Constraints on Wave Drag Parameterization Schemes for Simulating the Quasi-Biennial Oscillation. Part II: Combined Effects of Gravity Waves and Equatorial Planetary Waves.

NASA Astrophysics Data System (ADS)

Campbell, Lucy J.; Shepherd, Theodore G.

2005-12-01

This study examines the effect of combining equatorial planetary wave drag and gravity wave drag in a one-dimensional zonal mean model of the quasi-biennial oscillation (QBO). Several different combinations of planetary wave and gravity wave drag schemes are considered in the investigations, with the aim being to assess which aspects of the different schemes affect the nature of the modeled QBO. Results show that it is possible to generate a realistic-looking QBO with various combinations of drag from the two types of waves, but there are some constraints on the wave input spectra and amplitudes. For example, if the phase speeds of the gravity waves in the input spectrum are large relative to those of the equatorial planetary waves, critical level absorption of the equatorial planetary waves may occur. The resulting mean-wind oscillation, in that case, is driven almost exclusively by the gravity wave drag, with only a small contribution from the planetary waves at low levels. With an appropriate choice of wave input parameters, it is possible to obtain a QBO with a realistic period and to which both types of waves contribute. This is the regime in which the terrestrial QBO appears to reside. There may also be constraints on the initial strength of the wind shear, and these are similar to the constraints that apply when gravity wave drag is used without any planetary wave drag.In recent years, it has been observed that, in order to simulate the QBO accurately, general circulation models require parameterized gravity wave drag, in addition to the drag from resolved planetary-scale waves, and that even if the planetary wave amplitudes are incorrect, the gravity wave drag can be adjusted to compensate. This study provides a basis for knowing that such a compensation is possible.

Observational evidence of planetary wave influences on ozone enhancements over upper troposphere North Africa

NASA Astrophysics Data System (ADS)

Mengistu Tsidu, Gizaw; Ture, Kassahun; Sivakumar, V.

2013-07-01

MOZAIC instrument measured enhanced ozone on two occasions in February, 1996 and 1997 at cruise altitude over North Africa. The cause and source of ozone enhancements over the region are investigated using additional reanalysis data from ERA-Interim. The ERA-Interim reprocessed GOME ozone indicated existence of enhancement as well. Both observational data revealed that the increase in ozone has wider latitudinal coverage extending from North Europe upto North Africa. The geopotential heights and zonal wind from ERA-Interim have indicated existence of planetary-scale flow that allowed meridional airmass exchanges between subtropics and higher latitudes. The presence of troughs-ridge pattern are attributable to large amplitude waves of zonal wavenumber 1-5 propagating eastward in the winter hemisphere westerly current as determined from Hayashi spectra as well as local fractional variance spectra determined from Multitaper Method-Singular Value Decomposition (MTM-SVD) spectral method. MTM-SVD is also used to understand the role of these waves on ozone enhancement and variability during the observation period in a mechanistic approach. A joint analysis of driving field, such as wind and potential vorticity (PV) for which only signals of the dominant zonal wavenumbers of prevailing planetary waves are retained, has revealed strong linkage between wave activity and ozone enhancement over the region at a temporal cycle of 5.8 days. One of these features is the displacement of the polar vortex southward during the enhancements, allowing strong airmass, energy and momentum exchanges. Evidence of cutoff laws that are formed within the deep trough, characteristics of Rossby wave breaking, is also seen in the ozone horizontal distribution at different pressure levels during the events. The reconstruction of signals with the cycle of 5.8 days has shown that the time and strength of enhancement depend on the circulation patterns dictated by planetary-scale flow relative to the location of observation. The positive PV anomalies upstream or at the observation region bring ozone rich airmass to the region while a negative PV anomaly upstream does the opposite. The position of the anomalies with time changes in accordance with the period of the waves involved. The snap shot of coherent variation of PV and ozone at different time during half cycle of the 5.8-day period has indicated that a region could experience positive (enhancement) or negative (depletion) ozone anomalies of different degree as the wave propagates eastward.

