Changes between Initial Version and Version 1 of PDAF_diag_rmsd

Timestamp:

Apr 1, 2025, 9:02:54 AM (2 days ago)

Author:

lnerger

Comment:

--

PDAF_diag_rmsd

@@ +1 @@
+= PDAF_diag_rsmd = 
+
+This page documents the routine `PDAF_diag_rmsd` of PDAF, which was introduced with PDAF V3.0.
+
+This routine computes root mean square difference (RMSD) beween two input vectors. These could be the ensemble mean state and a reference state.
+
+The routine can be called in the pre/poststep routine of PDAF both before and after the analysis step to compute the ensemble statistics. 
+
+This variant computes the RMSD for the state vectors `stateA` and `stateB` over the full decomposed domain of a parallel model. The variant without parallelization is [wiki:PDAF_diag_rmsd_nompi].
+
+The interface is: 
+{{{
+SUBROUTINE PDAF_diag_rmsd(dim_p, stateA_p, stateB_p, &
+     rmsd_p, COMM_filter, status)
+
+  INTEGER, INTENT(in) :: dim_p                 !< state dimension
+  REAL, INTENT(in)    :: stateA_p(dim_p)       !< State vector A
+  REAL, INTENT(in)    :: stateB_p(dim_p)       !< State vector B
+  REAL, INTENT(out)   :: rmsd_p                !< RSMD
+  INTEGER, INTENT(in) :: COMM_filter           !< Filter communicator
+  INTEGER, INTENT(out) :: status               !< Status flag (0=success)
+}}}
+
+**Note:**
+ * The routine is used to compute the RMSD with regard to some reference state. To compute the ensemble-sampled standard deviation, i.e. the estimated RMSD from the data assimilation, there are the routines [wiki:PDAF_diag_stddev_nompi] and [wiki:PDAF_diag_stddev].
+ * The routine performs MPI operations to obtain the global result. These operations are done within the communicator `COMM_filter` which is specified as an argument. This allows to also use the routine if PDAF was not initialized by calling `PDAF_init`.