Fraction of shear-probe data altered by the de-spiking routine

Shear-probe data can be contaminated, or otherwise compromised, by collisions of the probe with plankton or debris in the water. Contamination can also come from collision with larger objects, such jellyfish, that cannot evade the the probe. These collisions cause a large extrema of the shear-probe signal that is not related to the shear of the water and must be removed from the data so that the variance of shear is not biased high. The data extrema, and a small neighbourhood around the extrema, are usually replaced with data of a constant value equal to the local mean, or by an interpolation of the data across the range affected by the collision.

There are no objective standards for the fraction of the data that can be altered before one should deem a dissipation estimate to be erroneous. A failure to remove extrema due to collisions will bias a dissipation estimate high - often by several factors of 10. Removing too much data will be bias an estimate low.

Intuition suggests that if more than 10% of the data used to make a dissipation estimate has been altered by a de-spiking routine, then the data quality must be poor. The shear probe was never envisioned to be used in an environment of high particle concentration.

Thus, a recommended criterion for the maximum fraction of data altered by a despiking routine should be set to a value of 0.05 to 0.1.

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