Feature request: alternative perturbs & increments

[hkershaw-brown]

From standup discussion 4th Sept 2025 - please edit/add as needed ☠️

Use case

What are you trying to accomplish? Sometimes there may already be a way to do what you need.

Testing where you want different ensemble members but not with Gaussian noise.
e.g. constant value added *ensemble member so so you can check model_interpolate for each ensemble member.

Also localization - increment with a constant so you can test get_close.

Is your feature request related to a problem?

Ease of testing.

Describe your preferred solution

Please provide enough detail here to help people have a discussion about your proposal
Not yet.

Describe any alternatives you have considered

None yet.

[hkershaw-brown]

e.g. to make a cyclinder/sphere (output.nc - input.nc) for get close:

diff --git a/assimilation_code/modules/assimilation/assim_tools_mod.f90 b/assimilation_code/modules/assimilation/assim_tools_mod.f90
index 0c595170b..9f57f91f3 100644
--- a/assimilation_code/modules/assimilation/assim_tools_mod.f90
+++ b/assimilation_code/modules/assimilation/assim_tools_mod.f90
@@ -2057,6 +2057,8 @@ endif

! Get the updated ensemble
if(.not. inflate_only) ens = ens + final_factor * increment
+ens = ens + final_factor * 1.0_r8
+

end subroutine obs_updates_ens