Relationship Between Sea-level Variability and Meteorological Conditions in Abu-Qir Bay (Alexandria – Egypt)

Abstract

This study shed light on the main sea-level characteristics of Abu-Qir Bay, which is one of the sensitive Egyptian coastal zones prone to sea-level variations and the sea-level rise problem. The present analysis was performed by the T_TIDE package for hourly sea-level records from January 2008 to December 2010. A simultaneous meteorological data set was obtained from the automated weather station at Alexandria International Airport. This comprised records of air temperature, atmospheric pressure and wind regime. Although few studies were previously conducted to examine the sea-level variations in Abu Qir Bay, this is the first to correlate these variations with the three main affecting meteorological conditions. Results revealed that the Bay had a mean sea level (MSL) of 50.1cm, which is relative to the tide gauge zero-level and exhibited a semidiurnal tidal cycle. The Bay exhibited a MSL seasonal behavior, with the lowest mean in spring (38.6cm) and the highest in autumn (58.7cm). 19 astronomical constituents were significant out of 69 with solar annual and semi-annual components having the highest amplitudes of 7.2 and 4.6cm, respectively. The M 2 principal lunar tidal constituent had an amplitude of only 1.5cm. The water levels had a spring-to-neap range ratio of 5. Residuals had the upper hand on the observed variations in the sea level of Abu-Qir Bay. Storm surges with elevations greater than 65cm contributed up to 7% of the observed sea level in the bay. Correlation coefficients between the sea level and the affecting meteorological conditions during the study period were calculated on both hourly and mean monthly basis. This revealed that air temperature is the key meteorological player in the observed variations and that the sea level is affected by the zonal wind component rather than the meridional one.