Malina, Edward; (2018) Global isotopic ratios of fugitive gas emissions from natural and anthropogenic sources from Earth observation satellites. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Methane is one of the most important greenhouse gases in the Earth’s atmosphere. The global growth of methane therefore presents a significant challenge for the scientific community. Global measurements currently provide high quality regional estimates of methane concentration, but little information on the origins of atmospheric methane. This thesis presents a range of studies aimed at determining the capability of current Earth Observation (EO) satellites for identifying methane sources and their origins on a global scale. Two key areas are studied: 1) source and seep detection using high spatial and temporal resolution measurements; and 2) identification of the origins of these sources through the measurement of the ratio of the main methane isotopologues 12CH4 and 13CH4. This ratio, otherwise known as δ13C, can be employed to identify the nature of a methane source, whether it originates from a biogenic source (e.g. marshlands) or abiogenic (industrial bi-products). The application of residual radiance and information content analysis techniques show that total column measurements of δ13C are feasible using the GOSAT-TANSO-FTS. Initial synthetic studies suggest total column retrieval errors of <20% or up to 3 ppbv can be anticipated on 13CH4. High spatial and temporal resolution data products from the satellites GOSAT and the Infrared Atmospheric Sounding Interferometer (IASI) are used to identify point sources of high methane output on the Earth’s surface. Measurements are focused on three known emissions points, and both instruments show significant capability for “hot-spot” detection, albeit with significant bias between the instruments. One of the previously published sources with SCIAMACHY is found to be missing in the GOSAT and IASI retrievals. Assessments are made into the potential error sources of these instruments, which show that although the current EO satellite IASI and GOSAT can potentially be powerful tools, careful error analysis must be made before making any definitive conclusions.

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