The interaction between an internal gravity wave and the planetary boundary layer. Part II: Effect of the wave on the turbulence structure

An atmospheric internal gravity wave was measured over a two‐hour period by a microbarograph array and a series of fast response wind and temperature sensors deployed along a 300m tower. the particularly monochromatic nature of the pressure signal at the ground enabled an explicit separation of the velocity field into mean, wave, and turbulent components. Large wave‐frequency fluctuations were observed in the turbulent Reynolds stresses. Their significance is discussed at length with special regard to their role in the budget of wave kinetic energy. It is shown that the quadrature relationship which they maintain with the components of wave‐shear, limits their effectiveness in reducing the wave amplitude. Analysis of the important time scales in the budget of turbulent kinetic energy reveals that the energy containing eddies have time scales longer than the wave period, and consequently the turbulence cannot remain in equilibrium with large, wave‐frequency fluctuations in shear production. the result is a boundary layer which never attains a true equilibrium state.