研究目的
Monitoring the spatial and temporal distributions of greenhouse gases in the Los Angeles basin using a high-resolution spectroscopic remote sensing technique to assess anthropogenic emissions and their impact on climate change.
研究成果
The CLARS-FTS system provides high-precision measurements of greenhouse gas column abundances in the Los Angeles basin, capturing diurnal variations and spatial differences. Enhancements over background levels indicate anthropogenic emissions. Future improvements include better radiative transfer modeling, calibration with aircraft data, and reduced systematic errors. The method supports monitoring and verification of emission control measures.
研究不足
Systematic errors from spectroscopic parameters, light path calculations, and instrument line shape affect accuracy. Aerosol scattering and pointing errors introduce uncertainties. Validation with independent methods (e.g., aircraft measurements) is needed but not currently available. The approach is limited to clear-sky conditions and specific geographic coverage of the Los Angeles basin.
1：Experimental Design and Method Selection:
The study uses a Fourier transform spectrometer (CLARS-FTS) deployed on Mt. Wilson to measure reflected near-IR solar radiation from ground targets in the Los Angeles basin. The method involves automated long-term measurements with high spectral resolution to retrieve column-averaged dry-air mole fractions of CO2, CH4, and CO.
2：Sample Selection and Data Sources:
Targets are selected based on imagery to ensure uniform surface albedo, with coordinates listed in supplementary materials. Data include spectra from ground targets and a Spectralon? plate for background reference.
3：List of Experimental Equipment and Materials:
CLARS-FTS spectrometer, pointing system with gimbal and mirror, InGaAs detector, He-Ne laser, weather stations (Davis Vantage and R.M. Young), Spectralon? plate, HCl gas cell for alignment checks.
4：Experimental Procedures and Operational Workflow:
Daily measurement sequences include Los Angeles Basin Surveys (pointing at ground targets), Spectralon? Viewing Observations (pointing at reference plate), and Instrument Status Evaluation Measurements (monthly checks). Interferograms are recorded, averaged, and processed to spectra.
5：Data Analysis Methods:
Interferograms are converted to spectra using uniform time sampling and Fourier transform. Spectral fitting is done with modified GFIT program to retrieve slant column densities, and column-averaged volume mixing ratios are computed using O2 columns for normalization. Precision and accuracy are estimated from spectral residuals and differences between spectral bands.
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