The transport of nitric oxide in the upper atmosphere by planetary waves and the zonal mean circulation

NASA Technical Reports Server (NTRS)

Jones, G. A.; Avery, S. K.

1982-01-01

A time-dependent numerical model was developed and used to study the interaction between planetary waves, the zonal mean circulation, and the trace constituent nitric oxide in the region between 55 km and 120 km. The factors which contribute to the structure of the nitric oxide distribution were examined, and the sensitivity of the distribution to changes in planetary wave amplitude was investigated. Wave-induced changes in the mean nitric oxide concentration were examined as a possible mechanism for the observed winter anomaly. Results indicate that vertically-propagating planetary waves induce a wave-like structure in the nitric oxide distribution and that at certain levels, transports of nitric oxide by planetary waves could significantly affect the mean nitric oxide distribution. The magnitude and direction of these transports at a given level was found to depend not only on the amplitude of the planetary wave, but also on the loss rate of nitric oxide at that level.

Effects of eddy initial conditions on nonlinear forcing of planetary scale waves by amplifying baroclinic eddies

NASA Technical Reports Server (NTRS)

Young, Richard E.

1986-01-01

The previous study of Young and Villere concerning growth of planetary scale waves forced by wave-wave interactions of amplifying intermediate scale baroclinic eddies is extended to investigate effects of different eddy initial conditions. A global, spectral, primitive equation model is used for the calculations. For every set of eddy initial conditions considered, growth rates of planetary modes are considerably greater than growth rates computed from linear instability theory for a fixed zonally independent basic state. However, values of growth rates ranged over a factor of 3 depending on the particular set of eddy initial conditions used. Nonlinear forcing of planetary modes via wave-wave coupling becomes more important than baroclinic growth on the basic state at small values of the intermediate-scale modal amplitudes. The relative importance of direct transfer of kinetic energy from intermediate scales of motion to a planetary mode, compared to baroclinic conversion of available potential energy to kinetic energy within that planetary mode, depends on the individual case. In all cases, however, the transfer of either kinetic or available potential energy to the planetary modes was accomplished principally by wave-wave transfer from intermediate scale eddies, rather than from the zonally averaged state. The zonal wavenumber 2 planetary mode was prominent in all solutions, even in those for which eddy initial conditions were such that a different planetary mode was selectively forced at the start. General characteristics of the structural evolution of the planetary wave components of total heat and momentum flux, and modal structures themselves, were relatively insensitive to variations in eddy initial conditions, even though quantitative details varied from case to case.

Wave Driven Non-Linear Flow Oscillator for the 22-Year Solar Cycle

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Wolff, C. L.; Hartle, R. E.; Einaudi, Franco (Technical Monitor)

2000-01-01

We propose that waves generate an oscillation in the Sun to account for the 22-year magnetic cycle. The mechanism we envision is analogous to that driving the Quasi Biennial Oscillation (QBO) observed in the terrestrial atmosphere, which is well understood in principal. Planetary waves and gravity waves deposit momentum in the background atmosphere and accelerate the flow under viscous dissipation. Analysis shows that such a momentum source represents a non-linearity of third or generally odd order, which generates also the fundamental frequency/period so that an oscillation is maintained without external time dependent forcing. For the Sun, we propose that the wave driven oscillation would occur just below the convection region, where the buoyancy frequency or convective stability becomes small to favor wave breaking and wave mean flow interaction. Using scale analysis to extrapolate from terrestrial to solar conditions, we present results from a simplified analytical model, applied to the equator, that incorporates Hines'Doppler Spread Parameterization for gravity waves (GW). Based on a parametric study, we conclude: (1) Depending on the adopted horizontal wavelengths of GW's, wave amplitudes < 10 m/s can be made to produce oscillating zonal winds of about 25 m/s that should be large enough to generate a corresponding oscillation in the main poloidal magnetic field; (2) The oscillation period can be made to be 22 years provided the buoyancy frequency (stability) is sufficiently small, which would place the oscillating wind field near the base of the convection region; (3) In this region, the turbulence associated with wave processes would be enhanced by low stability, and this also helps to produce the desired oscillation period and generate the dynamo currents that would produce the reversing magnetic field. We suggest that the above mechanism may also drive other long-period metronomes in planetary and stellar interiors.

