| 1 | = init_obsvar_l_pdaf = |

| 2 | |

| 3 | The page documents the user-supplied call-back routine `init_obsvar_l_pdaf`. |

| 4 | |

| 5 | The routine `init_obsvar_l_pdaf` (called `U_init_obsvar_l` inside the PDAF core routines) is a call-back routine that has to be provided by the user. |

| 6 | The routine is called in the local filters during the loop over all local analysis domains by the routine that computes a local adaptive forgetting factor (`PDAF_set_forget_l`). The routine has to initialize a local mean observation error variance for all observations used for the analysis in the specified local analysis domain. |

| 7 | The routine is only called if the local adaptive forgetting factor is used (`type_forget=2` in the example implementation). When the routine is called it has to return the mean observation error variance for the local observation domain. |

| 8 | |

| 9 | The interface is the following: |

| 10 | {{{ |

| 11 | SUBROUTINE init_obsvar_l_pdaf(domain_p, step, dim_obs_l, obs_l, meanvar_l) |

| 12 | }}} |

| 13 | with |

| 14 | * `domain_p` : `integer, intent(in)`[[BR]] Index of current local analysis domain |

| 15 | * `step` : `integer, intent(in)`[[BR]] Current time step |

| 16 | * `dim_obs_l` : `integer, intent(in)`[[BR]] Local dimension of observation vector |

| 17 | * `obs_l` : `real, intent(in), dimension(dim_obs_p)`[[BR]] Local observation vector |

| 18 | * `meanvar_l` : `real, intent(out)`[[BR]] Mean local observation error variance |

| 19 | |

| 20 | Notes: |

| 21 | * If the local adaptive forgetting factor is not used, this routine has only to exist for the compilation, but it does not need functionality. |