Showing papers on "Atmospheric wave published in 1978"
TL;DR: In this article, Hasselmann's equation was studied numerically for a Pierson-Moskowitz spectrum and it was shown that the apparent creation of order, due to the non-linear enhancement of the peak of the spectrum, occurs as the by-product of a large amount of disorder, created at high wavenumbers.
155 citations
TL;DR: In this article, a description and interpretation of two unusual types of isolated atmospheric gravity wave observed near Tennant Creek in central Australia is presented. Butler et al. made the conclusion that the majority of the observed isolated waves of elevation belong to the class of deep-fluid internal solitary waves considered by Benjamin and by Davis and Acrivos.
Abstract: This paper is concerned with a description and interpretation of two unusual types of isolated atmospheric gravity wave observed near Tennant Creek in central Australia. These waves occur in the form of solitary waves of elevation and solitary waves of depression. Comparison of experimental data with theory leads to the conclusion that the majority of the observed isolated waves of elevation belong to the class of deep-fluid internal solitary waves considered by Benjamin and by Davis and Acrivos. The second fundamentally different type of large-amplitude isolated wave is tentatively identified as a classical solitary wave of depression.A brief discussion is given of a number of possible source mechanisms which may give rise to internal solitary atmospheric waves. It is proposed that the following two dynamical processes play an important role in the creation of solitary atmospheric waves in the arid interior of Australia: 1) the interaction of nocturnal katabatic density currents with an existing...
95 citations
TL;DR: In this paper, the mean sound levels resulting from the interference between direct waves and those reflected from the ground are strongly influenced, especially at frequencies near interference minima, by fluctuations in phase and amplitude of the sound waves induced by propagation through atmospheric turbulence.
Abstract: The mean sound levels resulting from the interference between direct waves and those reflected from the ground are strongly influenced, especially at frequencies near interference minima, by fluctuations in phase and amplitude of the sound waves induced by propagation through atmospheric turbulence. Since it was found experimentally that the correlation length (∠1.1 m) of the meteorological fluctuations is comparable to the separation between the interfering sound paths, previous theoretical work by Ingard and Maling [J. Acoust. Soc. Am. 35, 1056–1058 (1963)] has been extended to allow for partial covariance between the two waves. The theory has been further extended to use the calculations of fluctuations in phase and amplitude of spherical waves, and to include the explicit calculation of the fluctuating acoustical index of refraction from the fluctuating values of temperature and wind velocity. Measurements (1–6 kHz) have been made of the interference spectrum at 15, 30, and 45 m from a point source 1....
69 citations
TL;DR: In this article, the authors applied the analytical and numerical methodology of Boyd (1978) to observed atmospheric waves and found that the structure and vertical wavelength of the stratospheric Kelvin wave of 15-day period and the tropospheric tropical wave of 40-50 day period are both negligibly affected by even the strongest shear.
Abstract: The analytical and numerical methodology of Boyd (1978) is applied to observed atmospheric waves. It is found that the structure and vertical wavelength of the stratospheric Kelvin wave of 15-day period and the tropospheric Kelvin wave of 40–50 day period are both negligibly affected by even the strongest shear. In contrast, the shear of the quasi-biennial oscillation can decrease the wavelength of the stratospheric n=0 mixed Rossby-gravity wave of 5-day period by 60% and produce changes of 50–100% in wave fluxes and velocities. The structure of synoptic-scale easterly waves (n=1 Rossby waves of 5-day period) is not drastically altered by shear, but the wavelength is tripled. This makes it unlikely that one can construct a quantitative wave-CISK theory of this mode without including latitudinal shear.
51 citations
TL;DR: In this paper, the role of gravity waves in the troposphere is briefly discussed and reviewed, and the physical processes involved in the interaction of gravity wave with mesoscale and planetary boundary layer phenomena are discussed.
