TransCom-2024: Quantifying errors in inversions of satellite trace gas retrievals
TransCom-2024: Quantifying errors in inversions of satellite trace gas retrievals
Location: NSF National Center for Atmospheric Research (NSF NCAR) Mesa Lab in Boulder, Colorado.
Date: Tuesday 28 May 2024
Meeting summary:
Inversions of atmospheric trace gas measurements to infer surface sources and sinks have long been used to assess the global budgets of CO2, CH4, N2O and other species; pushing these estimates to regional spatial scales and sub-annual time scales can yield insight into the processes driving the fluxes. The TransCom project has tried to quantify the uncertainties in such flux estimates, focusing on those errors related to the transport models underlying the inversions.
Recently, this ‘top-down’ approach has been enlisted for use in the policy realm: country-scale CO2 fluxes have been estimated from dense satellite XCO2 measurements and, once lateral fluxes are accounted for, converted into carbon stock changes; these may be compared to similar ‘bottom-up’ estimates that form the basis of the Paris Agreement emissions reduction efforts, providing a largely-independent check on the process. This year’s TransCom meeting focuses on quantifying errors in satellite-based flux inversions such as these, especially errors due to transport, but also those due to measurement biases, coverage/sampling issues, inversion method assumptions, lateral flux characterization, etc., from global down to regional and country scales.
Large differences have been found between satellite- and ground-based measurements of column-averaged trace gas concentrations and similar values derived from atmospheric transport models, even when such models assimilate the available (mostly surface-based) in situ data as a constraint. These differences show up in terms of global averages, latitudinal distributions, strat/trop exchange, and land/ocean differences, as well as at regional scales. Some reflect the real flux signals of interest, but most are due to measurement and transport errors that must be removed first. The transport model errors include those related to convection, spatial and temporal resolution, the treatment of water vapor in the models, and mixing out of the PBL, between hemispheres and into the stratosphere.
We welcome presentations that focus on understanding such transport errors, especially those affecting the satellite inversion problem. Collaborative work on flux inversion intercomparison is also sought, especially from global research community projects such as, e.g., REgional Carbon Cycle Assessment and Processes-2 (RECCAP2), the Global Carbon Project, the Orbiting Carbon Observatory-2 (OCO-2) flux inversion model intercomparison project (MIP), and other TransCom initiatives.
We envision both shorter and longer presentations in order to get everyone a chance to present and to facilitate discussion. The event will be hybrid and online participants are welcome to present.
Jointly with the NSF NCAR Climate & Global Dynamics seminar series, Dr. David Crisp, former OCO-2 science lead at NASA/JPL, will present a talk on top-down carbon fluxes supporting regional-scale carbon cycle science and national-scale greenhouse gas inventories.
Note that Monday, 27 May 2024 is a national holiday in the United States, with spring activities such as the BolderBoulder 10km race and many others.
The conference will be followed by the International Workshop on Greenhouse Gas Measurements from Space (IWGGMS-20), also at NSF NCAR.
It is also happening the week after the GML 52nd Global Monitoring Annual Conference.