Changes between Version 1 and Version 2 of ImplementAnalysislenkfOmi


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Timestamp:
Nov 18, 2020, 4:19:30 PM (7 days ago)
Author:
lnerger
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  • ImplementAnalysislenkfOmi

    v1 v2  
    2828== Overview ==
    2929
    30 For the analysis step of the LEnKF different operations related to the observations are needed. These operations are requested by PDAF by calling user-supplied routines. Intentionally, the operations are split into separate routines in order to keep the operations rather elementary. This procedure should simplify the implementation. The names of the required routines are specified in the call to the routine `PDAF_put_state_lenkf_omi` for the fully-parallel implementation (or `PDAF_put_state_lenkf_omi` for the 'flexible' implementation). With regard to the parallelization, all these routines are executed by the filter processes (`filterpe=.true.`) only.
    31 
    32 For completeness we discuss here all user-supplied routines that are specified in the interface to `PDAF_put_state_lenkf_omi`. Thus, some of the user-supplied routines that are explained on the page explaining the modification of the model code for the ensemble integration are repeated here.
     30For the analysis step of the LEnKF different operations related to the observations are needed. These operations are requested by PDAF by calling user-supplied routines. Intentionally, the operations are split into separate routines in order to keep the operations rather elementary. This procedure should simplify the implementation. The names of the required routines are specified in the call to the routine `PDAFomi_put_state_lenkf` for the fully-parallel implementation (or `PDAFomi_put_state_lenkf` for the 'flexible' implementation). With regard to the parallelization, all these routines are executed by the filter processes (`filterpe=.true.`) only.
     31
     32For completeness we discuss here all user-supplied routines that are specified in the interface to `PDAFomi_put_state_lenkf`. Thus, some of the user-supplied routines that are explained on the page explaining the modification of the model code for the ensemble integration are repeated here.
    3333
    3434The LEnKF implemented in PDAF follows the original LEnKF by Evensen (1994) including the correction for perturbed observations (Burgers et al. 1998). The LEnKF implemented in PDAF is reviewed by Nerger et al (2005) and described in more detail by Nerger (2004). The localization is covariance lozalization of PH^T and HPH^T as described in Houtekamer & Mitchell (2001) (See the [PublicationsandPresentations page on publications and presentations] for publications and presenations involving and about PDAF)
     
    3636In our studies (Nerger et al. 2005, Nerger et al. 2007), the EnKF showed performance deficiencies compared to the SEIK filter. Due to this, we focused more on the SEIK filter and the ETKF and ESTKF after these comparison studies. For real applications, we generally recommend using ESTKF or ETKF, or their local variants LESTKF or LETKF. However, the EnKF/LEnKF might have a good performance if very large ensemble can be used as this reduces the sampling errors.
    3737
    38 == `PDAF_assimilate_lenkf_omi` ==
    39 
    40 The general aspects of the filter specific routines `PDAF_assimilate_*` have been 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 is used, the routines `PDAF_put_state_*' is used as described further below. Here, we list once more the full interface of the routine. Subsequently, the full set of user-supplied routines specified in the call to `PDAF_assimilate_lenkf_omi` is explained.
     38== `PDAFomi_assimilate_lenkf` ==
     39
     40The general aspects of the filter specific routines `PDAF_assimilate_*` have been 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 is used, the routines `PDAF_put_state_*' is used as described further below. Here, we list once more the full interface of the routine. Subsequently, the full set of user-supplied routines specified in the call to `PDAFomi_assimilate_lenkf` is explained.
    4141
    4242The interface when using the LEnKF is the following:
    4343{{{
    44   SUBROUTINE PDAF_assimilate_lenkf_omi(U_collect_state, U_distribute_state, &
     44  SUBROUTINE PDAFomi_assimilate_lenkf(U_collect_state, U_distribute_state, &
    4545                                 U_init_dim_obs, U_obs_op, &
    46                                  U_prepoststep, U_localize, &
     46                                 U_prepoststep, U_localize_covar, &
    4747                                 U_next_observation, status)
    4848}}}
     
