EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The seasonal cycle of atmospheric CO2 in the southern hemisphere over the last ten years seen by GOSAT

Eva-Marie Schömann1, Sourish Basu2,3, Sanam N. Vardag1, Markus Haun1, Lena Schreiner1, and André Butz1
Eva-Marie Schömann et al.
  • 1Institut für Umweltphysik, Universität Heidelberg, Heidelberg, Germany
  • 2NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 3Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland, USA

In the southern hemisphere, the sparse coverage of in-situ CO2 measurements prevents a robust determination of regional carbon fluxes and leads to large uncertainties in inverse model results. Therefore, the extensive spatial coverage afforded by satellite CO2 measurements is especially valuable there. By analyzing satellite measurements, new insights on the carbon cycle can be derived and carbon cycle models can be validated for the southern hemisphere.

Here, we present a comparison of atmospheric CO2 data in Australia provided by the Greenhouse gases Observing SATellite (GOSAT) and the CarbonTracker (CT2019) inverse model from 2009 to 2018. We find that the seasonality of GOSAT CO2 is different from that of CarbonTracker across much of the southern hemisphere. This discrepancy follows a clear seasonal pattern with the largest difference of ~2ppm between October and December. We investigate the origin of the discrepancy by utilizing the CO2 components provided by CarbonTracker and different fire CO2 emission databases. Further, we conduct several sensitivity studies by assimilating GOSAT CO2 in the TM5-4DVar data assimilation system, and by transporting different surface fluxes through the TM5 transport model. Our results suggest that the underestimation of local and transported wildfire CO2 emissions could cause the observed discrepancy in the seasonality of column CO2 between GOSAT and inverse models such as CarbonTracker in the southern hemisphere.

How to cite: Schömann, E.-M., Basu, S., Vardag, S. N., Haun, M., Schreiner, L., and Butz, A.: The seasonal cycle of atmospheric CO2 in the southern hemisphere over the last ten years seen by GOSAT, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2044,, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.