Wave climate of the Hellenic Seas obtained from a wave hindcast for the period 1960-2001

The wave climate of the Hellenic Seas and particularly the climate extremes are investigated by means of a 42-year (1960-2001) model hindcast. The wave model, implemented over the Mediterranean basin, is forced by high-resolution winds generated upon downscaling of the ERA40 reanalysis. It is shown that the quality of the hindcast is overall satisfactory; however, extreme wave heights in the Aegean Sea are consistently overestimated. Accordingly, corrections to the original data are applied. The results show that the highest mean wave conditions are located east and west of Crete Island where the northerly air flow exits the Aegean Sea. Extreme waves are the highest outside the Aegean Sea, mainly in the southern Ionian Sea and south of Crete. Nevertheless, high waves also develop around the exits of the Aegean Sea and N-NE of the Cyclades islands. Despite a milder extreme wave climate in the Aegean Sea due to short fetch distances, the mean wave height range is very similar to that of the Ionian Sea. Moreover, in summer, the two seas exhibit similar extreme wave height conditions with the highest extremes found around the exits of the Aegean Sea to the Levantine basin. Storms of a longer duration are also observed in the Aegean Sea. The analysis of long-term trends in the wave climate shows that mean and extreme wave climate as well as the average intensity of extreme events have decreased in the Hellenic Seas. Nevertheless, this decrease has not been monotonic. A turning point is located around year 1981 with the mean and extreme wave height mostly increasing before this year and decreasing afterwards.