Search Results
correction for the effects of mooring motion using the method of Cronin and Watts (1996) . We applied a 3-day low-pass filter to the daily current and temperature time series, to match the treatment of cDrake data (see above). Current outliers with either component larger than 1 m s −1 were removed and replaced by linear interpolation before 3-day low-pass filtering. Because both rotor and acoustic velocity measurements may be affected by excessive instrument tilts, we excised velocity measurements at
correction for the effects of mooring motion using the method of Cronin and Watts (1996) . We applied a 3-day low-pass filter to the daily current and temperature time series, to match the treatment of cDrake data (see above). Current outliers with either component larger than 1 m s −1 were removed and replaced by linear interpolation before 3-day low-pass filtering. Because both rotor and acoustic velocity measurements may be affected by excessive instrument tilts, we excised velocity measurements at
deployment in 2007. Since an integral component of any velocity measurement is the determination of the instrument orientation using its compass, the compass deviation due to the iron in the vicinity has a direct effect on the velocity measurements. There are likely many mooring setups in which this introduces small errors in the velocity measurements, but there are also several mooring setups where the resulting errors are large. Fig . 1. The mooring setup discussed in this paper prior to deployment at
deployment in 2007. Since an integral component of any velocity measurement is the determination of the instrument orientation using its compass, the compass deviation due to the iron in the vicinity has a direct effect on the velocity measurements. There are likely many mooring setups in which this introduces small errors in the velocity measurements, but there are also several mooring setups where the resulting errors are large. Fig . 1. The mooring setup discussed in this paper prior to deployment at
perhaps surprising that the potential flow corrections are successful, given that surface roughness is ignored. However, the terrain errors are zero at the surface because the sampling volumes are not separated there, so surface effects do not contribute strongly. REFERENCES Behrens, P. , O’Sullivan J. , Archer R. , and Bradley S. , 2012 : Underestimation of mono-static sodar measurements in complex terrain . Bound.-Layer Meteor. , 143 , 97 – 106 . Bingol, F. , Mann J. , and Foussekis
perhaps surprising that the potential flow corrections are successful, given that surface roughness is ignored. However, the terrain errors are zero at the surface because the sampling volumes are not separated there, so surface effects do not contribute strongly. REFERENCES Behrens, P. , O’Sullivan J. , Archer R. , and Bradley S. , 2012 : Underestimation of mono-static sodar measurements in complex terrain . Bound.-Layer Meteor. , 143 , 97 – 106 . Bingol, F. , Mann J. , and Foussekis
temporal behavior of the SBI layer, Wi-BLEx observational data from a winter period of collocated radiosonde–acoustic sounding observations at the NWS PAFA station are provided. The high-resolution profiling of the ABL structure is displayed in this section to illustrate the fact that low-level inversions are effectively present at the levels at which the radiosonde retrieves them, consistently throughout the entire measurement period. In this case the selected period was 11–13 January 2010. The flow
temporal behavior of the SBI layer, Wi-BLEx observational data from a winter period of collocated radiosonde–acoustic sounding observations at the NWS PAFA station are provided. The high-resolution profiling of the ABL structure is displayed in this section to illustrate the fact that low-level inversions are effectively present at the levels at which the radiosonde retrieves them, consistently throughout the entire measurement period. In this case the selected period was 11–13 January 2010. The flow
, and (b) deep water whitecaps on Lake Washington in Seattle, Washington. For each field deployment, the methods are compared between “bursts” with weak wave breaking and with strong wave breaking, as quantified by a breaking rate from surface video data. For the Lake Washington tests, an independent measurement of the wave-breaking turbulent dissipation rate at one point in the vertical profile is obtained using an acoustic Doppler velocimeter (ADV) on board the SWIFT. In section 4 , all bursts
, and (b) deep water whitecaps on Lake Washington in Seattle, Washington. For each field deployment, the methods are compared between “bursts” with weak wave breaking and with strong wave breaking, as quantified by a breaking rate from surface video data. For the Lake Washington tests, an independent measurement of the wave-breaking turbulent dissipation rate at one point in the vertical profile is obtained using an acoustic Doppler velocimeter (ADV) on board the SWIFT. In section 4 , all bursts
