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| Titel |
Impact of future land-cover changes on HNO3 and O3 surface dry deposition |
| VerfasserIn |
T. Verbeke, J. Lathière, S. Szopa, N. de Noblet-Ducoudré |
| 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. 23 ; Nr. 15, no. 23 (2015-12-09), S.13555-13568 |
| Datensatznummer |
250120210
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| Publikation (Nr.) |
 copernicus.org/acp-15-13555-2015.pdf |
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| Zusammenfassung |
| Dry deposition is a key component of surface–atmosphere exchange of
compounds, acting as a sink for several chemical species. Meteorological
factors, chemical properties of the trace gas considered and land surface
properties are strong drivers of dry deposition efficiency and variability.
Under both climatic and anthropogenic pressure, the vegetation distribution
over the Earth has been changing a lot over the past centuries and could be
significantly altered in the future. In this study, we perform a modeling
investigation of the potential impact of land-cover changes between
the present day (2006) and the future (2050) on dry deposition velocities at the
surface, with special interest for ozone (O3) and nitric acid
(HNO3), two compounds which are characterized by very different
physicochemical properties. The 3-D chemistry-transport model LMDz-INCA is
used, considering changes in vegetation distribution based on the three
future projections, RCPs 2.6, 4.5 and 8.5, and present-day (2007)
meteorology. The 2050 RCP 8.5 vegetation distribution leads to a rise of up
to 7 % (+0.02 cm s−1) in the surface deposition velocity calculated for
ozone (Vd,O3) and a decrease of −0.06 cm s−1 in the surface deposition
velocity calculated for nitric acid (Vd,HNO3) relative to the
present-day values in tropical Africa and up to +18 and −15 %, respectively, in Australia. When taking into account the RCP 4.5 scenario, which shows
dramatic land-cover change in Eurasia, Vd,HNO3 increases by up to
20 % (annual-mean value) and reduces Vd,O3 by the same magnitude in
this region. When analyzing the impact of surface dry deposition change on
atmospheric chemical composition, our model calculates that the effect is
lower than 1 ppb on annual-mean surface ozone concentration for both the
RCP 8.5 and RCP 2.6 scenarios. The impact on HNO3 surface concentrations
is more disparate between the two scenarios regarding the spatial
repartition of effects. In the case of the RCP 4.5 scenario, a significant
increase of the surface O3 concentration reaching locally by up to 5 ppb (+5 %)
is calculated on average during the June–August period. This
scenario also induces an increase of HNO3 deposited flux exceeding
locally 10 % for monthly values. Comparing the impact of land-cover change
to the impact of climate change, considering a 0.93 °C increase of
global temperature, on dry deposition velocities, we estimate that the
strongest increase over lands occurs in the Northern Hemisphere during
winter, especially in Eurasia, by +50 % (+0.07 cm s−1) for Vd,O3 and
+100 % (+0.9 cm s−1) for Vd,HNO3. However, different regions are
affected by both changes, with climate change impact on deposition
characterized by a latitudinal gradient, while the land-cover change impact
is much more heterogeneous depending on vegetation distribution modification
described in the future RCP scenarios. The impact of long-term land-cover
changes on dry deposition is shown to be significant and to differ strongly
from one scenario to another. It should therefore be considered in
biosphere–atmospheric chemistry interaction studies in order to have a fully
consistent picture. |
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