Pseudo-data Inversions of California CO2 Fluxes Combining Tower Measurements of CO2 and 14CO2 with OCO2 Column CO2 Retrievals
Thursday, 18 December 2014
The majority (~ 80 %) of California’s greenhouse gas (GHG) emissions are likely CO2 produced by fossil fuel combustion (ffCO2). While bottom-up estimates of State-annual total ffCO2 emissions are expected to be accurate to ~ 5-10% (68% confidence), net CO2 exchange at smaller spatial and temporal scales (and emissions of other GHGs) are likely less certain. Here, we report initial results of a Carbon Monitoring System (CMS) pseudo-data inversion study combining simulated total and radiocarbon CO2 sampling from a 10-site ground-based tower network with OCO2 satellite column CO2 retrievals. Fossil and biosphere CO2 signals are computed for tower and OCO2 observations across urban and rural areas of California including the South Coast Air Basin (SoCAB), Central Valley, and San Francisco Bay Area using the WRF-STILT transport model simulations coupled with prior fluxes from VULCAN (ffCO2) and CASA (bioCO2) fluxes respectively. Nominal uncertainties are assigned to the prior ffCO2 fluxes and estimated for the model-measurement differences including WRF and STILT model uncertainties and background subtraction. Reductions in posterior uncertainties for regional ffCO2 emissions are estimated for the tower pseudo-data using Bayesian inversions for monthly periods in multiple seasons. Ongoing work will include incorporation of OCO2 pseudo-data to estimate additional uncertainty reductions obtained for ffCO2 and bioCO2 exchange signals across California’s urban and rural regions.