Retrievals of XCO2, XCH4 and XCO from portable, near-infrared Fourier transform spectrometer solar observations in Antarctica

• Main Authors: Pollard, David Frank, Hase, Frank, Sha, Mahesh Kumar, Dubravica, Darko, Alberti, Carlos, Smale, Dan
• Format: Text
• Language: English
• Published: 2022
• Subjects: Arrival Heights; Austral; New Zealand; Pollard; Ross Island; The Sentinel; Antarc*; Antarctica
• Online Access: https://doi.org/10.5194/essd-2022-130; https://essd.copernicus.org/preprints/essd-2022-130/

The Collaborative Carbon Column Observing Network (COCCON), uses low-resolution, portable EM27/SUN Fourier Transform Spectrometers (FTSs) to make retrievals of dry air mole fractions (DMFs, represented as X gas ) of CO 2 , CH 4 , CO and H 2 O from near infrared solar absorption spectra. The COCCON has developed rapidly over recent years and complements the Total Carbon Column Observing Network (TCCON). In this work we provide details of the first seasonal timeseries 5 of near infrared XCO 2 , XCH 4 and XCO retrievals from measurements made in Antarctica during the deployment of an EM27/SUN to the Arrival Heights laboratory on Ross Island (77.83° S, 166.66° E, 205 m AMSL) over the austral summer of 2019/20 under the auspices of the COCCON. The DMFs of all three species were lower in Antarctica than at mid-latitude and for XCO 2 and XCO the retrieved values were less variable. For XCH 4 however, the variability was significantly greater and it was found that this was strongly correlated to the proximity of the polar vortex. In order to ensure the stability of the instrument and the traceability of the retrievals, side-by-side comparisons to the TCCON station at Lauder, New Zealand (45.04° S, 169.68° E, 370 m AMSL) and retrievals of the Instrument Line Shape (ILS) were made before and after the measurements in Antarctica. These indicate that over the course of the deployment the instrument stability was such that the change in retrieved XCO 2 was well below 0.1 %. The value of this data for satellite validation is demonstrated by making comparisons with the Tropospheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor (S5P) satellite. The data set is available from the COCCON Central Facility hosted by the ESA Atmospheric Validation Data Centre (EVDC) https://doi.org/10.48477/coccon.pf10.arrivalheights.R02 (Pollard, 2021) .