Springtime UTLS ozone variability in East Asia: Insights from 16 years of IASI observations (2008–2023)

We investigated the springtime variability of ozone in the upper troposphere and lower stratosphere (UTLS) over East Asia using data from the Infrared Atmospheric Sounding Interferometer (IASI) onboard the Metop satellite series (Metop‐A, Metop‐B, and Metop‐C), complemented with ozonesonde observations and MERRA‐2 reanalysis data. The accuracy of the IASI ozone profiles was confirmed through validation against ozonesonde measurements, demonstrating their reliability for monitoring UTLS ozone dynamics. An empirical orthogonal function analysis revealed that the first principal component explained more than half of the variance in UTLS ozone during springtime, with strong positive correlations in regions influenced by the East Asian jet stream (EAJS). The analysis showed that the strengthening of the jet stream was associated with increased ozone concentrations, likely driven by enhanced baroclinic wave activity and stratospheric intrusion. Moreover, the intensification of the EAJS was associated with strengthening of the local Hadley Cells and the meridional temperature gradient over the upstream region even during springtime.