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David A. Schecter, Melville E. Nicholls, John Persing, Alfred J. Bedard Jr., and Roger A. Pielke Sr.

amplitude of the infrasound (at 5 km) can exceed the estimated 0.25-Pa threshold only if the characteristic velocity of the turbulence ( V ) is greater than about 40 m s −1 , and if the characteristic length scale is less than a few hundred meters. Although much higher velocity flows at smaller scales would produce notable signals, their existence would be extraordinary in any terrestrial storm system. Let us now briefly turn our attention to field measurements. Acoustic radiation from severe

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G. A. Davidson

).REFERENCESCole, J. E., and R.A. Dobbins, 1970: Propagation of sound through atmospheric fog. Y. Atmos. S-i., 27, 426-434. , and , 1971: Measurements of the attenuation of sound by a warm air fog. J. Atmos. S-i., 28, 202-209.Davidson, G. A., and D. S. Scott, 1973: Finite-amplitude acoustics of aerosols. J. A -oust. So~. A mer., 53, 1717-1729.Einaudi, F., and D. P. Latas, 1973: The propagation of acoustic gravity waves in a moist atmosphere. J. Atmos. S-i., 30, 365 376.Marble, F. E., 1969: Some

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John E. Cole III and Richard A. Dobbins

thermal relaxation time for the droplet, ~o the circular acoustic frequency, and C,, the liquidmass fraction), near unity where the effects of mass transfer are dominant. The tests are made in a Wilsoncloud chamber by measuring the rate of decay of the fundamental mode of acoustic oscillation which isexcited during the operation of the chamber. Measurements of pressure and volume are made continuouslyduring the expansion. Droplet size and concentration of the monodisperse fog are determined from

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John T. Merrill

) conditions. Meteorological instruments,including an acoustic echo sounder for time-height visualization, a spaced array of microbarographs and aheavily instrumented tower 150 m tall, provided measurements that were analyzed to determine the phasevelocity and amplitude of the wavelike fluctuations and the mean profiles of temperature and wind forthe shear flow. A linear, inviscid, dynamic stability analysis performed numerically using spline functionsfit through the observed profiles shows that the flow

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C. Gordon Little

.Incidenf plane wave ,IFio. 1. The scattering of a plane acoustic wave by a small sphere. The problem of the acoustical effects of the wakesproduced by precipitating hydrometeors is discussedbriefly.2. The scatter of sound waves by small spherical particles The scatter of sound waves by a spherical particlewhose diameter is small compared with the acousticwavelength was originally discussed by Rayleigh in1872. For the case (see Fig. 1) in which a plane wave ofwavelength X, propagating through a

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A. S. Frisch and S. F. Clifford

stationary and horizontallyscattered Doppler radar signals is a function of themean wind field and, under conditions to be specified,the second moment is a function of the turbulent dissipation rate. Some of these parameters appear in the turbulentkinetic energy equation [-Eq. (1)], and if they areknown we can deduce the relative importance of variousterms in this equation using the acoustic sounder andDoppler radar measurements. The turbulent kineticenergy equation may be written as

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I. Tolstoy and P. Pan

systematic andfairly accurate account of the far-field properties of guided internal and surface gravity waves havingperiods > 10 min. Simple formulae and numerical results are given for a variety of models allowing oneto determine the importance of such effects as compressibility, free vs rigid boundaries, layering, and theearth's rotation. The importance of coupling effects similar to those occurring in layered acoustic andelectromagnetic waveguides is emphasized. It is also shown, in the period

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M. Ference Jr., W. G. Stroud, J. R. Walsh, and A. G. Weisner

in the measurements of thesurface temperatures on the computed temperaturesin the layers shows that 1C error in the surface temperature introduces a 0.02 C error in the computedtemperature.The errors in the computed temperatures in thevarious layers due to the effects of the winds turn outto be the most serious that we have been able toFEBRUARY 1956 M. FERENCE, JR., W. G. STROUD, J. R. WALSH, AND A. G. WEISNER11identify. The acoustic speed within a layer is given by(4). In this expression, the

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T. K. Cheung, C. G. Little, and H. E. Ramm

I NOVEMBER 1990 T.K. CHEUNG, C. G. LITTLE AND H. E. RAMM 2537Thin Acoustic Scattering Layers Observed in the Low Marine Boundary Layer T. K. CHEUNG, C. G. LITTLE AND H. E. RAMMUCAR Scientists at the Atmospheric Directorate, Naval Oceanographic and Atmospheric Research Laboratory, Monterey, California(Manuscript received 12 September 1989, in final form 15 May 1990) ABSTRACT

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Hermann E. Gerber

of Minnesota's electrical particle analyzer (Whitby and Clark, 1965) tosize all the particles and the acoustical ice nucleuscounter (Langer, 1965) to simultaneously count theactive particles. [-The agreement between the presentresults for freezing and Langer's measurements withthe acoustical counter, in which the nucleation by smallAgI particles is now thought to be primarily as a resultof contact between the particles and droplets at thetemperatures discussed above (Langer, 1970; Middleton and

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