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Published October 24, 2008 | Published
Journal Article Open

Signature of stratospheric air at the Tibetan Plateau


Current estimates of gross carbon flux tend to ignore the downwelling flux of CO_2 from the stratosphere. Observations showed that there is a phase shift between the time series for the concentration of the standard isotopologue C^16O^16O and C^16O^18O at Waliguan, China (36°17'N, 100° 54'E, 3816 m) and several other places. Previous attempts to explain the shift have not been satisfactory. Here we show that the phase shift could be explained by the downwelling air from the stratosphere, and demonstrate that this source of CO_2 provides a useful tool for constraining the carbon cycle. Using O_3 as a proxy of stratosphere-troposphere exchange, we find excellent correlation between O_3 and C^16O^18O observed at the Waliguan Observatory. The observed variability of C^16O^18O is consistent with model predictions, thus supporting that the surface air has significant contributions from the stratosphere. Quantitative modeling may provide a powerful tool for constraining the sources and sinks of CO_2 using the isotopically enriched CO_2 from the stratosphere as a tracer.

Additional Information

© 2008 by the American Geophysical Union. Received 5 July 2008; revised 21 September 2008; accepted 23 September 2008; published 24 October 2008. This work was supported in part by NSC grant 97-2628-M-001-001 to Academia Sinica and the Natural Science Foundation of China 40875075. Special thanks are due Matthias Cuntz for sharing the biological model results and Shaw Liu for helpful discussion. The measurements of CO_2 and its isotopologues are a cooperative work between Chinese Academy of Meteorological Sciences and the National Oceanic and Atmospheric Administration (NOAA). YLY was supported by NSF grant ATM-9903790 to California Institute of Technology. Correspondence should be addressed to MCL (e-mail: mcl@rcec.sinica.edu.tw).

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