Articles | Volume 14, issue 18
Atmos. Chem. Phys., 14, 9883–9901, 2014
Atmos. Chem. Phys., 14, 9883–9901, 2014

Research article 18 Sep 2014

Research article | 18 Sep 2014

Drivers of column-average CO2 variability at Southern Hemispheric Total Carbon Column Observing Network sites

N. M. Deutscher1,2, V. Sherlock3,**, S. E. Mikaloff Fletcher3, D. W. T. Griffith1, J. Notholt2, R. Macatangay1,*, B. J. Connor4, J. Robinson5, H. Shiona5, V. A. Velazco1, Y. Wang2, P. O. Wennberg6, and D. Wunch6 N. M. Deutscher et al.
  • 1Centre for Atmospheric Chemistry, University of Wollongong, Wollongong, NSW, 2522, Australia
  • 2Institute of Environmental Physics, University of Bremen, 28334, Bremen, Germany
  • 3National Institute of Water and Atmospheric Research, Wellington, New Zealand
  • 4BC Consulting, Alexandra, New Zealand
  • 5National Institute of Water and Atmospheric Research, Lauder, New Zealand
  • 6California Institute of Technology, Pasadena, CA, USA
  • *now at: Institute of Environmental Science and Meteorology, University of the Philippines, Diliman, Quezon City, Philippines
  • **now at: Laboratoire des Sciences du Climat et l'Environnement, CEA-CNRS-UVSQ, IPSL, Gif sur Yvette, France

Abstract. We investigate factors that drive the variability in total column CO2 at the Total Carbon Column Observing Network sites in the Southern Hemisphere using fluxes tagged by process and by source region from the CarbonTracker analysed product as well as the Simple Biosphere model. We show that the terrestrial biosphere is the largest driver of variability in the Southern Hemisphere column CO2. However, it does not dominate in the same fashion as in the Northern Hemisphere. Local- and hemispheric-scale biomass burning can also play an important role, particularly at the tropical site, Darwin. The magnitude of seasonal variability in the column-average dry-air mole fraction of CO2, XCO2, is also much smaller in the Southern Hemisphere and comparable in magnitude to the annual increase. Comparison of measurements to the model simulations highlights that there is some discrepancy between the two time series, especially in the early part of the Darwin data record. We show that this mismatch is most likely due to erroneously estimated local fluxes in the Australian tropical region, which are associated with enhanced photosynthesis caused by early rainfall during the tropical monsoon season.

Final-revised paper