Validation of Multispectral GOSAT/TANSO-FTS CH4 Retrievals

Abstract:

The Thermal And Near infrared Sensor for carbon Observations–Fourier Transform Spectrometer (TANSO-FTS) instrument onboard the Greenhouse gases Observing SATellite (GOSAT) measures simultaneously the same field of view in the shortwave infrared (SWIR) and thermal infrared (TIR) spectral range with a high spectral resolution.

While SWIR observations provide CH₄ column densities with a high sensitivity near the ground, they cannot be used to discriminate different altitude layers in the atmosphere. TIR measurements on the other hand can be used to disentangle the concentrations of trace gases like CH₄ in the middle and lower troposphere, but its sensitivity to the planetary boundary layer is reduced by the thermal contrast between the surface and the first atmospheric layer. In this context, the ESA SIROCCO project aims at retrieving CH₄ profiles with increased sensitivity to its near-surface concentrations by combining shortwave infrared (SWIR) and thermal infrared (TIR) passive remote sensing measurements in a synergistic way.

As part of the SIROCCO activities, we presents a performance analysis and the validation results of the non-synergistic SWIR and TIR and synergistic SWIR-TIR GOSAT/TANSO-FTS CH₄ retrievals at 6 TCCON stations. With this work we want to better exploit the available data to provide information on CH₄ as close as possible to its associated sources, and thereby provide a better understanding and quantification of its budget.