Investigating greenhouse gases in Australia using atmospheric measurements with fourier transform spectrometry and atmospheric modeling

Author

Nicholas M. Deutscher, University of Wollongong

Year

2009

Degree Name

Doctor of Philosophy

Department

School of Chemistry, Faculty of Science

Recommended Citation

Deutscher, Nicholas M., Investigating greenhouse gases in Australia using atmospheric measurements with fourier transform spectrometry and atmospheric modeling, Doctor of Philosophy thesis, School of Chemistry, Faculty of Science, University of Wollongong, 2009. https://ro.uow.edu.au/theses/3112

Abstract

Anthropogenic emissions of greenhouse gases CO2, CH4 and N2O are important drivers of changes in radiative forcing and consequent climate changes. Despite their importance, estimates of the source and sink distributions of these gases to and from the atmosphere remain uncertain, largely because more measurements are needed to adequately constrain the problem. Because of the infrared signatures of these gases, Fourier Transform (InfraRed) Spectroscopy (FTS) provides an ideal method for simultaneous measurements.

This thesis investigates the potential of new Australian measurements to constrain estimates of CO2 fluxes in the Australian region. Initially, we use a pseudodata study to determine the utility of adding North-South transect measurements from Darwin to Adelaide on the Ghan train platform, as well as continuous measurements at a number of fixed sites. We see that even in the case of a transect occurring once per month, considerable constraint on the flux estimates is possible for several Australian regions, but that the train measurements fail to provide any detail about the diurnal variability of the fluxes.

The setup and calibration of a high resolution solar absorption FT spectrometer in Darwin is detailed. The instrument is shown to have high precision in measurements of column-average dry-air mole fractions, of the order of 0.1% for XCO2 within clear days. A calibration factor of 0.990 ± 0.003 is necessary to bring the measurements onto the WMO global standard CO2 scale.

FT spectroscopy is also used in an instrument measuring surface in situ concentrations. The instrument is described, along with a comparison to existing recognised instrumentation at Cape Grim Baseline Air Pollution Station, which shows that it is capable of continuous, high-precision simultaneous measurements of CO2, CH4, N2O, CO and 13CO2. Time series of measurements made with these instruments at Darwin, Lauder and Cape Grim are examined. We also look at a case study where one of theinstruments is deployed on the Ghan railway running from Adelaide to Darwin, and used, along with a modelling study, to infer methane emissions from tropical savannah wetlands.