Spatially informed Aggregation of Orbiting Carbon Observatory- 2 measured XCO2 for Global Flux Inversion Joaquim Teixeira, Amy Braverman, Jonathan Hobbs, Hai Nguyen (Jet Propulsion Laboratory/Caltech)

Orbiting Carbon Observatory-2 Orbiting Carbon Observatory-2 (OCO-2) infers column averaged CO2 ( XCO 2 ) by measuring spectral radiance OCO-2’s global measurements used in global CO2 flux inversion modelling OCO-2 soundings week of 2015-10-11

Objective and Approach OCO-2 native resolution very fine (1km) Global flux inversion requires coarse resolution (1° degree) Most common aggregated product has no spatial correlations + uncertainties derived from geophysical understanding Our approach: Localized Ordinary Block Kriging by orbit

𝑋𝐶𝑂 2 for sample orbit footprints and latitude-dependent trend Removing Latitudinal Dependence by Orbit 𝑋𝐶𝑂 2 for sample orbit footprints and latitude-dependent trend OCO-2 records data across 16 orbit tracks every day CO2 exhibits dependence on latitude Use LOESS to remove latitude trend for each orbit Outlier removal for stable covariance estimation Kriging requires stationary data Tedrend xco2 as a function of latitude LOESS figure kriging performed on detrended data

Definition of Spatial Field And Covariance Estimation Spatial field for sample degree box Discretize orbit into degree boxes Define spatial field for each box with 100km radius Assume exponential spatial covariance of detrended 𝑋𝐶𝑂 2 within spatial field Estimate covariance from variogram cloud Block Krige over degree box after detrend, define individual field for each 1x1 box choose center point choose all points within ~200km of center Detrended 𝑋𝐶𝑂 2

Preliminary Results Results +0.5 XCO 2 ppm difference between spatial aggregation and current approach over land -0.5 XCO 2 ppm difference between spatial aggregation and current approach over ocean ©2019 California Institute of Technology. Government sponsorship acknowledged.