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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":["As described in the methods section of “Direct Observation of Wave-coherent Pressure Work in the Atmospheric Boundary Layer”: Measurements were made from an open-lattice steel tower deployed in roughly 13 m water depth in Buzzards Bay, MA. Buzzards Bay is a 48 km by 12 km basin open on the SW side to Rhode Island Sound. The average depth is 11 m, with a tide range of 1 to 1.5 m, depending on the neap/spring cycles. Winds in Buzzards Bay are frequently aligned on the long-axis (from the NE or SW), and are commonly strong, particularly in the fall and winter. The tower was deployed near the center of the bay at 41.577638 N, 70.745555 W for a spring deployment lasting from April 12, 2022 to June 13th, 2022. Atmospheric measurements included three primary instrument booms that housed paired sonic anemometers (RM Young 81000RE) and high-resolution pressure sensors (Paros Scientific). The pressure sensor intakes were terminated with static pressure heads, which reduce the dynamic pressure contribution to the measured (static) pressure. The tower booms were aligned at 280 degrees such that the NE and SW winds would be unobstructed by the tower's main body. A fourth sonic anemometer (Gill R3) was extended above the tower such that it was open to all wind directions and clear of wake by the tower structure. A single point lidar (Riegl LD90-3i) was mounted to the highest boom, such that the lidar measured the water surface elevation underneath the anemometer and pressure sensors to within a few centimeters horizontally. All instruments were time synchronized with a custom "miniNode" flux logger, that aggregated the data streams from each instrument. Additional atmospheric and wave measurements on the tower included short-wave and long-wave radiometers (Kipp & Zonen), two RH/T sensors (Vaisala), and a standard lower-resolution barometer (Setra)."]}