Point source detection and validation using GOSAT and OCO-2 data: Volcanoes and Power Plants

Thursday, 18 December 2014
Florian M Schwandner, Jet Propulsion Laboratory, Pasadena, CA, United States, Simon A Carn, Michigan Technological University, Houghton, MI, United States, Fumie Kataoka, RESTEC, Tsukuba, Japan, Vincent J Realmuto, NASA Jet Propulsion Laboratory, Pasadena, CA, United States, Akihiko Kuze, JAXA Japan Aerospace Exploration Agency, EORC, Sagamihara, Japan and Kei Shiomi, Earth Obs. Res. Cntr. / JAXA, Tsukuba, Ibaraki, Japan
Point source emissions from power plants and non-erupting active volcanoes are continuous but variable in source strength and resulting plume direction. Power plant emission variations are driven by regular demand/load cycles, while volcanic CO2 emissions follow less regular oscillations. Two polar orbiting sun-synchronous satellites currently measure atmospheric CO2with sufficient sensitivity and spatial resolution to detect point sources and their plumes: GOSAT and OCO-2.

GOSAT, launched in January 2009 by JAXA, provides 260 km spaced single-sounding grid points at a 3-day repeat cycle with a circular field of view of 10km diameter, at ~0.25/s samples. OCO-2 (leading the A-train on the Calipso ground track, repeat cycle 16 days), launched in July 2014 by NASA continuously collects eight <3 km2 cross-track elements at 24/s samples along a ~10 km wide swath either along-track (nadir), or in glint direction. GOSAT has an agile pointing system, permitting a large number of custom targets per orbit, at the expense of spatial context. OCO-2 provides up to 10,000 soundings over a different pre-programmed ~100 km2area each day. Consequently, observation strategies for point sources differ between the two missions. GOSAT can precisely and frequently and repeatedly target at the central emission point, providing a great opportunity for time series observations at its fast repeat cycle. In contrast, OCO-2 is targeting mainly validation sites (maximum 1 per orbit), thus maximizing spatial data continuity. However, close incidental flyby detection of plumes, with some along-swath spatial context, is possible with OCO-2.

Synergetic opportunities exist to aid in CO2 plume identification, verification and validation. For OCO-2, other A-Train constellation satellites (e.g., OMI, MODIS, Calipso) provide independent parameters such as SO2 and aerosol information. GOSAT TIR data can be used to retrieve SO2values, providing plume validation, together with the GOSAT’s spatial aerosols data. GOSAT and OCO-2 offer synergies between each other through several near-coincident measurements per day, permitting direct cross-validation, as well as making use of the combination of incidental OCO-2 flybys at point sources and their plumes, and target mode time series from GOSAT.

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