• The first directly measured dataset of roller area under irregular waves. • An alternative to direct measurement of roller area based on a CFD model. • The parameterization outperforms existing approaches, reducing underestimation. Ocean waves breaking in nearshore regions generate wave rollers, which play a critical role in surf zone dynamics, particularly in energy dissipation and momentum flux. Despite their significance, direct measurements of roller area under irregular waves remain scarce, limiting the reliability of existing parameterizations under realistic sea states. This study integrates laboratory flume experiments and numerical simulations to quantify wave roller area across diverse bathymetry and wave conditions. The experiments yielded the first directly measured dataset of roller area under irregular waves, revealing its cross-shore evolution and sensitivity to wave properties, beach slope, and breaking intensity. Numerical simulations, applying a velocity-threshold criterion for roller identification, provided an effective alternative for obtaining such data without direct measurements and successfully reproduced the experimental observations. A new empirical formula for roller area was developed. It outperforms existing approaches, which tend to underestimate roller contributions due to neglect of other parameterized processes. Overall, the results fill a critical data gap and propose a parameterization that could contribute to improving the predictive capability of nearshore circulation models.
Wu et al. (Fri,) studied this question.