An FFT-Based Method for Wave Decomposition from Wave and Tide Monitoring Using A01NYUB Sensor

Abstract

Monitoring Sea level to obtain tide and wave values using acoustic sensors has the potential to be influenced by other factors. This causes the measurement results to have noise that can affect the quality of the resulting monitoring data. This study aims to decompose the monitoring results of the time series sea level data, to show the recorded wave variations. This study is located in Teluk Awur, Jepara, Indonesia. Sea level data was recorded for ten days using the A01NYUB ultrasonic sensor starting on November 4, 2022, to November 13, 2022. The results of the recording data from the A01NYUB sensor were decomposed using Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) based on the classification of the wave period. The results of the decomposition of sea level data from the sensor show that there are several classifications of waves with different periods. There are Ordinary Gravity Waves with a period of 15s-30s and an amplitude of ~1 cm; with Infragravity Waves a period of 30 s – 5 m and an amplitude of ~8.5 cm; are Long Period Waves with a period of 5min – 12h and an amplitude of ~60 cm; Ordinary Tide Waves with a period of 12h – 24h and an amplitude of ~10 cm; and Trans tidal Waves with a period of 12h – more and an amplitude of ~7.9 cm. The monitoring data were also adjusted to the MSL datum. The waters of Jepara have tidal characteristics, namely tidal asymmetry.The tides in Teluk Awur are mixed tides prevailing semi-diurnal. The A01NYUB ultrasonic sensor can record wave data with the lowest period which is Ordinary Gravity Waves and the highest period which is Trans Tidal Waves.