北京地区低能见度区域分布初探

选用了水平能见度小于1000m的低能见度作为影响城市交通运输的一个指标，并研究了低能见度在北京地区时空分布特征。按水平能见度小于1000m的出现频率，多年日均变化曲线及全年日均、月均、季均变化特征，将北京地区划分为3个区，即东南部平原地区、西北部山区及东北－西南部过渡区。同时讨论了雾、浮尘等天气现象对北京地区低能见度的影响，得出影响北京地区低能见度的主要因子是雾。

A Study on Regional Distribution of Low Horizontal Visibility in Beijing Area

The temporal and spatial distribution characteristics of the low horizontal visibility (lower than 1000 m) in Beijing are studied, which is chosen as an index that would affect urban traffic and transportation. According to both mean daily variation over many years and mean daily, monthly and seasonal variation in a year of low visibility frequency, Beijing is divided into three different parts, the southeastern plain area, the northwestern mountainous area, and northeastern to southwestern transitional area. The effect of some synoptic phenomena, such as fog, fly ash, and so on, upon the low visibility in Beijing is also discussed. It is shown that fog is the main factor affecting visibility.