Laboratory study of dense planetary interiors and giant impacts using laser-driven shock waves

NASA Astrophysics Data System (ADS)

Hicks, Damien

2005-10-01

The behavior of matter at Megabar pressures, a few times solid density, and eV temperatures presents a fundamental challenge, one that is critical to our understanding of dense planetary interiors, planetary evolution models, and giant impacts. Under these conditions bulk matter is strongly coupled, with temperatures approaching the Fermi energy and electron wavelengths comparable to the interatomic spacing - a quantum-classical ``transition'' regime not amenable to many of the traditional theoretical approaches used in condensed matter or plasma physics. The laser-driven shock wave has matured into a powerful tool for accessing and probing these conditions with several new techniques having been developed recently. Measurements of the equation-of-state and transport properties of important planetary materials including silica ( SiO2 ) and hydrogen have been performed. In particular, silica - the major constituent of terrestrial planets - has been shown to undergo an insulator-to-conductor transition above melting at conditions similar to those in giant impacts (such as the one believed to have created the Moon) and at the earth's core-mantle boundary. This continuous transformation, occurring at pressures between 1 to ˜4 Mbar, is accompanied by an anomalously high specific heat that returns to the Dulong-Petit value at completion of the transformation. This is suggestive of a ``bond-breaking'' process in the condensed system - analogous to dissociation in a gas - as the fluid transforms from liquid to dense plasma. Work performed in collaboration with T. R. Boehly, P. M. Celliers, J. H. Eggert, J. E. Miller, D. D. Meyerhofer, and G. W. Collins under the auspices of the US DOE by LLNL under Contract No. W-7405-ENG-48 and by the U. Rochester under Cooperative Agreement No. DE-FC03-92SF19460.

The planetary waves dynamics and interannual course of meteorological parameters of the high latitude stratosphere and mesosphere of the Northern and Southern Hemispheres during the 20th and 21st solar cycles and different phases of QBO

NASA Technical Reports Server (NTRS)

Kidiyarova, V. G.; Fomina, N. N.

1989-01-01

The part of energy of the planetary waves which enters the stratosphere depends on conditions of planetary wave generation and propagation through the tropopause, and the part of planetary wave energy which enters the mesosphere depends on conditions of planetary wave propagation through the stratopause. An attempt is made to estimate connections between extratropical middle atmosphere temperature long term variations and portions of energy of planetary waves which enter the mesosphere and stratosphere during winter seasons in Northern and Southern Hemispheres. Interannual variations of temperatures at the 30 km and 70 km levels are investigated for the central winter months of the period 1970 to 1986. This period includes the descending branch of the 20th solar cycle and the whole 21st cycle. Calculations are made on the basis of measurements at Heiss Island and Molodezhnaya.

Role of quasiresonant planetary wave dynamics in recent boreal spring-to-autumn extreme events

PubMed Central

Petoukhov, Vladimir; Petri, Stefan; Rahmstorf, Stefan; Coumou, Dim; Kornhuber, Kai; Schellnhuber, Hans Joachim

2016-01-01

In boreal spring-to-autumn (May-to-September) 2012 and 2013, the Northern Hemisphere (NH) has experienced a large number of severe midlatitude regional weather extremes. Here we show that a considerable part of these extremes were accompanied by highly magnified quasistationary midlatitude planetary waves with zonal wave numbers m = 6, 7, and 8. We further show that resonance conditions for these planetary waves were, in many cases, present before the onset of high-amplitude wave events, with a lead time up to 2 wk, suggesting that quasiresonant amplification (QRA) of these waves had occurred. Our results support earlier findings of an important role of the QRA mechanism in amplifying planetary waves, favoring recent NH weather extremes. PMID:27274064

Global QBO in circulation and ozone. Part 2: A simple mechanistic model

NASA Technical Reports Server (NTRS)

Tung, K. K.; Yang, H.

