Preparing the global CMS Flux system for application to carbon flux inventories via regional-scale, observation-based evaluations

The global Carbon Monitoring System (CMS) Flux inversion system uses satellite CO2 measurements to estimate global CO2 sources and sinks with state-of-the-art data assimilation algorithms. CMS Flux is developing a nested flux estimation system with high-resolution (0.5x0.625 degrees2) over North America to serve the needs of natural resource managers who need information specific to regional biomes and geopolitical units. The objective is to provide an inverse flux estimate that identifies regional discrepancies between atmospheric observations and ecosystem inventories. This project will: 1) Incorporate US forest, agricultural and grassland CO2 inventories into the prior flux estimates used in the CMS Flux system; 2) Use a suite of independent CO2 flux and mole fraction observations to evaluate and improve the CMS Flux system prior fluxes at regional, daily, and seasonal resolution over North America; 3) Evaluate and improve the CMS Flux system meteorology with a suite of North American wind speed and direction, and mixing depth observations; and 4) Use the improved CMS Flux system to evaluate US biological CO2 flux inventories. Our overall objective is to determine the degree to which the CO2 flux estimates from this improved inversion system provide a useful constraint on US inventories of agricultural and forest CO2 fluxes. We report on progress to date including: 1) A continental-scale, multi-year evaluation of boundary layer depth and tropospheric winds in the MERRA2 products used in CMS Flux; 2) Development of a transport ensemble built in response to this model-data assessment; and 3) Integration of agricultural and forest inventory data into CARDAMOM, the biospheric flux model used to create prior flux estimates for the CMS Flux system. These results are intermediate steps toward an observationally-constrained, ensemble-based North American regional CMS Flux inversion product. This work will provide a path for developing similar inventory assessments for other years, and in other parts of the globe.