source: NEMO/trunk/doc/rst/source/assimilation.rst @ 10279

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