A222-0007
Improvements in XCO2 accuracy from OCO-2 with the latest ACOS v10 product
Wednesday, 16 December 2020
Poster
Christopher O'Dell1, Annmarie Eldering2, Michael R Gunson3, David Crisp4, Cecilia Cheng5, Brenden Fisher5, Matthäus Kiel6, Le Kuai7, Joshua Laughner8, Aronne J Merrelli9, Robert R Nelson5, Vivienne Payne2, Robert Rosenberg6, Thomas Taylor1 and Paul O Wennberg10, (1)Colorado State University, Cooperative Institute for Research in the Atmosphere, Fort Collins, CO, United States, (2)NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (3)Jet Propulsion Lab, Pasadena, CA, United States, (4)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (5)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (6)Jet Propulsion Laboratory, Pasadena, CA, United States, (7)California Institute of Technology, Pasadena, CA, United States, (8)University of California Berkeley, Berkeley, CA, United States, (9)University of Wisconsin Madison, Madison, WI, United States, (10)California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, United States
Abstract:
While initial plans for measuring carbon dioxide from space hoped for 1-2 ppm levels of accuracy in the CO
2 column mean dry air mole fraction (XCO
2), in the past few years it has become clear that accuracies better than 0.5 ppm are required for most current science applications. These include measuring continental (1000+ km) and regional scale (100s of km) surface fluxes of CO
2 at monthly-average timescales. Considering the 400+ ppm background, this translates to an accuracy of roughly 0.1%, an incredibly challenging target to hit.
Improvements in both calibration and retrieval algorithms have led to increasing XCO2 accuracies over the past decade. The Atmospheric Carbon Observations from Space (ACOS) retrieval algorithm has demonstrated unprecedented accuracy with our latest algorithm version as applied to the Orbiting Carbon Observatory-2 (OCO-2) satellite sensor. This presentation will give details on the version 10 algorithm updates, including more accurate spectroscopy, a better solar model, improved radiometric calibration, an updated CO2 prior, and a better aerosol treatment among other refinements. These changes yield better agreement with TCCON over land and ocean, plus reduced biases over tropical oceans and desert areas as compared to a median of multiple global carbon inversion models, allowing better accuracy and faith in inferred regional-scale fluxes. Given the six-year and growing length of the OCO-2 data record, this also enables new studies on carbon interannual variability, plus, on the flip side, identification of more subtle and temporally-dependent errors. Finally, we will discuss the prospects of future improvements in the next planned version (v11), and the long-term prospects of greenhouse gas retrievals in the coming years.
