Abstract
The estimation accuracy of tidal harmonic constants is of great significance to maritime traffic and port construction. However, due to the long sampling period of satellite altimeters, tidal signals alias the mesoscale ocean frequencies. As a result, the harmonic analysis is affected by mesoscale environmental noise. In this study, the influence of the mesoscale ocean variability (MOV) on the estimation of tidal harmonic constants was quantified by analyzing 25 years of altimeter data from the Topex/Poseidon (T/P) and Jason satellites in the South China Sea (SCS). The results indicated that the absolute amplitude differences (AADs) of the eight major tidal constituents before and after the mesoscale variability correction (MVC) were generally within 10 mm, and most were within 6 mm. For the relative impact, M2, O1, and K1 were not obviously affected by the MOV because of their large amplitudes, and the AADs generally accounted for less than ±10% of the amplitudes. As a tidal constituent with amplitude less than 2 cm in the SCS, the amplitude of K2 was significantly affected by the MOV, with the ratios of the AADs to its own amplitudes ranging from −64.79% to 95.99% in space. In terms of phase, the K2 tide was most affected by the MOV: 63% of the data points before and after correction were over ±5°, and the maximum and minimum values were 86.46° and −176.27°, respectively. The absolute phase differences of other tidal constituents before and after the MVC were generally concentrated within ±5°. The impact of the MOV on the evolution of tidal amplitudes in the SCS was also explored. It was found that the MOV can cause pseudo-rapid temporal variations of tidal amplitudes in some regions of the SCS.
Highlights
Tides, one of the most prevalent ocean motions, are the periodic movements of sea water induced by the celestial tide-generating force from the sun and the moon
The accurate extraction of tidal characteristics could be used to provide reliable predictions for future tides, which is important for coastal construction and shipping transportation
The harmonic constants based on T/P-Jason satellite observations are usually mixed with the contributions of non-tidal components, and the mesoscale ocean variability (MOV)
Summary
One of the most prevalent ocean motions, are the periodic movements of sea water induced by the celestial tide-generating force from the sun and the moon. The satellite data have a long time span, the nontidal background noise still affects the accuracy of tidal harmonic constants to some extent, especially in the regions with strong mesoscale ocean variability (MOV). By comparing the estimated tidal constants, they found that high MOV clearly corrupted the altimeter-based tidal estimations even with data spanning a 17 year period They further used a multi-satellite mapped sea level anomalies (SLA) product as a “correction” for tide estimation, improving the accuracy of the altimeter-based harmonic constants [6].
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