Abstract: The nature and the role of gravity waves in the troposphere is briefly discussed and reviewed. After describing some basic properties of gravity waves and their generation mechanisms, we analyze their ability to influence phase changes, trigger and organize convective cells, to produce and interact with turbulence, and to affect diffusive processes in the atmosphere. Throughout, the emphasis is placed on the physical processes involved in the interaction of gravity waves with mesoscale and planetary boundary layer phenomena. Also discussed and reviewed are those remote sensing devices which are particularly useful in revealing and measuring such waves. Finally, an attempt is made to outline possible lines of future work for the purpose of fully understanding the role of gravity waves in mesoscale and microscale dynamics.
49 citations
TL;DR: The dominant response of the terminator is due to the change in thermospheric absorption of solar radiation, and leads to two types of atmospheric waves: (i) a ducted acoustic wave at altitudes below 100 km and (ii) a boundary wave concentrated along the mesopause as mentioned in this paper.
36 citations
TL;DR: In this article, the authors present further evidence that strengthens the case for their interpretation of many features in the Jovian atmosphere as solitary Rossby waves (solitons) and further interpretation of the interaction between observed features, and comparison with calculations of interaction between planetary solitons of a restricted class.
30 citations
TL;DR: In this paper, four microbarographs were used in an attempt to detect atmospheric pressure oscillations that were expected to accompany bow waves associated with the total solar eclipse of 23 October 1976, and these internal gravity waves were found to have a peak-to-peak amplitude of 0.1 to 0.2 Pa, a period of 23 min and a velocity of 3.1×102 ms−1.
Abstract: DURING a solar eclipse, the Moon's cool shadow, moving with supersonic speed through the Earth's atmosphere, should generate bow waves. In the experiments described here four microbarographs were used in an attempt to detect atmospheric pressure oscillations that were expected to accompany bow waves associated with the total solar eclipse of 23 October 1976. These internal gravity waves were found to have a peak-to-peak amplitude of 0.1 to 0.2 Pa, a period of 23 min and a velocity of 3.1×102 ms−1.
26 citations
TL;DR: In this paper, it was shown that many of the waves seem to be generated by shear instability of the upper troposphere winds and that the pressure amplitudes of gravity waves are greatly increased by the presence of large static stability in the lower troposphere.
Abstract: Atmospheric gravity wave records at Palisades, N.Y., during the two-mouth period November–December 1969 an investigated in the light of concurrent weather patterns and atmospheric soundings. Although it seems to be a characteristic of atmospheric gravity waves that no one mechanism affords a complete explanation for their behavior, it is shown that many of the waves seem to be generated by shear instability of the upper troposphere winds and that the pressure amplitudes of the waves are greatly increased by the presence of large static stability in the lower troposphere. A simple three-layer model is able to simulate these features. The synoptic applications of these observations are then investigated and it is shown that times of large-amplitude gravity waves often precede the onset of cyclonic precipitation by some 12–24 h while times of small-amplitude gravity waves usually indicate continuation of fair weather.
24 citations
TL;DR: In this paper, the effects of topography, midlatitude disturbances and condensational heat are eliminated one by one from a GFDL general circulation model during the period June and July.
Abstract: In order to study the generation of transient planetary waves in the tropics, the effects of topography, midlatitude disturbances and condensational heat are eliminated one by one from a GFDL general circulation model during the period June and July. The time development and three-dimensional propagation of waves are examined by a space-time spectral analysis using the maximum entropy method. It is found that the characteristic scale and period of Kelvin and mixed Rossby-gravity waves do not depend on land-sea contrast or the zonal variation of sea surface temperature. Even if midlatitude disturbances are eliminated, both these waves appear in the stratosphere due to the effect of latent heat release in the troposphere. In contrast to Kelvin waves, however, mixed Rossby-gravity waves can be significantly intensified by westward moving midiatitude disturbances which are found to propagate intermittently toward the equator.
