A Unique Mechanism of Ozone Surges Jointly Triggered by Deep Stratospheric Intrusions and the Tibetan Plateau Topographic Forcing

Abstract Given our poor understanding on mechanisms of stratospheric intrusions (SI) upon near‐surface ozone (O3) surges, predicting the SI‐induced O3 pollution pose inherent difficulties. Taking a wintertime O3 surge episode over the Sichuan Basin (SCB) as an example, we find SI contribute 47.8% to near‐surface O3 levels and reveal the underlying mechanisms. Tropopause folding nearly extends to the deep atmospheric boundary layer over the Tibetan Plateau (TP) due to topographic forcing, driving stratospheric O3 penetration into the TP's near‐surface. The intruded O3 is subsequently transported into the downstream SCB by strong downdrafts along the TP's leeward slope. Interestingly, the mountain‐plains solenoid between the TP and the SCB strengthens the downward intrusions of O3 during both daytime and nighttime, further amplifying the contribution of SI to the SCB's near‐surface O3 levels. This unique mechanism of O3 surges could provide new insights for the forecast of unexpected nocturnal high‐O3 episodes.