 |
| Titel |
Atmospheric CO2 measurement using dispersive infrared spectroscopy with a scanning Fabry-Pérot interferometer sensor |
| VerfasserIn |
Ka Lok Chan, Zhi Ning, Dane Westerdahl, Ka Chun Wong, You Wen Sun, Andreas Hartl, Mark Wenig |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088785
|
| Publikation (Nr.) |
 EGU/EGU2014-2937.pdf |
|
|
|
|
|
| Zusammenfassung |
| A novel infrared absorption spectroscopic based measurement technique was developed for
atmospheric CO2 measurement by using a new scanning Febry-Pérot interferometer sensor.
The sensor measures the optical spectra in the mid infrared (3900nm to 5220nm) wavelength
range with full width half maximum (FWHM) spectral resolution of 78.8 nm at the
CO2 absorption band (~4280 nm) and sampling resolution of 20 nm. The CO2
concentration is determined from the measured optical absorption spectra by fitting it to
the CO2 reference spectrum. Interference from other major absorbers in the same
wavelength range, e.g., carbon monoxide (CO) and water vapor (H2O), was taken
out by including their reference spectra in the fit as well. An iterative algorithm
to account for the non-linear response of the fit function to the absorption cross
sections due to the broad instrument function was developed and tested. The detailed
descriptions of the instrumental setup, the retrieval procedure, a modeling study for
error analysis as well as laboratory validation using standard gas concentrations are
presented.
A modeling study of the retrieval algorithm showed that errors due to instrument noise
can be considerably reduced by using the dispersive spectral information in the retrieval. The
mean measurement error of the prototype DIRS CO2 measurement for 1 minute averaged
data is about ± 2.5 ppmv, and down to ± 0.8 ppmv for 10 minute averaged data. A field test
of atmospheric CO2 measurements were carried out in an urban site in Hong Kong for a
month and compared to a commercial non-dispersive infrared (NDIR) CO2 analyzer. 10
minute averaged data shows good agreement between the DIRS and NDIR measurements
with Pearson correlation coefficient (R) of 0.99. A CO2 episode observed during the
measurement period was analysis by the Hybrid Single Particle Lagrangian Integrated
Trajectory (HYSPLIT) model. Result shows the air mass was recirculated in the region
which indicates that the CO2 episode may result from the accumulation of local
emissions. A pronounced bimodal CO2 diurnal profile was observed indicating the CO2
concentration is mainly related to the increase in traffic load during the rush hours. |
|
|
|
|
|
|