Expert: Heavy fog different from air pollution

Edited and Translated by People's Daily Online

Beijing, Nov.9 (People's Daily Online) --Foggy weather has occurred in China's eastern and central regions several times in October 2011. There have been three to seven foggy days in some areas of northern China and the Huanghuai Plains as well as southern areas of northeastern China, which is one to three days more than the average level of previous years.

However, no evidence has shown that the data is beyond the normal scope.

Some said that the repeated occurrences of heavy fogs are the signs of a decline in air quality. In response, Chen Zhenlin, a spokesman for the China Meteorological Administration, said that dense fogs are often mistaken for air pollution.

Air pollution refers to a type of haze in terms of meteorology that is fundamentally different from fog. The main difference between haze and fog is relative humidity, with the relative humidity of fog being higher than that of haze.

If the weather is characterized by low visibility and dry air, it can generally be considered haze weather. However, it is very difficult to distinguish them when the relative humidity of air stands between 80 percent and 90 percent, so people sometimes use "fog-like haze" to describe the weather. Foggy weather is closely associated with air pollution, but the occurrence of heavy fogs does not necessarily mean a decline in air quality.