| | 1 | = PDAF_assimilate_lenkf = |
| | 2 | |
| | 3 | This page documents the routine `PDAF_assimilate_enkf` of PDAF. The routine is used to execute the analysis step of the localized EnKF. |
| | 4 | |
| | 5 | The routine is typically called in `assimilate_pdaf` or directly in the model code. |
| | 6 | |
| | 7 | The general aspects of the filter specific routines `PDAF_assimilate_*` are 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 routines `PDAF_put_state_*' are used. |
| | 8 | |
| | 9 | The interface when using the LEnKF is the following: |
| | 10 | {{{ |
| | 11 | SUBROUTINE PDAF_assimilate_lenkf(U_collect_state, U_distribute_state, U_init_dim_obs, & |
| | 12 | U_obs_op, U_init_obs, U_prepoststep, U_localize, & |
| | 13 | U_add_obs_err, U_init_obscovar, U_next_observation, status_pdaf) |
| | 14 | }}} |
| | 15 | with the following arguments: |
| | 16 | * `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 `PDAF_get_state` as well as here. |
| | 17 | * `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. |
| | 18 | * `U_init_dim_obs`: The name of the user-supplied routine that provides the size of observation vector |
| | 19 | * `U_obs_op`: The name of the user-supplied routine that acts as the observation operator on some state vector |
| | 20 | * `U_init_obs`: The name of the user-supplied routine that initializes the vector of observations |
| | 21 | * `U_prepoststep`: The name of the pre/poststep routine as in `PDAF_get_state` |
| | 22 | * `U_localize`: The name of the routine that applied the covariance localization |
| | 23 | * `U_add_obs_err`: The name of the user-supplied routine that adds the observation error covariance matrix to the ensemble covariance matrix projected onto the observation space. |
| | 24 | * `U_init_obscovar`: The name of the user-supplied routine that initializes the observation error covariance matrix. |
| | 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_lenkf` is exited without errors. |
| | 27 | |
| | 28 | |
| | 29 | The user-supplied call-back routines are described on the page on [ImplementAnalysislenkf implementing the analysis step of the localized EnKF]. |
| | 30 | |
| | 31 | It is recommended that the value of `status_pdaf` is checked in the program after PDAF_assimilate_enkf is executed. Only if its value is 0 the initialization was successful. |
| | 32 | |
| | 33 | PDAF also has a [PdafSimplifiedInterface Simplified Interface] providing the routine `PDAF_assimilate_lenkf_si`. In the simplified interface, the name of the user-supplied routines have predefined names and do not appear in the call to `PDAF_assimilate_lenkf_si`. More information on the pre-defined names is provided in the [ImplementAnalysislenkf page on implementing the analysis step of the localized EnKF]. |
| | 34 | |
