Changes between Version 2 and Version 3 of OMI_observation_modules

Timestamp:

Nov 23, 2020, 10:38:43 AM (4 years ago)

Author:

lnerger

Comment:

--

OMI_observation_modules

@@ -18 +18 @@
 == obs_f data type == 
 
-To ensure the functionality within each obs-module, we rely on a derived data type called `obs_f` that describes the observation. One instance of this data type is allocated in each obs-module as the variable `thisobs`. a few of the elements of `obs_f` are initialized by the user when the observation information is initialized on `init_dim_obs_f`. Further variables is set in a call to the routine `PDAFomi_gather_obs`. This information is then used by all other routines in the obs-module. The template file obs_TYPE_pdafomi_TEMPLATE.F90 shows the different steps needed to initialize thisobs. 
+To ensure the functionality within each obs-module, we rely on a derived data type called `obs_f` that contains all information about the observation. One instance of this data type is allocated in each obs-module with the generic variable name `thisobs`. A few of the elements of `obs_f` are initialized by the user when the observation information is initialized on `init_dim_obs_f`. Further variables is set in a call to the routine `PDAFomi_gather_obs`. This information is then used by all other routines in the obs-module. The template file obs_TYPE_pdafomi_TEMPLATE.F90 shows the different steps needed to initialize thisobs. 
 
 The '''mandatory variables''' in `obs_f` that need to be set by the user are:
@@ -57 +57 @@
 == init_dim_obs_TYPE ==
 
+This is the main routine to initialize observation information. 
+
+Please see the template `templates/omi/obs_TYPE_pdafomi_TEMPLATE.F90` for a step-by-step description of the implementation steps.
+
+Each observation module uses the generic name '''thisobs''' for the variable with observation type `obs_f`. Elements of `thisobs` are accessed like
+`thisobs%doassim`.
+
+The main steps performed in this routine are
+ 1. `thisobs%doassim`: Specify whether this observation type is assimilated
+ 1. `thisobs%disttype`: Specify the type of distance computation
+ 1. `thisobs%ncoord`: Specify the number of dimensions used to compute distances 
+ 1. `dim_obs_p`: Count the number of available observations
+ 1. `obs_p`: Fill the vector of observations
+ 1. `ocoord_p`: store the coordinates of the observations
+ 1. `ivar_obs_p`: store the inverse error variance of each observation
+ 1. `thisobs%id_obs_p`: store the indices of state vector elements that correspond to an observation (A single value for observation at grid points, or multiple values for derived quantities or interpolation)
+
+When the observation operator performs interpolation, one further needs to initialize an array of interpolation coefficients (`thisobs%icoeff_p`).
+
+After these variables are filled, one calls
+{{{
+    CALL PDAFomi_gather_obs(thisobs, dim_obs_p, obs_p, ivar_obs_p, ocoord_p, &
+         thisobs%ncoord, local_range, dim_obs)
+}}}
+This routine will complete all required initializations for OMI. As such it is mandatory to call the routine