Direct Observation of Wave-coherent Pressure Work in the Atmospheric
Boundary Layer
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 and high pressure over
downward wave orbital motions 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 the transfer of
energy from wind to waves through wave-coherent atmospheric pressure
work. Measured pressure work cospectra are consistent with an existing
model for atmospheric pressure work. Measured pressure work energy
fluxes reach 0.1-0.2 W m$^{-2}$ during the largest measured wind
event (winds reaching 16.5 m s$^{-1}$). The implications for
these measurements and their importance to the turbulent kinetic energy
budget are discussed.