The global carbon cycle is experiencing continued increases in atmospheric carbon concentrations that are driving climatic change. Greenhouse gas satellites are designed to primarily observe seasonal to interannual variations of these atmospheric carbon concentrations to assess their anthropogenic and natural drivers. Recent work has shown that these satellites are further applicable beyond their design specifications for quantifying surface emissions at smaller spatiotemporal scales. For example, simple mass balance approaches have been used to rapidly estimate surface methane fluxes from satellite atmospheric column methane measurements. However, less attention has been placed on using these satellite observations and mass balance methods to evaluate surface CO2 fluxes from the terrestrial biosphere at shorter timescales. Such applications could be useful to monitor, in real time, biosphere carbon fluxes during climatic anomalies. Here, we assess the ability of Orbiting Carbon Observatory-2 (OCO-2) column-averaged dry air CO2 (XCO2) retrievals to rapidly detect and estimate terrestrial biosphere CO2 flux anomalies. Using CarbonTracker model reanalysis as a testbed, we first demonstrate that a previously developed, simple mass balance approach can successfully estimate monthly surface CO2 flux anomalies in the Western United States. The method is optimal when the chosen target region is spatially extensive enough to account for atmospheric mixing and has consistent advection conditions with contributions primarily from one background region. While errors in individual soundings partially reduce the ability of OCO-2 XCO2 to estimate more frequent, smaller surface CO2 flux anomalies, we found that OCO-2 XCO2 can often detect and estimate larger surface flux anomalies. OCO-2 is thus useful for near real time monitoring of the monthly timing and magnitude of regional terrestrial biosphere carbon anomalies, especially under extreme climate conditions. Any noise reduction in forthcoming greenhouse gas satellites and/or the existence of large surface carbon anomalies will enhance the ability to rapidly estimate surface fluxes at smaller spatiotemporal scales.
Topic : Theme 2: Strengthening the linkage of remote sensing GHG concentration measurements to emission fluxes.
Reference : T2-D4
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