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Ssalto/Duacs Multimission Altimeter Products

all sat merged: Daily Maps of Absolute Dynamic Topography (DT-MADT)

Duacs is the Ssalto multimission altimeter data processing system. It processes data from all altimeter missions (Jason-1&2, T/P, Envisat, GFO, ERS-1 & 2 and even Geosat) to provide a consistent and homogeneous catalogue of products for varied applications, both for near real time applications and offline studies. The Delayed Time (DT) component of SSALTO/DUACS system is responsible for the production of processed Jason-1, Jason-2, T/P, Envisat, GFO, ERS1/2 and even Geosat data in order to provide a homogeneous, inter-calibrated and highly accurate long time series of SLA and MSLA altimeter data. DT component is made of two processing series:

• "two sat merged" serie: this dataset is based on only two missions at most: Jason-2/AltiKa or Jason-2/Cryosat-2 or Jason-2 / Envisat  or Jason-1 / Envisat or Topex/Poseidon / ERS, with the same groundtrack. Thus it is homogeneous all along the available time period thanks to a stable sampling, but might not be the best in quality at a given time. The use of the "two sat merged" serie is mainly for application in need of great stability (but it must be kept in mind that the data might not be of the best possible quality). This serie corresponded to "Ref" serie before April 2014.

• "all sat merged" serie: up-to-date datasets with up to four satellites at a given time, using all missions available at a given time. Sampling and Long Wavelength Errors determination are improved, so this serie is better in quality but not homogeneous over the time period. This serie corresponded to "Upd" serie before April 2014.

The difference between these two processing series is thus the number of missions as key input of Optimal Interpola- tion (OI) Software for LWE (2.3.5.). This system finally delivers Delayed Time processed SLA and MSLA combining fully processed data from various altimetric missions (Topex/Poseidon, ERS-1/2, Jason-1, Envisat and OSTM/Jason-2) such as:

• High resolution Maps of Sea Level Anomaly (DT-MSLA) combining all satellites
• High resolution Maps of Absolute Dynamic Topography (DT-MADT), merging all satellites
• High resolution maps of geostrophic velocities anomalies derived from maps of Sea Level Anomaly combining all satellites
• High resolution maps of absolute geostrophic velocities derived from maps of Absolute Dynamic Topography combining all satellites

Variables	Absolute Dynamic Topography (m) U- Absolute Geostrophic Velocities Anomalies (m/s) V- Absolute Geostrophic Velocities Anomalies (m/s)
Zonal	Global by 1/4 deg
Meridional	Global by 1/4 deg
Vertical	N/A
Temporal	Jan 1, 1993 to May 5, 2016 by 1 day(s)
Static?	no
Volume	117MB per variable per day
Server	private:
Source	http://www.aviso.altimetry.fr/en/data/products/sea-surface-height-products/global/madt.html
Acquired	Aug 28, 2014 (Updated Mar 2017)
APDRC contact
Supplements	SSALTO/DUACS User Handbook