Changes between Version 1 and Version 2 of GeneralImplementationConcept

Sep 24, 2010, 4:05:22 PM (10 years ago)



  • GeneralImplementationConcept

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    2222The right hand side of Figure 2 shows the extensions required for the assimilation system (marked yellow):
    2323 * Close to the start of the model code the routine `init_parallel_pdaf` as added to the code. If the model itself is parallelized the correct location is directly after the initialization of the parallelization in the model code. `init_parallel_pdaf` creates the parallel environment that allows to perform several time stepping loops at the same time.
    24  * After the initialization part of the model,
     24 * After the initialization part of the model, a routines `init_pdaf` is added. In this routine, parameters for PDAF can be defined and then the core initialization routine PDAF_init is called. This core routine also initializes the array of ensemble states.
     25 * In order to allow for the integration of the state ensemble an unconditional loop is added around the time stepping loop of the model. This will allow to compute the time stepping loop multiple time during the model integration. PDAF provide an exit-flag for this loop. (There are some conditions, under which this external loop is not required. Some note on this are given further below.)
     26 * Inside the external loop the PDAF core routine `PDAF_get_state` is added to the code. This routine initializes model fields form the array of ensemble states and initialized the number of time step that have to be computed and ensured that the ensemble integration is performed correctly.
     27 * At the end of the external loop, the PDAF core routine `PDAF_put_state` is added to the model code. This routine write the propagated model fields back into a state vector of the ensemble array. Also it checks whether the ensemble integration is complete. If not, the next ensemble member will be integrated. If the ensemble integration is complete, the analysis step (i.e. the actual assimilation of the observations) is computed.
     29With the implementation strategy of PDAF, four routines and the external loop have to be added to the model code. While this looks like a large change in figure 2, this change does actually only affect the general part of the model code. In addition, the amount of source code of the numerical model will be much longer than the addition for the data assimilation system.
     32Some remarks
     33 * The implementation concept of PDAF does not require that the time stepping part of the model is implemented as a subroutine. Instead the control of the ensemble integration is added around the code performed the time stepping. However, if the time stepping part is implemented as a subroutine, the code will look clearer.
     34 *