Potential error in PES calculation for footprint

[jfburkhart]

Migrated from pflexible, issue from (harishgadhavi):

Hi,
I am using pflexible version 0.9.5. I believe the way get_slabs function normalises the potential emission sensitivity (PES) values obtained using backward runs may be erroneous.
The plot_footprint or plot_at_level routines uses H.C.slabs variable to plot the output. The variable "H.C.slabs" is created from "H.C.grids" variable using get_slabs function. Under one of the option i.e. normAreaHeight = True which is also default option, grid values are divided by "H.Heightnn" variable.
When ioro is set to 1, Heightnn variable contains Orthographic height + level of Z. Hence dividing grid with Heightnn in this case will result in skewed image. Where regions at higher height will appear to show low sensitivity compare to regions at lower height without any apparent reason. I am not sure but I guess PES values may have been divided by H.outheight variable instead of H.Heightnn, if one wanted to normalise with respect to thickness of output layer.
I wish some-one on this forum can clarify why is the option normAreaHeight provided in get_slabs function? Under what circumstances, people use it? Also, what units needs to be displayed on colorbar when values are normalised with this option?
Thanks.
Harish