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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, D07306, doi:10.1029/2003JD003988, 2004

Constraints on the sources of tropospheric ozone from 210Pb-7Be-O3 correlations

Hongyu Liu

Department of Earth and Planetary Sciences and Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA


Daniel J. Jacob

Department of Earth and Planetary Sciences and Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA


Jack E. Dibb

Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, New Hampshire, USA


Arlene M. Fiore

Department of Earth and Planetary Sciences and Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA


Robert M. Yantosca

Department of Earth and Planetary Sciences and Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA


Abstract

The 210Pb-7Be-O3 relationships observed in three aircraft missions over the western Pacific (PEM-West A and B, TRACE-P) are simulated with a global three-dimensional chemical tracer model (GEOS-CHEM) driven by assimilated meteorological observations. Results are interpreted in terms of the constraints that they offer on sources of tropospheric ozone (O3). Aircraft observations of fresh Asian outflow show strong 210Pb-O3 correlations in September–October, but such correlations are only seen at low latitudes in February–March. Observations further downwind over the Pacific show stronger 210Pb-O3 correlations in February–March than in September–October. The model reproduces these results and attributes the seasonal contrast to strong O3 production and vertical mixing over east Asia in September–October, seasonal shift of convection from China in September–October to Southeast Asia in February–March, and slow but sustained net O3 production in Asian outflow over the western Pacific in February–March. Seasonal biomass burning over Southeast Asia in February–March is responsible for the positive 210Pb-O3 correlations observed at low latitudes. The model reproduces the observed absence of 7Be-O3 correlations over the western Pacific during September–October, implying strong convective and weak stratospheric influence on O3. Comparison of observed and simulated 7Be-O3 correlations indicates that the stratosphere contributes less than 20–30% of O3 in the middle troposphere at northern midlatitudes even during spring.

Received 18 July 2003; accepted 12 February 2004; published 10 April 2004.

Index Terms: 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305).

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Citation: Liu, H., D. J. Jacob, J. E. Dibb, A. M. Fiore, and R. M. Yantosca (2004), Constraints on the sources of tropospheric ozone from 210Pb-7Be-O3 correlations, J. Geophys. Res., 109, D07306, doi:10.1029/2003JD003988.