PDAF_localfilter

This page documents the function PDAF_localfilter of PDAF, which was introduced with PDAF 3.0.

The function is an alternative to the subroutine PDAF_get_localfilter. In PDAF_localfilter the return value of the function is directly used, while for PDAF_get_localfilter the return value is an argument of the routine.

The function returns the information whether the chosen filter is a domain-localized filter (LESTKF, LETKF, LSEIK, LNETF). It also indicates the ENSRF since these filters use the same observation handling of the domain-localized filters. The function can be called in assimilate_pdaf to control whether to call either PDAF3_assimilate_global or PDAF3_assimilate_local (or PDAF3_put_state_global or PDAF3_put_state_local). The function can only be used if PDAF was initialized before by a call to PDAF_init.

The interface is:

  INTEGER FUNCTION PDAF_localfilter()

without arguments. The return value is

• 1 for local filters (including ENSRF/EAKF),
  
• 0 for global filters (including LEnKF, which performs covariance localization)

The return value can be directly used, e.g. as

  IF (PDAF_localfilter() == 1) THEN
    CALL PDAF3_assimilate_local(...)
  ELSE
    CALL PDAF3_assimilate_global(...)
  ENDIF

Notes:

• The difference between the return values 0 and 1 is mainly the way how PDAF-OMI handles observations.
• For the ENSRF/EAKF, PDAF_localfilter() also returns the value 1. This is because the observation handling for the ENSRF/EAKF uses the same approach as for domain-localized filters