On the resolutions of ocean altimetry maps
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Published:2019-08-20
Issue:4
Volume:15
Page:1091-1109
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ISSN:1812-0792
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Container-title:Ocean Science
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language:en
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Short-container-title:Ocean Sci.
Author:
Ballarotta Maxime, Ubelmann Clément, Pujol Marie-Isabelle, Taburet Guillaume, Fournier FlorentORCID, Legeais Jean-François, Faugère Yannice, Delepoulle Antoine, Chelton Dudley, Dibarboure Gérald, Picot Nicolas
Abstract
Abstract. The Data Unification and Altimeter Combination System (DUACS) produces sea level global and regional
maps that serve oceanographic applications, climate forecasting centers,
and geophysics and biology communities. These maps are generated using an
optimal interpolation method applied to altimeter observations. They are
provided on a global 1∕4∘ × 1∕4∘ (longitude × latitude) and daily grid resolution framework
(1∕8∘ × 1∕8∘ longitude × latitude grid for the regional products) through the Copernicus Marine Environment Monitoring Service (CMEMS). Yet, the dynamical content of these maps does not have full 1∕4∘ spatial and 1 d temporal resolutions due to the
filtering properties of the optimal interpolation. In the present study, we
estimate the effective spatial and temporal resolutions of the newly
reprocessed delayed-time DUACS maps (a.k.a. DUACS-DT2018). Our approach is
based on the ratio between the spectral content of the mapping error and the
spectral content of independent true signals (along-track and tide gauge
observations), also known as the noise-to-signal ratio. We found that the
spatial resolution of the DUACS-DT2018 global maps based on sampling by
three altimeters simultaneously ranges from ∼100 km wavelength
at high latitude to ∼800 km wavelength in the equatorial band
and the mean temporal resolution is ∼34 d. The mean
effective spatial resolution at midlatitude is estimated to be ∼200 km. The mean effective spatial resolution is ∼130 km for
the regional Mediterranean Sea and for the regional Black Sea products. An
intercomparison with previous DUACS reprocessing systems (a.k.a., DUACS-DT2010
and DUACS-DT2014) highlights the progress of the system over the past 8 years, in particular a gain of resolution in highly turbulent regions. The same diagnostic applied to maps constructed with two altimeters and maps with three altimeters confirms a modest increase in resolving capabilities and accuracies in the DUACS maps with the number of missions.
Publisher
Copernicus GmbH
Subject
Cell Biology,Developmental Biology,Embryology,Anatomy
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