| 25 | | == External ensemble loop == |
| 26 | | |
| 27 | | The external loop for the ensemble integration has to enclose the time stepping loop of the model. Next to the external loop, a control structure for exiting the external loop as well as two calls to subroutines of PDAF have to be added. These are the calls to `PDAF_get_state` and a filter-specific routine like `PDAF_put_state_seik` for the SEIK filter. Both routines are described in sections below. |
| 28 | | |
| 29 | | The extended model code can look like this for the SEIK filter: |
| 30 | | {{{ |
| 31 | | pdaf_modelloop: DO |
| 32 | | |
| 33 | | CALL PDAF_get_state(nsteps, ..., doexit, ...) |
| 34 | | |
| 35 | | ! Check whether forecast has to be performed |
| 36 | | ifcontrol: IF (doexit /= 1) THEN |
| 37 | | |
| 38 | | IF (nsteps > 0) THEN |
| 39 | | |
| 40 | | ... Time stepping code of the model ... |
| 41 | | |
| 42 | | END IF |
| 43 | | |
| 44 | | CALL PDAF_put_state_seik(...) |
| 45 | | |
| 46 | | ELSE ifcontrol |
| 47 | | |
| 48 | | ! No more assimilation work; exit loop |
| 49 | | EXIT pdaf_modelloop |
| 50 | | |
| 51 | | END IF ifcontrol |
| 52 | | |
| 53 | | END DO pdaf_modelloop |
| 54 | | }}} |
| 55 | | In this example, which is taken from the example implementation in `testsuite/src/dummymodel_1D`, we use an unconditional DO loop (while loop). The exit flag `doexit` for this loop is set within `PDAF_get_state`. In addition, the variable `nsteps` is initialized, which defines the number of time steps to be performed during the current forecast phase. Thus, we only execute the time stepping code if `nsteps>0`. (If this has to be implemented using an IF-clause as in the example should be checked for the particular code). |
