Symmetric influence of forward and opposing tidal currents on rogue wave statistics

TL;DR

This paper investigates how both forward and opposing tidal currents similarly influence rogue wave probability and magnitude, using long-term North Sea data, revealing comparable amplification effects despite different current directions.

Contribution

It provides the first observational evidence that opposing and following currents have symmetric effects on rogue wave statistics in natural ocean conditions.

Findings

Opposing and following currents similarly increase rogue wave probability.

Amplification effects are consistent across broad-banded sea states.

Observed rogue wave statistics match laboratory experiment results.

Abstract

Rogue waves are associated with various ocean processes, both at the coast and in the open ocean. In either zone, inhomogeneities in the wave field caused by shoaling, crossing seas or current interactions disturb wave statistics, increasing rogue wave probability and magnitude. Such amplification of the frequency of rogue waves and their intensity, i.e. the maximum normalized height, have been attested in numerical simulations and laboratory studies, in particular for wave-current interactions. In this study, we investigate the effect of the current intensity and direction on rogue wave probability, by analyzing long-term observations from the southern North Sea. We observe that the amplification is similar for opposing and following currents. Despite the sea states being dominantly broad-banded and featuring a large directional spread, anomalous statistics are of the same order of magnitude as those observed in unidirectional laboratory experiments for stationary currents.