Retrieval of atmospheric CO<sub>2</sub> vertical profiles from ground-based near-infrared spectra

Abstract. We evaluate vertical profile retrievals of CO2 from 0.02 cm?1 resolution ground-based near-infrared solar absorption spectra with the GFIT2 algorithm, using improved spectroscopic line lists and shapes. With these improvements, profiles were obtained sequential in five spectral windows different sensitivities synthetic real spectra. A sensitivity study shows that leading source uncertainty retrieved is error a priori temperature profile, even 3-hourly reanalysis profiles. 2 ?C lower troposphere between 0.6 0.85 atm causes deviations are larger than typical variations CO2. To distinguish effect errors meteorology trace gas concentration those instrument alignment parameters, we retrieve atmospheric while an built coincident AirCore, radiosonde, surface situ measurements at Lamont, Oklahoma (USA), Total Carbon Column Observing Network station. In cases, also CO2, suggesting remaining forward model limit accuracy Implementing retrieval or correction quantifying modeling imperfect critical to improve retrievals. Without significant advances alignment, improvements presents no clear advantage over scaling for purpose ascertaining total column.