Retrieval of Atmospheric COand CHVariations Using Ground-Based High Resolution Fourier Transform Infrared Spectra

High resolution fourier transform near ir solar spectra are used to estimate the column-averaged dry-air mole fraction (dmf) of coand ch 4 variations in the atmosphere. the preliminary retrieval results for coand ch 4 variations 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 priori gases 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 obtain vc d co 2 and vc d ch 4 (which represent vertical column density of coand ch 4,resp.). furthermore,the vc d o 2 is 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 coand ch 4 under strong atmospheric background. spectral fitting residuals for both vc d co 2 and vc d ch 4 are less than 0.5%. finally,coand ch 4 diurnal variations are investigated based on a typical observation. about 2 ppm amplitude for dmf c o 2 diurnal variations and less than 15 ppb amplitude for d mf ch 4 are observed. © 2015 tian yuan et al.