Changes between Version 10 and Version 11 of ImplementationConceptOffline

Timestamp:

May 3, 2013, 9:17:15 PM (11 years ago)

Author:

lnerger

Comment:

--

ImplementationConceptOffline

@@ -22 +22 @@
 In the forecast phase the user has to run the numerical model as many times as there are ensemble members. Each model forecast has to be initialized by the state fields of the ensemble member. At the end of each single forecast integration the forecast fields are written into regular output files of the model. Within the offline mode of PDAF, we leave it to the user to control the integrations. As these are regular model integrations, it should be easiest to use the regular scripts used also to perform a free model integration without data assimilation. However, the user has to take care that the output files from each ensemble member are stored separately. 
 
-The assimilation program is a simplified implementation of what is required when PDAF is used in its online mode. In particular, no explicit linkage to the model code and no forecast phase are required. The general structure of the program for the offline assimilation program is depicted in figure 1.
+The assimilation program is a simplified implementation of what is required when PDAF is used in its online mode. In particular, no explicit linkage to the model code and no forecast phase are required. Essentially, one just needs to driver program that calls the PDAF routines. The general structure of the program for the offline assimilation program is depicted in figure 1.
 
 [[Image(//pics/PDAF_offline.png)]]
@@ -35 +35 @@
 
  * With the offline mode of PDAF, no direct coupling between PDAF and the model code is required. The exchange of information between the model and the assimilation program is performed solely through the output and restart files of the model. It requires that the user implements routines to read the model fields from the forecast files. In addition, routines are necessary that write the analysis state ensemble into restart files of the model. 
- * Model-specific operations like the initialization of the array of ensemble states in `PDAF_init` are actually performed by user-supplied routines. These routines are called through the standard interface of `PDAF`. Details on the interface and the required routines are given on the pages describing the implementation steps.
+ * Model-specific operations like the initialization of the array of ensemble states in `PDAF_init` are actually performed by user-supplied call-back routines. These routines are called through the standard interface of `PDAF`. They can be implemented int he users programming style and just have to be consistent with the interface. Details on the interface and the required routines are given on the pages describing the implementation steps. The concept of the call-back routines is depicted in Fig. 2.
+[[Image(//pics/PDAF_callback_offline.png)]]
+[[BR]]'''Figure 1:''' The assimilation program consist of the driver program, the PDAF core, and user-supplied call-back routines.
+
  * With regard to the parallelization, the assimilation program can be run on a single processor, i.e. without parallelization. The variables for the parallelization still have to be initialized by a call to `init_parallel_pdaf`. However, one does not need to compile with an MPI library, but it is sufficient to use the dummy implementation of the MPI-routines that is supplied with PDAF. If the model is parallelized, one needs to ensure that the model fields are read correctly. In particular, if in the parallel model each process writes a separate file, one has to read these files sequentially in order to initialize an ensemble array holding the global state information.
  * For large-scale models, it can be useful to execute the assimilation program with parallelization. Perhaps, following the domain decomposition of the model is the easiest strategy for this. In this case the decomposition information from the model has to be read into the assimilation program in order to initialize the state dimension of the sub-domains as well as the coordinates for each sub-domain.