Drag Coefficient Parameterization under Hurricane Wind Conditions

Abstract

The influence of small-scale processes at the ocean–atmosphere boundary layer such as spray and foam on the surface waves prediction is studied. Estimates of the effect of including the exact number of specific fragmentation “parachute” type in the spray on the resulting drag coefficient is shown. For the estimates, the numerical simulations within WAVEWATCH III wave model are performed. The parameterizations of wind input are tested within WAVEWATCH III wave model: default ST4 and ST6 parameterizations and the ST1 and ST6 parameterizations used together with the implemented drag coefficient parameterization. The proposed parameterization takes into account the presence of foam and spay. The obtained results are compared with the NDBC buoys data. The importance of small-scale processes for waves at hurricane winds prediction and the prospects for their inclusion in modern numerical wave models is shown.

Parameterization scheme of the sea surface drag coefficient considering the influence of wave states and sea spray stress

“…This discrepancy occurs because the linear relationship of the surface drag coefficient with the wind speed proposed by Wu (1980) overestimates the drag coefficient at high wind speeds (Moon et al, 2003). Recent studies have indicated a decay in the surface drag coefficient at high wind speeds (Chen et al, 2022;Kuznetsova et al, 2023). To elucidate the attenuation mechanism of the sea surface drag coefficient influenced by droplets at high wind speeds, an analysis was conducted based on Equation ( 5), considering the influence of droplets on the surface drag coefficient.…”