High resolution methane flux estimate from multi-species and mass balance methods

David Noone,  University of Auckland,  david.noone@auckland.ac.nz (Presenter)

While methane emissions are dominated by intense localized sources from natural gas extraction in some locations, more disperse sources from agriculture and natural ecosystems dominate elsewhere, and are more challenging to detect due to their weaker spatial gradients. High spatial resolution (few km) and multi-species sensors from either shortwave infrared or thermal infrared are nonetheless found to provide constraints on these weaker sources. Traditional flux estimation makes use of atmospheric models to provide a deterministic estimate of transport, which places a strong requirement for accurate wind estimates to be obtained from high resolution meteorological modeling. Indeed the atmospheric transport at scales within the boundary layer or associated with km-scale topography is often not well constrained, even if the transport is constrained at the larger synoptic scale. Moreover, the most prevalent inversion approach was developed on a heritage that sought to leverage high precision measurements from a small number of locations, and was adapted to a moderate data volume from remote sensing. We explore two complementary methods that are enabled with the higher spatial resolution remote sensing of current generation data products. First a method is developed that exploits the fact that atmospheric transport is common for many trace species, and utilizes the correlation structure between multiple trace species to account for transport separately from a deterministic (or adjoint) calculation. Second a method is developed that exploits the high resolution measurements directly in the context of a time mean atmospheric balance calculation. The multi species approach exploits the similarity of water, water isotope ratios and carbon monoxide in attributing column enhancements above background values to local fluxes as a function of meteorology. Both methods seek to leverage the new capacities at the spatially high resolution data from AIRS and TROPOMI. A southern hemisphere example is chosen as it represents an ideal natural laboratory where fugitive fossil fuel sources are weak, where the background concentrations are more homogeneous over ocean, and where robust inventories are available to offer independent prior constraints.

Poster: Poster_Noone__111_25.pdf 

Presentation Type: Poster

Session: 3.5a Flux estimates and atmospheric inversions from space-based GHG measurements

Session Date: Wednesday (6/16) 12:00 PM