( McClatchie et al. 2000 ). Because the frequency response of acoustic scattering from animals is affected by a combination of their size and material properties, the combination of multiple, discrete acoustic frequencies can aid interpretation ( Holliday 1977 ). However, propagation losses increase with increasing frequencies, limiting the effective range of multifrequency acoustic techniques to the range of the highest frequency utilized. In addition to increasing signal loss with range, the effects of
( McClatchie et al. 2000 ). Because the frequency response of acoustic scattering from animals is affected by a combination of their size and material properties, the combination of multiple, discrete acoustic frequencies can aid interpretation ( Holliday 1977 ). However, propagation losses increase with increasing frequencies, limiting the effective range of multifrequency acoustic techniques to the range of the highest frequency utilized. In addition to increasing signal loss with range, the effects of
Automatic Classification of Biological Targets in a Tidal Channel Using a Multibeam Sonar2-week period and targets were automatically tracked in postprocessing using a nearest-neighbor algorithm. These target tracks were parameterized by morphometric measurements (e.g., size, intensity) and behavior (e.g., velocity, direction of travel) to aid in manual classification. Similarly, in Jepp (2017) , targets were detected and tracked using a nearest-neighbors approach, then classified based on manually tuned target size thresholds. In addition, targets moving with a constant velocity
2-week period and targets were automatically tracked in postprocessing using a nearest-neighbor algorithm. These target tracks were parameterized by morphometric measurements (e.g., size, intensity) and behavior (e.g., velocity, direction of travel) to aid in manual classification. Similarly, in Jepp (2017) , targets were detected and tracked using a nearest-neighbors approach, then classified based on manually tuned target size thresholds. In addition, targets moving with a constant velocity
A Comparative Study of Moored/Point and Acoustic Tomography/Integral Observations of Sound Speed in Fram Strait Using Objective Mapping Techniquesthrough data assimilation. The high noise of the observations overwhelms the signals of interest to the ocean modelers and introduces the effects of aliasing. Other observing approaches, such as glider or conductivity–temperature–depth (CTD) sections, have obvious, different sets of complications or deficiencies. It is clear that no one type of measurement offers a comprehensive solution to the observation problem in Fram Strait. Fig . 1. (top) Observational deployments within Fram Strait. The 2008
through data assimilation. The high noise of the observations overwhelms the signals of interest to the ocean modelers and introduces the effects of aliasing. Other observing approaches, such as glider or conductivity–temperature–depth (CTD) sections, have obvious, different sets of complications or deficiencies. It is clear that no one type of measurement offers a comprehensive solution to the observation problem in Fram Strait. Fig . 1. (top) Observational deployments within Fram Strait. The 2008
came to light that the contribution of gravity acting on the “new modes” is quite small, comparable perhaps to the neglected effects of sound-speed variations or nonlinearity. It therefore seems advantageous to consider them as very slightly modified acoustic modes, which can be treated much more quickly, and for which other known effects can be included that may be more important in long-distance propagation (e.g., refraction, nonlinearity, scattering, and subbottom propagation or penetration
came to light that the contribution of gravity acting on the “new modes” is quite small, comparable perhaps to the neglected effects of sound-speed variations or nonlinearity. It therefore seems advantageous to consider them as very slightly modified acoustic modes, which can be treated much more quickly, and for which other known effects can be included that may be more important in long-distance propagation (e.g., refraction, nonlinearity, scattering, and subbottom propagation or penetration
additional site-9 instrumentation was provided by the U.S. Army Research Office under DURIP Grant W911NF-10-1-0238, and we are grateful to Dr. Walter Bach for his interest and support. Glenn Hunter of PSU assisted with WRF data processing; Dr. Kenneth Underwood and Mr. Josh Underwood at Atmospheric Systems Corporation provided sodar installation services, maintenance assistance, and knowledge of sodar operating principles; and Dr. Dennis Thomson lent helpful insight on acoustic measurements of the
additional site-9 instrumentation was provided by the U.S. Army Research Office under DURIP Grant W911NF-10-1-0238, and we are grateful to Dr. Walter Bach for his interest and support. Glenn Hunter of PSU assisted with WRF data processing; Dr. Kenneth Underwood and Mr. Josh Underwood at Atmospheric Systems Corporation provided sodar installation services, maintenance assistance, and knowledge of sodar operating principles; and Dr. Dennis Thomson lent helpful insight on acoustic measurements of the
