The OCO-2 Level 4 Flux Product and Associated Uncertainties

The OCO-2 Model Intercomparison Project (OCO-2 MIP) has organized simulations among ten participating global atmospheric CO2 inverse model with the goal of understanding the flux information present in OCO-2 land observations. The model ensemble has diverse simulated atmospheric transport, data assimilation technique, and prior flux assumptions.

In this presentation, we will discuss the OCO-2 MIP flux results for the ensemble as a whole, and then proceed to examine the sensitivity of the posterior fluxes with a subset of the modeling approaches that utilize PCTM and TM5 with a suite of prior mean fluxes and prior uncertainties. In particular, we note that the flux constraint provided by OCO-2 in the northern hemisphere extratropics in the boreal winter is particularly sensitive to these assumptions due to seasonal distribution of soundings. Tropical fluxes are also sensitive, though to a lesser degree. This sensitivity, particularly with regard to the seasonal cycle, is important to take into account in any conclusions about surface fluxes of CO2 inferred from OCO-2 retrievals.