How to determine column height over which XCO2 is averaged

[mblackhurst]

I'm trying to find details regarding the column height over which XCO2 measurements are averaged. Any guidance is appreciated.

[GES DISC - mgreene]

Looking at the standard product, OCO2_L2_Standard, you probably need to check three variables to get a sense of the atmospheric level contribution to the final column xCO2, all in the RetrievalResults group:
vector_pressure_levels
xco2_pressure_weighting_function
xco2_avg_kernel_norm

All of these are per sounding, so while the column height and weighting is different for every sounding, you should see the top level contribution start at about 0.1 hPa.

[mblackhurst]

Thanks for this. Does the first "retrieval_altitude" in the RetrievalResults group describe the column height over which values of xco2 are averaged? What are the units of retrieval_altitude?