Changes between Version 5 and Version 6 of GeneralImplementationConcept


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Timestamp:
Sep 26, 2010, 11:15:22 AM (10 years ago)
Author:
lnerger
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  • GeneralImplementationConcept

    v5 v6  
    88 * Filter:[[BR]] The filter algorithms combine the model and observational information.
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    10 Generally,a ll three components are independent. In particular, the filters are implemented in the core part of PDAF. To combine the model and observational information one has to define the relation of the observations to the models fields (For example, model fields might be directly observed or the observed quantities are more complex functions of the model fields? In addition, the observations might be available on grid points. If not, interpolation is required.) In addition one has to define the relation of the state vector that is considered in the filter algorithms to the model fields. These relations are defined in separate routines that are supplied to the assimilation system by the user. These routines are called through a well-defined standard interface. To ease the implementation complexity, these user-defined routines can be implemented like routines of the model code. Thus, if a user has experience with the model, it should be rather easy to extend it by the routines required for the assimilation system.
     10Generally, all three components are independent. In particular, the filters are implemented in the core part of PDAF. To combine the model and observational information one has to define the relation of the observations to the models fields (For example, model fields might be directly observed or the observed quantities are more complex functions of the model fields? In addition, the observations might be available on grid points. If not, interpolation is required.) In addition one has to define the relation of the state vector that is considered in the filter algorithms to the model fields. These relations are defined in separate routines that are supplied to the assimilation system by the user. These routines are called through a well-defined standard interface. To ease the implementation complexity, these user-defined routines can be implemented like routines of the model code. Thus, if a user has experience with the model, it should be rather easy to extend it by the routines required for the assimilation system.
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    1212
    1313== Attaching PDAF to a model ==
     14
     15There are two possibilities to build a data assimilation system
     16 1. '''Offline mode:''' The model is executed separately from the assimilation/filter code. Output files from the model are used as inputs for the assimilation program.
     17 1. '''Online mode:''' The model code is extended by calls to PDAF core routines. A single executable is compiled. Whlie running this single executable the necessary ensemble integrations and the actualy assimilation is performed.
     18PDAF supports both the online and offline modes. Generally, we recommend to use the online mode because it is more efficient on parallel computers. However, the required coding is simpler for the offline than the online mode.
     19
     20Here we describe the extensions of the model code for the online mode of PDAF.
    1421
    1522The assimilation system is built by adding call to PDAF-routines to the general part of the model code. As only minimal changes to the model code are required, we refer to this as "attaching" PDAF to the model.