Multi-year evolution of tropospheric ozone pollution and its main drivers over East Asia during spring analyzed from multispectral satellite observations and in situ measurements

Air quality is a major societal concern in East Asia, contributing to (approximately) two million premature deaths annually. Rapid economic growth in regions such as the North China Plain and Punjab, combined with extensive urbanization of megacities, has led to a significant rise in air pollutant emissions. Ozone precursors emitted from this region are transported across long distances, undergoing chemical transformations and affecting downwind regions, including Japan and even North America. This long-range transport highlights the need to better understand the processes driving ozone eastward dispersion across the Pacific Ocean.

The primary objective of this study is to provide a robust, multi-year quantification of tropospheric ozone transport from East Asia, particularly from air pollution hotspots and its transport to downwind regions. We aim to characterize key conditions influencing eastward ozone transport:  meteorological patterns, stratosphere-troposphere exchange (STE), surface emissions of ozone precursors including biomass burning, etc. For our study, we use long-term satellite observations from the IASI+GOME2 multispectral satellite product offering particularly enhanced sensitivity in the lowermost troposphere (below 3 km of altitude) and ground-based in situ measurements from surface stations and ship. Meteorological models are used to analyze atmospheric transport and atmospheric conditions.

Preliminary analyses indicate that eastward transport events occur during the spring, specifically in March, mainly influenced by meteorological condition (the rising of temperature and insolation) that leads to an increase of photochemistry and the active presence of sources, such as agricultural biomass burning. Moreover, the study allows us to highlight several transport pathways of tropospheric ozone reaching the Pacific Ocean.