= Implementation of the analysis step with OMI (PDAF2) =

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<div class="wiki-toc">
<h4>Implementation Guide: Analysis Step in PDAF2</h4>
<ol>
<li></a href="OMI_ImplementationofAnalysisStep_PDAF23">Main page: Implementing the analysis step with OMI</a></li>
<ol>
<li><b>Ensemble filters</b></li>
<ol>
<li> <a href="ImplementFilterAnalysisOverview_PDAF23"> General overview for ensemble filters</a></li>
<li><a href="ImplementAnalysisGlobal_PDAF23">Implementation for Global Filters</a></li>
<li><a href="ImplementAnalysisLocal_PDAF23">Implementation for Local Filters</a></li>
<li><a href="ImplementAnalysislenkfOmi_PDAF23">Implementation for LEnKF</a></li>
</ol>
<li><b>3D-Var methods</b></li>
<ol>
<li> <a href="Implement3DVarAnalysisOverview_PDAF23"> General overview for 3D-Var methods</a></li>
<li><a href="ImplementAnalysis_3DVar_PDAF23">Implementation for 3D-Var</a></li>
<li><a href="ImplementAnalysis_3DEnVar_PDAF23">Implementation for 3D Ensemble Var</a></li>
<li><a href="ImplementAnalysis_Hyb3DVar_PDAF23">Implementation for Hybrid 3D-Var</a></li>
</ol>
</ol>
</div>
}}}

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<b> This page can be reached from different<br>parts of the documentation:</b>
<p>Back to <b><a href="OfflineImplementationGuide_PDAF23">Offline Mode: Implementation Guide</a></b></p>
<p>Back to <b><a href="ImplementationGuide_PDAF23">Online Mode: Implementation Guide</a></b></p>
<p>Back to <b><a href="PDAF_OMI_Overview_PDAF23">PDAF-OMI Guide</a></b></p>
</div>
}}}

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<div class="wiki-toc">
<h4>PDAF-OMI Guide for PDAF2</h4>
<ol><li><a href="PDAF_OMI_Overview_PDAF23">Overview</a></li>
<li><a href="OMI_Callback_obs_pdafomi_PDAF23">callback_obs_pdafomi.F90</a></li>
<li><a href="OMI_observation_modules_PDAF23">Observation Modules</a></li>
<li><a href="OMI_observation_operators_PDAF23">Observation operators</a></li>
<li><a href="OMI_error_checking_PDAF23">Checking error status</a></li>
<li><a href="OMI_debugging_PDAF23">Debugging functionality</a></li>
<li></a href="ImplementationofAnalysisStep_PDAF23">Implementing the analysis step with OMI</a></li>
<li><a href="Porting_to_OMI_PDAF23">Porting an existing implementation to OMI</a></li>
<li><a href="PDAFomi_additional_functionality_PDAF23">Additional OMI Functionality</a></li>
<li><a href="OMI_use_global_obs_PDAF23">Using domain-limited observations</a></li>
<li><a href="OMI_nondiagonal_observation_error_covariance_matrices_PDAF23">Using nondiagonal R-matrices</a></li>
</ol>
</div>
}}}

|| This page describes the implementation approach of PDAF2. This is intended for reference for existing implementations performed for PDAF2. See the [wiki:ImplementationofAnalysisStep_PDAF3 page on implementing the analysis step with PDAF3] for the updated recommendations. ||

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.

While different routines are used for the online and offline modes of PDAF, the implementation of the analysis is generally generic. As such we combine this here for both the online and offline modes.


There are three different routines that call the filter analysis step.
 * [wiki:ImplementFilterAnalysisOverview_PDAF23 General overview] of routines required to implement the analysis step for ensemble filters.
 1. [wiki:ImplementAnalysisGlobal_PDAF23 Implementation of the analysis for Global Filters]
 1. [wiki:ImplementAnalysisLocal_PDAF23 Implementation of the analysis for Local Filters]
 1. [wiki:ImplementAnalysislenkfOmi_PDAF23 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):
 * [wiki:Implement3DVarAnalysisOverview_PDAF23 General overview] of routines required to implement the analysis step for 3D-Var.
 1. [wiki:ImplementAnalysis_3DVar_PDAF23 Implementation of the analysis for 3D-Var with parameterized background covariance matrix]
 1. [wiki:ImplementAnalysis_3DEnVar_PDAF23 Implementation of the analysis for 3D Ensemble Var ]
 1. [wiki:ImplementAnalysis_Hyb3DVar_PDAF23 Implementation of the analysis for hybrid 3D-Var]


== Implementation of the analysis step without OMI ==

PDAF-OMI was introduced with version 1.16 of PDAF. While we recommend using OMI, the [wiki:ImplementationofAnalysisStep_noOMI implementation of the analysis step without OMI] using PDAF's full interface is still possible.


== 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'.