source: NEMO/trunk/doc/rst/source/data_assimilation.rst @ 10201

Last change on this file since 10201 was 10201, checked in by nicolasmartin, 2 years ago

Various modifications related to the setting of a NEMO Quick Start Guide

  • Add missing namelist blocks from ICE and TOP
  • Create a hidden .global.rst to gather common URL links
  • Convert animated gif to frames images for PDF export
  • Place different README.rst appropriately in the code structure and refer to them with symbolic links in doc/rst/source
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1Data assimilation
2=================
3
4.. include:: .global.rst
5
6.. contents::
7   :local:
8
9The assimilation interface to NEMO is split into three modules.
10- OBS for the observation operator
11- ASM for the application of increments and model bias correction (based on the assimilation increments).
12- TAM the tangent linear and adjoint model.
13
14Please see the `NEMO reference manual`_ for more details including information about the input file formats and
15the namelist settings.
16
17--------------------------------------
18Observation and model comparison (OBS)
19--------------------------------------
20
21The observation and model comparison code (OBS) reads in observation files (profile temperature and salinity,
22sea surface temperature, sea level anomaly, sea ice concentration, and velocity) and
23calculates an interpolated model equivalent value at the observation location and nearest model timestep.
24The resulting data are saved in a feedback file (or files).
25The code was originally developed for use with the NEMOVAR data assimilation code, but
26can be used for validation or verification of model or any other data assimilation system.
27This is all controlled by the namelist.
28To build with the OBS code active ``key_diaobs`` must be set.
29
30More details in the `NEMO reference manual`_ chapter 12.
31
32Standalone observation operator (SAO)
33-------------------------------------
34
35The OBS code can also be run after a model run using saved NEMO model data.
36This is accomplished using the standalone observation operator (SAO)
37(previously known the offline observation operator).
38
39To build the SAO use makenemo.
40This means compiling NEMO once (in the normal way) for the chosen configuration.
41Then include ``SAO`` at the end of the relevant line in ``cfg.txt`` file.
42Then recompile with the replacement main program in ``./src/SAO``.
43This is a special version of ``nemogcm.F90`` (which doesn't run the model, but reads in the model fields, and
44observations and runs the OBS code.
45See section 12.4 of the `NEMO reference manual`_.
46
47-----------------------------------
48Apply assimilation increments (ASM)
49-----------------------------------
50
51The ASM code adds the functionality to apply increments to the model variables:
52temperature, salinity, sea surface height, velocity and sea ice concentration.
53These are read into the model from a NetCDF file which may be produced by separate data assimilation code.
54The code can also output model background fields which are used as an input to data assimilation code.
55This is all controlled by the namelist nam_asminc.
56To build the ASM code ``key asminc`` must be set.
57
58More details in the `NEMO reference manual`_ chapter 13.
59
60--------------------------------
61Tangent linear and adjoint (TAM)
62--------------------------------
63
64This is the tangent linear and adjoint code of NEMO which is useful to 4D VAR assimilation.
65
66.. _NEMO reference manual: http://doi.org/10.5281/zenodo.
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