1 | ***************** |
---|
2 | Data assimilation |
---|
3 | ***************** |
---|
4 | |
---|
5 | .. contents:: |
---|
6 | :local: |
---|
7 | |
---|
8 | The assimilation interface to NEMO is split into three modules. |
---|
9 | - OBS for the observation operator |
---|
10 | - ASM for the application of increments and model bias correction (based on the assimilation increments). |
---|
11 | - TAM the tangent linear and adjoint model. |
---|
12 | |
---|
13 | Please see the `NEMO manual`_ for more details including information about the input file formats and |
---|
14 | the namelist settings. |
---|
15 | |
---|
16 | Observation and model comparison (OBS) |
---|
17 | ====================================== |
---|
18 | |
---|
19 | The observation and model comparison code (OBS) reads in observation files (profile temperature and salinity, |
---|
20 | sea surface temperature, sea level anomaly, sea ice concentration, and velocity) and |
---|
21 | calculates an interpolated model equivalent value at the observation location and nearest model timestep. |
---|
22 | The resulting data are saved in a feedback file (or files). |
---|
23 | The code was originally developed for use with the NEMOVAR data assimilation code, but |
---|
24 | can be used for validation or verification of model or any other data assimilation system. |
---|
25 | This is all controlled by the namelist. |
---|
26 | To build with the OBS code active ``key_diaobs`` must be set. |
---|
27 | |
---|
28 | More details in the `NEMO manual`_ chapter 12. |
---|
29 | |
---|
30 | Standalone observation operator (SAO) |
---|
31 | ------------------------------------- |
---|
32 | |
---|
33 | The OBS code can also be run after a model run using saved NEMO model data. |
---|
34 | This is accomplished using the standalone observation operator (SAO) |
---|
35 | (previously known the offline observation operator). |
---|
36 | |
---|
37 | To build the SAO use makenemo. |
---|
38 | This means compiling NEMO once (in the normal way) for the chosen configuration. |
---|
39 | Then include ``SAO`` at the end of the relevant line in ``cfg.txt`` file. |
---|
40 | Then recompile with the replacement main program in ``./src/SAO``. |
---|
41 | This is a special version of ``nemogcm.F90`` (which doesn't run the model, but reads in the model fields, and |
---|
42 | observations and runs the OBS code. |
---|
43 | See section 12.4 of the `NEMO manual`_. |
---|
44 | |
---|
45 | Apply assimilation increments (ASM) |
---|
46 | =================================== |
---|
47 | |
---|
48 | The ASM code adds the functionality to apply increments to the model variables: |
---|
49 | temperature, salinity, sea surface height, velocity and sea ice concentration. |
---|
50 | These are read into the model from a NetCDF file which may be produced by separate data assimilation code. |
---|
51 | The code can also output model background fields which are used as an input to data assimilation code. |
---|
52 | This is all controlled by the namelist nam_asminc. |
---|
53 | To build the ASM code ``key asminc`` must be set. |
---|
54 | |
---|
55 | More details in the `NEMO manual`_ chapter 13. |
---|
56 | |
---|
57 | Tangent linear and adjoint (TAM) |
---|
58 | ================================ |
---|
59 | |
---|
60 | This is the tangent linear and adjoint code of NEMO which is useful to 4D VAR assimilation. |
---|