Pulse-to-pulse coherent Doppler measurements of waves and turbulence

This paper presents laboratory and field testing of a pulse-to-purse cohere nt acoustic Doppler profiler for the measurement of turbulence in the ocean . In the laboratory, velocities and wavenumber spectra collected From Doppl er and digital particle image velocimeter measurements compare very well. T urbulent velocities are obtained by identifying and filtering out deep wate r gravity waves in Fourier space and inverting the result. Spectra of the v elocity profiles then reveal the presence of an inertial subrange in the tu rbulence generated by unsteady breaking waves. In the field, comparison of the profiler velocity records with a single-point current measurement is sa tisfactory. Again wavenumber spectra are directly measured and exhibit an a pproximate -5/3 slope. It is concluded that the instrument is capable of di rectly resolving the wavenumber spectral levels in the inertial subrange un der breaking waves, and therefore is capable of measuring dissipation and o ther turbulence parameters in the upper mixed layer or surface-wave zone.