1994-01-01

Although the phenomenon of equatorial quasi-biennial oscillation is relatively well understood, the problem of how the equatorially confined quasi-biennial oscillation (QBO) wave forcing can induce a signal in the extratropics of comparable or larger magnitude remains unsolved. A simple mechanistic model is constructed to provide a quantitative test of the hypothesis that the phenomenon of extratropical QBO is mainly caused by an anomalous seasonal circulation induced by an anomalous Eliassen-Palm (E-P) flux divergence. The anomaly in E-P flux divergence may be caused in turn by the relative poleward and downward shift of the region of irreversible mixing (breaking) of the extratropical planetary waves during the easterly phase of the equatorial QBO as compared to its westerly phase. The hemispheric nature of the anomaly wave forcing in solstice seasons (viz., no wave breaking in the summer hemisphere) induces a global circulation anomaly that projects predominantly into the first few zonal Hough modes of Plumb. Such a global QBO circulation pattern, although difficult to measure directly, is reflected in the distribution of stratospheric tracers transported by it. Our model produces a global pattern of QBO anomaly in column ozone that appears to account for much of the unfiltered interannual variability in the column ozone observed by the total ozone mapping spectrometer (TOMS) instrument aboard the Nimbus satellite. Furthermore, the model produces the characteristic spectrum of the observation with peaks at periods of 20 and 30 months.

Global QBO in circulation and ozone. Part 2: A simple mechanistic model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tung, K.K.; Yang, H.

1994-10-01

Although the phenomenon of equatorial quasi-biennial oscillation is relatively well understood, the problem of how the equatorially confined quasi-biennial oscillation (QBO) wave forcing can induce a signal in the extratropics of comparable or larger magnitude remains unsolved. A simple mechanistic model is constructed to provide a quantitative test of the hypothesis that the phenomenon of extratropical QBO is mainly caused by an anomalous seasonal circulation induced by an anomalous Eliassen-Palm (E-P) flux divergence. The anomaly in E-P flux divergence may be caused in turn by the relative poleward and downward shift of the region of irreversible mixing (breaking) of themore » extratropical planetary waves during the easterly phase of the equatorial QBO as compared to its westerly phase. The hemispheric nature of the anomaly wave forcing in solstice seasons (viz., no wave breaking in the summer hemisphere) induces a global circulation anomaly that projects predominantly into the first few zonal Hough modes of Plumb. Such a global QBO circulation pattern, although difficult to measure directly, is reflected in the distribution of stratospheric tracers transported by it. Our model produces a global pattern of QBO anomaly in column ozone that appears to account for much of the unfiltered interannual variability in the column ozone observed by the total ozone mapping spectrometer (TOMS) instrument aboard the Nimbus satellite. Furthermore, the model produces the characteristic spectrum of the observation with peaks at periods of 20 and 30 months.« less

Simulation of breaking waves using the high-order spectral method with laboratory experiments: Wave-breaking onset

NASA Astrophysics Data System (ADS)

