Articles | Volume 17, issue 7
Research article
10 Apr 2017
Research article |  | 10 Apr 2017

Impact of typhoons on the composition of the upper troposphere within the Asian summer monsoon anticyclone: the SWOP campaign in Lhasa 2013

Dan Li, Bärbel Vogel, Jianchun Bian, Rolf Müller, Laura L. Pan, Gebhard Günther, Zhixuan Bai, Qian Li, Jinqiang Zhang, Qiujun Fan, and Holger Vömel

Abstract. In the frame of the SWOP (sounding water vapour, ozone, and particle) campaign during the Asian summer monsoon (ASM), ozone and water vapour profiles were measured by balloon-borne sensors launched from Lhasa (29.66° N, 91.14° E, elevation 3650 m), China, in August 2013. In total, 24 soundings were launched, nearly half of which show strong variations in the relationship between ozone and water vapour in the tracer–tracer correlation in the upper troposphere and lower stratosphere (UTLS). For each sounding, 20-day backward trajectories were calculated using the trajectory module of the Chemical Lagrangian Model of the Stratosphere (CLaMS) to analyse these variations. The trajectory calculations demonstrate that three tropical cyclones (tropical storm Jebi, typhoons Utor and Trami), which occurred over the western Pacific Ocean during August 2013, had a considerable impact on the vertical distribution of ozone and water vapour by uplifting marine air masses to altitudes of the ASM anticyclone. Air parcels subsequently arrived at the observation site via two primary pathways: firstly via direct horizontal transport from the location of the typhoon to the station within approximately 3 days, and secondly via transport following the clockwise wind flow of the ASM within a timescale of 1 week. Furthermore, the interplay between the spatial position of the ASM anticyclone and tropical cyclones plays a key role in controlling the transport pathways of air parcels from the boundary layer of the western Pacific to Lhasa in horizontal and vertical transport. Moreover, the statistical analysis shows that the strongest impact by typhoons is found at altitudes between 14.5 and 17 km (365–375 K). Low ozone values (50–80 ppbv) were observed between 370 and 380 K due to the strong vertical transport within tropical cyclones.

Short summary
High-resolution ozone and water vapour profiles over Lhasa, China, were measured in August 2013. The correlations between ozone and water vapour profiles show a strong variability in the upper troposphere. These relationships were investigated using CLaMS trajectory calculations. The model results demonstrate that three tropical cyclones (Jebi, Utor, and Trami), occurring over the western Pacific, had a strong impact on the vertical structure of ozone and water vapour profiles.
Final-revised paper