Improved retrievals of carbon dioxide from Orbiting Carbon Observatory-2 with the version 8 ACOS algorithm

作者：Christopher W O'dell, A. Eldering, Paul O. Wennberg, David Crisp, Michael R. Gunson, Brendan M. Fisher, Christian Frankenberg, Matthäus Kiel, Hannakaisa Lindqvist, Lukas Mandrake, Aronne J. Merrelli, Vijay Natraj, Robert Nelson, Gregory B. Osterman, Vivienne H. Payne, Thomas E. Taylor, Debra B. Wunch, Brian J. Drouin, Fabiano Oyafuso, Albert Yen Chang, James McDuffie, Mike Smyth, D. F. Baker, Sourish Basu, Frédéric Chevallier, Sean Crowell, Liang Feng, Paul I. Palmer, Manvendra K. Dubey, Omaira García, David W. T. Griffith, Frank Hase, Laura T. Iraci, Rigel Kivi, Isamu Morino, Justus Notholt, Hirofumi Ohyama, Christof Petri, Coleen M. Roehl, Mahesh Kumar Sha, Kimberly Strong, Ralf Sussmann, Yao Té, Osamu Uchino, Voltaire Almario Velazco · 发表于：Atmospheric measurement techniques · 年份：2018 · DOI：10.5194/amt-11-6539-2018 · 被引用次数：455 · 研究领域：Atmospheric and Environmental Gas Dynamics、Atmospheric Ozone and Climate、Atmospheric chemistry and aerosols

Since September 2014, NASA's Orbiting Carbon Observatory-2 (OCO-2) satellite has been taking measurements of reflected solar spectra and using them to infer atmospheric carbon dioxide levels. This work provides details of the OCO-2 retrieval algorithm, versions 7 and 8, used to derive the column-averaged dry air mole fraction of atmospheric CO 2 (XCO2) for the roughly 100 000 cloud-free measurements recorded by OCO-2 each day. The algorithm is based on the Atmospheric Carbon Observations from Space (ACOS) algorithm which has been applied to observations from the Greenhouse Gases Observing SATellite (GOSAT) since 2009, with modifications necessary for OCO-2. Because high accuracy, better than 0.25 %, is required in order to accurately infer carbon sources and sinks from XCO2, significant errors and regional-scale biases in the measurements must be minimized. We discuss efforts to filter out poor-quality measurements, and correct the remaining good-quality measurements to minimize regional-scale biases. Updates to the radiance calibration and retrieval forward model in version 8 have improved many aspects of the retrieved data products. The version 8 data appear to have reduced regional-scale biases overall, and demonstrate a clear improvement over the version 7 data. In particular, error variance with respect to TCCON was reduced by 20 % over land and 40 % over ocean between versions 7 and 8, and nadir and glint observations over land are now more consistent. While this paper ...