Changes between Version 2 and Version 3 of ImplementAnalysislseik


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Timestamp:
Sep 1, 2010, 3:57:03 PM (10 years ago)
Author:
lnerger
Comment:

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  • ImplementAnalysislseik

    v2 v3  
    7575See [ModifyModelforEnsembleIntegration#U_collect_statecollect_state.F90 here] for the description of this routine.
    7676
    77 === `U_next_observation` (next_observation.F90) ===
    78 
    79 The interface for this routine is
    80 {{{
    81 SUBROUTINE U_next_obs(stepnow, nsteps, doexit, timenow)
    82 
    83   INTEGER, INTENT(in)  :: stepnow  ! Number of the current time step
    84   INTEGER, INTENT(out) :: nsteps   ! Number of time steps until next obs
    85   INTEGER, INTENT(out) :: doexit   ! Whether to exit forecasting (1 for exit)
    86   REAL, INTENT(out)    :: timenow  ! Current model (physical) time
    87 }}}
    88 
    89 The routine is called once at the beginning of each forecast phase. It is executed by all processes that participate in the model integrations.
    90 
    91 Based on the information of the current time step, the routine has to define the number of time steps `nsteps` for the next forecast phase. In addition, the flag `doexit` has to be initialized to provide the information if the external ensemble loop can be exited. `timenow` is the current model time. This variable should also be initialized. It is particularly important, if an ensemble task integrates more than one model state. In this case `timenow` can be used to correctly jump back in time.
    92 
    93 Some hints:
    94  * If the time interval between successive observations is known, `nsteps` can be simply initialized by dividing the time interval by the size of the time step
    95  * `doexit` should be 0 to continue the assimilation process. In most cases `doexit` is set to 1, when `PDAF_get_state` is called after the last analysis for which observations are available.
    96  * At the first call to `U_next_obs` the variable `timenow` should be initialized with the current model time. At the next call a forecast phase has been completed. Thus, the new value of `timenow` follows from the timer interval for the previous forecast phase.
    97 
    98 === `U_distribute_state` (distribute_state.F90) ===
    99 
    100 The interface for this routine is
    101 {{{
    102 SUBROUTINE distribute_state(dim_p, state_p)
    103 
    104   INTEGER, INTENT(in) :: dim_p           ! State dimension for PE-local model sub-domain
    105   REAL, INTENT(inout) :: state_p(dim_p)  ! State vector for PE-local model sub-domain
    106 }}}
    107 
    108 This routine is called during the forecast phase as many times as there are states to be integrated by a model task. Again, the routine is executed by all processes that belong to model tasks.
    109 
    110 When the routine is called a state vector `state_p` and its size `dim_p` are provided. As the user has defined how the model fields are stored in the state vector, one can initialize the model fields from this information. If the model is not parallelized, `state_p` will contain a full state vector. If the model is parallelized using domain decomposition, `state_p` will contain the part of the state vector that corresponds to the model sub-domain for the calling process.
    111 
    112 Some hints:
    113  * If the state vector does not include all model fields, it can be useful to keep a separate array to store those additional fields. This array has to be kept separate from PDAF, but can be defined using a module like `mod_assimilation`.
    114 
    11577=== `U_prepoststep` (prepoststep_seik.F90) ===
    11678
    117 The interface of the routine is identical for all filters. However, the particular operations that are performed in the routine can be specific for each filter algorithm. Here, we exemplify the interface on the example of the SEIK filter.
     79See [ModifyModelforEnsembleIntegration#U_prepoststepprepoststep_seik.F90 here] for the description of this routine.
    11880
    119 The interface for this routine is
    120 {{{
    121 SUBROUTINE prepoststep(step, dim_p, dim_ens, dim_ens_p, dim_obs_p, &
    122                        state_p, Uinv, ens_p, flag)
    123 
    124   INTEGER, INTENT(in) :: step        ! Current time step
    125                          ! (When the routine is called before the analysis -step is provided.)
    126   INTEGER, INTENT(in) :: dim_p       ! PE-local state dimension
    127   INTEGER, INTENT(in) :: dim_ens     ! Size of state ensemble
    128   INTEGER, INTENT(in) :: dim_ens_p   ! PE-local size of ensemble
    129   INTEGER, INTENT(in) :: dim_obs_p   ! PE-local dimension of observation vector
    130   REAL, INTENT(inout) :: state_p(dim_p) ! PE-local forecast/analysis state
    131                          ! The array 'state_p' is not generally not initialized in the case of SEIK.
    132                          ! It can be used freely here.
    133   REAL, INTENT(inout) :: Uinv(dim_ens-1, dim_ens-1) ! Inverse of matrix U
    134   REAL, INTENT(inout) :: ens_p(dim_p, dim_ens)      ! PE-local state ensemble
    135   INTEGER, INTENT(in) :: flag        ! PDAF status flag
    136 }}}
    137 
    138 The routine `U_prepoststep` is called once at the beginning of the assimilation process. In addition, it is called during the assimilation cycles before the analysis step and after the ensemble transformation. The routine is called by all filter processes (that is `filterpe=1`).
    139 
    140 The routine provides for the user the full access to the ensemble of model states. Thus, user-controlled pre- and post-step operations can be performed.  For example the forecast and the analysis states and ensemble covariance matrix can be analyzed, e.g. by computing the estimated variances. In addition, the estimates can be written to disk.
    141 
    142 Hint:
    143  * If a user considers to perform adjustments to the estimates (e.g. for balances), this routine is the right place for it.
    144 
    145 
    146 === `U_collect_state` (collect_state.F90) ===
    147 
    148 The interface for this routine is
    149 {{{
    150 SUBROUTINE collect_state(dim_p, state_p)
    151 
    152   INTEGER, INTENT(in) :: dim_p           ! State dimension for PE-local model sub-domain
    153   REAL, INTENT(inout) :: state_p(dim_p)  ! State vector for PE-local model sub-domain
    154 }}}
    155 
    156 This routine is called during the forecast phase as many times as there are states to be integrated by a model task. It is called at the end of the integration of a member state of the ensemble. The routine is executed by all processes that belong to model tasks.
    157 
    158 When the routine is called, a state vector `state_p` and its size `dim_p` are provided. The operation to be performed in this routine is inverse to that of the routine `U_distribute_state`. That is, the state vector `state_p` has to be initialized from the model fields. If the model is not parallelized, `state_p` will contain a full state vector. If the model is parallelized using domain decomposition, `state_p` will contain the part of the state vector that corresponds to the model sub-domain for the calling process.
    159 
    160 Some hints:
    161  * If the state vector does not include all model fields, it can be useful to keep a separate array to store those additional fields. This array has to be kept separate from PDAF, but can be defined using a module like `mod_assimilation`.