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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 104, NO. D19, PAGES 23,823–23,840, 1999

Global impact of fossil fuel combustion on atmospheric NO x

Larry W. Horowitz

Advanced Study Program and Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado


Daniel J. Jacob

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


Abstract

Fossil fuel combustion is the largest global source of NO x to the troposphere. This source is concentrated in polluted continental boundary layers, and the extent to which it impacts tropospheric chemistry on a global scale is uncertain. We use a global three-dimensional model of tropospheric chemistry and transport to study the impact of fossil fuel combustion on the global distribution of NO x during nothern hemisphere summer. In the model, we tag fossil fuel NO x and its reservoir NO y species in order to determine the relative contribution of fossil fuel combustion to NO x concentrations in different regions of the world. Our model includes a detailed representation of NO x -O3-nonmethane hydrocarbon (NMHC) chemistry, which is necessary to properly simulate the export of reactive nitrogen, including organic nitrates such as peroxyacyl nitrates (PANs), from the continental boundary layer. We find that fossil fuel combustion accounts for over 40% of NO x . concentrations in the lower and middle troposphere throughout the extratropical northern hemisphere. PANs are shown to provide an important mechanism for transporting NO x from source regions to the remote troposphere, accounting for over 80% of the fossil fuel NO x in the lower troposphere over most of the ocean. Sources in the United States are found to contribute about half of the fossil fuel NO x over the North Atlantic Ocean. Emissions from China, which are expected to increase rapidly in the coming decades, currently account for about half of the fossil fuel NO x over the western North Pacific Ocean; the influence of these emissions extends into the tropics. Because of this tropical influence, emissions from China have more potential than emissions in the United States to perturb the global oxidizing power of the atmosphere.

Received 1 October 1998; accepted 23 March 1999.

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Citation: Horowitz, L. W., and D. J. Jacob (1999), Global impact of fossil fuel combustion on atmospheric NO x , J. Geophys. Res., 104(D19), 23,823–23,840.