Methane Footprint Measurements with IASI and GOSAT – Identification of Source Regions from Space

Abstract:

To date, satellite instruments such as SCIAMACHY and GOSAT-TANSO-FTS have largely focused on regional scale methane output (Kort, A. E., et al. 2014), in order to gain insight into significant methane source regions (such as the Four Corners). However, such an approach does not tackle the root of the issue; the individual sources of methane that account for the total global methane budget, e.g. oil wells and marshland. In this study we aim to use existing satellite sensors onboard Metop and GOSAT to locate point sources of methane from space.

We use nine years of global methane measurements from Metop-IASI A/B in order to exploit the exceptionally high global coverage of the instruments (total coverage of the Earth twice a day), and its relatively small spatial footprint in order to accurately identify these methane source regions. Using these data we show which regions have persistent sources (such as the Four Corners), and which are fugitive (methane bubbles in the Arctic), changing from one month to the next.

Following the identification of significant source regions using IASI, we increase the resolution by cross-referencing with the higher spatial resolution (but patchy) GOSAT data, in order to answer the question of whether individual gas sources can be identified from space. This study partially follows the method proposed by Kort, who used SCIAMACHY to identify general areas of high methane release in the USA, focusing on the oilrigs in the Four Corners region. This study takes Kort’s work further and attempts to identify individual sources (both natural and anthropogenic) using the GOSAT/IASI combination, backed up with ground-based knowledge of sources, such as the FrackTracker database and known natural sources such as the “Door to Hell” in Turkmenistan.

Finally we show validation by comparing the individual footprints against methane measurements from the TCCON (Wunch, D., et al. 2010), thus providing confidence in the use of individual satellites footprints as accurate measurement tools.

References

Kort, A. E., et al. (2014). Four Corners: The Largest US Methane Anomaly Viewed from Space.  Geophysical Research Letters. 41(19): 6898-6903.

Wunch, D., et al. (2011). The Total Carbon Column Observing Network. Philosophical Transactions of the Royal Society. 369: 2087-2112.