Raw data review (QA1): Difference between revisions
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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: | 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 = | == Data quality is poor == | ||
<div class="mw-collapsible mw-collapsed" id="poor quality" data-collapsetext="Collapse" data-expandtext="Expand"> | <div class="mw-collapsible mw-collapsed" id="poor quality" data-collapsetext="Collapse" data-expandtext="Expand"> | ||
#* Low correlation values | #* Low correlation values | ||
| Line 9: | Line 9: | ||
</div> | </div> | ||
= Unrealistic velocity values = | == Unrealistic velocity values == | ||
<div class="mw-collapsible mw-collapsed" id="unrealistic" data-collapsetext="Collapse" data-expandtext="Expand"> | <div class="mw-collapsible mw-collapsed" id="unrealistic" data-collapsetext="Collapse" data-expandtext="Expand"> | ||
#* Evidence of phase wrapping | #* Evidence of phase wrapping | ||
| Line 20: | Line 20: | ||
#* Orientation deviates from expected values | #* Orientation deviates from expected values | ||
</div> | </div> | ||
= There is wave or periodic motion = | == There is wave or periodic motion == | ||
<div class="mw-collapsible mw-collapsed" id="waves?" data-collapsetext="Collapse" data-expandtext="Expand"> | <div class="mw-collapsible mw-collapsed" id="waves?" data-collapsetext="Collapse" data-expandtext="Expand"> | ||
#* Periodic motion at wave frequencies observed in velocity data | #* Periodic motion at wave frequencies observed in velocity data | ||
</div> | </div> | ||
= Velocity shear is too large = | == Velocity shear is too large == | ||
<div class="mw-collapsible mw-collapsed" id="highshear" data-collapsetext="Collapse" data-expandtext="Expand"> | <div class="mw-collapsible mw-collapsed" id="highshear" data-collapsetext="Collapse" data-expandtext="Expand"> | ||
#* earth velocities indicate significant horizontal shear | #* earth velocities indicate significant horizontal shear | ||
</div> | </div> | ||
= Stationary assumption may be violated = | == Stationary assumption may be violated == | ||
<div class="mw-collapsible mw-collapsed" id="nonstationary" data-collapsetext="Collapse" data-expandtext="Expand"> | <div class="mw-collapsible mw-collapsed" id="nonstationary" data-collapsetext="Collapse" data-expandtext="Expand"> | ||
#* variance of velocity bursts shows spatial or temporal trends | #* variance of velocity bursts shows spatial or temporal trends | ||
</div> | </div> | ||
= Stratification is too large = | == Stratification is too large == | ||
<div class="mw-collapsible mw-collapsed" id="toostratified" data-collapsetext="Collapse" data-expandtext="Expand"> | <div class="mw-collapsible mw-collapsed" id="toostratified" data-collapsetext="Collapse" data-expandtext="Expand"> | ||
#* Temperature and salinity (if available) indicate local stratification | #* Temperature and salinity (if available) indicate local stratification | ||
Revision as of 09:40, 16 November 2021
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
- Low correlation values
- Echo intensity anomalies
- Low percent good values
- Data return rate varies
Unrealistic velocity values
- Evidence of phase wrapping
- Velocities outside nominal measurement range
- Velocities outside expected distribution
Significant instrument motion and orientation
- High variability in pitch, heading and roll
- Orientation deviates from expected values
There is wave or periodic motion
- Periodic motion at wave frequencies observed in velocity data
Velocity shear is too large
- earth velocities indicate significant horizontal shear
Stationary assumption may be violated
- variance of velocity bursts shows spatial or temporal trends
Stratification is too large
- Temperature and salinity (if available) indicate local stratification
Next step: Compute structure functions and dissipation estimates
Previous step: Deployment
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