科研之友
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摘要
The California Laboratory for Atmospheric Remote Sensing Fourier transform spectrometer (CLARS-FTS) deployed at Mount Wilson, California, has been measuring column abundances of greenhouse gases in the Los Angeles (LA) basin in the near-infrared spectral region since August 2011. CLARS-FTS measures reflected sunlight and has high sensitivity to absorption and scattering in the boundary layer. In this study, we estimate the retrieval biases caused by aerosol scattering and present a fast and accurate approach to correct for the bias in the CLARS column averaged CO2 mixing ratio product, X-CO2. The high spectral resolution of 0.06cm(-1) is exploited to reveal the physical mechanism for the bias. We employ a numerical radiative transfer model to simulate the impact of neglecting aerosol scattering on the CO2 and O-2 slant column densities operationally retrieved from CLARS-FTS measurements. These simulations show that the CLARS-FTS operational retrieval algorithm likely underestimates CO2 and O-2 abundances over the LA basin in scenes with moderate aerosol loading. The bias in the CO2 and O-2 abundances due to neglecting aerosol scattering cannot be canceled by ratioing each other in the derivation of the operational product of X-CO2. We propose a new method for approximately correcting the aerosol-induced bias. Results for CLARS X-CO2 are compared to direct-Sun X-CO2 retrievals from a nearby Total Carbon Column Observing Network (TCCON) station. The bias-correction approach significantly improves the correlation between the X-CO2 retrieved from CLARS and TCCON, demonstrating that this approach can increase the yield of useful data from CLARS-FTS in the presence of moderate aerosol loading.
- 出版日期2015-7-27
