4 years of global carbon cycle observed from OCO-2 v9 and in situ data

The column average CO₂ retrievals from the Orbiting Carbon Observatory-2 (OCO-2) has been used in numerous studies and have shown potential to provide new information on the carbon cycle through various techniques, including the use of top-down atmospheric inversion methods.

The OCO-2 model intercomparison project (MIP) provides a means of analysis of results from many different inversions using different chemistry transport models, prior emissions and optimization techniques. The objective of this project is to quantify the constraint of OCO-2 data as well as associated uncertainties. The initial MIP results using v7 OCO-2 retrievals and in situ data showed interesting differences between the OCO-2 observing modes, as well as departures from the in situ constrained inversions, particularly in the tropics. The second round of the OCO-2 MIP using v9 OCO-2 X_CO2 data has been released, spanning 2015-2018.

In this presentation, we will discuss the differences between the v7 and v9 flux constraints, as well as the new findings related to the 2017-2018 period following the 2015-2016 El Nino. Early results indicate that this period following the El Nino years is a relative recovery period (or return to normal) for the tropics, though that the ensemble spread remains relatively large. These differences can partially be ascribed to transport differences among the models, as fluxes tend to group by transport model for some regions.