Iterations

De-spiking is usually done in iterations. Shear-probe data are replaced if they meet certain criterion for threshold and other properties. The range that is replaced usually includes a small neighbourhood surrounding an anomaly. However, the range that is replaced may not include all anomalies and consequently a subsequent attempt is usualy made to identify and remove the remaining anomalies. These attempts are repeated until no more anomalies (or data extrema) are identified.

The number of passes or attempts made to clean the shear-probe data is a quality-control metric. If many attempts are required to clean the data then the anomalies are extremely long and may be caused by collisions with objects large than the typical size of zooplankton such as, for example, jellyfish.

There is no objective criterion for the maximum number of passes that should be tolerated. However, experience indicates that more than about 8 passes indicates that the data are very unusual and should not be used for the estimation of the rate of dissipation.

The number of de-spiking passes used to clean the shear data should be noted for every dissipation estimate and from every shear probe. Similarly, the maximum number of passes that causes the estimate to be flagged for exclusion must also be noted.