Spectral Analysis of Satellite Altimeter and Tide Gauge Data around the Northern Australian Coast

Zahra Gharineiat,Xiaoli Deng

doi:10.3390/rs12010161

Zahra Gharineiat, Xiaoli Deng

Open Access

https://doi.org/10.3390/rs12010161

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Abstract

The north of Australia is known for its complex tidal system, where the highest astronomical tides (HATs) reach 12 m. This paper investigates the tidal behaviour in this region by developing spectral climatology for tide gauge and altimetry data. Power spectral density analysis is applied to detect the magnitude of ocean tides in 20 years of sea-level data from multimission satellite altimeters and tide gauges. The spectra of altimetry sea level anomaly (SLA) time series have their strongest peaks centred at approximately 2.11, 5.88, and 7.99 cycles per year (cpy), corresponding to the diurnal and semidiurnal tidal constituents K1, M2, and O1, respectively. Closer to the coastline, the spectra peak at high-frequency overtide and shallow-water constituents such as M4, MK4, and MK3. There have been many large, high-frequency spectral peaks near the coastline, indicating the difficulty of predicting tidal signals by coastal altimetry. Similar to altimetry observations, there are dominant semidiurnal and diurnal tidal peaks in tide gauge SLA time series accompanying a number of overtides. The semidiurnal and diurnal peaks are mostly higher on the northwest coast of Australia compared with the north and northeast coast. The results from both altimetry and tide gauges indicate that tidal range increases with increasing continental shelf.

Highlights

Tides are the periodic rise and fall of the ocean due to changes in the gravitational attractive forces of the Moon, Sun, and Earth
M2 and S2 have aliased periods of about 60 days with respect to T/P sampling rate, which is equivalent to the 12 h of tide gauge data
We show that altimetry data, despite the low sampling rate, contain valuable inforImnatthioisn satnuddcya, nwbee suhsoewd fothrattidaalltipmreedtriyctidoant.aT, adbelsep2itperothveidleoswa csoammpplairnigsornabtee,twcoenetnaitnhevsapluecatbrlael iannfaolrymsiastoiofntidanedgacuagnebaenudseadltifmoretteidr asleap-rleedviecltoiobnse. rTvaabtlieon2sp. rTohveidtiedsaal aconmalypsairsisreosnubltestfwroementtwhoe dspaetacstreatsl wanearleycsiosmopfatriadbelegaanudgecoannfidrmaletdimtheteeerxsisetae-nlecveeolfosbesmeridviautironnasl.tiTdhael ctoidnastlitauneanltyssiins trheesunlotsrtfhreoamst tawndo dnoatrathsewtseswt oefreAucostmrapliaar.able and confirmed the existence of semidiurnal tidal constituents in the northeast and northwest of Australia

Summary

Introduction

Tides are the periodic rise and fall of the ocean due to changes in the gravitational attractive forces of the Moon, Sun, and Earth. Ocean tides are accountable for almost 80% of sea-level variability [1,2]. Understanding the tidal behaviour is important for the coastal environment and ecosystems and for accurate estimations of surge components of sea level and the rate of sea-level rise [3]. Time-series analysis has been widely used in assessing sea-level measurements and detecting the tidal components of sea-level variations [4]. By decomposing a sea-level time series into a time–frequency space, the spectral analysis method determines the dominant tidal component and variation of components over time

Results

Discussion

Conclusion