Len Zedel's Home Page
Professor, Memorial University of Newfoundland
Course Web Pages:
P6317
Gros Morne summit in March!
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Background
I received my B.Sc. degree in physics from
the University of Victoria, Canada in 1982, my M.Sc. degree in physics
from the University of Victoria, Canada in 1985. At that point, I
took a period of time off studies and worked as an Experimental
Scientist at the CSIRO
Marine Laboratories in Hobart, Tasmania.
At CSIRO, I configured and developed the data acquisition system for
one of the early RD Instruments, Acoustic Doppler Current Profilers
on the RV Franklin. I returned to Canada in 1987 and began work on
my Ph.D. at the University of British Columbia Oceanography Department.
Working with the IOS
Ocean Acoustics group my thesis research involved the use
of acoustics to study near surface ocean
processes. After graduating in 1991, I took up a position
as a Research Associate with Dr. Alex Hay at
Memorial University of Newfoundland
(MUN), in St. John's, NF
studying sediment transport processes using acoustic systems.
I accepted a post of Assistant Professor in the
Dept of Physics and Physical
Oceanography at
MUN in 1996.
Research activities involve
the exploration of oceanographic processes through the use of
acoustic systems. The revolution in electronics and computing
capabilities provide many opportunities for instrument development in oceanography. Current interests include; the processes responsible for
ambient sound in the ocean, the use of coherent Doppler sonar for
high resolution water velocity profiling, the suspension of
sediment in the nearshore zone, and the application of acoustic
systems to fisheries acoustics.
I believe that it is fundamental that any instrument development
be motivated
by scientific need and not simply by technological capability.
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I can be reached at:
Dr. Len Zedel
Dept of Physics and Physical
Oceanography
Memorial University of Newfoundland
St. John's, NF
Canada, A1B 3X7
Phone: (709) 864-3106
Fax: (709) 864-8739
Oceanographic Acoustics
Even in the clearest water, light does not penetrate more than about 100 m
in the ocean and radio waves are similarly blocked by sea water. Sound
however can carry great distances underwater (signals have successfully been
transmitted half way around the world). As a result, where applications
such as radar use radio waves in the atmosphere, similar systems in the ocean
must use sound. The recent revolution in small, high
performance computing systems is making many new applications of
underwater acoustic systems possible.
My research activities involve
the exploration of
these new applications to make contributions to oceanographic
studies. It is fundamental that any instrument development be motivated
by scientific need and not simply technological capability
Recent Research Results
Recent Presentations
Ocean Predict 2019 (Halifax, NS):
Comparing Doppler Profiler Observations from Seismic Survey Ship with Ocean Model Output
Energy 3 (Halifax, NS):
Doppler Sonar Observations of Fish Populations
Underwater Acoustics Conference and Exhibition (Crete, Greece):
Multi-beam Doppler for Scanning Water Velocities
Student Opportunities
Through the Interdisciplinary Marine Engineering Research and Industrial Training (iMERIT is an NSERC funded CREATE program with funding from 2019-2025) I have the following projects available for students. Student stipends for these projects will be in the order of c$30,000 per year depending on student TA support.
Development of Doppler sonar for tracking fish
Development of Split-beam sonar algorithms
Development of Acoustic Temperature Profiling System
Fishmass: Fisheries Acoustics
The technique of fish detection using sonar systems is well developed.
Echo integration allows for efficient surveys of fish biomass and more
recent developments based on split-beam and dual-beam technology allow for
the counting (and sizing) of individual fish targets. These sonar
techniques combined with conventional ship trawl surveys provide a
snapshot in time of fish or biomass distribution. Also important is a
knowledge of fish movements over extended time periods; with conventional
. Patro, T. Knutsen, 2005:
uent (and expensive) ship surveys.
An alternative approach to acquiring long-term time series of fish
motion would be to deploy a moored, internally recording instrument. It
is important to note that simple fish detection in a self-recording
instrument is not sufficient; it is necessary to determine the net motion
of fish to distinguish between a resident population and a migration.
This capability would provide a cost-effective method to monitor fish
complimenting the existing ship based spatial surveys. Example
applications in Canadian waters include the monitoring of Northern Cod on
the east coast, and the various salmon species on the west coast. Many
similar applications exist wherever fish are known to form well-defined
migrations.
Tests of such a system monitoring the motion of herring
have been undertaken along the coast of Norway. The following figure
provides an example of the migration speed of a school of these herring.
Zedel, L., F.Y. Cyr-Racine, 2009:
Extracting Fish and Water Velocity from Doppler Profiler Data. ICES Journal of
Marine Science, 66, 1846-1852.
