| OVERVIEW |
General information :DUACS (Data Unification and Altimeter Combination System) is part of the CNES multi-mission ground segment (SSALTO). It processes data from all altimeter missions: Jason-1, T/P, ENVISAT, GFO, ERS1/2 and even GEOSAT. DUACS provides a consistent and homogeneous catalogue of products for varied applications, both for near real time applications and offline studies.
Processing information : To produce (M)SLA and (M)ADT in near-real time, the SSALTO/DUACS system uses the latest high-quality altimeter data produced in Near-Real-Time (IGDR).
SALTO/DUACS system acquires then synchronize altimeter data and auxiliary data; each mission is homogenized using the same models and corrections.
The Input Data Quality Control check that the system uses the best altimeter data. The multi-mission cross-calibration process removes any residual orbit error, or long wavelength error (LWE), as well as large scale biases and discrepancies between various data flows; all altimeter fields are interpolated at crossover locations and dates.
After a repeat-track analysis, a mean profile is substracted to compute sea level anomaly. Data are then cross validated, filtered from residual noise and small scale signals, and finally sub-sampled (Sea level Anomaly product, SLA). Absolute Dynamic Topography (ADT) products are obtained by computing ADT = SLA + MDT, where MDT is a specific regional Mean Dynamic Topography.
SSALTO/DUACS final mapping procedure generates one map for each altimeter mission but also a combined map merging measurements from all available altimeter missions (Maps of Absolute Dynamic Topography product, MADT). Geostrophic velocity maps are computed using finite differences and provided in separated files.
Maps of Absolute Dynamic Topography product contents:
- absolute dynamic topography on a 1/8° Mercator grid
- corresponding geostrophic velocities on a 1/8° Mercator grid
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| PARAMETERS GROUP |
| (from BODC) |
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| PARAMETERS
(parameter, unit, convention)
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- sea_surface_height_above_geoid,m,CF
- surface_eastward_sea_water_velocity,m s-1,CF
- surface_northward_sea_water_velocity,m s-1,CF
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