Approximately a dozen records are verified hard flags for each kurtosis and skewness in both RASEX and Microfronts95 (appendix). These flags occur less frequently for the BOREAS aircraft data. In RASEX, several of the cases with large virtual temperature kurtosis appear to be related to frequent spiking associated with water collecting on the transducers. The duration of the resulting contamination of the signal is too long to qualify for the spiking flag and too erratic to be flagged by the dropout criteria.
Figure 3a shows a RASEX virtual temperature record hard flagged for large skewness and kurtosis. During this period, the winds are strong (9.5 m s−1) and from the west with long ocean fetch. The fluctuations of 3°C are too large to be physical. There was precipitation during this period.
Figure 3b shows a BOREAS vertical velocity record hard flagged for exceeding the absolute limits, skewness, kurtosis, dropouts, and Haar variance (see next section) thresholds. Near the 5-km mark into the record, the measured alongwind component, vertical velocity, static pressure, and the aircraft airspeed are all affected by the same electronic problem.