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| Titel |
Comparison of tropospheric NO2 observations by GOME and ground stations over Tokyo, Japan |
| VerfasserIn |
K. Noguchi, H. Itoh, T. Shibasaki, S. Hayashida, I. Uno, T. Ohara, A. Richter, J. P. Burrows |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024747
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| Zusammenfassung |
| Nitrogen oxides (NOx = NO + NO2) are anthropogenically emitted as a form of NO in the
high-temperature burning processes of fossil fuels mainly in energy generations and vehicles.
Because NOx is a precursor of ozone, which is composed of a so-called photochemical smog,
and is a health-hazard matter, the monitoring of NO2 is important to control air quality. The
satellite observation is one of the most suitable methods for the monitoring of air pollution
because satellite observations can obtain a global distribution of the pollutants. However, the
observation of tropospheric gases by satellites still includes technically challenging problems,
and the field is developing.
To test whether satellite observations could successfully detect the behavior of
tropospheric NO2, we compared satellite and ground-based observations of tropospheric NO2
over the Tokyo region. The satellite data were tropospheric NO2 vertical column density
(VCD) derived from Global Ozone Monitoring Experiment (GOME) spectrometer
measurements (hereafter GOME-NO2) [Richter et al., 2005], and the ground-based data were
surface NO2 volume mixing ratio (VMR) observed by the network of air-quality monitoring
stations in Tokyo. The analysis was performed for the data from January 1996 to June
2003.
We found a strong correlation between GOME-NO2 and the surface VMR. They showed
a similar seasonal variation with a maximum in winter and a minimum in summer. The result
suggested that GOME was observing the behavior of NO2 near the surface in the Tokyo
region. A more rigorous comparison was conducted by scaling the surface NO2 VMR to
the tropospheric VCD with vertical NO2 VMR profiles. The NO2 profiles were
calculated by using the chemical transport model CMAQ/REAS [Uno et al., 2007;
Ohara et al., 2007]. This second comparison indicated that the GOME observations
represent the behavior of NO2 more closely at the relatively unpolluted ground
stations than at the highly polluted ground stations of the air-quality monitoring. This
tendency could be attributed to the horizontal heterogeneity within a GOME footprint
(320kmX40km). Comparison with a previous study in northern Italy [Ordonez et al., 2006]
showed that the GOME-NO2 measurements tended to be smaller over Tokyo than
over northern Italy. There would be two reasons for such a difference. First, areas
of ocean intruding into the GOME pixels could lower the observed GOME-NO2
because Tokyo is located in a coastal land region with a gulf. Second, the pollution in
Tokyo is so spatially concentrated that the rural regions contaminating GOME pixels
could also reduce the observed NO2 concentration from its true spatially resolved
value. |
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