Synthesis of methane observations across scales: Strategies for deploying a multi-tiered observing network.

Regional methane emissions monitoring is rapidly expanding with increased coverage of surface, airborne, and satellite instruments. We pilot a multi-tiered observing system in the Los Angeles Basin. We combine surface methane measurements from the Los Angeles Megacities Carbon Project, mountaintop retrievals from the CLARS-FTS instrument, and space-based XCH4 retrievals from the TROPOMI instrument into a single monitoring framework. We simulate these observations using a high-resolution tracer transport model. Using inverse methods, we compare the sensitivity of each observing system component to various emissions sources. Combining multiple observing system into one framework allows for increased spatial and temporal sensitivity to methane emissions. We find a close correspondence between these inverse flux trends and independent airborne AVIRIS-NG methane plume trends over a large landfill in the Los Angeles basin. These results show that multi-tiered observing systems can reveal insights about sub-basin scale methane emissions, which can be used to drive decision support