Measurement and quantification of CO2 from space

Satellite retrievals are used to observe the distribution of CO2 in the troposphere and to determine if the net surface fluxes in the lower troposphere can be calculated through combining normalised column CO2 data. Satellites used are the Atmospheric Infrared Sounder (AIRS) and Scanning Imaging Absorption spectrometer for Atmospheric CHartographY (SCIAMACHY), which are sensitive to the upper and lower troposphere respectively. Annual variations in CO2 concentrations are small in the upper troposphere producing seasonal cycle amplitudes between 1.1 and 7.7 ppmv, lower tropospheric seasonal cycles are much greater with amplitudes ranging from 6.7 and 22.6 ppmv. Subtracting the CO2 column data (SCIAMACHY – AIRS), the residual variability reflects in part the surface CO2 variations. Comparisons are made with fractional green vegetation (FGV), the agreement between the data is very good, producing correlation values up to 0.96. SCIAMACHY column data also produced good agreement with the FGV data, suggesting that the subtracted data can measure the net surface fluxes, it is unclear whether the subtracted data represents the net surface fluxes better or worse than the SCIAMACHY data, further investigations are proposed. Numerical Atmospheric Dispersion Model (NAME) is used to calculate the origin of tropospheric over different vegetation types. Results showed that lower tropospheric data originated from the surface beneath, upper tropospheric data emanated from multiple areas, indicating that the CO2 in the upper troposphere is well mixed.