JKAU: Mar. Sci., Vol. 21, No. 1, pp: 133-149 (2010 A. D. / 1431 A. H.) DOI: 10. 4197/Mar. 21-1.8 133 Tide and Sea Level Characteristics at Juaymah, West Coast of the Arabian Gulf Abdullah M. Al-Subhi Faculty of Marine Science King Abdul-Aziz University, Jeddah, Saudi Arabia amalsubhi@kau.edu.sa Abstract. Based on hourly values of the sea level record for the year 2000 and 2005 at Juaymah, Arabian Gulf, the harmonic tidal analysis was performed. It showed a mixed type of tide (F ≈ 0.44) with semidiurnal dominance. On an annual basis, the astronomical tide comprised about 90% of the water level variations. Most of the residual variation (observed minus astronomical component) depends on the variation in atmospheric pressure, water density, and the wind stress. The atmospheric pressure seems to be important compared to density variation and the wind stress in both years. The atmospheric pressure is higher in winter and lower in summer with a consequence of lower residual sea level in winter and higher in summer. Keywords: Arabian Gulf, harmonic tidal analysis, observed tide astronomical tide, meteorological tide, mean sea level. Introduction The Arabian Gulf extends about 1000 km in length and maximum width is approximately 370 km. The average depth is about 36 m and surface area is approximately 239×10 3 km 2 (Emery, 1956). It is located in an arid region and mostly dominated by the Shamal; a northwesterly wind which occurs almost year round (Perrone, 1979). The evaporation rate is nearly 2 m/yr (Privett, 1959; Hastenrath and Lamb, 1979; Meshal and Hassan, 1986; and Ahmad and Sultan, 1991). The net freshwater input by precipitation and river discharge is 0.15 m/yr (Johns et al., 2003). The major fresh water source in the Arabian Gulf is through the Shatt-Al- Arab, at the head of the Gulf and fed by the Euphrates, Tigris and Karun