A Novel Sea Surface Roughness Parameterization Based on Wave State and Sea Foam

Difu Sun,Xiaoyong Li,Hongze Leng,Junqiang Song,Kaijun Ren

doi:10.3390/jmse9030246

Abstract

A wave state related sea surface roughness parameterization scheme that takes into account the impact of sea foam is proposed in this study. Using eight observational datasets, the performances of two most widely used wave state related parameterizations are examined under various wave conditions. Based on the different performances of two wave state related parameterizations under different wave state, and by introducing the effect of sea foam, a new sea surface roughness parameterization suitable for low to extreme wind conditions is proposed. The behaviors of drag coefficient predicted by the proposed parameterization match the field and laboratory measurements well. It is shown that the drag coefficient increases with the increasing wind speed under low and moderate wind speed conditions, and then decreases with increasing wind speed, due to the effect of sea foam under high wind speed conditions. The maximum values of the drag coefficient are reached when the 10 m wind speeds are in the range of 30–35 m/s.

Highlights

The momentum transfer between the atmosphere and the ocean plays an important role in the evolution of weather and climate [1,2,3]
We further compared the P90, normalized bias (NB), and normalized root-mean-square-error (NRMSE) predicted by TY01, DN03, and the combined scheme for the total eight datasets (Table 7); the results show that the performance of the combined scheme is much better than TY01 in P90 and NRMSE, and slightly better than that of DN03, NB predicted by the combined scheme is slightly worse than DN03
Compared with parameterization of momentum flux based on wind speed, parameterization based on wave state can describe the nature of the air–sea interface more directly

Summary

Introduction

The momentum transfer between the atmosphere and the ocean plays an important role in the evolution of weather and climate [1,2,3]. Parameterization of the momentum transfer across the air–sea interface is essential to the modeling of many air–sea interaction activities, such as tropical cyclones and ocean waves [4]. The air–sea momentum flux τ is usually estimated from the drag coefficient Cd as follows:. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affilwhere ρ is the air density, u∗ is the friction velocity, and U10 is the wind speed at 10 m elevation above the sea surface. The logarithmic wind profile law can be expressed as [5,6,7]: iations.

Results

Discussion

Conclusion