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| Titel |
Sensitivity of pre-industrial tropospheric ozone and ozone radiative forcing to historic land cover change. |
| VerfasserIn |
Michael Hollaway, Stephen Arnold, William Collins, Gerd Folberth, Alex Rap |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082109
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| Zusammenfassung |
| Estimates of anthropogenic radiative forcing due to changes in tropospheric ozone are based
on model simulations of present day and pre-industrial tropospheric ozone distributions.
However, there are large uncertainties in simulations of the pre-industrial tropospheric ozone
budget, and there is evidence to suggest that models may overestimate pre-industrial surface
ozone concentrations compared with a limited set of observations from the turn of the
nineteenth century. Here, we use a coupled Earth system model (HadGEM2-ES) with
interactive vegetation and photosynthetically-driven isoprene emissions, to investigate
the impacts of 1865 to present-day land cover change on tropospheric ozone. We
investigate separately the impacts of changes in climate, land surface cover and
atmospheric CO2 on dry deposition of ozone and precursors, and on biogenic isoprene
emissions.
Our results show that changes in dry deposition from differences in the vegetation surface
resistance produce localised decreases of several ppbv in surface ozone. Changes in
isoprene emissions produce large-scale ozone distribution changes, with localised
decreases in ozone in regions of increased isoprene and low NOx loading. Widespread
ozone increases are produced in the remote background atmosphere under 1865
climate and land cover due to tropical isoprene increases under pre-industrial CO2
and resultant enhanced PAN formation from biomass burning–sourced NO2. Our
simulations produce a pre-industrial ozone burden of 200-221 Tg with the range resulting
from differences in the model land vegetation distribution, the CO2 mixing ratio
the vegetation is exposed to and the model climate setup. The response of ozone
concentrations to land cover changes is greater than the response to changes in the
CO2 mixing ratio the vegetation is exposed to. The resultant estimated range in
pre-industrial to present day radiative forcing from our simulations is 0.227 to 0.244
Wm-2. |
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