= Overview of the Analysis step of Ensemble filters =

For the analysis step of ensemble filters several routines need to be implemented. We prove a conceptional overview here. The detailed interfaces are then described on the following pages.

[[Image(//pics/Analysis_EnFs_web.png)]]
[[BR]]'''Figure 1:''' Required routines for the analysis step of ensemble filters. There are threee groups of routines: The interface to the model (orange), the observation module (red), and state localization in case of domain-localized filters like LETKF/LESTKF/LNETF (purple).

Figure 1 gives an overview of the different routines that might need to be provided to the analysis step of an ensemble filter. The actual routines depend on the chosen filter method. The routines are organized in three groups:

 * '''Model Interface:'''[[BR]]
 The model Interface consists of the routines `collect_state_pdaf` and `distribute_state_pdaf`. These routine perform the concersion between model fields and state vector. The routines have been discussed in the context of the [ModifyModelforEnsembleIntegration modification of the model for the ensemble integration]. 
 * '''OMI Observation Module:'''[[BR]]