The Collaborative Carbon Column Observing Network (COCCON): Current status.

Precise measurements of atmospheric abundances of greenhouse gases (GHGs), especiallycarbon dioxide (CO2) and methane (CH4), are of utmost importance for the estimation ofemission strengths and flux changes. Furthermore, these measurements offer the prospect ofbeing usable for the evaluation of emission reductions as specified by international treaties,e.g. the Paris COP21 agreement. The existing Total Carbon Column Observing Network (TCCON) measurescolumn-averaged dry air mole fractions of CO2 (XCO2) and CH4 (XCH4) with referencequality. However, the instruments used by this network are rather expensive and need largeinfrastructure to be set up as well as expert maintenance, which has to be performed on site.Therefore TCCON stations have sparse global coverage, especially in Africa, South Americaand large parts of Asia. Current satellites like the Orbiting Carbon Observatory-2 (OCO-2)and the Greenhouse Gases Observing Satellite (GOSAT) on the other hand offer globalcoverage. Nonetheless, they suffer from coarse temporal resolution and limited singlemeasurement precision. The Collaborative Carbon Column Observing Network (COCCON) is intended to offer aframework for operating the EM27/SUN Fourier transform infrared spectrometer. Currently,about 18 working groups are contributing to these GHG observations. We expect thatCOCCON will become an important supplement to TCCCON and will increase the globaldensity of column-averaged greenhouse gas observations and due to the fact that thespectrometers are portable will especially contribute to the quantification of local sources.Therefore, the COCCON results can be used for the validation of satellite data as well (e.g.for ESAs Sentinel-5 precursor satellite, which carries the Tropospheric MonitoringInstrument TROPOMI). For achieving an optimal network performance, as well as for traceability andaccessibility of data, common standards for instrumental calibration, quality checks for newspectrometers before deployment, and finally a centralized processing and data storagefacility are desirable. This framework will be provided by COCCON. Within the ongoingESA supported project COCCON-PROCEEDS a common preprocessing tool and acentralized data handling facility (CPDHF) demonstrator is under construction. We presentthe already operational components of COCCON (quality checks of new spectrometers,instrumental calibration of all devices) and the current status of COCCON-PROCEEDS. [ABSTRACT FROM AUTHOR]