Seiffert, Betsy R.; Ducrozet, Guillaume; Bonnefoy, Félicien

2017-11-01

This study investigates a wave-breaking onset criteria to be implemented in the non-linear potential flow solver HOS-NWT. The model is a computationally efficient, open source code, which solves for the free surface in a numerical wave tank using the High-Order Spectral (HOS) method. The goal of this study is to determine the best method to identify the onset of random single and multiple breaking waves over a large domain at the exact time they occur. To identify breaking waves, a breaking onset criteria based on the ratio of local energy flux velocity to the local crest velocity, introduced by Barthelemy et al. (2017) is selected. The breaking parameter is uniquely applied in the numerical model in that calculations of the breaking onset criteria ratio are not made only at the location of the wave crest, but at every point in the domain and at every time step. This allows the model to calculate the onset of a breaking wave the moment it happens, and without knowing anything about the wave a priori. The application of the breaking criteria at every point in the domain and at every time step requires the phase velocity to be calculated instantaneously everywhere in the domain and at every time step. This is achieved by calculating the instantaneous phase velocity using the Hilbert transform and dispersion relation. A comparison between more traditional crest-tracking techniques shows the calculation of phase velocity using Hilbert transform at the location of the breaking wave crest provides a good approximation of crest velocity. The ability of the selected wave breaking criteria to predict single and multiple breaking events in two dimensions is validated by a series of large-scale experiments. Breaking waves are generated by energy focusing and modulational instability methods, with a wide range of primary frequencies. Steep irregular waves which lead to breaking waves, and irregular waves with an energy focusing wave superimposed are also generated. This set of waves provides a wide range of breaking-wave strengths, types and scales for validation of the model. A comparison of calculations made using HOS-NWT with experimental measurements show that the model is successful at predicting the occurrence of wave breaking, as well as accurately calculating breaking onset time and location. Although the current study is limited to a unidirectional wave field, the success of the wave-breaking model presented provides the basis for application of the model in a multidirectional wave field. By including wave breaking onset with the addition of an appropriate energy dissipation model into HOS-NWT, we can increase the application range of the model, as well as decrease the occurrence of numerical instabilities that are associated with breaking waves in a potential flow solver. An accurate description of the wave field is useful for predicting the dynamic response of offshore vessels and marine renewable energy devices, predicting loads on marine structures and the general physics of ocean waves, for example.

The role of planetary waves in the tropospheric jet response to stratospheric cooling

NASA Astrophysics Data System (ADS)

Smith, Karen L.; Scott, Richard K.

2016-03-01

An idealized general circulation model is used to assess the importance of planetary-scale waves in determining the position of the tropospheric jet, specifically its tendency to shift poleward as winter stratospheric cooling is increased. Full model integrations are compared against integrations in which planetary waves are truncated in the zonal direction, and only synoptic-scale waves are retained. Two series of truncated integrations are considered, using (i) a modified radiative equilibrium temperature or (ii) a nudged-bias correction technique. Both produce tropospheric climatologies that are similar to the full model when stratospheric cooling is weak. When stratospheric cooling is increased, the results indicate that the interaction between planetary- and synoptic-scale waves plays an important role in determining the structure of the tropospheric mean flow and rule out the possibility that the jet shift occurs purely as a response to changes in the planetary- or synoptic-scale wave fields alone.

Simulation of breaking waves using the high-order spectral method with laboratory experiments: wave-breaking energy dissipation

NASA Astrophysics Data System (ADS)

