Changes between Version 51 and Version 52 of AddFilterAlgorithm

Timestamp:

Nov 10, 2024, 7:33:09 PM (11 days ago)

Author:

lnerger

Comment:

--

AddFilterAlgorithm

@@ -217 +217 @@
 The 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. 
 
-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.
-
+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 methods.
+
+=== Global Methods ===
+
+For localized Methods, e.g. ESTKF, ETKF or NETF, the general structure of `PDAF_X_update` is:
+
+{{{
+   IF (fixed ensemble, i.e. subtype==2 or subtype==3) THEN
+      Add central state for ensemble perturbations
+   ENDIF
+
+   CALL U_prepoststep    # Perform pre/poststep before analysis update
+
+   CALL PDAF_X_analysis  # Compute global analysis update of ensemble
+
+   CALL PDAF_smoother   # Only for filters for which a smoother is implemented
+  
+   CALL U_prepoststep    # Perform pre/poststep after analysis update
+}}}   
+You 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.
+
+This 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`.
+
+
+=== Local Methods ===
+
+For 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:
+
+{{{
+   IF (fixed ensemble, i.e. subtype==2 or subtype==3) THEN
+      Add central state for ensemble perturbations
+   ENDIF
+
+   CALL U_prepoststep          # Perform pre/poststep before analysis update
+
+   CALL U_init_n_domains       # Determine number of local analysis domains (n_domains_p)
+
+   # Perform global operations on observations
+   CALL U_init_dim_obs         # Determine number of observations (PDAF-OMI routine init_dim_obs_pdafomi)
+   DO i = 1, dim_ens
+      CALL U_obs_op            # Apply observation operator to all ensemble state (PDAF-OMI routine obs_op_pdafomi)
+   ENDDO
+   Compute mean forecast state (state_p)
+   Compute mean observed forecast state (HXbar_f)
+
+   # --- Perform local analysis loop
+   DO i = 1, n_domains_p  
+     CALL U_init_dim_l         # Set size of local state vector 
+     CALL U_init_dim_obs_l     # Set number of observations within radius (PDAF-OMI routine init_dim_obs_l_pdafomi)
+     DO i = 1, dim_ens
+        CALL U_g2l_state       # Get local state vector for all ensemble states
+     ENDDO
+
+     CALL PDAF_X_analysis      # Compute local analysis update of ensemble
+
+     DO i = 1, dim_ens
+        CALL U_l2g_state       # Update global state vector for all ensemble states
+     ENDDO
+     CALL U_l2g_state          # Update global state vector for ensemble mean state
+
+     CALL PDAF_smoother_local  # Only for filters for which a smoother is implemented
+   ENDDO
+   # --- End of local analysis loop
+  
+   CALL U_prepoststep          # Perform pre/poststep after analysis update
+}}}   
+You 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.
+
+This 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`.