Abstract
Abstract. The research infrastructure IAGOS (In-Service Aircraft for a Global Observing System) equips commercial aircraft with instruments to monitor the composition of the atmosphere during flights around the world. In this article, we use data from two China Airlines aircraft based in Taipei (Taiwan) which provided daily measurements of ozone, carbon monoxide and water vapour throughout the summer of 2016. We present time series, from the surface to the upper troposphere, of ozone, carbon monoxide and relative humidity near Taipei, focusing on periods influenced by the passage of typhoons. We examine landing and take-off profiles in the vicinity of tropical cyclones using ERA-5 reanalyses to elucidate the origin of the anomalies in the vertical distribution of these chemical species. Results indicate a high ozone content in the upper- to middle-troposphere track of the storms. The high ozone mixing ratios are generally correlated with potential vorticity and anti-correlated with relative humidity, suggesting stratospheric origin. These results suggest that tropical cyclones participate in transporting air from the stratosphere to troposphere and that such transport could be a regular feature of typhoons. After the typhoons passed Taiwan, the tropospheric column was filled with substantially lower ozone mixing ratios due to the rapid uplift of marine boundary layer air. At the same time, the relative humidity increased, and carbon monoxide mixing ratios fell. Locally, therefore, the passage of typhoons has a positive effect on air quality at the surface, cleansing the atmosphere and reducing the mixing ratios of pollutants such as CO and O3.
Highlights
Tropospheric ozone (O3) is an important trace gas from a climate and air-quality perspective
Tropospheric ozone is formed from the action of sunlight on precursors such as carbon monoxide (CO), nitrogen oxides (NOx=NO + NO2) and volatile organic compounds which are emitted through natural processes and by human activities
200 ppbv observed near the surface, which suggests that the dry, ozone-rich layer did not result from the upward transport of polluted boundary layer air but more likely from the stratosphere-to-troposphere inflow revealed by potential vorticity, relative humidity and vertical velocity fields
Summary
Tropospheric ozone (O3) is an important trace gas from a climate and air-quality perspective. There is a contribution to tropospheric ozone from stratosphere-to-troposphere transport (Holton et al, 1995) in synoptic events along the polar or subtropical jet stream such as tropopause folds and cut-off lows (Stohl et al, 2003; Gettelman et al, 2011) and related to deep convection associated with synoptic-scale circulations or mesoscale convective systems (Pan et al, 2014) Lightning activity is another source of ozone through the production of nitrogen oxides, which are efficient ozone precursors (Lelieveld and Crutzen, 1994). Tropical cyclones (TCs) – named hurricanes in the Atlantic and the eastern North Pacific and typhoons in the western North Pacific – are deep convective synoptic-scale systems that can persist for several days They are associated with significant vertical transport that can make significant perturbations to the structure and chemical composition of the UTLS.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call