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| Titel |
Quantitative evaluation of ozone and selected climate parameters in a set of EMAC simulations |
| VerfasserIn |
M. Righi, V. Eyring, K.-D. Gottschaldt, C. Klinger, F. Frank, P. Jöckel, I. Cionni |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 3 ; Nr. 8, no. 3 (2015-03-23), S.733-768 |
| Datensatznummer |
250116184
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| Publikation (Nr.) |
 copernicus.org/gmd-8-733-2015.pdf |
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| Zusammenfassung |
| Four simulations with the ECHAM/MESSy Atmospheric Chemistry (EMAC)
model have been evaluated with the Earth System Model Validation
Tool (ESMValTool) to identify differences in simulated ozone and
selected climate parameters that resulted from (i) different setups
of the EMAC model (nudged vs. free-running) and (ii) different
boundary conditions (emissions, sea surface temperatures (SSTs) and
sea ice concentrations (SICs)). To assess the relative performance
of the simulations, quantitative performance metrics are calculated
consistently for the climate parameters and ozone. This is important
for the interpretation of the evaluation results since biases in
climate can impact on biases in chemistry and vice versa. The
observational data sets used for the evaluation include ozonesonde
and aircraft data, meteorological reanalyses and satellite
measurements. The results from a previous EMAC evaluation of a model
simulation with nudging towards realistic meteorology in the
troposphere have been compared to new simulations with different
model setups and updated emission data sets in free-running time slice
and nudged quasi chemistry-transport model (QCTM) mode. The latter
two configurations are particularly important for chemistry-climate
projections and for the quantification of individual sources
(e.g., the transport sector) that lead to small chemical perturbations of
the climate system, respectively. With the exception of some
specific features which are detailed in this study, no large
differences that could be related to the different setups (nudged vs.
free-running) of the EMAC simulations were found, which offers
the possibility to evaluate and improve the overall model with the
help of shorter nudged simulations. The main differences between the
two setups is a better representation of the tropospheric and
stratospheric temperature in the nudged simulations, which also
better reproduce stratospheric water vapor concentrations, due to
the improved simulation of the temperature in the tropical
tropopause layer. Ozone and ozone precursor concentrations, on the
other hand, are very similar in the different model setups, if
similar boundary conditions are used. Different boundary conditions
however lead to relevant differences in the four simulations. Biases
which are common to all simulations are the underestimation of the
ozone hole and the overestimation of tropospheric column ozone, the
latter being significantly reduced when lower lightning emissions of nitrogen
oxides are used. To further investigate possible other reasons for
such bias, two sensitivity simulations with an updated scavenging
routine and the addition of a newly proposed HNO3-forming
channel of the HO2+NO reaction were performed. The
update in the scavenging routine resulted in a slightly better
representation of ozone compared to the reference simulation. The
introduction of the new HNO3-forming channel significantly
reduces the overestimation of tropospheric ozone. Therefore, including the new reaction rate could
potentially be important for a realistic simulation of tropospheric
ozone, although laboratory experiments and other model studies need
to confirm this hypothesis and some modifications to the rate, which
has a strong dependence on water vapor, might also still be needed. |
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