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| Titel |
Dynamic adjustment of climatological ozone boundary conditions for air-quality forecasts |
| VerfasserIn |
P. A. Makar, W. Gong, C. Mooney, J. Zhang, D. Davignon, M. Samaali, M. D. Moran, H. He, D. W. Tarasick, D. Sills, J. Chen |
| 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 ; 10, no. 18 ; Nr. 10, no. 18 (2010-09-28), S.8997-9015 |
| Datensatznummer |
250008792
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| Publikation (Nr.) |
 copernicus.org/acp-10-8997-2010.pdf |
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| Zusammenfassung |
| Ten different approaches for applying lateral and top climatological
boundary conditions for ozone have been evaluated using the off-line
regional air-quality model AURAMS, driven with meteorology provided by the
GEM weather-forecast model. All ten approaches employ the same
climatological ozone profiles, but differ in the manner in which they are
applied, via the inclusion or exclusion of (i) a dynamic adjustment of the
climatological ozone profile in response to the model-predicted tropopause
height, (ii) a sponge zone for ozone on the model top, (iii) upward
extrapolation of the climatological ozone profile, and (iv) different mass
consistency corrections. The model performance for each approach was
evaluated against North American surface ozone and ozonesonde observations
from the BAQS-Met field study period in the summer of 2007. The original
daily one-hour maximum surface ozone biases of about +15 ppbv were greatly
reduced (halved) in some simulations using alternative methodologies.
However, comparisons to ozonesonde observations showed that the reduction in
surface ozone bias sometimes came at the cost of significant positive biases
in ozone concentrations in the free troposphere and upper troposphere. The
best overall performance throughout the troposphere was achieved using a
methodology that included dynamic tropopause height adjustment, no sponge
zone at the model top, extrapolation of ozone when required above the limit
of the climatology, and no mass consistency corrections (global mass
conservation was still enforced). The simulation using this model version
had a one-hour daily maximum surface ozone bias of +8.6 ppbv, with small
reductions in model correlation, and the best comparison to ozonesonde
profiles. This recommended and original methodologies were compared for two
further case studies: a high-resolution simulation of the BAQS-Met
measurement intensive, and a study of the downwind region of the Canadian
Rockies. Significant improvements were noted for the high resolution
simulations during the BAQS-Met measurement intensive period, both in formal
statistical comparisons and time series comparisons of events at surface
stations. The tests for the downwind-Rockies region showed that the coupling
between vertical transport associated with troposphere/stratosphere
exchange, and that associated with boundary layer turbulent mixing, may
contribute to ozone positive biases. The results may be unique to the
modelling setup employed, but the results also highlight the importance of
evaluating boundary condition and mass consistency/correction algorithms
against three-dimensional datasets. |
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