On what scales can GOSAT flux inversions constrain anomalies in terrestrial ecosystems?

Abstract

Abstract. Interannual variations in temperature and precipitation impact the carbon balance of terrestrial ecosystems, leaving an imprint in atmospheric CO2. Quantifying the impact of climate anomalies on the net ecosystem exchange (NEE) of terrestrial ecosystems can provide a constraint to evaluate terrestrial biosphere models against, and may provide an emergent constraint on the response of terrestrial ecosystems to climate change. We investigate the spatial scales over which interannual variability in NEE can be constrained using atmospheric CO2 observations from the Greenhouse Gases Observing Satellite (GOSAT). NEE anomalies are calculated by performing a series of inversion analyses using the GEOS-Chem model to assimilate GOSAT observations. Monthly NEE anomalies are compared to proxies, variables which are associated with anomalies in the terrestrial carbon cycle, and to upscaled NEE estimates from FLUXCOM. Strong agreement is found in the timing of anomalies in the GOSAT flux inversions with soil temperature and FLUXCOM. Strong correlations are obtained (P RNINO3.4) in the tropics on continental and larger scales, and in the northern extratropics on sub-continental scales during the summer (R2 ≥ 0.49). These results, in addition to a series of observing system simulation experiments that were conducted, provide evidence that GOSAT flux inversions can isolate anomalies in NEE on continental and larger scales. However, in both the tropics and northern extratropics, the agreement between the inversions and the proxies/FLUXCOM is sensitive to the flux inversion configuration. Our results suggest that regional scales are likely the minimum scales that can be resolved in the tropics using GOSAT observations, but obtaining robust NEE anomaly estimates on these scales may be difficult.

Cropland Carbon Uptake Delayed and Reduced by 2019 Midwest Floods

“…From the top‐down, measurements of the atmospheric CO 2 can provide constraints on net ecosystem exchange (NEE)—the net exchange of CO 2 between an ecosystem and the atmosphere, determined as autotrophic and heterotrophic respiration minus GPP (Bolin & Keeling, ; Gurney et al, ; Yin et al, ). Space‐based measurements of column‐averaged dry‐air mole fractions of CO 2 (X CO2 ) have been shown to provide information on NEE anomalies at large subcontinental scales (Byrne et al, ; Byrne et al, ; Guerlet et al, ; Ishizawa et al, ; Liu, Bowman, et al, ; Liu et al, ; Yin et al, ) and for point sources (Nassar et al, ; Schwandner et al, ) but are untested on smaller regional scales, such as the Midwest croplands. The Orbiting Carbon Observatory 2 (OCO‐2), launched in 2014, provides X CO2 to monitor the atmospheric signal of the event.…”