Satellite Observations of C2H2 and C2H6 in the Upper Troposphere

In this thesis, the potential for the observation of acetylene (C2H2) and ethane (C2H6) from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) infrared limb emission spectra is assessed. C2H2 is primarily produced from biomass and biofuel burning with C2H6 also emitted during natural gas production. The ability to successfully observe such species at high spatial and temporal resolutions allows a detailed study of their sources and transport to be conducted, an area of uncertainty in global tropospheric chemistry. A fast detection algorithm for both C2H2 and C2H6 in the upper troposphere/lower stratosphere (UTLS) was developed (Chapter 4), capable of performing a “first look” at MIPAS data. Monthly C2H2 detection results for 2003 were analysed and shown to be well-correlated to retrieval results. This allowed African and Asian biomass burning transport, the relative influence of biomass burning to natural gas sources and the Asian monsoon anticyclone formation to be investigated. An optimal estimation retrieval was developed for both gases and successfully applied for August 2003 (Chapter 5). This enabled the vertical structure of the distributions to be examined in the context of deep convection as well as the chemical isolation of the Asian monsoon anticyclone and biomass burning export. Of particular note were the results that C2H2 was clearly isolated within the anticyclone and the observation of uplift via deep convection of C2H2 over South-East Asia (Chapter 6). Evidence for the penetration of C2H2 from the troposphere into the stratosphere above the anticyclone is also presented. Ratios of the gas concentrations were examined (Chapter 6). The C2H2/CO ratio provides information on the photochemical evolution of the biomass burning plumes. The C2H2/C2H6 ratio suggests differentiation of biomass burning and fossil fuel production sources. C2H6 enhancements observed over Mexico are attributed to the processing of natural gas.