As human activities increase over the ocean, scientists are paying closer attention to changes in atmospheric composition. In May and June 2023, researchers from the Institute of Atmospheric Physics, Chinese Academy of Sciences (CAS), along with collaborators from the Nansha Marine Ecological and Environmental Research Station and the South China Sea Institute of Oceanology/CAS, conducted the first shipborne ozone-sounding campaign in the South China Sea. The campaign fills a key gap in high-resolution ozone measurements over China’s oceanic regions, offering valuable data for understanding marine atmospheric chemistry. The campaign report is published in  Advances in Atmospheric Scienceson August 8.

Ozone is a major secondary pollutant in the troposphere, with variations influenced by photochemical reactions, emissions from natural and human sources, and atmospheric transport. Marine air differs significantly from continental air in both physical and chemical properties, and the ocean acts as an important sink for ozone. While long-term ozone soundings have been conducted over land in China, this marks the first such effort over the ocean, particularly the South China Sea.

Ozonesonde is released from the ship.  (Image by Cao Jing-He)

The findings reveal that summer ozone concentrations in the South China Sea’s boundary layer are higher than those at typical tropical marine sites. The soundings also captured much finer vertical ozone structures compared to satellite and reanalysis data. Notably, typhoon-related deep convection caused a sharp drop in ozone mixing ratios in the upper troposphere (around 13.5 km), while subsidence near the tropopause led to a slight increase in mid-tropospheric ozone.

"This experiment not only confirms the feasibility of shipborne ozone soundings in marine environments but also provides key observational data for studying ozone distribution over coastal and offshore regions," said Dr. Li Dan, the study’s lead author.

The team plans to expand shipborne observations in the future, aiming to establish a long-term ozone monitoring network from the ocean surface to the stratosphere.

Citation: Li, D., J.-C. Bian, Z.-X. Bai, Z.-Y. Ouyang, J.-H. Cao, and Z. Qiao, 2025: The first detection of shipborne ozone soundings in the south china sea. Adv. Atmos. Sci., https://doi.org/10.1007/s00376-025-5162-6.