Using Orbiting Carbon Observatory-2 (OCO-2) column CO 2 retrievals to rapidly detect and estimate biospheric surface carbon flux anomalies

[摘要] The global carbon cycle is experiencing continued perturbationsvia increases in atmospheric carbon concentrations, which are partly reducedby terrestrial biosphere and ocean carbon uptake. Greenhouse gas satelliteshave been shown to be useful in retrieving atmospheric carbon concentrationsand observing surface and atmospheric CO 2 seasonal-to-interannualvariations. However, limited attention has been placed on using satellitecolumn CO 2 retrievals to evaluate surface CO 2 fluxes from theterrestrial biosphere without advanced inversion models at low latency. Suchapplications could be useful to monitor, in near real time, biosphere carbonfluxes during climatic anomalies like drought, heatwaves, and floods, beforemore complex terrestrial biosphere model outputs and/or advanced inversionmodelling estimates become available. Here, we explore the ability ofOrbiting Carbon Observatory-2 (OCO-2) column-averaged dry air CO 2 (XCO 2 ) retrievals to directly detect and estimate terrestrial biosphereCO 2 flux anomalies using a simple mass-balance approach. An initialglobal analysis of surface–atmospheric CO 2 coupling and transportconditions reveals that the western US, among a handful of other regions, isa feasible candidate for using XCO 2 for detecting terrestrial biosphereCO 2 flux anomalies. Using the CarbonTracker model reanalysis as a test bed,we first demonstrate that a well-established mass-balance approach canestimate monthly surface CO 2 flux anomalies from XCO 2 enhancementsin the western United States. The method is optimal when the study domain isspatially extensive enough to account for atmospheric mixing and hasfavorable advection conditions with contributions primarily from onebackground region. We find that errors in individual soundings reduce theability of OCO-2 XCO 2 to estimate more frequent, smaller surfaceCO 2 flux anomalies. However, we find that OCO-2 XCO 2 can oftendetect and estimate large surface flux anomalies that leave an imprint onthe atmospheric CO 2 concentration anomalies beyond the retrievalerror/uncertainty associated with the observations. OCO-2 can thus be usefulfor low-latency monitoring of the monthly timing and magnitude of extremeregional terrestrial biosphere carbon anomalies.

[学科分类] 医学（综合）