    5353 * [#U_obs_opcallback_obs_pdafomi.F90 U_obs_op]: The name of the user-supplied routine that acts as the observation operator on some state vector
    5454 * [#U_prepoststepprepoststep_ens_pdaf.F90 U_prepoststep]: The name of the pre/poststep routine as in `PDAF_get_state`
    55  * [#U_localizecallback_obs_pdafomi.F90 U_localize]: Apply covariance localization to the matrices HP and HPH^T^
     55 * [#U_localize_covarcallback_obs_pdafomi.F90 U_localize_covar]: Apply covariance localization to the matrices HP and HPH^T^
    5656 * [#U_next_observationnext_observation_pdaf.F90 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`.
    57  * `status`: The integer status flag. It is zero, if `PDAF_assimilate_lenkf_omi` is exited without errors.
    58 
    59 == `PDAF_put_state_lenkf_omi` ==
    60 
    61 When the 'flexible' implementation variant is chosen for the assimilation system, the routine `PDAF_put_state_lenkf_omi` has to be used instead of `PDAF_assimilate_lenkf_omi`. The general aspects of the filter specific routines `PDAF_put_state_*` have been described on the page [ModifyModelforEnsembleIntegration Modification of the model code for the ensemble integration]. The interface of the routine is identical with that of `PDAF_assimilate_lenkf_omi` with the exception the specification of the user-supplied routines `U_distribute_state` and `U_next_observation` are missing.
     57 * `status`: The integer status flag. It is zero, if `PDAFomi_assimilate_lenkf` is exited without errors.
     58
     59== `PDAFomi_put_state_lenkf` ==
     60
     61When the 'flexible' implementation variant is chosen for the assimilation system, the routine `PDAFomi_put_state_lenkf` has to be used instead of `PDAFomi_assimilate_lenkf`. The general aspects of the filter specific routines `PDAF_put_state_*` have been described on the page [ModifyModelforEnsembleIntegration Modification of the model code for the ensemble integration]. The interface of the routine is identical with that of `PDAFomi_assimilate_lenkf` with the exception the specification of the user-supplied routines `U_distribute_state` and `U_next_observation` are missing.
    6262
    6363The interface when using the LEnKF is the following:
    6464{{{
    65   SUBROUTINE PDAF_put_state_lenkf_omi(U_collect_state, &
     65  SUBROUTINE PDAFomi_put_state_lenkf(U_collect_state, &
    6666                                 U_init_dim_obs, U_obs_op, &
    6767                                 U_prepoststep, U_localize, &
     
    7272== User-supplied routines ==
    7373
    74 Here all user-supplied routines are described that are required in the call to `PDAF_assimilate_lenkf_omi`. For some of the generic routines, we link to the page on [ModifyModelforEnsembleIntegration modifying the model code for the ensemble integration].
     74Here all user-supplied routines are described that are required in the call to `PDAFomi_assimilate_lenkf`. For some of the generic routines, we link to the page on [ModifyModelforEnsembleIntegration modifying the model code for the ensemble integration].
    7575
    7676To indicate user-supplied routines we use the prefix `U_`. In the template directory `templates/` as well as in the example implementation in `testsuite/src/dummymodel_1D` these routines exist without the prefix, but with the extension `_pdaf.F90`. In the section titles below we provide the name of the template file in parentheses.
     
    196196== Execution order of user-supplied routines ==
    197197
    198 For the :EnKF, the user-supplied routines are essentially executed in the order they are listed in the interface to `PDAF_assimilate_lenkf_omi`. The order can be important as some routines can perform preparatory work for later routines. For example, `U_init_dim_obs` can prepare an index array that provides the information for executing the observation operator in `U_obs_op`.
     198For the :EnKF, the user-supplied routines are essentially executed in the order they are listed in the interface to `PDAFomi_assimilate_lenkf`. The order can be important as some routines can perform preparatory work for later routines. For example, `U_init_dim_obs` can prepare an index array that provides the information for executing the observation operator in `U_obs_op`.
    199199
    200200Before the analysis step is called the following routine is executed:
     
    209209 1. [#U_prepoststepprepoststep_ens_pdaf.F90 U_prepoststep] (Call to act on the analysis ensemble, called with (positive) value of the time step)
    210210
    211 In case of the routine `PDAF_assimilate_enkf_omi`, the following routines are executed after the analysis step:
     211In case of the routine `PDAFomi_assimilate_enkf`, the following routines are executed after the analysis step:
    212212 1. [#U_distribute_statedistribute_state_pdaf.F90 U_distribute_state]
    213213 1. [#U_next_observationnext_observation_pdaf.F90 U_next_observation]