Aviso+/CMEMS Observations ========================= Overview -------- This short description of the ``SEALEVEL_GLO_SLA_L3_REP_OBSERVATIONS_008_018`` product is repeated from the **INFORMATION** tab from the `Copernicus Marine Environment Monitoring Service `__ online catalogue (in April 2017). For the Global Ocean- Mono altimeter satellite along-track sea surface heights computed with respect to a twenty-year mean. Previously distributed by Aviso+, no change in the scientific content. All the missions are homogenized with respect to a reference mission which is currently Jason-2. This product is computed with an optimal and centered computation time window (6 weeks before and after the date). Two kinds of datasets are proposed: filtered (nominal dataset) and unfiltered. The main researcher for this project was Fred Castruccio. The ``convert_aviso.f90`` program is designed to read a `netCDF `__ file containing the (Level 3) sea surface anomalies from any of the following platforms: "Jason-1", "Envisat", or "Geosat Follow On". One of those platforms must be listed in the netCDF file global attribute: ``platform`` The data files have names like: - dt_global_j1_sla_vfec_20080101_20140106.nc, - dt_global_en_sla_vfec_20080101_20140106.nc, or - dt_global_g2_sla_vfec_20080101_20140106.nc corresponding to the "Jason-1", "Envisat", and the "Geosat Follow On" platforms. The DART observation TYPE corresponding to each of these platforms are ``J1_SEA_SURFACE_ANOMALY``, ``EN_SEA_SURFACE_ANOMALY``, and ``GFO_SEA_SURFACE_ANOMALY``, respectively and are defined in `obs_def_ocean_mod.f90 <../../forward_operators/obs_def_ocean_mod.html>`__. Fred wrote a python script (``shell_scripts/convert_aviso.py``) to repeatedly call ``convert_aviso`` and decided it was easiest to simply provide the input file name as a command line argument and always have the output file have the name ``obs_seq.aviso``. As such, there is no input namelist specifically for these parameters, but other DART modules still require run-time crontrol specified by ``input.nml``. After creating a large number of output observation sequence files, it is usually necessary to consolidate the files and subset them into files containing just the timeframe required for a single assimilation. **NOTE**: the ``obs_sequence_tool`` is constructed for just this purpose. The ``shell_scripts/makedaily.sh`` script attempts to consolidate all the SLA observations and those that may have been (separately) converted from the World Ocean Database into 24-hour segments centered at midnight GMT. You will have to modify the ``makedaily.sh`` script to suit your filesystem and naming convention. It is provided as a starting point. **Reminder**: (according to the data providers): In order to compute Absolute Dynamic Topography, the Mean Dynamic Topography (MDT) can be added. It is distributed by Aviso+ ( http://www.aviso.altimetry.fr/en/data/products/auxiliary-products/mdt.html ). Fred was using this product in assimilations with POP, so he chose a different source for MDT - consistent with POP's behavior. Data sources ------------ The Copernicus Marine and Environment Monitoring Service (CMEMS) has taken over the processing and distribution of the Ssalto/Duacs multimission altimeter products formerly administered by Aviso+. After a registration process, the along-track sea level anomalies (SLA) may be downloaded from `http://marine.copernicus.eu/services-portfolio/access-to-products/ `__ - search for the ``SEALEVEL_GLO_SLA_L3_REP_OBSERVATIONS_008_018`` if it does not come up directly. Programs -------- +------------------------------------+--------------------------------------------------------------------------------+ | ``convert_aviso.f90`` | does the actual conversion from netCDF to a DART observation sequence file, | | | which may be ASCII or binary. | +------------------------------------+--------------------------------------------------------------------------------+ | ``shell_scripts/convert_aviso.py`` | python script to convert a series of input files and datestamp the output | | | files. | +------------------------------------+--------------------------------------------------------------------------------+ | ``shell_scripts/makedaily.sh`` | shell script to repeatedly call ``obs_sequence_tool`` to consolidate multiple | | | observation sequence files into an observation sequence file that has ALL the | | | observations from ALL platforms in a single file. ``makedaily.sh`` is capable | | | of looping over time ranges and creating observation sequences for each time | | | range. | +------------------------------------+--------------------------------------------------------------------------------+ Namelist -------- There is no namelist for ``convert_aviso``, but other namelists control aspects of the execution, namely ``&obs_sequence_nml:write_binary_obs_sequence``. see :doc:`../../../assimilation_code/modules/observations/obs_sequence_mod`. Modules used ------------ :: assimilation_code/location/threed_sphere/location_mod.f90 assimilation_code/modules/assimilation/assim_model_mod.f90 assimilation_code/modules/io/dart_time_io_mod.f90 assimilation_code/modules/observations/obs_kind_mod.f90 assimilation_code/modules/observations/obs_sequence_mod.f90 assimilation_code/modules/utilities/ensemble_manager_mod.f90 assimilation_code/modules/utilities/null_mpi_utilities_mod.f90 assimilation_code/modules/utilities/random_seq_mod.f90 assimilation_code/modules/utilities/sort_mod.f90 assimilation_code/modules/utilities/time_manager_mod.f90 assimilation_code/modules/utilities/types_mod.f90 assimilation_code/modules/utilities/utilities_mod.f90 models/template/model_mod.f90 observations/forward_operators/obs_def_mod.f90 observations/obs_converters/AVISO/convert_aviso.f90 observations/obs_converters/utilities/obs_utilities_mod.f90