[10460] | 1 | ***************** |
---|
| 2 | Data assimilation |
---|
| 3 | ***************** |
---|
[10201] | 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 | |
---|
[10279] | 13 | Please see the `NEMO manual`_ for more details including information about the input file formats and |
---|
[10201] | 14 | the namelist settings. |
---|
| 15 | |
---|
| 16 | Observation and model comparison (OBS) |
---|
[10279] | 17 | ====================================== |
---|
[10201] | 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 | |
---|
[10279] | 28 | More details in the `NEMO manual`_ chapter 12. |
---|
[10201] | 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. |
---|
[10279] | 43 | See section 12.4 of the `NEMO manual`_. |
---|
[10201] | 44 | |
---|
| 45 | Apply assimilation increments (ASM) |
---|
[10279] | 46 | =================================== |
---|
[10201] | 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 | |
---|
[10279] | 55 | More details in the `NEMO manual`_ chapter 13. |
---|
[10201] | 56 | |
---|
| 57 | Tangent linear and adjoint (TAM) |
---|
[10279] | 58 | ================================ |
---|
[10201] | 59 | |
---|
| 60 | This is the tangent linear and adjoint code of NEMO which is useful to 4D VAR assimilation. |
---|