Changes between Version 16 and Version 17 of AvailableOptionsforInitPDAF

Timestamp:

May 31, 2025, 8:05:40 AM (3 days ago)

Author:

lnerger

Comment:

--

AvailableOptionsforInitPDAF

@@ -16 +16 @@
 Overview of integer options for ensemble Kalman filters. The parameters are explained in the list of options as they are displayed using `subtype=-1`, which are shown further below.
 
-Parameters shown in italic font have changed in PDAF V3 compared to PDAF V2.3.1. The index position in PDAF V2.3.1 is shown in parenthesis.
+Parameters shown in ''italic'' have changed in PDAF V3 compared to PDAF V2.3.1. The index position in PDAF V2.3.1 is shown in parenthesis.
 
 ||= iparam =||= SEIK =||= LSEIK =||= EnKF =||= LEnKF =||= ETKF =||= LETKF =||= ESTKF =||= LESTKF =||= //ENSRF// =||
@@ -91 +91 @@
 
 In the overview 'solver param1' to 'solver param4' denote different integer and real-valued parameters that control the different solvers used in the 3D-Var methods.
+
+== Generic options ==
+
+Some options are used for all DA methods.
+
+=== `dim_p` and `dim_ens` ===
+
+These are the dimension of the state vector (`dim_p`) and the ensemble size (`dim_ens`).
+
+=== `obs_ens`, iparam(8) ===
+
+The option `obs_ens`  is optional. In controls how the observed ensemble mean, used in the innovation, is computed.
+Thus, it controls whether the observation operator **H** is applied directly to the ensemble mean state, or whether it is applied to all ensemble members states and then the mean of the observed ensemble is computed. 
+
+The values for this option are
+* 0: Apply **H** to ensemble mean to compute innovation
+* 1: Apply **H** to ensemble states; then compute innovation from their mean (default; recomended for nonlinear H)
+
+=== `type_obs`, iparam(9) ===
+
+The option `type_obs` is optional. It controls whether the observations are initialized before or after PDAF calls `prepoststep_pdaf` for the forecast, thus before the analysis step. Initializing observations before `prepoststep_pdaf` allows one to compare the forecast ensemble with the observation that will be assimilated. The [wiki:PDAFomi_observation_diagnostics PDAFD-OMI observation diagnostics] can be used for this comparison.
+
+For compatibility with previous PDAF releases the observations are by default initialized afer the call to `prepoststep_pdaf`.
+
+The values for this option are
+* 0: Initialize observations before call to `prepoststep_pdaf`
+* 1: Initialize observations after call to `prepoststep_pdaf` (default)
+
+Note: For DA methods that apply covariance inflation by explicitly inflating the ensemble perturbations this inflation will be done before the observations are intitialized. In this case, the estimated ensemble standard deviation, which is commonly computed in `prepoststep_pdaf`, will be different for the cases that observations are intiialized before or after `prepoststep_pdaf`.