Contribution of atmospheric circulations changes to the variations of summertime lower tropospheric ozone over East Asia during recent decades

The formation of O3 pollution not only depends on the emission of the O3 precursors, but also is closely related to the atmospheric circulation. However, to what extent atmospheric circulation changes contribute to the variations of O3 concentration has not been well understood over East Asia. Here, the O3 concentration data from the ERA5 Reanalysis are employed to investigate the contribution of the atmospheric circulation to the summertime lower tropospheric O3 changes in East Asian continent (EC) during 1979-2021. Results show that the summertime lower tropospheric O3 displays the same-sign variations in the whole EC during 1979-2021. The Silk Road-like atmospheric teleconnection is identified as a key circulation factor to drive the variations of summer O3 concentration in EC. The deep anomalous anticyclone over EC not only strengthens the descending motion and increases the sunlight and air temperature in the lower troposphere, resulting in the acceleration of formation of O3, but also transports more O3 from northern East Asia to lower latitudes of EC, leading to more increasing of the O3 concentration in central and eastern China. Further analysis indicates that the Silk Road-like atmospheric wave train is associated with the North Atlantic sea surface temperature (SST) variability that accounts for about 43% of total variance of O3 concentration in EC. Sensitivity experiments run with ECHAM5 model confirm the impact of the North Atlantic SST anomalies on this atmospheric wave train. Hence, our finding provides an insight of the cause of the lower tropospheric O3 variations in EC.