The seasonal cycle of atmospheric CO2 in South America over the last ten years seen by GOSAT

The number of in-situ CO₂ measurements in the Southern Hemisphere is very limited. This leads to large 
uncertainties in estimates of regional carbon fluxes by in-situ based inverse models. Satellite-based CO₂ 
measurements, on the other hand, are available in the Southern Hemisphere with a dense spatial 
coverage. By evaluating these, the regional carbon cycle can be studied in more detail and the results of 
carbon cycle models can be validated against the satellite data.

Here, we present a comparison of atmospheric CO₂ data provided by the Greenhouse gases Observing 
SATellite (GOSAT) and in-situ based inverse models for South America from 2009 to 2019. The seasonal 
cycle of atmospheric CO₂ concentrations measured by the GOSAT satellite shows differences in both,
amplitude and timing, compared to in-situ based atmospheric inversions. To determine the reason for
these discrepancies, we use the TM5-4DVar atmospheric inversion model assimilating GOSAT satellite 
data to obtain GOSAT based land-surface fluxes. This allows us to identify sub-regions responsible for the 
differences. In order to gain a deeper understanding of the underlying processes, we also analyse various 
climate parameters, fire emission data, and vegetation proxies (for example Solar Induced Fluorescence, 
SIF). By doing so, we aim at improving our understanding of the mechanisms that influence the seasonal 
carbon cycle in South America.