Abstract
Stratosphere-troposphere exchange could be enhanced by tropopause folding, linked to variability in the subtropical jet stream. Relevant to tropospheric biogeochemistry is irreversible transport from the stratosphere, associated with deep intrusions. Here, oxygen anomalies in near surface air CO2 are used to study the irreversible transport from the stratosphere, where the triple oxygen isotopes of CO2 are distinct from those originating from the Earth’s surface. We show that the oxygen anomaly in CO2 is observable at sea level and the magnitude of the signal increases during the course of our sampling period (September 2013-February 2014), concordant with the strengthening of the subtropical jet system and the East Asia winter monsoon. The trend of the anomaly is found to be 0.1‰/month (R2 = 0.6) during the jet development period in October. Implications for utilizing the oxygen anomaly in CO2 for CO2 biogeochemical cycle study and stratospheric intrusion flux at the surface are discussed.
Highlights
Stratosphere-troposphere exchange could be enhanced by tropopause folding, linked to variability in the subtropical jet stream
Stratospheric intrusions in East Asia occurs in close association with the presence of the subtropical jet stream[25,26,27,28,29,30,31]
Convective activities occurring during the northeast monsoon and accompanied by the passage of mid-latitude cold fronts are largely responsible for the changing meteorology in fall
Summary
Stratosphere-troposphere exchange could be enhanced by tropopause folding, linked to variability in the subtropical jet stream. This finding is consistent with the fact that the stratospheric intrusions bringing O3 into the troposphere reach their seasonal maximum in the summer[27,28]. This is primarily due to unusually strong winds associated with the polar and subtropical jet streams over the east Asian coast and the persistence of cyclogenesis over the western Pacific, resulting in frequent tropopause folding and significant intrusion of O3 into the troposphere[10,25,29,30,31,32]. Symbol Δ is frequently used to quantify the deviation from the mass-dependent fractionation line, and is defined by
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