21 citations
TL;DR: In this paper, the phase and amplitude relationship between the density fluctuations of individual atmospheric constituents were found to be consistent with AE-C satellite observations of wavelike structure only over a narrow range of wave periods.
Abstract: When wave-induced diffusion is included in the equations governing acoustic-gravity wave propagation in an atmosphere in diffusive equilibrium, it is found that phase and amplitude relationships between the density fluctuations of individual atmospheric constituents agree with AE-C satellite observations of wavelike structure only over a narrow range of wave periods. For a 400-km horizotal wavelength, the observations are consistent with internal gravity waves of periods 11.5-22 minutes propagating at phase speeds 300-600 m/sec.
TL;DR: In this article, the authors analyzed the growth and decay of the atmospheric wave motions in middle latitudes, and computed the composite average of each term in the kinetic energy equation at various stages in the life cycle of atmospheric waves.
Abstract: To study the growth and decay of the atmospheric wave motions in middle latitudes, we have analyzed the mechanism for the kinetic energy change in wavenumber domain, and computed the composite average of each term in the kinetic energy equation at various stages in the life cycle of the atmospheric waves. It is found that for the first 1 to 2 days the extra-long waves of wavenumbers 1 and 3 grow by receiving kinetic energy from other finite amplitude waves through nonlinear interactions; in the next 1 to 2 days, they grow by gaining energy through nonlinear interactions and converting available potential to kinetic energy. These waves then maintained their peak energy for 3 to 4 days through the balance between the energy supply from conversion of available potential energy to kinetic energy and nonlinear interactions, and the energy lost by dissipation. The contribution of nonlinear interactions then changes to negative; and in the next 3 to 4 days, the waves decay by losing energy through nonlinear interactions and dissipation. The average life cycle of these extra-long waves is about 10 to 11 days. Similar results have been found with regard to the synoptic-scale waves of wavenumbers 4 to 8. They also intensify by receiving energy and decay by losing energy through nonlinear interactions among finite amplitude waves. Nevertheless, the conversion of the available potential energy to kinetic energy plays a more important role in the growing stage of the synoptic-scale waves than for the extra-long waves. The average life cycle for the synoptic-scale waves is about 6 to 8 days. It is interesting to note that the characteristics of waves of wavenumber 2 are quite different from those of the other waves. In all stages of its life cycle, the contribution of nonlinear interactions is negative and the conversion term always has large positive values. We have also analyzed the intensification and decay of the subtropical jet stream, and found that it is greatly affected by the convergence and divergence of eddy momentum flux. The fluctuations of the net momentum flux are mainly contributed by the synoptic-scale waves of wavenumbers 4 to 8. DOI: 10.1111/j.2153-3490.1978.tb00814.x
01 Jan 1978
TL;DR: In this paper, the modulation of short wind waves (centimeter to decimeter long) by long gravity waves is investigated under field and laboratory conditions using a wave follower capable of tracking ocean waves with frequencies less than 1.0 Hz and heights less than 2.0 m.
Abstract: The modulation of short wind waves (centimeter to decimeter long) by long gravity waves is investigated under field and laboratory conditions. The field study employed a wave follower capable of tracking ocean waves with frequencies less than 1.0 Hz and heights less than 2.0 m. A high response laser-optical system was used to detect upwind-downwind and cross-wind slopes of short waves. Cross correlations of short wave slopes with long waves reveal the presence of definite coupling between the two. A well defined peak appears in the cross-correlation function at 45° downwind of the long wave crest, suggesting higher density waves there.
TL;DR: In this article, the temperature profile has been retrieved from measurements of the average brightness at different elevation angles and measurements of both the variance and the low-frequency spectrum of the radiometer output signal have been performed to obtain information on the intensity, scale length and spectra of temperature fluctuations.
