Research progress on COllaborative Carbon Column Observing Network(COCCON)and prospects of its methane monitoring application in China
Ground-based remote sensing technology is an effective tool for monitoring atmospheric greenhouse gas column concentrations to calibrate satellites and study carbon sinks.The COllaborative Carbon Column Observing Network(COCCON)is a global network of portable Fourier transform infrared(FTIR)spectrometers EM27/SUN and is compact and mobile.The COCCON instrument is appropriate for field campaigns and for long-term deployment at a site which effectively complements the Total Carbon Column Observing Network(TCCON).In addition,its excellent robust and reliable characteristics have been demonstrated in several successful field campaigns.Karlsruhe Institute of Technology(KIT)conducts optimization by subjecting each unit to an expert performance assessment and fine-tuning.KIT also calibrates it in reference to the EM27/SUN spectrometer utilized at KIT and the TCCON site in Karlsruhe.KIT,as part of European Space Agency initiatives,has developed open-source and freely accessible codes for processing and analyzing COCCON measurement spectra.In this study,we introduce the Instrumental Line Shape(ILS),which is a critical factor for obtaining precise information from measurements.The ILS parameters can be derived by conducting an open-path observation of a few meters of lab air.In addition,the high-precision inversion algorithm called PROFFAST is proposed.This algorithm is designed for the retrieval of column-averaged dry-air mole fractions of gas(Xgas).This work also presents various studies on satellite validation and methane emission from urban areas,coal mines,and livestock using COCCON methane observations.Furthermore,we provide preliminary applications of COCCON instruments in monitoring methane levels within urban region(Xuzhou)and coal mining region(Shanxi)in China.Initial analyses have revealed that methane concentrations in the coal mines under study in China surpass those observed in European contexts.These elevated concentrations are closely related to variations in mining activities in different coal mines.Subsequent findings are currently being prepared for further publication.Considering that the COCCON network is mainly applied in western countries,developing region-specific ground-based remote sensing inversion techniques is necessary for assessing EM27/SUN methane emissions in China.This urgency stems from the complex nature of emission sources and high-concentration pollution scenarios unique to China.Two different aspects should be considered:dual influences of diffusion and transport,such as mutual diffusion effects among multiple coal mine emissions;the effects of complex atmospheric boundary layer changes under aerosol-atmospheric boundary layer interactions.
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