Tollefsen, C.D.S., L. Zedel, 2003: Evaluation of a Doppler sonar system for
fisheries applications. ICES Journal of Marine Research, 60, 692-699.
Zedel, L., R. Patro, T. Knutsen, 2005:
Fish behaviour and orientation dependent backscatter. ICES Journal of Marine Science, 62, 1191-1201.
Zedel, L., T. Knutsen, R. Patro, 2003:
ADCP Observations of Herring Movement. ICES Journal of Marine Science,
60, 846-859.
Tollefsen, C.D.S., L. Zedel, 2003: Evaluation of a Doppler sonar
system for fisheries applications.
ICES Journal of Marine Science,
60: 692-699.
Dopbeam: Coherent Doppler Sonar
The study of nearshore sediment transport poses many challenges to accurate
observations. One of the key areas of difficulty results from instrumentation
disturbing the flow field. Dopper current profiling avoids this problem
by making measurement remotely. Working jointly with Dr. A.E. Hay of Dalhousie
University, we have developed several instruments based on short range fully coherent Doppler.
These systems, working at between 1 and 2 MHz frequency provide velocity profiles over a range
of order 1 m with 0.5 cm depth resolution at a rate of 50 profiles/second with
accuracy of order 1 cm/s (in the vertical direction).
Zedel, L., A. Hay, G.W. Wilson, J. Hare, 2019: Pulse Coherent Doppler Profiler Measurement of Sediment Transport:
Computer Simulation and Laboratory Trials. JGR-Earth Surface, in review .
Hay, A.E., L. Zedel, and N. Stark, 2014: Sediment dynamics on a steep, mega-tidal, mixed sand-gravel-cobble beach.
E. Surf. Dyn., 2, 443-453.
Hare, J., A.E. Hay, L. Zedel, R. Cheel, 2014: Observations of the Space-time Structure of Flow and Stress over
Orbital-scale ripples. JGR-Oceans, 119, 1876-1898.
Stark, N., A.E. Hay, R. Cheel, L. Zedel, D. Barclay, 2014: Laboratory measurements of
coarse sediment bedload transport
velocity using a prototype wide-band coherent Doppler profiler (MFDop). J. Atmos. and
Oceanic Tech., 89, 295-301.
Dillon, J., L. Zedel, and A.E. Hay, 2012: On the Distribution of Velocity Measurements from
Pulse-to-Pulse Coherent Doppler Sonar., IEEE J. Oceanic Eng., 37, 613-635.
Hay, A.E., L. Zedel, R. Cheel, J. Dillon, 2012: On the Vertical and Temporal Structure of Flow and Stress
within the Turbulent Oscillatory Boundary Layer Above Evolving Sand Ripples, Continental Shelf Research.
Hay, A.E., L. Zedel, J. Dillon, 2012: Observations of the Vertical Structure of Turbulent Oscillatory
Boundary Layers Above Fixed Roughness using a Prototype Wide-band Coherent Doppler Profiler: 2.
Turbulence and Stress, J. Geophysical Research Oceans, 117, DOI: 10.1029/2011JC007114.
Hay, A.E., L. Zedel, J. Dillon, 2012: Observations of the Vertical Structure of Turbulent Oscillatory
Boundary Layers Above Fixed Roughness using a Prototype Wide-band Coherent Doppler Profiler: 1. The
Oscillatory Component of the Flow, submitted to J. Geophysical Research Oceans, DOI: 10.1029/2011JC007113.
Dillon, J., L. Zedel, and A.E. Hay, 2012: Simultaneous Velocity Ambiguity Resolution and Noise
Suppression for Multi-Frequency Coherent Doppler Sonar, Journal of Atmospheric and Oceanic
Technology, 29, 450-463.
Dillon, J., L. Zedel, and A.E. Hay, 2011: Asymptotic Properties of an Autocorrelation Coefficient for
Coherent Doppler Sonar. Journal of Atmospheric and Oceanic Technology, 966-973.
Zedel, L., and A.E. Hay, 2010: Multi-Frequency, Pulse-to-pulse
Coherent Doppler Sonar. IEEE
Journal of Oceanic Engineering. DOI: 10.1109/JOE.2010.2066710
Zedel, L. 2008: Modeling Pulse-to-pulse Coherent Doppler Sonar, Journal
of Atmospheric and Oceanic Technology, 25, 1834-1844.
Smyth, C.E., L. Zedel, A.E. Hay, 2002: Coherent Doppler profiler
measurements of near-bed suspended sediment fluxes and the influence
of bedforms. Journal of Geophysical Research, 107, C8, 19.1-19.20.
