nine regions, mutual transfer of pollutants in these areas, including four formed the largest regional regional haze problem. In the North China Plain, Beijing, Tianjin and Shandong and Henan region Guanzhong Plain and other places draw a haze in the East China region, the main area of the haze Yangtze River Delta region, but has been covering Hubei, Anhui and other in the Southern Region, it is in the Pearl River Delta as the center, spread wings haze region to Guangdong and in the Southwest region, Sichuan Basin is "occupied" for the Chinese new haze area.
When confronted with adverse weather conditions, these areas due to their enormous emissions of pollutants, it is easy to form fog and haze. Areas such as Beijing, Tianjin, Hebei coal itself, Beijing motor vehicle, Tianjin Petrochemical industrial emissions of air pollutants on the great, once bad weather, the entire region could fall into a very heavy pollution days. Every fall and winter season, the possibility of conversion, Beijing, Tianjin and areas affected by wind, humidity and other conditions, pollutants become difficult to spread, it is easy to accumulate a high concentration, so this season haze appeared greater .
This is also the reason often appear during October in Beijing, Tianjin Region haze days. We can see these three years, this time of year the public will set off for haze-day crusade.
But other times, as long as the weather conditions are bad, the same situation can cause heavy pollution days. For example, in early 2013, severe haze days in Beijing, Tianjin and continued for several weeks, is due to weak cold air activities, wind speed and relative humidity of air near the ground is conducive to the formation of fog. Plus static stability weather meteorological conditions, air pollutants easy to spread of pollutants in the atmosphere near the ground gradually accumulate. Until the final days of the formation of serious pollution.
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