Institute for Meteorology and Climate Research, Atmospheric Trace Gases and Remote Sensing (IMK-ASF, KIT)

KIT – The Research University in the Helmholtz Association www.kit.edu

The Collaborative Carbon Column Observing Network COCCON: overview and current status

M. Frey and the COCCON team

IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

IntroductionEM27/SUN Spectrometer

Instrument OverviewInstrumental Line Shape and CalibrationLong Term Stability

Network COCCONCOCCON ServiceComparison to TCCONMeasurement CampaignsCOCCON-Proceeds

Summary and Outlook

Outline

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IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

Existing ground-based GHG networksValidation of satelite measurementsNDACC: Network for the Detection of Atmospheric Composition ChangeTCCON: Total Carbon Column Network (Near-IR)

Geographic coverage limited, instruments not portableGood infrastructure and expert maintenance required

New upcoming ground-based GHG networkCOCCON: Collaborative Carbon Column Observing NetworkEM27/SUN spectrometer network

Portable and easy to set up instrumentHigh instrumental stability and reliabilityLow-cost interferometer (100 k€)Low infrastructure requirements

Introduction

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Fig. source: TCCON network

IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

Rock SolidTM pendulum interferometer2 cube corners, CaF2 beamsplitter

Double sided interferogramsMaximum OPD: 1.8 cmResolution: 0.5 cm-1

Dimensions: 35 x 40 x 27 cmMass with tracker: ~25 kgInGaAs detector

Spectral range: 5000 – 11000 cm-1

Second CO channel availableSpectral range: 4000 – 5500 cm-1

EM27/SUN – Instrument Overview

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[Hase et al., AMT, 2016]

IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

Instrumental Line Shape (ILS)Accurate ILS knowledge of highest importance

1% ∆MEA at MOPD à 0.15% ∆XCO2

Absorption lines of lab air water vaporNo gas cell necessary

Long Term Stability (LTS)Reference EM27/SUN spectrometerModulation Efficiency Amplitude (MEA)

0.9862± 0.0015 à ∆XCO2< 0.03%Phase Error

0.0019± 0.0018

EM27/SUN – ILS and Stability

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[Frey et al, AMT, 2015]

IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

Calibration measurementsSide-by-side calibration of instruments to common scalePerformed before and after several campaigns at IMK-ASF office building

Additional pressure and temperature measurementsOn site from tall tower at the KIT campus north

More than 30 devices operated worldwide

EM27/SUN – Calibration

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IMK-ASF, KIT

IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

COCCON: Collaborative Carbon Column Observing NetworkFramework for EM27/SUN spectrometersCheck of new instruments at KIT (before delivery to customer)

Solar measurements together with reference EM27/SUN andco-located TCCON instrumentAlignment check and ILS measurementsILS ensemble mean: 0.985 ± 0.008XCO2, XCH4, XH2O and XCO scaling factors

Loan of instruments possible for campaign deploymentRetrieval algorithm available

PROFFIT and PROFFASTTraining at KIT possible

Central facility for EM27/SUN spectraCentral processing facilityCentral data handling facilityà COCCON-proceeds

COCCON – Service

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[Frey et al., AMT, 2019]

IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

High resolution spectrometerBruker IFS 125HR (KIT)

Low resolution intercomparisonPROFFIT retrieval SW(same procedure for bothdata sets)Excellent agreement

Low versus high resolutionDifferent retrieval SW(PROFFIT vs. GFIT)Different resolutions àDiffering averaging kernels(0.5 cm-1 vs 0.02 cm-1)Seasonal variabilityNo significant long term drift

COCCON – Comparison to TCCON

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XCH4

XCO2 XCO2

XCH4

[Frey et al, AMT, 2019]

IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

Measurement campaigns with partner institutionsParis, Berlin, Boulder, Tokyo, etc.City emissions, fracking, dairy farms, coal mining, etc

[Vogel et al., ACP, 2019][Kille et al., GRL, 2019][Luther et al., AMTD, 2019]etc

COCCON – Measurement Campaigns

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IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

COCCON – PhilosophyCommon standards for GHG measurements

Define and maintain an instrumental standard (EM27/SUN)Verify performance of each device before deliveryCommon way of data processing and analysis à COCCON-proceeds

COCCON-Proceeds (project funded by ESA)Pre-processing (by the user community member)

Measured IFG à Absorption spectra (binary files)Quality checks (selection of good spectra)

Central processing and data handling facilityUpload pre-processed dataAnalysis of absorption spectraData dissemination to user community

COCCON-Proceeds

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IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

Calculation of Solar positionRead IFG (OPUS format), DC correctionIFG truncation to nominal resolutionNumerical apodization functionPerform FFT, phase correction and resamplingQuality checks

Minimum DC value to available ADC rangeMaximum variability of DC in IFGCenterburst amplitudes of FWD/BWD scansCenterburst location in the IFGRelative amplitudes of out-of band artefactsSlope, curvature, and change of curvatureof phase spectrumSpectral calibration based on cross-correlationof spectral structure wrt a reference spectrum

COCCON-Proceeds – Pre-processing

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Error flags

IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

New retrieval algorithm PROFFAST designed for lowresolution spectra30 times faster than previous PROFFIT algorithmInternal postprocessing (airmass correction)Possibility to use TCCON map files as a priori profilesSoftware and code available via KIT websitePreprocessing software and PROFFAST successfully used forthe analysis of the MEGEI-MAD campaign measurements

COCCON-Proceeds – Retrieval algorithm

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IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

Central processing and data handling facilityUpload pre-processed binary filesAnalysis of absorption spectraData dissemination to the user community

Interface for data uploadLinux server systemSecure File Transfer Protocol (SFTP)Login interface (e.g. Bitvise for Windows)(username, phassphrase, etc.)

COCCON-Proceeds – Central Facility

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ServerClient

Login interface (Bitvise)

IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

COCCON – Next Step

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Fairbanks

Thessaloniki

Palapye (no CO channel)Gobabeb

Operational Site

Bucharest

YekaterinenburgSt. Petersburg

Toronto (4 instruments) Boston (2 instruments)

Mexico City (2 instruments)

Munich (2 instruments)

Kiruna (no CO channel)

Izana

Tsukuba

Karlsruhe

Sodankyla

Wollongong

Hefei

IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

EM27/SUN spectrometerILS, LTS and Calibration

COCCONService, Comparison to TCCON and Campaigns

COCCON-ProceedsPre-processing with quality checksCentral processing and data handling facility

SW-distribution to external usersPre-processing tool and PROFFAST

Future plan: Global EM27/SUN data set

Acknowledgement: COCCON-Proceeds project is funded by ESA

Summary and Outlook

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IMK-ASF, KITM. Frey and the COCCON teamCOCCON – overview and current status

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Thank you for your attention