Effect of Atmospheric CO2 Observations in Asia on the Optimization of Surface CO2 Flux
Abstract:Understanding sources and sinks of atmospheric CO2 is important to estimate the impact of CO2 on climate change and environment. Although surface CO2 sources and sinks in Asia affect the global carbon cycle considerably, the atmospheric CO2 observation network is sparse in Asia. Due to the sparse observations in Asia, the estimated surface CO2 fluxes in the Eurasian Boreal region differ considerably depending on the inversion systems used in the estimation. In this study, to investigate the effect of additional CO2 observations in the Eurasian Boreal region on the surface carbon flux analysis in the globe and Asia, two experiments using different observation data set were performed with CarbonTracker developed in NOAA. One experiment was conducted using a data set that includes additional observations of Siberian tower measurement data (Japan-Russia Siberian Tall Tower Inland Observation Network: JR-STATION) and data observed in China and India, and the other experiment was conducted using a data set without the above additional observations.
Global balance of the source and sink of surface CO2 fluxes was maintained for both experiments with and without additional observations. While the magnitude of the optimized surface CO2 flux uptake in Siberia was decreased for the experiment with the additional observations, the magnitude of the optimized surface CO2 flux uptake in Western Europe and North America was increased. This result implies that the impact of the Siberian observation data is as large as other continuous measurements (e.g., tower measurements in North America). The average RMSE and bias of the model CO2 concentrations calculated using the optimized CO2 flux exhibited better agreement with the observed CO2 concentrations when the additional observations were used, which implies that the additional observations provide beneficial impact on the surface CO2 flux analysis in Asia.