Figure
2: Total column-integrated abundance shown as a function of season and
latitude. The figure includes all data points in the synergy dataset.
Note that no binning or selection has been done, and data points are
partially overlapping with more recent observations on top.
Several selection criteria were applied to the PFS and SPICAM
measurements when assembling the synergy dataset, yet not all selected
retrievals yielded satisfying results. Some data points have a retrieved
CIA below 1 pr-μm, which is considered to be below the sensitivity limit
of the synergy method, and a few retrievals also have extremely high
values that are deemed unlikely to occur, others yield poor fits and
high χ2 values.
The aforementioned benefit of an increased DOF by the use of a spectral
synergy approach is demonstrated in Figure 3. While water vapor column
abundances from all available co-located observations were shown in
Figure 2, only data points with a reduced χ2 of the
retrieval equal to or smaller than 4 are shown in Figure 3, where the
distribution of abundance-to-noise ratios (ANR) and the DOFs for the
synergy are shown along with the parameters from SPICAM/NIR and PFS/TIR.
Note that the data points are layered according to method, with the
higher synergistic values in the far back, and the method providing the
lowest average values in the front.