Vertically constrained CO2 retrievals from TCCON measurements

Abstract

Partial column-averaged carbon dioxide (CO2) mixing ratio in three tropospheric layers has been retrieved from Total Carbon Column Observing Network (TCCON) spectra in the 1.6μm CO2 absorption band. Information analysis suggests that a measurement with ∼60 absorption lines provides three or more pieces of independent information, depending on the signal-to-noise ratio and solar zenith angle. This has been confirmed by retrievals based on synthetic data. Realistic retrievals for both total and partial column-averaged CO2 over Park Falls, Wisconsin on July 12, 15, and August 14, 2004, agree with aircraft measurements. Furthermore, the retrieved total column averages are always underestimated by less than 1%. The results above provide a basis for CO2 profile retrievals using ground-based observations in the near-infrared region.