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| Titel |
Mapping greenhouse gas emissions in the Los Angeles basin by remote sensing using a Fourier Transform Spectrometer on Mt. Wilson |
| VerfasserIn |
Kam Weng Wong, Dejian Fu, Stanley Sander, Thomas Pongetti, Eric Kort, Sally Newman, Yuk Yung |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250084213
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| Zusammenfassung |
| Carbon dioxide (CO2) and methane (CH4) are long-lived greenhouse gases (GHGs) that play
crucial roles in climate change. According to the 2007 IPCC report, anthropogenic CO2 and
CH4 contribute 80% of the radiative forcing from all long-lived GHGs and more than
two-thirds of the radiative forcing from all GHGs. Since megacities, such as Los Angeles, are
significant sources of anthropogenic GHGs, it is critical to monitor their emissions. Currently,
top-down estimates of GHGs are based on in-situ measurements, at the ground or by aircraft,
and satellite data. However, these measurements have limitations – in-situ ground
measurements are too sensitive to local emissions, aircraft measurements are too expensive
for long-term observations and satellite measurements are usually not sensitive to
emission variations in the boundary layer, where emissions are located. Here we
present the estimations of greenhouse gases using ground-based remote sensing.
A Fourier Transform Spectrometer (FTS), located on Mt Wilson at 1.7 km ASL,
points downward at 29 different targets in the Los Angeles basin to measure the
slant column abundances of CO2, CH4, N2O and CO using reflected sunlight in
the near- infrared region. This technique allows the spatial coverage of the Los
Angeles basin at different times of the day. In addition, we measure GHG column
abundances above Mt. Wilson using the direct solar beam. Here we present 1-year of data
acquired during the period from August 2011 to August 2012. Using direct sun
measurements, the contribution above Mt. Wilson is subtracted in order to calculate the basin
contribution. The path-averaged dry-air mixing ratio, XCO2, XCH4 and XCO, in the Los
Angeles basin showed significant spatial and temporal variability and covariance.
Using morning XGAS values as background values, we computed the XGAS excess
assigned to anthropogenic emissions. Here we present the maps of emission ratios of
CH4:CO2, CH4:CO and CO:CO2 calculated using XGAS excess in the Los Angeles
basin and comparisons between ratios calculated from in-situ and total column data. |
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