Least Squares Techniques for Extracting Water Level Fluctuations in the Persian Gulf and Oman Sea

Extracting the main cyclic fluctuations from sea level changes of the Persian Gulf and Oman Sea is vital for understanding the behavior of tides and isolating non-tidal impacts such as those related to climate and changes in the ocean-sea circulations. This study compares two spectral analysis methods including: Least Squares Spectral Analysis (LSSA) and Least Squares Harmonic Estimation (LSHE), to analyze satellite altimetry derived sea surface height changes of the Persian Gulf and Oman Sea. SSH data are derived from about ۱۶ years of satellite altimetry observations (۱۹۹۲ to ۲۰۰۸), including the Topex/Poseidon and Jason-۱ missions. By analyzing the real data, we extract significant tidal components in the spectrum of LSSA and LS-HE including those with the period of ۶۲.۰۷, ۱۷۳.۳, ۵۸.۷۱, ۴۵.۶۸, ۸۸.۸۶, ۳۶۴.۲ and ۱۱۷.۵ days, which are interpreted as Principal Lunar semi-diurnal, Luni-Solar Diurnal, Principal Solar Semi-diurnal, Principal Lunar Diurnal, GAM۲, annual, Solar Diurnal periods are dominant in the level fluctuations. Moreover, some tidal components appear in the spectrum of LSSA and LS-HE, from which the Moon's semi-diurnal component  is dominant. Also, to evaluate the efficiency of these two techniques, we run three experiments in each extracted frequency from LSSA, LS-HE, and astronomical tide tables are separately used to predict the sea level in the Persian Gulf and Oman Sea for three years. The results of this prediction indicate that RMSE from LSSA, astronomical table, and LS-HE is ۰.۱۰۱ m, ۰.۰۹۳ m, and ۰. ۰۸۶ m, respectively. According to the results LS-HE is found a more efficient technique to analyze cyclic fluctuations from altimetry measurements.

Keywords:

Persian Gulf and Oman Sea , Least Square Spectral Analysis (LSSA) , Least Square Harmonic Estimation (LS-HE) , Satellite altimetry