Search Results

You are looking at 81 - 90 of 2,704 items for :

  • Acoustic measurements/effects x
  • All content x
Clear All
Wayne M. Angevine and W. L. Ecklund

radio acoustic sounding systems forthe measurement of temperature has been substantially improved. The temperature accuracy can now be affectedby a number of factors that have been considered negligible in previous work. This paper describes two typesof errors, those due to atmospheric effects and those due to approximations in the temperature retrieval equation.The errors are examined in a set of convective boundary layer RASS and radiosonde data. In the category ofatmospheric effects, two errors

Full access
Arlin B. Super, Jack T. McPartland, and James A. Heimbach Jr.

)ABSTRACT A field method of estimating the persistence of a commonly used silver iodide seeding agent is described.The method involved measurement of the AgI plume structure at two downwind distances from the groundgenerator(s). Distances between the nine available pairs of downwind measurement planes ranged fromapproximately I0 to 100 kin. An NCAR acoustical ice nucleus counter in a light twin aircraft was used tosample the AgI plumes. A series of passes was made through the entire vertical and

Full access
T. K. Chereskin and A. J. Harding

FEBRUARY 1993 CHERESKIN AND HARDING 41Modeling the Performance of an Acoustic Doppler Current Profiler T. K. CHERESKIN AND A. J. HARDING Scripps Institution of Oceanography, La Jo[[a, California (Manuscript received 13 January 1992, in final form 15 July 1992)ABSTRACT A systematic examination of measurement error in acoustic

Full access
R. F. Marsden and R. G. Ingram

1. Introduction The acoustic Doppler current profiler (ADCP) has taken an increasingly important role in the measurement of both first-order (mean) and second-order (eddy correlation) current statistics. First-order statistics have been used to identify both larger-scale barotropic and baroclinic tidal ( Foreman and Freeland 1991 ; Marsden and Greenwood 1994 ) and mean flows. At second order, van Haren et al. (1994) and Stacey et al. (1999) have estimated vertical profiles of eddy

Full access
H. Melling and Roland List

mow, of those from atmospheric thermal turbulenceand of the acoustic noise background. On the basis of the demonstrated statistical behavior of echo sounder signals, a procedure is describedfor the estimation from digitized data of this kind of mean-scattering cro~s sections and mean velocitiesof turbulent air parcels, and for the suppression of the effects of background noise.1. Introduction The frequency of sound waves scattered from atmospheric turbulence is changed by an amount relatedto

Full access
David Shonting and Foster Middleton

the sound observations. Most noise records have lacked such proximate environmental measurements.Furthermore, most ambient noise has been recorded at depths of 250-4000 m and the data were low-passfiltered, both effects minimizing the acoustic response from small-scale and (or) short-term surface phenomena. Near-surface observations of ambient sound associated with rapidly changing wind and rainfall events weremade using the Self Contained Ambient Noise Recorder (SCANR) system which provides

Full access
Eirwen Williams and John H. Simpson

quality measurements of turbulent dissipation (e.g., Dewey et al. 1987 ; Simpson et al. 1996 ). The method is, however, very labor intensive and therefore limited to short observational periods. A recent alternative development in turbulence studies is a method of determining the Reynolds stresses ( − u ′ w ′ , etc.) using a high-frequency acoustic Doppler current profiler (ADCP). This approach enables us to obtain much longer time series of turbulent parameters without the labor and ship time costs

Full access
William E. Johns

602 JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY VOLUME5Near-Surface Current Measurements in the Guff Stream Using an Upward-Looking Acoustic Doppler Current Profiler WILLIAM E. JOHNSRosenstiel School of Marine and.4tmospheric Science, Division of Meteorology & Physical Oceanography, University of Miami, Miami, Florida (Manuscript received 3 July

Full access
E. R. Westwater, Y. Han, V. G. Irisov, V. Leuskiy, E. N. Kadygrov, and S. A. Viazankin

appreciable amount of acoustic attenuation that limits its upper-altitude coverage. For the system deployed by ETL during this experiment, the relative frequency of data availability is given in Table 4 . Relative sample sizes were roughly cut in half for each consecutive range gate above 495 m. 4. Concluding remarks Scanning radiometers at 5-mm wavelengths, both of ATTEX and of ETL, gave excellent comparisons with in situ temperature measurements during winter conditions at the BAO 300-m tower; several

Full access
Stephen D. Pierce, John A. Barth, and Robert L. Smith

1. Introduction When bottom tracking is not available, accurate ship velocities from navigation are vital for referencing acoustic Doppler current profiler (ADCP) measurements to earth coordinates. The global positioning system (GPS) continues to be of great assistance in this regard to the shipboard ADCP user. The presence of selective availability (SA) degrades the accuracy of a conventional GPS receiver to about ±50 m root-mean-square (rms) ( Hofmann-Wellenhof et al. 1997 ). The P

Full access