Changes between Version 1 and Version 2 of ImplementationConceptOffline

Timestamp:

May 18, 2011, 1:57:26 PM (14 years ago)

Author:

lnerger

Comment:

--

ImplementationConceptOffline

@@ -5 +5 @@
 In case of the offline mode of PDAF, the ensemble integrations are performed by the numerical model without required changes. After all ensemble members are integrated to the time when observations are to be assimilated, the assimilation program containing PDAF is started. The program reads the files from the model for all ensemble members. Subsequently, the analysis step of the chosen filter algorithm is computed. Finally, the updated ensemble states are written into input or restart files of the model. This completes the analysis step such that the next forecast phase can be computed.
 
-The 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.
+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 general concept is depicted in figure 1. The left hand side shows a typical abstract structure of a numerical model. When the program is executed, the following steps are performed:
- 1. The model is initialized. Thus arrays for the model fields are allocated and filled with initial fields. Thus, the model grid is build up virtually in the program. 
- 2. After the initialization the time stepping loop is performed. Here the model fields are propagated through time.
- 3. When the integration of the model fields is completed after a defined number of time steps, various post-processing operations are performed. Then the program stops.
+The assimilation program is a simplified implementation of what is required for the 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.
 
 [[Image(//pics/da_extension.png)]]