The Impact of Meteorology on Air Pollution in the Lower Atmosphere over the North China Plain in Spring 2016

Abstract:

The Air chemistry Research in Asia (ARIAs) campaign was designed to characterize and quantify the composition of trace gases and aerosols over the North China Plain to improve modeling tools used to evaluate the effectiveness of air pollution reduction policies. We present a study assessing how different meteorological conditions affected the vertical distribution and transport of trace gases and aerosols in May and June 2016. Back trajectories from the National Oceanic and Atmospheric Administration’s Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) combined with airborne measurements identifies synoptic conditions associated with high pollution loadings. The prevailing meteorology for most of ARIAs flights were predominantly high-pressure conditions, although several cyclonic systems traversed the experimental domain. High concentrations of O₃ and its precursors were pervasive throughout the campaign region. Box modeling results estimate the high amounts of NO_x and VOCs led to production rates of O₃ ~3 ppbv/hour in the lower free troposphere and continued to produce O₃ as the airmass traveled downwind. We identify key VOCs, such as toluene, ethylene, m/p-xylene, and propylene, that warrant emission control by assessing OH reactivity and Ozone Formation Potential. We present results during a persistent high pressure system from May 17-22, ensuring weak synoptic flow, reduced winds speeds, and increased surface temperatures. These conditions enhanced the production of O₃, allowing for numerous violations of Chinese Ambient Air Quality Standards. By combining our airborne observations with surface measurements and the concurrent NASA Korea-United States Air Quality Study (KORUS-AQ), we assess the influence of these synoptic conditions on local and regional air pollution.