Ozone impacts of gas–aerosol uptake in global chemistry transport models
The impact of six heterogeneous gas–aerosol uptake reactions on tropospheric ozone and nitrogen species was studied using two chemical transport models, the Meteorological Synthesizing Centre-West of the European Monitoring and Evaluation Programme (EMEP MSC-W) and the European Centre Hamburg g...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/3147/2018/acp-18-3147-2018.pdf |
| Summary: | The impact of six heterogeneous gas–aerosol uptake reactions
on
tropospheric ozone and nitrogen species was studied using two
chemical transport models, the Meteorological Synthesizing
Centre-West of the European Monitoring and Evaluation Programme
(EMEP MSC-W) and the European Centre Hamburg general circulation model combined
with versions of the Hamburg Aerosol Model and Model for Ozone and Related chemical Tracers (ECHAM-HAMMOZ). Species
undergoing heterogeneous reactions in both models include
N<sub>2</sub>O<sub>5</sub>, NO<sub>3</sub>, NO<sub>2</sub>, O<sub>3</sub>, HNO<sub>3</sub>,
and HO<sub>2</sub>. Since heterogeneous reactions take place at the
aerosol surface area, the modelled surface area density (<i>S</i><sub>a</sub>) of both
models was compared to a satellite product retrieving the surface
area. This comparison shows a good agreement in global pattern and
especially the capability of both models to capture the extreme
aerosol loadings in east Asia.
<br><br>
The impact of the heterogeneous reactions was evaluated by the
simulation of a reference run containing all heterogeneous reactions
and several sensitivity runs. One reaction was turned off in each
sensitivity run to compare it with the reference run. The analysis
of the sensitivity runs confirms that the globally most important
heterogeneous reaction is the one of N<sub>2</sub>O<sub>5</sub>. Nevertheless,
NO<sub>2</sub>, HNO<sub>3</sub>, and HO<sub>2</sub> heterogeneous reactions
gain relevance particularly in east Asia due to the presence of high
NO<sub><i>x</i></sub> concentrations and high <i>S</i><sub>a</sub> in the same
region. The heterogeneous reaction of O<sub>3</sub> itself on dust is
of minor relevance compared to the other heterogeneous
reactions. The impacts of the N<sub>2</sub>O<sub>5</sub> reactions show strong
seasonal variations, with the biggest impacts on O<sub>3</sub> in springtime
when photochemical reactions are active and N<sub>2</sub>O<sub>5</sub>
levels still high. Evaluation of the models with northern
hemispheric ozone surface observations yields a better agreement of
the models with observations in terms of concentration levels,
variability, and temporal correlations at most sites when the
heterogeneous reactions are incorporated. Our results are loosely
consistent with results from earlier studies, although the magnitude
of changes induced by N<sub>2</sub>O<sub>5</sub> reaction is at the low end of
estimates, which seems to fit a trend, whereby the more recent the
study the lower the impacts of these reactions. |
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| ISSN: | 1680-7316 1680-7324 |