introducing perturbations to GOCART2G

At NOAA we are developing ensemble DA for UFS-Aerosols model that relies on GOCART2G.
In the past we developed perturbations to emissions for GEFS-Aerosols model (an older NOAA model) using a scheme called SPPT that creates spatially and temporally correlated patterns. This scheme was developed at ECMWF to parameterize model errors and was shown to have benefits for ensemble data assimilation at this institution and also at NCEP. We demonstrated similar benefits for aerosol DA with GEFS-Aerosols. We are considering two, possibly three options to include perturbations in UFS-Aerosols:

1. passing SPPT perturbations to GOCART code (i.e. in-line);
2. perturbing emission input files, distinct for each ensemble member (i.e. off-line);
3. using *.rc files to provide 2D perturbations (i.e. off-line but not sure if at all possible with 2D files).
   We think that option 1) is the most robust for various reasons that I could elaborate on if there is interest. In short, we would like to pass SPPT perturbations from the physics part of the NOAA model to GOCART in the form of 2D multiplicative coefficients. The coefficients would be applied to sources of dust, sea-salt, carbon/dust from wildfires and anthropogenic aerosols. As a default there would be no perturbations and the results would be identical to the original.
   Please let me know what you think about these ideas and if NASA would support the concept and let us introduce perturbation codes to the repository.

Start by reviewing the GOCART interfaces and the existing SPPT implementation referenced in the issue; no specific files, tests, or entry points are named. Compare the three proposed approaches for passing 2D multiplicative coefficients to aerosol sources, and confirm the default path remains identical to the unperturbed model before proposing an implementation plan.