Changes between Version 2 and Version 3 of ModifyModelforEnsembleIntegrationFullpar


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Timestamp:
Apr 28, 2014, 3:29:15 PM (7 years ago)
Author:
lnerger
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  • ModifyModelforEnsembleIntegrationFullpar

    v2 v3  
    1919== Overview ==
    2020
    21 Numerical models are typically implemented for normal integration of some initial state. For the data assimilation with filter algorithm, an ensemble of model states has to be integrated for limited time until observations are available and an analysis step of the filter is computed. Subsequently, the updated ensemble has to be integrated again. To allow for these alternating ensemble integrations and analysis steps the model code has to be extended. The recommended implementation strategy for PDAF is to add an additional loop outside of the regular time-stepping loop of the model. This strategy has the potential to reduce the required chances in the model code to the minimum. In addition, a routine that simulates model errors might be required to be inserted into the time stepping loop of the model. The required extensions are described below.
     21Numerical models are typically implemented for normal integration of some initial state. For the data assimilation with a filter algorithm, an ensemble of model states has to be integrated for limited time until observations are available and an analysis step of the filter is computed. Subsequently, the updated ensemble has to be integrated further. To allow for the interruption of the integrations by the analysis step, the model code has to be extended. There are two options for the ensemble integration:
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     25The recommended implementation strategy for PDAF is to add an additional loop outside of the regular time-stepping loop of the model. This strategy has the potential to reduce the required chances in the model code to the minimum. In addition, a routine that simulates model errors might be required to be inserted into the time stepping loop of the model. The required extensions are described below.
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    2327Operations that are specific to the model and to the assimilated observations are performed by routines that are supplied by the user. These are called through the defined interface of PDAF. Generally, these user-supplied routines have to provide quite elementary operations, like initializing a model state vector for PDAF from model fields or providing the vector of observations. PDAF provides examples for these routines and templates that can be used as the basis for the implementation. As only the interface of these routines is specified, the user can implement the routines like a routine of the model. Thus, the implementation of these routines should not be difficult.