Abstract

The vertical distributions of ozone (O₃) over a mega city (Beijing, China), and the horizontal O₃ distributions in the lower troposphere (2-3.6 km) over Beijing and its surrounding areas located in the North China Plain (NCP), were analyzed based on the aircraft measurements from 159 flights duri... Show moreThe vertical distributions of ozone (O₃) over a mega city (Beijing, China), and the horizontal O₃ distributions in the lower troposphere (2-3.6 km) over Beijing and its surrounding areas located in the North China Plain (NCP), were analyzed based on the aircraft measurements from 159 flights during 2007-2010. The results are highlighted as follows: (1) There was a peak of O₃ concentration occurring at ~1 km over Beijing, and the peak values ranged between 60 and 120 ppbv. (2) There was an O₃ minimum at the surface. The minimum was largely caused by the chemical reaction of NO + O₃. This process produced about 30 ppbv of the O₃ reduction below 0.5 km in the morning (9:00-10:00). (3) There was a transition altitude (~1 km), below which the ozone formation was in a VOC-limited condition, and above which the ozone formation was in a NOx-limited condition. (4) The analysis of the horizontal distribution shows that O₃ concentrations were enhanced in the downwind of the city plumes. This result suggests that there was an important regional O₃ chemical production in the NCP region. Show less