Using Lidar, in-situ measurements and Trajectory Analysis to observe air pollution in Beijing, 2014

We present combined Mie lidar, ozone lidar and wide-range particle spectrometer observations that were carried out in Beijing, north China during two periods—one haze period before the Asia-Pacific Economic Cooperation (APEC) meeting and one moderate pollution period during the meeting in 2014. High extinction coefficient, moderate ozone concentration and variable particle number concentration were obtained throughout the first haze observation period. The mean extinction coefficients in the two pollution periods were 0.52 km-1 and 0.23 km-1, respectively, at 532 nm. The ozone concentration during the first haze phase was more various with higher average value of 49 ppb compared to that in the second pollution observations (32 ppb). The comparison of aerosols and ozone in different heights indicate different pollution sources and complicated ozone process of generation and disappearance. The four-day back trajectories from a HYSPLIT model indicate that the air masses in the lower boundary layer were advected from the densely populated south regions of China and the long pollution transportation passing through northern China