Preliminary Results from the First Year of Operations of the NASA Orbiting Carbon Observatory-2 (OCO-2)

Abstract:

On September 6, 2014, OCO-2 began routinely returning almost 10⁶ soundings over the sunlit hemisphere each day. Over 10% of these soundings are sufficiently cloud free to yield full-column estimates of the column-averaged CO₂ dry air mole fraction, X_CO2. Nadir soundings over land yield X_CO2 estimates with single-sounding random errors of 0.5 - 1 ppm at solar zenith angles (SZA) < 60° while ocean glint soundings yield precisions near 0.5 ppm at SZA < 70°. Nadir soundings over the ocean and glint soundings over high-latitude land are less precise. Initially, OCO-2 recorded only nadir soundings or glint soundings on alternate, 16-day ground-track repeat cycles. This provided adequate coverage of the globe each month, but produced 16-day gaps in ocean coverage while observing nadir, and similar gaps over high-latitude land while observing glint. In July 2015, this strategy was modified to alternate between glint and nadir soundings on consecutive orbits to yield more continuous coverage each day.

While X_CO2 and other products are being validated to identify and correct biases, global X_CO2 maps are starting to reveal the most robust features of the atmospheric carbon cycle. X_CO2 enhancements co-located with intense fossil fuel emissions in eastern U.S. and eastern China are most obvious in the fall, when the north-south X_CO2 gradient is small. Enhanced X_CO2 coincident with biomass burning in the Amazon, central Africa, and Indonesian is also obvious in the fall. In mid spring, when the north-south X_CO2 gradient was largest, these sources were less apparent in global maps. From late May to mid-July, OCO-2 maps show a 2-3% reduction in X_CO2 across the northern hemisphere, as the land biosphere rapidly absorbs CO₂. As the carbon cycle community continues to analyze these OCO-2 data, quantitative estimates of regional-scale emission sources and natural sinks are expected to emerge. This presentation will summarize the OCO-2 mission status, early products, and near-term plans.