Figure
4: Illustration of the benefit of utilising the synergistic retrieval
by altitude, latitude and season. Each panel represents an altitude
level, with the given altitude in km given on the left. Within each
panel, the y-axis represents latitude, with major ticks every 30°. Data
were averaged in bins of 2° latitude and 2° Ls. The retrieved posterior
errors are divided by the MCD prior errors, such that values below 1
represent retrievals where the uncertainty has been reduced, and thus
the co-located observation has injected additional information into the
retrieval process.
The benefits of using two spectral ranges is clearly visible, with more
than 55% of all synergy retrievals fulfilling all criteria compared to
only 24% for SPICAM/NIR, and 16% for PFS/TIR, effectively
demonstrating that the synergy yields more information than separately
using the SPICAM or the PFS dataset. For all cases the
χ2 is the most restrictive requirement (except for
PFS/TIR where the DOF is the most restrictive), while the ANR is the
least restrictive. The DOF increase provided by synergy compared to
retrievals from single spectral domains is a direct evaluation of how
much additional information synergy brings to constrain water vapor
distribution. Only the measurements fulfilling all four requirements are
considered in the following analysis.