Raw data review (QA1)

The objective of the raw data review is to ensure that the velocity data used for the calculation of the structure functions are of good quality before proceeding with the turbulence analysis. Bad data are typically identified from the velocity data themselves and other ancillary data (e.g. correlations). It is recommended that velocity data should be flagged if the following are observed:

Data quality is poor

Expand

Poor data qualifiers include:

• Low correlation values
• Echo intensity anomalies
• Low percent good values
• Data return rate varies

Unrealistic velocity values

Expand

Velocities are unrealistic if there are

• Evidence of phase wrapping
• Velocities outside nominal measurement range
• Velocities outside expected distribution

Significant instrument motion and orientation

Expand

Reject data if there is:

• High variability in pitch, heading and roll
• Orientation deviates from expected values

Wave or periodic motion contamination

Expand

• Periodic motion at wave frequencies observed in velocity data

Velocity shear is too large

Expand

• earth velocities indicate significant horizontal shear

Stationary assumption may be violated

Expand

• variance of velocity bursts shows spatial or temporal trends

Stratification is too large

Expand

• Temperature and salinity (if available) indicate local stratification

---

Next step: Compute structure functions and dissipation estimates

Previous step: Deployment

Return to ADCP Flow Chart front page