Atmos. Chem. Phys. Discuss., 11, 25605-25654, 2011
www.atmos-chem-phys-discuss.net/11/25605/2011/
doi:10.5194/acpd-11-25605-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Impact of the isoprene photochemical cascade on tropical ozone
F. Paulot1, D. K. Henze2, and P. O. Wennberg1,3
1Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California, USA
2Department of Mechanical Engineering, University of Colorado, Boulder, Colorado, USA
3Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA

Abstract. Tropical tropospheric ozone affects Earth's radiative forcing and the oxidative capacity of the atmosphere. Considerable work has been devoted to the study of the processes controlling its budget. Yet, large discrepancies between simulated and observed tropical tropospheric ozone remain. Here, we characterize some of the mechanisms by which the photochemistry of isoprene impacts the budget of tropical ozone. At the regional scale, we find that isoprene nitrates can account for up to 70% of the local NOx sink. Using forward sensitivity simulations, we show that the modulation of Ox by isoprene nitrates photochemistry can be characterized by their net impact on NOx. We use adjoint sensitivity simulations to demonstrate that the oxidation of isoprene can affect ozone outside of continental regions through the transport of NOx over near-shore regions (e.g., South Atlantic) and the oxidation of isoprene outside of the boundary layer far from its emissions regions. The latter mechanism is promoted by the simulated low boundary-layer oxidative conditions. In our simulation, ~20% of the isoprene is oxidized above the boundary layer in the tropics. Changes in the interplay between regional and global effect are discussed in light of the forecasted increase in anthropogenic emissions in tropical regions.

Citation: Paulot, F., Henze, D. K., and Wennberg, P. O.: Impact of the isoprene photochemical cascade on tropical ozone, Atmos. Chem. Phys. Discuss., 11, 25605-25654, doi:10.5194/acpd-11-25605-2011, 2011.
 
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