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| Titel |
A novel downscaling technique for the linkage of global and regional air quality modeling |
| VerfasserIn |
Y. F. Lam, J. S. Fu |
| 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 ; 9, no. 23 ; Nr. 9, no. 23 (2009-12-07), S.9169-9185 |
| Datensatznummer |
250007784
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| Publikation (Nr.) |
 copernicus.org/acp-9-9169-2009.pdf |
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| Zusammenfassung |
Recently, downscaling global atmospheric model outputs (GCTM) for the USEPA
Community Multiscale Air Quality (CMAQ) Initial (IC) and Boundary Conditions
(BC) have become practical because of the rapid growth of computational
technologies that allow global simulations to be completed within a
reasonable time. The traditional method of generating IC/BC by profile data
has lost its advocates due to the weakness of the limited horizontal and
vertical variations found on the gridded boundary layers. Theoretically,
high quality GCTM IC/BC should yield a better result in CMAQ. Unfortunately,
several researchers have found that the outputs from GCTM IC/BC are not
necessarily better than profile IC/BC due to the excessive transport of
O3 aloft in GCTM IC/BC. In this paper, we intend to investigate the
effects of using profile IC/BC and global atmospheric model data. In
addition, we are suggesting a novel approach to resolve the existing issue
in downscaling.
In the study, we utilized the GEOS-Chem model outputs to generate
time-varied and layer-varied IC/BC for year 2002 with the implementation of
tropopause determining algorithm in the downscaling process (i.e., based on
chemical (O3) tropopause definition). The comparison between the
implemented tropopause approach and the profile IC/BC approach is performed
to demonstrate improvement of considering tropopause. It is observed that
without using tropopause information in the downscaling process, unrealistic
O3 concentrations are created at the upper layers of IC/BC. This
phenomenon has caused over-prediction of surface O3 in CMAQ. In
addition, the amount of over-prediction is greatly affected by temperature
and latitudinal location of the study domain. With the implementation of the
algorithm, we have successfully resolved the incompatibility issues in the
vertical layer structure between global and regional chemistry models to
yield better surface O3 predictions than profile IC/BC for both summer
and winter conditions. At the same time, it improved the vertical O3
distribution of CMAQ outputs. It is strongly recommended that the tropopause
information should be incorporated into any two-way coupled global and
regional models, where the tropospheric regional model is used, to solve the
vertical incompatibility that exists between global and regional models. |
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