Outlier removal filters spurious mixing height retrievals that are caused by instrument noise, transient small-scale aerosol features, or other artifacts that cannot be removed by traditional averaging techniques. However, this retains important details of the boundary layer evolution throughout the day.
To avoid removing valid mixing heights, the algorithm relaxes the figure-of-merit criteria for distinguishing valid retrievals from outliers. For each retrieval, the outlier removal method computes a figure-of-merit score based on proximity (in height) to other retrievals in the preceding 4 minutes. The algorithm deems retrievals with an insufficient number of neighbors (a low figure-of-merit score) as outliers and replaces them by the most recent valid retrieval.