In:
Ocean Science, Copernicus GmbH, Vol. 15, No. 2 ( 2019-03-13), p. 269-290
Abstract:
Abstract. During the last 15 years, substantial progress has been achieved
in altimetry data processing, now providing data with enough accuracy to
illustrate the potential of these observations for coastal applications. In
parallel, new altimetry techniques improve data quality by reducing
land contamination and enhancing the signal-to-noise ratio. Satellite
altimetry provides more robust and accurate measurements ever closer to the
coast and resolve shorter ocean signals. An important issue is now to learn
how to use altimetry data in conjunction with other coastal observing
techniques. Here, we cross-compare and combine the coastal currents provided by large
datasets of ship-mounted acoustic Doppler current profilers (ADCPs), gliders,
high-frequency (HF) radars and altimetry. We analyze how the different
available observing techniques, with a particular focus on altimetry, capture
the Northern Current variability at different timescales. We also study the
coherence, divergence and complementarity of the information derived from the
different instruments considered. Two generations of altimetry missions and
both 1 Hz and high-rate measurements are used: Jason-2 (nadir Ku-band radar)
and SARAL/AltiKa (nadir Ka-band altimetry); their performances are compared. In terms of mean speed of the Northern Current, a very good spatial
continuity and coherence is observed at regional scale, showing the
complementarity among the types of current measurements. In terms of
current variability, there is still a good spatial coherence but the Northern
Current amplitudes derived from altimetry, glider, ADCP and HF radar data
differ, mainly because of differences in their respective spatial and
temporal resolutions. If we consider seasonal variations, 1 Hz altimetry
captures ∼60 % and ∼55 % of the continental slope current
amplitude observed by the gliders and by the ADCPs, respectively. For
individual dates this number varies a lot as a function of the
characteristics of the Northern Current on the corresponding date, with no
clear seasonal tendency observed. Compared to Jason-2, the SARAL altimeter
data tend to give estimations of the NC characteristics that are closer to in
situ data in a number of cases. The much noisier high-rate altimetry data
appear to be more difficult to analyze but they provide current estimates
that are generally closer to the other types of current measurements. Thus,
satellite altimetry provides a synoptic view of the Northern Current
circulation system and variability, which helps to interpret the other
observations. Its regular sampling allows for the observation of many features
that may be missed by irregular in situ data.
Type of Medium:
Online Resource
ISSN:
1812-0792
DOI:
10.5194/os-15-269-2019
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2019
detail.hit.zdb_id:
2183769-7
