Characteristics of Dust Haze in Taiyuan and Its Causative Factors

Based on routine surface meteorological data, upper air sounding data, and atmospheric pollutant observation data collected from 2008 to 2012 in Taiyuan, haze characteristics and its formation mechanism were analyzed under the main synoptic situations, typical meteorological elements, and air pollution. The results show that: 1) The frequency of haze occurrence has obvious seasonal and hourly variations with a high probability in the winter half of the year (65.7%) and during the day from 0800 LST to 1300 LST. 2) The frequency of the static wind is high, and southeast winds prevail on haze days. Heavy haze occurs under higher relative humidity conditions. 3) Stable stratification plays a leading role in atmospheric stability on haze days. The mixed layer is approximately 100 m lower on haze days than on no-haze days. The frequency of inversion conditions at 0800 LST is higher than at 2000 LST. Both the average inversion strength and thickness on haze days are higher than on no-haze days. 4) The high pressure weather situation has a significant effect on haze, and the cyclone weather situation is less likely to give rise to haze. 5) The concentrations of PM10, SO₂, and NO₂ decrease by 32.6%, 48.6%, and 21.7%, respectively, on no-haze days compared with haze days. The concentration of particles and SO₂ significantly increase with higher haze levels. 6) The surface solar radiation intensity is weak and sunshine duration is less on haze days.