Analysis of sea level variability on the costal zone of Fortaleza, Ceará State

Abstract

The present paper assesses the water level variability on the costal zone of Fortaleza, Ceará State, based on water level and wave records. The main goal is to evaluate statistically the occurrences of positive levels above the reference level of spring tide low water at solstice, and the effects of waves that may produce negative anomalies. The results are important to the local harbor activities. Water level records were obtained from a tide-gauge operated by Brazilian Institute of Geography and Statistics (IBGE) at the pier of Port of Mucuripe. Wave maximum height data were obtained from observations carried out offshore Port of Pecém and available by National Institute of Hydrographic Research (INPH). Probability density functions (PDF) were calculated for wave and water level. The number of hours per year that the water level is above the zero level was calculated from the water level PDF. Both density functions were convoluted to give a joint probability distribution, using the negative wave amplitude. Negative levels produced by spring tide low water and high wave height accounted for less than 0.5% of the time, what means nearly 15 days per year.