Retrieval of Atmospheric CO2and CH4Variations Using Ground-Based High Resolution Fourier Transform Infrared Spectra

[摘要] High resolution Fourier transform near IR solar spectra are used to estimate the column-averaged dry-air mole fraction (DMF) of CO2andCH4variations in the atmosphere. The preliminary retrieval results for CO2andCH4variations in the area of Hefei, China, are presented, and the underlying error sources are also analyzed. Both a forward analysis and an inversion algorithm are included in the retrieval. The forward analysis uses the modeled atmospheric transmittance to line-by-line (LBL) convolute the instrument line shape function. The influences of the temperature, pressure, humidity, and a priorigases are considered in the atmospheric transmittance model. The inversion algorithm is based on the nonlinear iterative and nonlinear least squares spectral fitting, which is used to obtainVCDCO2andVCDCH4(which representvertical column density of CO2andCH4, resp.). Furthermore, theVCDO2is also retrieved for converting the VCDs into DMFs. DMFs are final products of data analysis. The inversion results can clearly resolve the tiny variations of CO2andCH4under strong atmospheric background. Spectral fitting residuals for bothVCDCO2andVCDCH4are less than 0.5%. Finally, CO2andCH4diurnal variations are investigated based on a typical observation. About 2 ppm amplitude forDMFCO2diurnal variations and less than 15 ppb amplitudeforDMFCH4are observed.

[学科分类] 光谱学