Wind-Sea and Swell Climate in the Black and Azov Seas, Based on 42-Year Spectral Wave Hindcast

Long-term wave climates of the Black and Azov Seas are widely assessed based on the bulk wave parameters of the mixed sea. However, studies based on spectral wave partitions are rarely documented. Assessment of the wave climate based on the individual wave systems provides a more reliable description of the sea states' characteristics and the variability in the long-term wave climate. For instance, the wind-sea climate may reflect a real change in the local climate. However, local change in swell characteristics may not necessarily reflect a change in the local climate, and it can locally influence the mixed sea climate variability. This study assessed the spatial distributions of the long-term averages and maxima of mixed seas, wind-sea, and swell partitions at annual and seasonal scales. The contributions of wind-sea and swell partitions to the mixed-sea were computed, and their spatial and temporal variability was also assessed for overall and extreme sea state conditions. Finally, the occurrence in main wave systems' directions and occurrence of crossing, opposing, and following wind-sea and swell interactions were computed. The wind-sea contribution to the mixed-sea exceeds 70 % in all Black Sea and >95 % in the Azov Sea. The swells are more dominant on the Northeastern and Northwestern Black Sea basins. Thus, the results show spatial and temporal variability in the wind-sea climate close to the mixed sea but largely different compared to the swell climate. The inter-annual trends in the swell partitions and wind-sea are inversed at some locations.