Flow chart for shear probes

The processing of shear-probe data can be divided into the following five major steps and these steps apply to data collected with any platform or vehicle. There are many sub-steps to these major steps. The major steps are;

Conversion to physical units.

• Determine the speed of profiling of the shear-probe through the water.

The speed of profiling can be determined with a variety of different methods. It must be determined because it is required for the conversion of the shear-probe samples into physical units and for transforming frequency spectra into wavenumber spectra. Methods for determining the speed of profiling include, but are not limited to:

• Using the rate-of-change of pressure for a vertical profiler.
• Using the rate-of-change of pressure, the pitch angle, and the angle of attack for a glider.
• Using a flight model for a glider.
• Using an onboard current meter.
• Using a constant speed.
• Using the speed recorded by an independent instrument after its record has been carefully aligned in time with the shear-probe data.

• Determine the temperature of the water.
• Convert the shear probe data samples into physical units
• Convert all other signals per the recommendations of the manufacturer of the sensor or instruments that produce these signals.

"Section" selection.

1. Before you can process your shear-probe data to derive the rate of dissipation you must select the section of data that you wish to process. You must make sure that the selection is meaningful and sensible. For example, the shear probe must be profiling through the water with a speed, direction, and orientation that is fairly stationary. The selection of data can be partially automated by requiring that the kinematics of your instrument achieve certain minimum criteria. The steps to profile selection are as follows:

   • Choose the minimum speed of profiling.
   • Choose the direction of the vertical velocity of the profiler.
   • Choose the minimum depth.
   • Choose the maximum pitch and roll of the profiler.
   • Choose the minimum duration over which the minimum speed through maximum pitch and roll must be satisfied.

Choosing the processing parameters for shear probes.

• Choose the length of data (in meters) used for each dissipation estimate – diss-length.
• Choose the lowest wavenumber of spectral estimation – fft-length.
• Translate (a) and (b) into duration (time).
• Round these up to nearest power-of-two number of samples.
• Choose a high-pass filter cut-off frequency to be consistent with (b).
• Choose de-spiking parameters.
• Choose vibration-coherent noise removal.

Apply quality-control metrics.

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