Seiffert, Betsy R.; Ducrozet, Guillaume

2018-01-01

We examine the implementation of a wave-breaking mechanism into a nonlinear potential flow solver. The success of the mechanism will be studied by implementing it into the numerical model HOS-NWT, which is a computationally efficient, open source code that solves for the free surface in a numerical wave tank using the high-order spectral (HOS) method. Once the breaking mechanism is validated, it can be implemented into other nonlinear potential flow models. To solve for wave-breaking, first a wave-breaking onset parameter is identified, and then a method for computing wave-breaking associated energy loss is determined. Wave-breaking onset is calculated using a breaking criteria introduced by Barthelemy et al. (J Fluid Mech https://arxiv.org/pdf/1508.06002.pdf, submitted) and validated with the experiments of Saket et al. (J Fluid Mech 811:642-658, 2017). Wave-breaking energy dissipation is calculated by adding a viscous diffusion term computed using an eddy viscosity parameter introduced by Tian et al. (Phys Fluids 20(6): 066,604, 2008, Phys Fluids 24(3), 2012), which is estimated based on the pre-breaking wave geometry. A set of two-dimensional experiments is conducted to validate the implemented wave breaking mechanism at a large scale. Breaking waves are generated by using traditional methods of evolution of focused waves and modulational instability, as well as irregular breaking waves with a range of primary frequencies, providing a wide range of breaking conditions to validate the solver. Furthermore, adjustments are made to the method of application and coefficient of the viscous diffusion term with negligible difference, supporting the robustness of the eddy viscosity parameter. The model is able to accurately predict surface elevation and corresponding frequency/amplitude spectrum, as well as energy dissipation when compared with the experimental measurements. This suggests the model is capable of calculating wave-breaking onset and energy dissipation successfully for a wide range of breaking conditions. The model is also able to successfully calculate the transfer of energy between frequencies due to wave focusing and wave breaking. This study is limited to unidirectional waves but provides a valuable basis for future application of the wave-breaking model to a multidirectional wave field. By including parameters for removing energy due to wave-breaking into a nonlinear potential flow solver, the risk of developing numerical instabilities due to an overturning wave is decreased, thereby increasing the application range of the model, including calculating more extreme sea states. A computationally efficient and accurate model for the generation of a nonlinear random wave field is useful for predicting the dynamic response of offshore vessels and marine renewable energy devices, predicting loads on marine structures, and in the study of open ocean wave generation and propagation in a realistic environment.

Modelling wave-induced sea ice break-up in the marginal ice zone

NASA Astrophysics Data System (ADS)

Montiel, F.; Squire, V. A.

2017-10-01

A model of ice floe break-up under ocean wave forcing in the marginal ice zone (MIZ) is proposed to investigate how floe size distribution (FSD) evolves under repeated wave break-up events. A three-dimensional linear model of ocean wave scattering by a finite array of compliant circular ice floes is coupled to a flexural failure model, which breaks a floe into two floes provided the two-dimensional stress field satisfies a break-up criterion. A closed-feedback loop algorithm is devised, which (i) solves the wave-scattering problem for a given FSD under time-harmonic plane wave forcing, (ii) computes the stress field in all the floes, (iii) fractures the floes satisfying the break-up criterion, and (iv) generates an updated FSD, initializing the geometry for the next iteration of the loop. The FSD after 50 break-up events is unimodal and near normal, or bimodal, suggesting waves alone do not govern the power law observed in some field studies. Multiple scattering is found to enhance break-up for long waves and thin ice, but to reduce break-up for short waves and thick ice. A break-up front marches forward in the latter regime, as wave-induced fracture weakens the ice cover, allowing waves to travel deeper into the MIZ.

Modelling wave-induced sea ice break-up in the marginal ice zone

PubMed Central

Squire, V. A.

2017-01-01

A model of ice floe break-up under ocean wave forcing in the marginal ice zone (MIZ) is proposed to investigate how floe size distribution (FSD) evolves under repeated wave break-up events. A three-dimensional linear model of ocean wave scattering by a finite array of compliant circular ice floes is coupled to a flexural failure model, which breaks a floe into two floes provided the two-dimensional stress field satisfies a break-up criterion. A closed-feedback loop algorithm is devised, which (i) solves the wave-scattering problem for a given FSD under time-harmonic plane wave forcing, (ii) computes the stress field in all the floes, (iii) fractures the floes satisfying the break-up criterion, and (iv) generates an updated FSD, initializing the geometry for the next iteration of the loop. The FSD after 50 break-up events is unimodal and near normal, or bimodal, suggesting waves alone do not govern the power law observed in some field studies. Multiple scattering is found to enhance break-up for long waves and thin ice, but to reduce break-up for short waves and thick ice. A break-up front marches forward in the latter regime, as wave-induced fracture weakens the ice cover, allowing waves to travel deeper into the MIZ. PMID:29118659

Modelling wave-induced sea ice break-up in the marginal ice zone.

