CO_2 in the upper troposphere: Influence of stratosphere-troposphere exchange

Creators: Shia, Run-Lie; Liang, Mao-Chang; Miller, Charles E.; Yung, Yuk L.

Abstract

A two-dimensional transport model constrained to measured surface CO_2 concentrations was used to simulate the spatial and temporal variation of CO_2 in the atmosphere for the period from 1975 to 2004. We find that the amplitude, phase and shape of the CO_2 seasonal cycle vary as a function of both altitude and latitude. Cross tropopause exchanges, especially the downward branch of the Brewer-Dobson circulation, which brings stratospheric air to the upper troposphere at middle and high latitudes, change the CO_2 concentration and seasonal cycle in the extra-tropics. The model results match recent aircraft measurements of CO_2 in the upper troposphere (Matsueda et al., 2002) remarkably well. We conclude that upper tropospheric CO_2 volume mixing ratios will provide a valuable tool for validating vertical transport. The implications of the CO_2 variation caused by the stratosphere-troposphere exchange for remote sensing of CO_2 are discussed.

Additional Information

© 2006 The American Geophysical Union. Received 24 February 2006; Revised 19 May 2006; Accepted 5 June 2006; Published 26 July 2006. We thank M. Gerstell, A. Ingersoll, N. Krakauer and L. Chen for reading the manuscript and helpful comments. This work was supported by NASA grant NNG04GD76G to California Institute of Technology. The building of the tropospheric model was supported by NSF grant ATM-0225829 to California Institute of Technology. The research at the Jet Propulsion Laboratory, California Institute of Technology, was performed under contract with the National Aeronautics and Space Administration.

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