Acquiring Long-Term Turbulence Measurements from Moored Platforms Impacted by Motion

For measurements from either profiling or moored instruments, several processing techniques exist to estimate the dissipation rate of turbulent kinetic energy ϵ, a core quantity used to determine oceanic mixing rates. Moored velocimeters can provide long-term measurements of ϵ, but they can be plagued by motion-induced contamination. To remove this contamination, two methodologies are presented that use independent measurements of the instrument’s acceleration and rotation in space. The first is derived from the relationship between the spectra (cospectra) and the variance (covariance) of a time series. The cospectral technique recovers the environmental (or true) velocity spectrum by summing the measured spectrum, the motion-induced spectrum, and the cospectrum between the motion-induced and measured velocities. The second technique recovers the environmental spectrum by correcting the measured spectrum with the squared coherency, essentially assuming that the measured signal shares variance with...