Aviso+/CMEMS Observations

DART project logo

Jump to DART Documentation Main Index
version information for this file:
$Id: AVISO.html 11474 2017-04-13 15:26:47Z nancy@ucar.edu $

DATA SOURCES / PROGRAMS / NAMELIST / MODULES / ERRORS / FUTURE PLANS / TERMS OF USE

Overview

convert_aviso was contributed by Frederic Castruccio - Thanks Fred!

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 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.

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.

[top]

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.

[top]

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.

[top]

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 obs_sequence_mod.html.

[top]

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

[top]

KNOWN BUGS

none

[top]

FUTURE PLANS

none

[top]

Terms of Use

DART software - Copyright UCAR. This open source software is provided by UCAR, "as is", without charge, subject to all terms of use at http://www.image.ucar.edu/DAReS/DART/DART_download

Contact: Tim Hoar
Revision: $Revision: 11474 $
Source: $URL: https://svn-dares-dart.cgd.ucar.edu/DART/releases/Manhattan/observations/obs_converters/AVISO/AVISO.html $
Change Date: $Date: 2017-04-13 09:26:47 -0600 (Thu, 13 Apr 2017) $
Change history:  try "svn log" or "svn diff"