1. Operational Oceanography and Meteorology
Processing Acoustic Doppler Current Profiler Data for Score 1 January 28 – July 10, 2006
Operational Oceanography and Meteorology
OC 3570
LT Cristal Armijo
September 7, 2007

2. Purpose How: What do the currents look like? does the ADCP work?
was it set up to sample?
was data processed?
good data is distinguished from bad data?
What do the currents look like?

3. Acoustic Doppler Current Profiler RD Instruments

4. Score 1: Mooring and Location Lat: 32° 55.726°N Long: 118° 36.503°W
Courtesy of Tarry Rago

5. How Does the ADCP work? Broadband ADCP
4 Beam Transducer w/ 20 degree beam angle
Doppler effect
“pings” at kHz
Backscatters
Doppler shift
Assumes currents are homogeneous/averaging/ trigonometry = u, v, w velocity components
Repetitive Sampling & “Gating” = “Profile” of the water column over a range of depths

6. How did the ADCP Sample? Burst Sample set up
26 bins & 15,633 ensembles
Bin size is 4 m
Sends out 40 * 1 sec pings per ensemble
Averages 40 velocities of u, v, & w per bin to produce one set of u, v, & w at that bin
15 min/ensemble (quiet for 14 min & 20 sec)

7. How good data is distinguished from bad data?
Workhorsepro1
Uvflags
Flagpoints
Despiker
Linear interpolate
Saves the flagged data
Flagged bad data criteria:
Correlation magnitude (cm) is less than 64 counts in any of the beams
Percent good (pg3 & pg4) if combined are less than 25%
Echo Intensity – plot ET verses bin number, visually average bin cutoff = bin 25

8. Continue with good data….
Workhorsepro2
Loads initially processed data from workhorsepro1
Princax – rotates the principal axis
Uses a ‘lowpass’ 4th order Butterworth filter to remove the tides w/ cutoff frequency set at .01
Math2true – changes from math to geographic (true) coordinates

9. Scatterplot and Principal Axis Direction
Rotates the axis to a new coordinate system in order in which the max (min) variance is associated with major (minor) axis.

10. Vertically Averaged Flow Velocities & Contour plots: Outflow and Cross Shelf Velocities

11. Progressive Vector Diagram
Integrate velocity to produce a trajectory.

12. Empirical Orthogonal Functions for VR component
Modes 1-3 account 80% spatial and temporal variability (variance) of the data series.
1 = 55%
2 = 17%
3 = 8%
Modes are uncorrelated

13. Conclusion
Next to step is to look at the data in smaller segments to look for significant variations and try to explain what is causing the variations?
Investigate the spectra of the data set.
To run a Foreman tidal analysis.
Use the KE to how much energy is removed.
Process 2007 ADCP data and compare it to 2006.

14. Special Thanks and References
Special thanks to Prof. Collins, Fred Bahr, Tarry Rago & Marla Stone
Emery, W.J. and Thomson, R.E., 2001, Data Analysis Methods in Physical Oceanography, Elsevier, p
Gordon, Lee, 1996, Acoustic Doppler current profiler – Principles of operation: A practical primer: RD Instruments, San Diego, CA.