Optimal estimation of North American methane emissions using GOSAT data: A contribution to the NASA Carbon Monitoring System
Abstract
We use methane observations from the Greenhouse Gases Observing SATellite (GOSAT) to constrain methane emissions from North America in support of the NASA Carbon Monitoring System. We apply two methods: (1) an adjoint-based 4DVAR inversion, and (2) an analytical inversion with an optimally reduced state vector enabling full characterization of the solution. The GOSAT methane retrievals are validated using aircraft data from the HIPPO campaign, and our overall 4DVAR framework is shown to compare successfully to a Lagrangian inversion of CalNex aircraft data over California. The adjoint-based method has high resolution but does not suitably characterize the information content of the data or the error in the optimized emissions. The analytical inversion is based on a Gaussian Mixture Model (GMM) to explore the actual information content of the GOSAT data by optimally reducing the dimensionality of the state vector. The Maximum A Posteriori (MAP) solution from the analytical inversion yields emission constraints consistent with the 4DVAR approach while allowing construction of the full posterior solution, averaging kernel matrix, and posterior covariance matrix in an easily parallelizable framework. We find that methane emissions from the Canadian wetlands are overestimated in current inventories and that the EDGARv4.2 anthropogenic inventory underestimates emissions over the south-central US. We will show preliminary results applying the GMM method over the duration of the GOSAT record. This method can evolve into an operational tool for monitoring of methane emissions from North America using satellite data and including characterization of uncertainties.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.A11I..08T
- Keywords:
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- 0322 ATMOSPHERIC COMPOSITION AND STRUCTURE Constituent sources and sinks;
- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE Troposphere: composition and chemistry;
- 1610 GLOBAL CHANGE Atmosphere;
- 0399 ATMOSPHERIC COMPOSITION AND STRUCTURE General or miscellaneous