Zedel, L., and A.E. Hay, 2002:
A Three Component Bistatic Coherent Doppler Velocity Profiler:
Error Sensitivity and System Accuracy. IEEE Journal of Oceanic
Engineering, 27, 717-725.
Zedel, L., A.E. Hay, 1998: Direct Observations of Wave Induced Sediment
Flux and Turbulent Velocities in a Wave Flume. to be presented at
ICCE in Copenhagen.
Zedel, L., A.E. Hay, R. Cabrera, and A. Lohrmann, 1996:
Performance of a Single Beam, Pulse-to-Pulse Coherent Doppler Profiler.
IEEE Journal of Oceanic Technology, 21, 290-297.
Zedel, L., A.E. Hay, 1996: Acoustic Doppler Velocity Observations
in a Turbulent Particle Laden Jet. submitted to Journal of the
Acoustical Society of America.
Zedel, L., A.E. Hay, 1995: Coherent Acoustic Profiling of Sediment
Suspension Under Waves. in Proceedings
of the 1995 Canadian Coastal Conference - October 18-21, Dartmouth.
This figures provides an example of Dopbeam data collected during trials in
the NRC prototype scale wave flume facility.
7 s of Dopbeam data are shown collected during
a run of 50 cm height waves of 3.5 s period. a) horizontal velocity,
b) vertical velocity, c) suspended sediment concentration. Height is
indicated on the vertical axis in cm, colour scale values are indicated
in panels on right.
Other Recent Contributions
Razaz, M., L. Zedel, A. Hay, 2019: SwathDopp: Multibeam Pulse-Coherent Doppler Sonar for Scanning 2-D Velocity Section near the Sediment-Water Interface. J. Atmos. and Oceanic Tech. in press
Zedel, L., Y. Wang, F. Davidson, J. Xu, 2017: Comparing ADCP data collected during seismic survey off the
coast of Newfoundland with analysis data from the CONCEPTS operational ocean model.
J. Operational Oceanography. DOI 10.1080/1755876X.2018.1465337
Hay, A.E., L. Zedel, S. Nylund, R. Craig, J. Culina, 2015: The Vectron: A pulse-coherent Doppler system for remote turbulence resolving velocity measurements. Proceedings of the IEEE/OES Eleventh Current Waves and Turbulence Measurements Workshop, March 2015, St. Petersburg Florida.
Alsarayreh and Zedel, L., 2011: Quantifying Snowfall Rates using Underwater Sound. Atmosphere-Ocean., 49:2, 61-66.
OASIS: Ocean Ambient Sound System
The OASIS system measures wind speed and direction from an acoustic instrument
package positioned several hundred meters beneath the ocean surface.
When waves brake at the ocean surface they generate sound just as
breaking waves make sound in the air. It has been established that the
sound level is proportional to wind speed and these sound levels have been used
to estimate wind speed. Knowledge of wind speed is of course of interest but
of equal importance is knowledge of wind direction. Wind direction can
be inferred from beneath the ocean surface by considering the behaviour of
near surface drift currents. These currents are normally difficult to measure
because of complications associated with surface waves. It is however
possible to
measure these currents remotely using Doppler sonar technique.
Zedel, L., 2001: Using ADCP Background Sound Levels to Estimate
Wind Speed. Journal of Atmospheric and Oceanic Technology, 18, 1867-1881.
Zedel, L., L. Gordon, S. Osterhus, 1999: Ocean ambient sound instrument
system: Acoustic Esimtation of Wind Speed and Directionfrom a
Sub-Surface Package. submitted to, Journal of Oceanic and Atmospheric
Technology.
Zedel, L., G. Crawford, L. Gordon, 1996: On the determination of
wind direction using an upward looking ADCP.
Journal of Geophysical Research, 101, C5, 12163-12176.
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Scatter plots between observed wind
speeds and OASIS wind speed estimates
using ambient sound at a) 2 kHz, b) 4 kHz, c)
8 kHz, and d) 16 kHz: the standard deviation (wind speed - oasis speed) for
these estimates are 1.5, 1.4, 1.4, and 1.9 m/s respectively.
Data are hourly samples from the OWS Mike in the Norwegian Sea
starting May 17, 1996 and lasting for 40 days.
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This figure compares anemometer wind direction measurements with estimates
made using the OASIS system. Near surface current structure is used to
estimate wind direction. Data points represent 12 hour averages and
are for the 80 day period starting
April 16, 1997.
Data were collected in the North Atlantic Ocean (close
to Ocean Weather Station Mike).
A big old ASCII data file
Last Updated on January, 2019 by Len Zedel.
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