High-resolution long-term wave climate and storm characteristics over the eastern Mediterranean Sea

Abstract

This study aims to assess the mean and extreme wave climate, storm characteristics and long-term variability in the eastern Mediterranean Sea by evaluating the ERA5 and CFSR wind-forced SWAN model for the period 1981-2020. Extreme sea conditions were analyzed in detail at four locations diversified by noteworthy wave climate features. Across most of the study area, the significant wave height trends derived from CFSR data have stronger statistical significance than those obtained from ERA5. In the northern Aegean Sea, both datasets reveal an increasing trend in annual mean significant wave heights over the 40-year period, with a significant increase for CFSR (exceeding 20 %) and with a lower significance for ERA5 (exceeding 5 %). In the southern (Egyptian coast) and eastern (Coasts of Lebanon and Israel) Levantine basin, the 99th percentile significant wave heights show a significant increasing trend (exceeding 15 %) in 40 years compared to their initial values (in 1981) for both datasets. The model forced with CFSR wind data results in more intense extreme conditions compared to ERA5. In the results obtained using the CFSR data in the northern Aegean Sea, where orographic barriers are intense, more than 10 storm events occur per year with total durations exceeding 300 h, indicating a significant increasing trend in storm activity. The northern Levantine (e.g., Antalya Bay) basin is characterized by relatively lower mean and extreme wave heights. Extreme value analysis (GEV) shows that for return periods greater than 60 years, this region may encounter high significant wave heights similar to those in the southern and eastern Levantine basin (exceeding 7.5 m for CFSR and 6.5 m for ERA5). The results highlight significant spatial variability in wave trends and storm behaviour, with notable discrepancies between the two datasets that must be considered in regional wave climate assessments.