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

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?

Acoustic Doppler Current Profiler RD Instruments

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

How Does the ADCP work? Broadband ADCP 4 Beam Transducer w/ 20 degree beam angle Doppler effect “pings” at 307.2 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

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)

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

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

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.

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

Progressive Vector Diagram Integrate velocity to produce a trajectory.

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

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.

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. 319-343. Gordon, Lee, 1996, Acoustic Doppler current profiler – Principles of operation: A practical primer: RD Instruments, San Diego, CA.