Abstract: Measurement of atmospheric brightness at different wavelengths in the infrared can give information about several parameters which characterize the vertical structure of the lower troposphere. In this paper some of the results obtained from a six-month experiment carried out in 1975 are reported. The temperature profile has been retrieved from measurements of the average brightness at different elevation angles. In addition, measurements of both the variance and the low-frequency spectrum of the radiometer output signal have been performed to obtain information on the intensity, scale length and spectra of temperature fluctuations. Particularly under stable tropospheric conditions, sharp periodicity of the radiometer signal has occasionally been observed, suggesting the occurrence of a periodic variation of the atmospheric parameters such as that associated with atmospheric waves. The data which have been collected appear to confirm the capability of ground-based radiometry for the accurate and timely monitoring of the static and dynamic state of the lower troposphere.
TL;DR: In this article, the authors studied the growth and decay of the eddy available potential energy associated with the large-scale atmospheric waves and computed composite averages of the terms in the wave-number domain.
Abstract: To study the growth and decay of eddy available potential energy associated with the large-scale atmospheric waves, we have computed composite averages of the terms in the available potential energy equation in the wave-number domain. We found that the eddy available potential energies of the ultra-long waves of wave numbers 1 and 3 grow essentially by receiving energy through the resultant meridional and vertical eddy heat transport process; whereas during the period of decay, the energy loss is essentially through the non-linear heat transport process. We also found that the eddy available potential energies of the synoptic-scale waves of wave numbers 4 to 8 increase by receiving energy and decay by losing energy through both the non-linear and the resultant meridional and vertical eddy heat transport processes. However, the main source of eddy available potential energy for wave number 2 is the contribution of diabatic processes, although diabatic processes contribute to the maintenance of the seasonal mean but not to the growth and decay of the eddy available potential energy of wave number 2. Its time change is also determined by the eddy heat transport processes. It is also found that the amplitude oscillations of eddy available potential energy are generally in-phase with those of eddy kinetic energy in the same wave number. However, the growth of the former usually occurs slightly behind that of the latter. The growth of eddy available potential energy may be interpreted as an indirect consequence of the growth of the eddy kinetic energy of the wave, which enhances the eddy heat transport, thereby increasing the available potential energy of the wave; whereas the growth of the eddy kinetic energy is a result of the receipt of kinetic energy from other waves through barotropic non-linear exchange processes as described by Tsay and Kao (1978). DOI: 10.1111/j.2153-3490.1978.tb00854.x
TL;DR: In this article, the sky brightness oscillations, observed during May 1976 and November 1977, can be associated with atmospheric waves, perhaps on the aerosol boundary layer; this discovery also has a bearing on experiments now investigating solar diameter oscillations.
Abstract: WE report here the discovery of sky brightness oscillations, observed during May 1976 and November 1977, which can be associated with atmospheric waves, perhaps on the aerosol boundary layer; this discovery also has a bearing on experiments now investigating solar diameter oscillations.
Journal Article•
TL;DR: A specially instrumented NASA B-57B Canberra, capable of measuring turbulence velocities, winds and temperatures, flew several data runs on 26 March 1975 at 13 km altitude, east of the Sierra Nevada mountains of California as mentioned in this paper.
Abstract: A specially instrumented NASA B-57B Canberra, capable of measuring turbulence velocities, winds and temperatures, flew several data runs on 26 March 1975 at 13 km altitude, east of the Sierra Nevada mountains of California. An area of light to moderate clear air turbulence extended for 120 km and contained zones of more intense turbulence. One zone, 10–20 km wide, occurred in a warm region centered over Death Valley. Significant variations of meteorological parameters included a wind shift of 13 m s−1 and 40° in 7 km, temperature changes of 3.5–5°C in 0.02 to 0.12 km, and variations in the mean vertical turbulence velocity of 3–4 m s−1 over distances of 15–25 km. The turbulence apparently originated after atmospheric waves had formed along show interfaces where low-velocity stratospheric air descended into a region of strong winds above Death Valley. The waves were amplified and broke down into turbulence when large vertical shear reduced the Richardson number below the critical value.