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| Titel |
Using ground-based solar and lunar infrared spectroscopy to study the diurnal trend of carbon monoxide in the Mexico City boundary layer |
| VerfasserIn |
W. Stremme, I. Ortega, M. Grutter |
| 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. 20 ; Nr. 9, no. 20 (2009-10-26), S.8061-8078 |
| Datensatznummer |
250007710
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| Publikation (Nr.) |
 copernicus.org/acp-9-8061-2009.pdf |
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| Zusammenfassung |
| Carbon monoxide (CO) is an important pollutant in urban agglomerations. Quantifying
the total burden of this pollutant in a megacity is challenging because not
only its surface concentration but also its vertical dispersion present
different behaviours and high variability. The diurnal trend of columnar CO
in the boundary layer of Mexico City has been measured during various days
with ground-based infrared absorption spectroscopy. Daytime CO total columns
are retrieved from solar spectra and for the first time, nocturnal CO total
columns using moonlight have been retrieved within a megacity. The
measurements were taken at the Universidad Nacional Autónoma de
México (UNAM) campus located in Mexico City (19.33° N,
99.18° W, 2260 m a.s.l.) from October 2007 until February 2008 with
a Fourier-transform infrared spectrometer at 0.5 cm−1 resolution. The
atmospheric CO background column was measured from the high altitude site
Altzomoni (19.12° N, 98.65° W, 4010 m a.s.l.) located
60 km southeast of Mexico City. The total CO column within the city presents
large variations. Fresh CO emissions at the surface, the transport of cleaner
or more polluted air masses within the
field-of-view of the instrument and other processes contribute to this
variability. The mean background value above the boundary mixing layer was
found to be (8.4±0.5)×1017 molecules/cm2, while
inside the city, the late morning mean on weekdays and Sundays was found to
be (2.73±0.41)×1018 molecules/cm2 and
(2.04±0.57)×1018 molecules/cm2, respectively. Continuous
CO column retrieval during the day and night (when available), in conjunction
with surface CO measurements, allow for a reconstruction of the effective
mixing layer height. The limitations from this simplified approach, as well
as the potential of using continuous column measurements in order to derive
top-down CO emissions from a large urban area, are discussed. Also, further
monitoring will provide more insight in daily and weekly emission patterns
and a usable database for the quantitative validation of CO from satellite
observations in a megacity. |
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