Analysis of a haze event by micro-pulse light laser detection and ranging measurements in Shanghai

A haze event in Shanghai between December 19 and 21 in 2008 is analyzed in this study. The haze data ( including aerosol extinction and vertical profile) was measured by a Micro-Pulse Lidar in Pudong,Shanghai. In order to evaluate the Lidar aerosol measurement,the surface aerosol measurement at the same site is compared with the Lidar result. The analysis of haze occurrences from a long term measurement ( between June,2008 and May,2009) suggests that the highest occurrences of haze events were in winter and spring,and the most severe haze events occurred in winter. The haze occurrences were fewer in fall and summer than in winter and spring. The analysis shows that the severe haze events often occurred under clam wind and weak radiation conditions in Shanghai. The humidity has important impact on visibility during the severe haze events. The altitude variation of the Planetary Boundary Layer( PBL) decide the haze intensity. The Planetary Boundary Layer ( PBL) was 1000 meters in the median haze event and 600 meters in the severe haze events. During the median and severe haze days,the aerosol extinction coefficients were about 0. 15 and 0. 30 km -1, respectively. The emission of the particles( PM1 and PM2.5) also affect the haze event,and the contribution from the scattering aerosol are more than from the absorbing aerosol in extinction. In mild haze days,the concentrations of PM2.5 and BC were about 50 and 5 μg·m -3,respectively,with an extinction coefficient of 200 Mm -1. By contrast,in severe haze days,the concentrations of PM2.5 and BC reached about 200 and 24μg·m -3,respectively,with an extinction coefficient of 1400 Mm -1. The aerosol optical depth ( AOD) at 550 nm in the severe haze event was high with a maximum value of 0. 6. At the same time,a decrease in Angstrom index suggested that the concentrations of large particles were high and the long range transportation of aerosols played an important role in the severe event.