Changes between Version 28 and Version 29 of GeneralImplementationConcept

Timestamp:

May 30, 2025, 6:04:13 PM (2 days ago)

Author:

lnerger

Comment:

--

GeneralImplementationConcept

@@ -37 +37 @@
 == Online and offline assimilation systems ==
 
-There are two possibilities to build a data assimilation system 
+There are two possibilities to build a data assimilation system as sketched in Figure 2:
  1. '''Online mode:''' [[BR]] In the online mode, calls to subroutines for the data assimilation are inserted into the model code. Thesse routines call the PDAF core routines. A single data-assimilative model program is compiled. While running this single program, the necessary ensemble integrations and the actual assimilation are performed. The information transfer between the model and the data assimilation functions are performed in memory.
  1. '''Offline mode:''' [[BR]] In the offline mode, the model is executed separately from the assimilation program. The model write restart files, which are used as inputs for the assimilation program. After computing the analysis step with the DA method, the assimilation program writes new restart files for the model, which is then started to compute the next forecast phase. In Figure 1, the model on the bottom left side is replaced by the reading and writing of files.
+
+[[Image(//pics/DAextension_offline-online_V3.png)]]
+[[BR]]'''Figure 2:''' Left: offline-coupled DA system with separate programs for model and assimilation; right: online-coupled DA system using model extended by data assimilation functionality. 
 
 PDAF supports both the online and offline modes. The online mode is usually more efficient on parallel computers, since less files have to be written to disks and the model does not need to be restarted after the analysis step. However, the required programming is simpler for the offline more than the online mode, since no modification to the model source code is necessary.