Currents and sea level variability of Alexandria coast in association with wind forcing

Abstract EN

Data records of wind, current and sea level were arranged and smoothed to hourly data off Alexandria coast, Egypt.

The first data records in (1996) was collected at the Eastern Harbor (EH), and the second data set (2008) collected at the Western Harbor (WH) of Alexandria at the monthly duration.

Currents speed data were statistically analyzed and showed a variation from 0 to 43.2 cm/sec at (EH), while in the (WH) varied from 0 to 27.2 cm/sec.

Based on the frequency occurrence percentage, the long-shore NE current component was found highly dominated under the influence of the alongshore wind component of the prevailing NW.

The rotary tidal current strength was elongated close to the shore and found directed either in the NE-SW or in the ENE-WSW directions in (EH).

Currents in (WH) were generated by the dominant NW wind, and partially due to the huge amount of polluted water discharged from El-Max Bay via El-Umoum drain.

At both Harbors, the average tidal current contribution was estimated as 30 % of the total current energy at both sites.

Sea level data were statistically analyzed, and it was found that the range of sea level variation in the (EH) was about (0.53 m), while inside the (WH) was (0.57 m).

Harmonic analysis showed a mixed semi-diurnal tidal regime at both sites with significant dominant constituents.

Spectral analysis displayed a tidal energy contribution to the sea surface oscillations at both sites (EH) and (WH) of 22 % and 13 % of the total sea level variability, respectively.

While surge energy was estimated as 78 % and 87 %, respectively at both harbors.

In general, the results implied that, tide-generating forces are responsible for generating less than 30 % of the total current and total sea level oscillation, while more than 70 % of the total energy in both sea level and current data were mainly due to the wind forcing and other non-tidal factors.