Temporal Sea Level Variation in the West Coast of Sri Lanka

K.W. Indika, W.R.W.M.A.P. Weerakoon,S.S.L. Hettiarachchi

The temporal variation of sea level can be observed as hours, days, weeks, months, seasonal, annual, inter annual and as long term. Meanwhile, some extreme variations are governed by disturbed weather system such as storms, meteo-tsunami etc. A series of tide-gauge data were obtained from the Intergovernmental Oceanographic Commission (IOC) whereas from a global satellite based database, i.e. Achieving, Validation and Interpretation of Oceanographic Satellite (AVISO) data. Eight years of automated sea level gauge data in one minute frequency were used to analyze daily, weekly and seasonal variations while twenty years of satellite data were analyzed for long term variations. The outcomes of both data were super positioned to appraise the accuracy of the data sources. The T_TIDE harmonic analysis function of time series analysis in MATLAB’ software was used to quantify the tidal constituents. According to the form factor (0.33), the type of tide was mixed semi diurnal. The spring tide range was 0.652m according to the statistical quantification of Hikes 2006. The average seasonal variation was 20-30 cm where the highest variation was identified during December and January while the minimum was identified during July and August. The observed long term sea level variation indicates a positive trend of 1.9 mm yr-1 in the west coast of Sri Lanka.