Hi all,
I struggled a bit to set up absorption lookup tables for our Odin/SMR
processing. For some frequency modes we extend the retrieval into the
thermosphere, and this causes problems. My reference temperature profile
is about 170 K at the mesopause, and accordingly abs_t_pert can not go
below about -160 K. This means that I have only a 160 K margin downwards
in the thermosphere, which is by far too narrow.
My present solution is to not allow the reference temperature be above
300 K, and instead have a abs_t_pert going to high positive values (+600
K). This works and is OK.
However, this got me to think. The simplest for me would in fact to set
abs_t to be e.g. 250 K at all altitudes, that would basically would give
me a fixed t_grid. Further, with modern computers where memory is not a
problem, maybe it is time to give up on using abs_t + abs_t_pert, and
instead just having a t_grid. That is, to have a standard "rectangular"
set-up, with a standard pressure and temperature grid.
I suggest to switch to a fixed t_grid as I think it could speed up the
interpolation significantly. I assume that with present abs-table, new
temperature grid positions must be calculated for each altitude (as
abs_t(i)+abs_t_pert varies). Stefan: Can you confirm this? Have you
considered the speed impact of this?
With a fixed t_grid, a given temperature has the same grid position at
all altitudes.
Any comments?
Bye,
Patrick
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