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Impact of the isoprene photochemical cascade on tropical ozone

Paulot, F. and Henze, D. K. and Wennberg, P. O. (2012) Impact of the isoprene photochemical cascade on tropical ozone. Atmospheric Chemistry and Physics, 12 (3). pp. 1307-1325. ISSN 1680-7316. doi:10.5194/acp-12-1307-2012.

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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 use forward sensitivity simulation to explore the sensitivity to the representation of isoprene nitrates. We find that isoprene nitrates can account for up to 70% of the local NO_x = NO+NO_2 sink. The resulting modulation of ozone can be well characterized by their net modulation of NO_x. We use adjoint sensitivity simulations to demonstrate that the oxidation of isoprene can affect ozone outside of continental regions through the transport of NO_x 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.

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URLURL TypeDescription DOIArticle
Paulot, F.0000-0001-7534-4922
Wennberg, P. O.0000-0002-6126-3854
Additional Information:© 2012 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 20 July 2011 – Published in Atmos. Chem. Phys. Discuss.: 13 September 2011. Revised: 22 December 2011 – Accepted: 13 January 2012 – Published: 2 February 2012. This manuscript greatly benefited from the comments of two anonymous reviewers. The authors also thank M. R. Beaver, J. D. Crounse and Y. Xie for helpful discussions. F. P. was supported by a NASA Earth and Space Science Fellowship. DKH was supported by the NASA New Investigator Program. Simulations were performed on Caltech’s Division of Geological and Planetary Sciences Dell cluster.
Funding AgencyGrant Number
NASA Earth and Space Science FellowshipUNSPECIFIED
Issue or Number:3
Record Number:CaltechAUTHORS:20120322-084644461
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Official Citation:Paulot, F., Henze, D. K., and Wennberg, P. O.: Impact of the isoprene photochemical cascade on tropical ozone, Atmos. Chem. Phys., 12, 1307-1325, doi:10.5194/acp-12-1307-2012, 2012
Usage Policy:This work is distributed under the Creative Commons Attribution 3.0 License.
ID Code:29804
Deposited By: Tony Diaz
Deposited On:17 Apr 2012 22:29
Last Modified:09 Nov 2021 19:30

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