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Abstract In this work, we seek to address the validity of Monin–Obukhov similarity theory (MOST) in the wave-affected surface boundary layer of the atmosphere. While bulk flux formulas which rely on MOST have been tested with and applied to measurements and models of air/sea interaction for several decades, the influences of surface wave–mediated fluxes on MOST have not been thoroughly quantified. We assess several months of direct covariance data from a stationary tower deployed with instruments inside the wave-affected surface layer. These measurements are analyzed in the context of the turbulent kinetic energy (TKE) equation and MOST, extending previous work due to the inclusion of directly estimated wave-coherent energy fluxes. Scaled TKE dissipation rates are reduced from what is predicted by MOST during events with large wave-coherent surface fluxes, resulting in a dissipation deficit in the energy budget (roughly 30%). However, we find that shear is much less impacted by these wave events showing much smaller deviations from baselines (less than 10%). During much of the experiment, the dissipation deficit is balanced by the wave-coherent pressure work, suggesting a general understanding of the combined turbulent and wave-driven energetics. However, several large storms in the fall of 2022 yielded much larger dissipation deficits than can be explained by the wave-coherent pressure work, highlighting that more work is needed to understand energetics in the wave-affected surface layer more generally. Significance StatementThe exchanges of heat, momentum, and gases between the air and the ocean are important for weather and climate prediction, ocean simulation, and wave models that are important for safe operations at sea. A current theory for these exchanges was designed for use over land but has been applied successfully over the ocean for several decades. One reason the overland theory [Monin–Obukhov similarity theory (MOST)] may not work as well is due to ocean waves, which change the nature of the surface in comparison with unmoving overland features like hills, mountains, and other topography. In particular, ocean waves grow with the wind, which means that they must draw down momentum and energy from the air above. In this paper, we work to understand why this theory for heat and momentum exchange at the surface (MOST) works well over ocean waves despite the unique physics when compared to wind over land. We find that the influence of waves is visible in some parts of the theory but that for the majority of conditions, the predictions from MOST should work well. 

Abstract Surface waves grow through a mechanism in which atmospheric pressure is offset in phase from the wavy surface. A pattern of low atmospheric pressure over upward wave orbital motions (leeward side) and high pressure over downward wave orbital motions (windward side) travels with the water wave, leading to a pumping of kinetic energy from the atmospheric boundary layer into the waves. This pressure pattern persists above the air–water interface, modifying the turbulent kinetic energy in the atmospheric wave-affected boundary layer. Here, we present field measurements of wave-coherent atmospheric pressure and velocity to elucidate the transfer of energy from the atmospheric turbulence budget into waves through wave-coherent atmospheric pressure work. Measurements show that the phase between wave-coherent pressure and velocity is shifted slightly above 90° when wind speed exceeds the wave phase speed, allowing for a downward energy flux via pressure work. Although previous studies have reported wave-coherent pressure, to the authors’ knowledge, these are the first reported field measurements of wave-coherent pressure work. Measured pressure work cospectra are consistent with an existing model for atmospheric pressure work. The implications for these measurements and their importance to the turbulent kinetic energy budget are discussed. Significance StatementSurface waves grow through a pattern of atmospheric pressure that travels with the water wave, acting as a pump against the water surface. The pressure pumping, sometimes called pressure work, or the piston pressure, results in a transfer of kinetic energy from the air to the water that makes waves grow larger. To conserve energy, it is thought that the pressure work on the surface must extract energy from the mean wind profile or wind turbulence that sets the shape of the wind speed with height. In this paper, we present direct measurements of pressure work in the atmosphere above surface waves. We show that the energy extracted by atmospheric pressure work fits existing models for how waves grow and a simple model for how waves reduce energy in the turbulent kinetic energy budget. To our knowledge, these are the first reported field measurements of wave-coherent pressure work. 

Abstract Rainfall alters the physical and chemical properties of the surface ocean, and its effect on ocean skin temperature and surface heat fluxes is poorly represented in many air‐sea interaction models. We present radiometric observations of ocean skin temperature, near‐surface (5 cm) temperature from a towed thermistor, and bulk atmospheric and oceanic variables, for 69 rain events observed over the course of 4 months in the Indian Ocean as part of the DYNAMO project. We test a state‐of‐the‐art prognostic model developed by Bellenger et al. (2017,https://doi.org/10.1002/2016JC012429) to predict ocean skin temperature in the presence of rain, and demonstrate a physically motivated modification to the model that improves its performance with increasing rain rate. We characterize the vertical skin‐bulk temperature gradient induced by rain and find that it levels off at high rain rates, suggestive of a transition in skin‐layer physics that has been previously hypothesized in the literature. We also quantify the small bias that will be present in turbulent sensible heat fluxes parameterized from ocean temperature measurements made at typical “bulk” depths during a rain event. Finally, a wind threshold is observed above which the surface ocean remains well‐mixed during a rain event; however, the skin temperature is observed to decrease at all wind speeds in the presence of rain.