Note
This document is written as if your experiment was run with single_file_out = .true.
. The potential permutations of filenames output by filter is enormous, so it isn't feasible to write documentation for all possible cases.
After filter executes without error and produces an obs_seq.final
file, a preassim.nc
file, and an analysis.nc
file, the first questions to ask are:
- Is the model state output from
filter
different from the input? - Were any observations successfully assimilated?
You can check check if the output model state data was changed by the assimilation by using the ncdiff
tool to create a file containing the difference of the preassim.nc
and analysis.nc
files. If you are running with single_file_in = .true.
and single_file_out = .true.
use ncdiff
on the files output for the analysis and preassim stages:
$ ncdiff analysis.nc preassim.nc increments.nc
Otherwise, if you are running with single_file_in = .false.
and single_file_out = .false.
, use ncdiff
on the ensemble mean files for the analysis and preassim stages:
$ ncdiff analysis_mean.nc preassim_mean.nc increments.nc
ncdiff
generates a file, increments.nc
, that contains the increments, or innovations, created by filter
. You can view the increments using ncview
:
$ ncview increments.nc
to examine the ensemble mean variables. If all values are 0, then the assimilation changed nothing in the state.