Tropical Cyclones Reduce Ozone in the Tropopause Region Over the Western Pacific: An Analysis of 18 Years Ozonesonde Profiles

Typhoons play a key role in causing low ozone concentrations in the upper troposphere and lower stratosphere (UTLS) over the western Pacific. In this study, 18 years records (2000-2017) of balloon-borne ozone measurements in Hong Kong (22.3 degrees N, 114.2 degrees E) and Naha (26.2 degrees N, 127.7 degrees E) are combined with trajectory calculations to quantitatively assess the impact of western Pacific typhoons on ozone in the UTLS. The results show that 46.3% (44.9%) of the ozone profiles in Hong Kong (Naha) are impacted by western Pacific typhoons from July to October, with negative ozone anomalies exceeding -20%. Vertical transport by intense typhoons affects 16.8% (18.8%) of the ozone profiles in Hong Kong (Naha) with even larger negative anomalies (<-40%). Vertical transport of tropical cyclones reduces ozone by about 20-60 ppbv compared to the mean ozone profile near the tropopause. Ozone values below 60 ppbv in the upper troposphere in Hong Kong and Naha are mainly caused by the uplift in the western Pacific typhoons and by horizontal transport within the Asian summer monsoon (ASM) anticyclone. The horizontal transport in the ASM anticyclone has larger contributions to the low ozone values measured over Hong Kong than over Naha.

Automated summary

This study quantitatively assesses the impact of western Pacific typhoons on ozone in the upper troposphere and lower stratosphere. Results show that typhoons negatively affect ozone concentrations in Hong Kong and Naha, with vertical transport by intense typhoons causing even larger negative anomalies. Horizontal transport within the Asian summer monsoon anticyclone also contributes to the low ozone values measured in the region.