PubMed

Montiel, F; Squire, V A

2017-10-01

A model of ice floe break-up under ocean wave forcing in the marginal ice zone (MIZ) is proposed to investigate how floe size distribution (FSD) evolves under repeated wave break-up events. A three-dimensional linear model of ocean wave scattering by a finite array of compliant circular ice floes is coupled to a flexural failure model, which breaks a floe into two floes provided the two-dimensional stress field satisfies a break-up criterion. A closed-feedback loop algorithm is devised, which (i) solves the wave-scattering problem for a given FSD under time-harmonic plane wave forcing, (ii) computes the stress field in all the floes, (iii) fractures the floes satisfying the break-up criterion, and (iv) generates an updated FSD, initializing the geometry for the next iteration of the loop. The FSD after 50 break-up events is unimodal and near normal, or bimodal, suggesting waves alone do not govern the power law observed in some field studies. Multiple scattering is found to enhance break-up for long waves and thin ice, but to reduce break-up for short waves and thick ice. A break-up front marches forward in the latter regime, as wave-induced fracture weakens the ice cover, allowing waves to travel deeper into the MIZ.

A comparative study of the mechanisms of migrating diurnal tidal variability due to interaction with propagating planetary waves

NASA Astrophysics Data System (ADS)

Chang, Loren; Palo, Scott; Liu, Hanli

The migrating diurnal tide is one of the dominant dynamical features of the Earth's Mesosphere and Lower Thermosphere (MLT) region, particularly at low latitudes. As an actively forced disturbance with a period of 24 hours and westward zonal wave number 1, the migrating diurnal tide represents the atmospheric response to the largest component of solar forcing, propagating upwards from excitation regions in the lower atmosphere. While the seasonal evolution of the migrating diurnal tide has been well explored, ground-based observations of the tide have exhibited a modulation of tidal amplitudes at periods related to those of propagating planetary waves generally present in the region, as well as a decrease in tidal amplitudes during large planetary wave events. Past studies have attributed tidal amplitude modulation to the presence of child waves generated as a byproduct of nonlinear wave-tide interactions. The resulting child waves have frequencies and wavenumbers that are the sum and difference of those of the parent waves. Many questions still remain about the nature and physical drivers responsible for such interactions. The conditions under which various planetary waves may or may not interact with the atmospheric tides, the overall effect on the tidal response, as well as the physical mechanisms coupling the planetary wave and the tide interaction, which has not clearly been determined. These questions are addressed in a recent modeling study, by examining two general categories of planetary waves that are known to attain significant amplitudes in the low latitude and equa-torial region where the migrating diurnal tide is dominant. These are the eastward propagating class of ultra fast Kelvin (UFK) waves with periods near three days which attain their largest amplitudes in the temperature and zonal wind fields of the equatorial lower thermosphere. The second wave examined is the quasi-two day wave (QTDW) which is a westward propagating Rossby wave and can amplify raplidly due to a nonlinear interaction with the mean flow and attain large amplitudes in both components of the wind field and the temperature field in the summer hemisphere over a period of a few days during post-solstice periods. The NCAR Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM) and Whole Atmosphere Community Climate Model (WACCM) are both state of the art general circulation models and are utilized to simulate the aforementioned planetary waves. The goal of this study is to identify specific changes in the structure of the migrat-ing diurnal tide due to interaction with these planetary waves and to understand the driving processes. The physical mechanisms that serve to couple the tide and the planetary waves are identified through analysis of the tidal momentum tendencies, the background atmosphere, as well as changes in tidal propagation. Results showing the impact of these planetary waves on the structure and evolution of the migrating diurnal tide will be presented.

Effects of orography on planetary scale flow

NASA Technical Reports Server (NTRS)

Smith, R. B.

