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| Titel |
Uncertainties in isoprene photochemistry and emissions: implications for the oxidative capacity of past and present atmospheres and for climate forcing agents |
| VerfasserIn |
P. Achakulwisut, L. J. Mickley, L. T. Murray, A. P. K. Tai, J. O. Kaplan, B. Alexander |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 14 ; Nr. 15, no. 14 (2015-07-20), S.7977-7998 |
| Datensatznummer |
250119913
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| Publikation (Nr.) |
 copernicus.org/acp-15-7977-2015.pdf |
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| Zusammenfassung |
| Isoprene and its oxidation products are major players in the oxidative
chemistry of the troposphere. Current understanding of the factors
controlling biogenic isoprene emissions and of the fate of isoprene oxidation
products in the atmosphere has been evolving rapidly. We use a
climate–biosphere–chemistry modeling framework to evaluate the sensitivity of
estimates of the tropospheric oxidative capacity to uncertainties in isoprene
emissions and photochemistry. Our work focuses on two climate transitions:
from the Last Glacial Maximum (LGM, 19 000–23 000 years BP) to the
preindustrial (1770s) and from the preindustrial to the present day (1990s).
We find that different oxidants have different sensitivities to the
uncertainties tested in this study. Ozone is relatively insensitive, whereas
OH is the most sensitive: changes in the global mean OH levels for the
LGM-to-preindustrial transition range between −29 and +7 % and those
for the preindustrial-to-present-day transition range between −8 and
+17 % across our simulations. We find little variability in the
implied relative LGM–preindustrial difference in methane emissions with
respect to the uncertainties tested in this study. Conversely, estimates of
the preindustrial-to-present-day and LGM-to-preindustrial changes in the
global burden of secondary organic aerosol (SOA) are highly sensitive. We
show that the linear relationship between tropospheric mean OH and
tropospheric mean ozone photolysis rates, water vapor, and total emissions of
NOx and reactive carbon – first reported in Murray et al. (2014) – does
not hold across all periods with the new isoprene photochemistry mechanism.
This study demonstrates how inadequacies in our current understanding of
isoprene emissions and photochemistry impede our ability to constrain the
oxidative capacities of the present and past atmospheres, its controlling
factors, and the radiative forcing of some short-lived species such as SOA
over time. |
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