Investigation of Air-Sea Turbulent Momentum Flux over the Aegean Sea with a Wind-Wave Coupling Model

Panagiotis Portalakis,John Kalogiros,Aggeliki Dandou,Qing Wang,Maria Tombrou

doi:10.3390/atmos12091208

Abstract

Near surface turbulent momentum flux estimates are performed over the Aegean Sea, using two different approaches regarding the drag coefficient formulation, a wave boundary layer model (referred here as KCM) and the most commonly used Coupled Ocean–Atmosphere Response Experiment (COARE) algorithm. The KCM model incorporates modifications in the energy-containing wave spectrum to account for the wave conditions of the Aegean Sea, and surface similarity to account for the stratification effects. Airborne turbulence data during an Etesian outbreak over Aegean Sea, Greece are processed to evaluate the simulations. KCM estimates found up to 10% higher than COARE ones, indicating that the wave-induced momentum flux may be insufficiently parameterized in COARE. Turbulent fluxes measured at about 150 m, and reduced to their surface values accounting for the vertical flux divergence, are consistently lower than the estimates. Under unstable atmospheric stratification and low to moderate wind conditions, the residuals between estimates and measurements are less than 40%. On the other hand, under stable stratification and strong winds, the majority of the residuals are more than 40%. This discrepancy is associated with the relatively high measurement level, shallow boundary layer, and the presence of a low level jet.

Highlights

IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The performance of Simulating Waves Nearshore (SWAN) is examined with respect to computational time-step and space resolution as well as nesting approach
The analysis demonstrated that there are no significant spatial or temporal differences, except at the outer boundaries of the innermost domain, due to the absence of boundary forcing in the case without nesting

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The atmosphere-ocean interface differs significantly from that of the atmosphereland interface due to the presence of surface gravity waves. Several studies [1,2] have demonstrated that Monin-Obukhov (MO) similarity theory, developed over land, is applicable in the Surface Layer (SL) of the Marine Atmospheric Boundary Layer (MABL). The usual application of MO theory should be confined to the upper portion of the SL where turbulent fluxes are assumed to be almost constant with height, above the shallow layer that is directly influenced by the waves, the Wave-influenced Boundary

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Conclusion