| 1 | = PDAF_generate_obs = |
| 2 | |
| 3 | This page documents the routine `PDAF_generate_obs` of PDAF. |
| 4 | |
| 5 | The routine is typically called in `assimilate_pdaf` or directly in the model code. |
| 6 | |
| 7 | This routine is used to generate synthetic observations. It bases on the usual implementation strategy for PDAF which is described on the page [ModifyModelforEnsembleIntegration Modification of the model code for the ensemble integration] and its sub-page on [InsertAnalysisStep inserting the analysis step]. The routine is used in the fully-parallel implementation variant of the data assimilation system. When the 'flexible' implementation variant, the routine `PDAF_put_state_generate_obs' is used. |
| 8 | |
| 9 | |
| 10 | |
| 11 | The interface is the following: |
| 12 | {{{ |
| 13 | SUBROUTINE PDAF_generate_obs(U_collect_state, U_distribute_state, & |
| 14 | U_init_dim_obs_f, U_obs_op_f, U_get_obs_f, U_init_obserr_f, & |
| 15 | U_prepoststep, U_next_observation, status_pdaf) |
| 16 | }}} |
| 17 | with the following arguments: |
| 18 | * `U_collect_state`: The name of the user-supplied routine that initializes a state vector from the array holding the ensemble of model states from the model fields. This is basically the inverse operation to `U_distribute_state` used in [ModifyModelforEnsembleIntegration#PDAF_get_state PDAF_get_state] |
| 19 | * `U_distribute_state`: The name of a user supplied routine that initializes the model fields from the array holding the ensemble of model state vectors. |
| 20 | * `U_init_dim_obs_f`: The name of the user-supplied routine that provides the size of the full observation vector |
| 21 | * `U_obs_op_f`: The name of the user-supplied routine that acts as the full observation operator on some state vector |
| 22 | * `U_get_obs_f`: The name of the user-supplied routine that receives the full vector of generated synthetic observations from PDAF |
| 23 | * `U_init_obserr_f`: The name of the user-supplied routine that initializes the vector of observations error standard deviations for for full observation vector |
| 24 | * `U_prepoststep`: The name of the pre/poststep routine as in `PDAF_get_state` |
| 25 | * `U_next_observation`: The name of a user supplied routine that initializes the variables `nsteps`, `timenow`, and `doexit`. The same routine is also used in `PDAF_get_state`. |
| 26 | * `status_pdaf`: The integer status flag. It is zero, if `PDAF_assimilate_lestkf` is exited without errors. |
| 27 | |
| 28 | It is recommended that the value of `status_pdaf` is checked in the program after PDAF_generate_obs is executed. Only if its value is 0 the initialization was successful. |
| 29 | |
| 30 | PDAF also has a [PdafSimplifiedInterface Simplified Interface] providing the routine `PDAF_generate_obs_si`. In the simplified interface, the name of the user-supplied routines have predefined names and do not appear in the call to `PDAF_generate_obs_si`. |