Abstract:  Based on the visibility, relative humidity, precipitation, synoptic situations and the concentration of PM10 from 2006 to 2010 in Fujian province, the characteristics of low visibility weather and its impacting factors were analyzed, and the coastal cities were divided into three city groups, i.e. the north, the middle and the south. The results indicate that the annual haze days are from 8 to 26 days in the north city group and the low visibility is caused by (light) fog, while it is caused by haze in other two city groups. The (light) fog and haze weather usually occur in December to June and seldom in other months. The mean visibility is higher in summer and autumn than in winter and spring. The short duration for the low visibility weather, light fog and haze is prevailing, and then is half a day; the least is the whole day in three city groups. The light fog usually occurs under low vortex shear condition, and then under upper trough and warm zone convergence condition, the third is under transformed surface cold high condition, while haze is often under warm zone convergence, upper trough and transformed surface cold high conditions. The mass concentrations of PM₁₀ are 0.068-0.109 mg·m^-3, 0.044-0.064 mg·m^-3 and 0.041-0.072 mg·m^-3 under haze, (light) fog and non-low visibility weather conditions.

Key words: (Light) fog, Haze, Synoptic situation, PM₁₀