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| Titel |
Comparison of lidar-derived PM10 with regional modeling and ground-based observations in the frame of MEGAPOLI experiment |
| VerfasserIn |
P. Royer, P. Chazette, K. Sartelet, Q. J. Zhang, M. Beekmann, J.-C. Raut |
| 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 ; 11, no. 20 ; Nr. 11, no. 20 (2011-10-28), S.10705-10726 |
| Datensatznummer |
250010153
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| Publikation (Nr.) |
 copernicus.org/acp-11-10705-2011.pdf |
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| Zusammenfassung |
| An innovative approach using mobile lidar measurements was implemented to
test the performances of chemistry-transport models in simulating mass
concentrations (PM10) predicted by chemistry-transport models. A
ground-based mobile lidar (GBML) was deployed around Paris onboard a van
during the MEGAPOLI (Megacities: Emissions, urban, regional and Global
Atmospheric POLlution and climate effects, and Integrated tools for
assessment and mitigation) summer experiment in July 2009. The measurements
performed with this Rayleigh-Mie lidar are converted into PM10 profiles
using optical-to-mass relationships previously established from in situ
measurements performed around Paris for urban and peri-urban aerosols. The
method is described here and applied to the 10 measurements days (MD). MD of
1, 15, 16 and 26 July 2009, corresponding to different levels of pollution
and atmospheric conditions, are analyzed here in more details. Lidar-derived
PM10 are compared with results of simulations from POLYPHEMUS and CHIMERE
chemistry-transport models (CTM) and with ground-based observations from
the AIRPARIF network. GBML-derived and AIRPARIF in situ measurements have been
found to be in good agreement with a mean Root Mean Square Error RMSE (and a
Mean Absolute Percentage Error MAPE) of 7.2 μg m−3 (26.0%) and
8.8 μg m−3 (25.2%) with relationships assuming peri-urban and
urban-type particles, respectively. The comparisons between CTMs and lidar
at ~200 m height have shown that CTMs tend to underestimate wet PM10
concentrations as revealed by the mean wet PM10 observed during the 10 MD
of 22.4, 20.0 and 17.5 μg m−3 for lidar with peri-urban
relationship, and POLYPHEMUS and CHIMERE models, respectively. This leads to a
RMSE (and a MAPE) of 6.4 μg m−3 (29.6%) and 6.4 μg m−3 (27.6%)
when considering POLYPHEMUS and CHIMERE CTMs, respectively. Wet
integrated PM10 computed (between the ground and 1 km above the ground
level) from lidar, POLYPHEMUS and CHIMERE results have been compared and
have shown similar results with a RMSE (and MAPE) of 6.3 mg m−2 (30.1%)
and 5.2 mg m−2 (22.3%) with POLYPHEMUS and CHIMERE when
comparing with lidar-derived PM10 with periurban relationship. The values
are of the same order of magnitude than other comparisons realized in
previous studies. The discrepancies observed between models and measured
PM10 can be explained by difficulties to accurately model the background
conditions, the positions and strengths of the plume, the vertical turbulent
diffusion (as well as the limited vertical model resolutions) and
chemical processes as the formation of secondary aerosols. The major
advantage of using vertically resolved lidar observations in addition to
surface concentrations is to overcome the problem of limited spatial
representativity of surface measurements. Even for the case of a well-mixed
boundary layer, vertical mixing is not complete, especially in the surface
layer and near source regions. Also a bad estimation of the mixing layer
height would introduce errors in simulated surface concentrations, which can
be detected using lidar measurements. In addition, horizontal spatial
representativity is larger for altitude integrated measurements than for
surface measurements, because horizontal inhomogeneities occurring near
surface sources are dampened. |
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