Interannual variations in ozone pollution with a dipole structure over Eastern China associated with springtime thermal forcing over the Tibetan Plateau.

The Tibetan Plateau (TP) is essential in modulating climate change in downstream Eastern China (EC). As a meteorology-sensitive pollutant, changes in ozone (O) in connection with the TP have received limited attention. In this study, using climate analysis of the China High Air Pollutants O product and ERA5 reanalysis data of meteorology for 1980-2020, the effect of springtime TP thermal forcing on the warm season (April-September) O pollution over EC was investigated. The strong TP thermal effect significantly modulates the interannual variations in O pollution with a dipole pattern over EC, inducing more O pollution in northern EC regions and alleviating O pollution in the southern regions. In northern (southern) EC, strong TP thermal forcing triggers a significant anomalous high (low) pressure center accompanied by anticyclonic (cyclonic) anomalies, resulting in decreased (increased) total cloud cover, increased (reduced) surface downward solar radiation and air temperature, which are conducive to the anomalous increase (decrease) in surface O concentrations. Moreover, the key sources of springtime thermal forcing over the TP influence the major O pollution regions over southern and northern EC with an inverse pattern, depending on their locations and orientations to the large topography of the TP. This research reveals an important driving factor for the dipole interannual variation in O pollution over EC, providing a new prospect for the effect of the TP on atmospheric environmental change.