1. 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)

2. 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

3. 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

4. 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

5. 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

6. 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.