Using the COllaborative Carbon Column Observing Network for validating space borne GHG sensors

The COllaborative Carbon Column Observing Network (COCCON) is an emerging network, initiated by Karlsruhe Institute of Technology (KIT), focusing on greenhouse gas measurements using portable EM27/SUN spectrometers. All instruments follow common instrumental standards, calibration and data analysis procedures, which ensure an unprecedented level of network homogeneity and comparability. Side-by-side measurements at several Total Carbon Column Observing Network (TCCON) locations showed excellent performance and calibration stability of the portable spectrometers. The spectrometers are ideal to be used as campaign instruments, for the observation of localized sources of greenhouse gases, as a travel standard as well as for long-term deployment. Therefore, COCCON complements the TCCON and expands the global coverage of ground-based reference measurements of the major greenhouse gases (CO2, CH4 and H2O) and CO. The EM27/SUN FTIR spectrometer in its dual detector configuration uses DC-coupled RT InGaAs detectors (covering the 5500–11000 cm-1 and 4000–5500 cm-1 spectral ranges) which allow the simultaneous retrieval of column abundances of CO2, CH4, CO, H2O and O2. The retrievals are performed either by the site PIs or by using the COCCON central processing facility (then performing only the pre-processing on site) following the COCCON processing chain (PREPROCESS + PROFFAST). The tools for the processing and generation of the output files are open source and freely available. Currently more than 50 EM27/SUNs are operated around the world as campaign deployments or permanent stations. This offers an extension of ground-based reference total column data for a wide range of surface conditions, latitude bands, and atmospheric conditions that are not fully covered by TCCON or NDACC-IRWG stations. In this presentation, we will demonstrate for the first time the use of the global COCCON data for the validation of the satellite data products. We use the COCCON data for the validation of the XCH4, XCO and XH2O products from the Tropospheric Monitoring Instrument (TROPOMI) onboard Sentinel-5 Precursor and XCO2 data from Orbiting Carbon Observatory-2 (OCO-2). We will show the validation results focusing on the identification and quantification of the accuracy and the precision of the satellite products.