Implementing the analysis step

The implementation of the analysis step requires that the user-supplied routines whose names are given in the call to the filter-specific put-state routine are implemented with full functionality.

With PDAF-OMI many of the routines are general and hence usable for all filter algorithms. There are some differences between the local and global filters and the LEnKF. The general routines will be repeated, but they are marked as general.

There is a universal routine that calls the filter analysis step for all filter methods.

• General overview of routines required to implement the analysis step for ensemble filters.

1. Implementation of the analysis

1. Implementation of the analysis for Global Filters
2. Implementation of the analysis for Local Filters
3. Implementation of the analysis for the LEnKF using covariance localization

For the application of the 3D-Var methods there are separate routines (added with PDAF 2.0):

• General overview of routines required to implement the analysis step for 3D-Var.

1. Implementation of the analysis for 3D-Var with parameterized background covariance matrix
2. Implementation of the analysis for 3D Ensemble Var
3. Implementation of the analysis for hybrid 3D-Var

Older implementation variants

PDAF-OMI implementation

In PDAF2 the implementation was done using PDAF-OMI as described on the Page on implementing the analysis with PDAF-OMI

Implementation using the full interface

Before the introduction of PDAF-OMI only the full interface routines of PDAF were used. This approach required a larger amount of coding. This implementation of the analysis step using PDAF's full interface is still possible. This approach should be considered as an 'expert mode'.

Testing the full implementation

After the implementation of the user-supplied routines for the analysis step, the data assimilation system is fully implemented. In order to test the program one has to compile it without setting 'PDAF_NO_UPDATE'.