Changes between Version 51 and Version 52 of AddFilterAlgorithm


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Timestamp:
Nov 10, 2024, 7:33:09 PM (2 days ago)
Author:
lnerger
Comment:

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  • AddFilterAlgorithm

    v51 v52  
    217217The actual DA analysis update is computed in the routine `PDAF_X_update`. The routine is provided with the names of the call-back routines, the arrays as well of the relevant dimensions as describe above.
    218218
    219 The structure of the operations in `PDAF_X_update` can be designed freely when implementing a new DA method. The existing methods follow the recommended structure in which `PDAF_x_update` only performes preparations for the actual analysis update and then calls `PDAF_X_analysis` for the computation of the actual update. Here, the operations are different for global and local filters.
    220 
     219The structure of the operations in `PDAF_X_update` can be designed freely when implementing a new DA method. The existing methods follow the recommended structure in which `PDAF_x_update` only performes preparations for the actual analysis update and then calls `PDAF_X_analysis` for the computation of the actual update. Here, the operations are different for global and local methods.
     220
     221=== Global Methods ===
     222
     223For localized Methods, e.g. ESTKF, ETKF or NETF, the general structure of `PDAF_X_update` is:
     224
     225{{{
     226   IF (fixed ensemble, i.e. subtype==2 or subtype==3) THEN
     227      Add central state for ensemble perturbations
     228   ENDIF
     229
     230   CALL U_prepoststep    # Perform pre/poststep before analysis update
     231
     232   CALL PDAF_X_analysis  # Compute global analysis update of ensemble
     233
     234   CALL PDAF_smoother   # Only for filters for which a smoother is implemented
     235 
     236   CALL U_prepoststep    # Perform pre/poststep after analysis update
     237}}}   
     238You will find this structure e.g. in `PDAF_ESTKF_update.F90`. This structure is also valid for the LEnKF. The actual implementation, e.g. in `PDAF_ESTKF_update.F90` contains additional functionality e.g. calls for timers and normal screen output or debug outputs. Also there can be different calls `PDAF_X_analysis` depending on the subtype of a filter.
     239
     240This general structure should be widely usable. Thus, when implementing a new global ensemble method one could copy an existing file and adapt it for the new method. The main functionality of the new DA method would then be implemented in `PDAF_X_analysis`.
     241
     242
     243=== Local Methods ===
     244
     245For domain-localized Methods, e.g. LESTKF, LETKF or LNETF the general structure of `PDAF_X_update` is different from the global methods because the local analysis loop is contained in `PDAF_X_update` and only a local analysis routine is called. The general structure is:
     246
     247{{{
     248   IF (fixed ensemble, i.e. subtype==2 or subtype==3) THEN
     249      Add central state for ensemble perturbations
     250   ENDIF
     251
     252   CALL U_prepoststep          # Perform pre/poststep before analysis update
     253
     254   CALL U_init_n_domains       # Determine number of local analysis domains (n_domains_p)
     255
     256   # Perform global operations on observations
     257   CALL U_init_dim_obs         # Determine number of observations (PDAF-OMI routine init_dim_obs_pdafomi)
     258   DO i = 1, dim_ens
     259      CALL U_obs_op            # Apply observation operator to all ensemble state (PDAF-OMI routine obs_op_pdafomi)
     260   ENDDO
     261   Compute mean forecast state (state_p)
     262   Compute mean observed forecast state (HXbar_f)
     263
     264   # --- Perform local analysis loop
     265   DO i = 1, n_domains_p 
     266     CALL U_init_dim_l         # Set size of local state vector
     267     CALL U_init_dim_obs_l     # Set number of observations within radius (PDAF-OMI routine init_dim_obs_l_pdafomi)
     268     DO i = 1, dim_ens
     269        CALL U_g2l_state       # Get local state vector for all ensemble states
     270     ENDDO
     271
     272     CALL PDAF_X_analysis      # Compute local analysis update of ensemble
     273
     274     DO i = 1, dim_ens
     275        CALL U_l2g_state       # Update global state vector for all ensemble states
     276     ENDDO
     277     CALL U_l2g_state          # Update global state vector for ensemble mean state
     278
     279     CALL PDAF_smoother_local  # Only for filters for which a smoother is implemented
     280   ENDDO
     281   # --- End of local analysis loop
     282 
     283   CALL U_prepoststep          # Perform pre/poststep after analysis update
     284}}}   
     285You will find this structure e.g. in `PDAF_LESTKF_update.F90`. This structure is not used for the LEnKF because this filter doe snot use a local analysis loop. The actual implementation, e.g. in `PDAF_LESTKF_update.F90` contains additional functionality e.g. calls for timers and normal screen output or debug outputs. Also there can be different calls `PDAF_X_analysis` depending on the subtype of a filter.
     286
     287This general structure should be widely usable for DA methods that use domain localization. Accordingly, when implementing a new local ensemble method one could copy an existing file and adapt it for the new method. The main functionality of the new DA method would then be implemented in `PDAF_X_analysis`.