Carbon dioxide retrieval from OCO-2 satellite observations using the RemoTeC algorithm and validation with TCCON measurements
Lianghai Wu1,Otto Hasekamp1,Haili Hu1,Jochen Landgraf1,Andre Butz2,3,Joost aan de Brugh1,Ilse Aben1,Dave F. Pollard4,David W. T. Griffith5,Dietrich G. Feist6,Dmitry Koshelev7,Frank Hase8,Geoffrey C. Toon9,Hirofumi Ohyama10,Isamu Morino10,Justus Notholt11,Kei Shiomi12,Laura Iraci13,Matthias Schneider15,Martine de Mazière14,Ralf Sussmann15,Rigel Kivi16,Thorsten Warneke11,Tae-Young Goo17,and Yao Té7Lianghai Wu et al. Lianghai Wu1,Otto Hasekamp1,Haili Hu1,Jochen Landgraf1,Andre Butz2,3,Joost aan de Brugh1,Ilse Aben1,Dave F. Pollard4,David W. T. Griffith5,Dietrich G. Feist6,Dmitry Koshelev7,Frank Hase8,Geoffrey C. Toon9,Hirofumi Ohyama10,Isamu Morino10,Justus Notholt11,Kei Shiomi12,Laura Iraci13,Matthias Schneider15,Martine de Mazière14,Ralf Sussmann15,Rigel Kivi16,Thorsten Warneke11,Tae-Young Goo17,and Yao Té7
1SRON Netherlands Institute for Space Research, Utrecht, the Netherlands
2Institute of Atmospheric Physics, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Wessling-Oberpfaffenhofen, Germany
Received: 21 Nov 2017 – Discussion started: 30 Jan 2018 – Revised: 01 May 2018 – Accepted: 03 May 2018 – Published: 30 May 2018
Abstract. In this study we present the retrieval of the column-averaged dry air mole fraction of carbon dioxide (XCO2) from the Orbiting Carbon Observatory-2 (OCO-2) satellite observations using the RemoTeC algorithm, previously successfully applied to retrieval of greenhouse gas concentration from the Greenhouse Gases Observing Satellite (GOSAT). The XCO2 product has been validated with collocated ground-based measurements from the Total Carbon Column Observing Network (TCCON) for almost 2 years of OCO-2 data from September 2014 to July 2016. We found that fitting an additive radiometric offset in all three spectral bands of OCO-2 significantly improved the retrieval. Based on a small correlation of the XCO2 error over land with goodness of fit, we applied an a posteriori bias correction to our OCO-2 retrievals. In overpass averaged results, XCO2 retrievals have an SD of ∼ 1.30 ppm and a station-to-station variability of ∼ 0.40 ppm among collocated TCCON sites. The seasonal relative accuracy (SRA) has a value of 0.52 ppm. The validation shows relatively larger difference with TCCON over high-latitude areas and some specific regions like Japan.