1986-01-01

The earth's orography is composed of a wide variety of scales, each contributing to the spectrum of atmospheric motions. A well studied subject (originating with Charney and Eliassen) is the direct forcing of planetary scale waves by the planetary scale orography: primarily the Tibetan plateau and the Rockies. However, because of the non-linear terms in the equations of dynamic meteorology, even the smallest scales of mountain induced flow can contribute to the planetary scale if the amplitude of the small scale disturbance is sufficintly large. Two possible mechanisms for this are illustrated. First, preferentially located lee cyclones can force planetary waves by their meridional transport of heat and momentum (Hansen and Chen). Recent theories are helping to explain the phenomena of lee cyclogenesis (e.g., Smith, 1984, J.A.S.). Second, mesoscale mountain wave and severe downslope wind phenomena produce such a large local drag, that planetary scale waves can be produced. The mechanism of upscale transfer is easy to understand in this case as the standing planetary scale wave has a wavelength which depends on the mean structure of the atmosphere, and not on the width of the mountain (just as in small scale lee wave theory). An example of a theoretical description of a severe wind flow with very large drag is shown.

Planetary and tidal wave-type oscillations in the ionospheric sporadic E layers over Tehran region

NASA Astrophysics Data System (ADS)

Karami, K.; Ghader, S.; Bidokhti, A. A.; Joghataei, M.; Neyestani, A.; Mohammadabadi, A.

2012-04-01

It is believed that in the lower ionosphere, particularly in the ionospheric sporadic E (Es) layers (90-130 km), the planetary and tidal wave-type oscillations in the ionized component indicate the planetary and tidal waves in the neutral atmosphere. In the present work, the presence of wave-type oscillations, including planetary and tidal waves in the ionospheric sporadic E layers over Tehran region is examined. Data measured by a digital ionosonde at the ionospheric station of the Institute of Geophysics, University of Tehran, from July 2006 to June 2007 are used to investigate seasonal variations of planetary and tidal waves activities. For the purpose of accurate comparison between different seasons, wavelet transform is applied to time series of foEs and h‧Es, namely, the critical frequency and virtual height of Es layers, respectively. The results show that the sporadic E layers over Tehran region are strongly under the influence of upward propagation of waves from below. More specifically, among diverse range of periodicities in the sporadic E layers, we found that diurnal (24 hours) and semidiurnal (12 hours) oscillations in all seasons for both parameters. Moreover, terdiurnal (8 hours) tide-like variation is observed during spring and summer for foEs parameter and summer and winter for h‧Es. Furthermore, the results show that diurnal tidal waves obtain their maximum activities during autumn and winter seasons, and their activities decrease during the late spring and summer. In addition, periods of about 2, 4, 6, 10, 14, and 16 days in our observation verifies the hypothesis of upward propagation of planetary waves from lower atmosphere to the ionosphere. Moreover, planetary waves have their maximum activities during equinox.

Raman amplification in the coherent wave-breaking regime.

PubMed

Farmer, J P; Pukhov, A

2015-12-01

In regimes far beyond the wave-breaking threshold of Raman amplification, we show that significant amplification can occur after the onset of wave breaking, before phase mixing destroys the coherent coupling between pump, probe, and plasma wave. Amplification in this regime is therefore a transient effect, with the higher-efficiency "coherent wave-breaking" (CWB) regime accessed by using a short, intense probe. Parameter scans illustrate the marked difference in behavior between below wave breaking, in which the energy-transfer efficiency is high but total energy transfer is low, wave breaking, in which efficiency is low, and CWB, in which moderate efficiencies allow the highest total energy transfer.

Evaluating crude oil chemical dispersion efficacy in a flow-through wave tank under regular non-breaking wave and breaking wave conditions.

PubMed

Li, Zhengkai; Lee, Kenneth; King, Thomas; Boufadel, Michel C; Venosa, Albert D

2009-05-01

Testing dispersant effectiveness under conditions similar to that of the open environment is required for improvements in operational procedures and the formulation of regulatory guidelines. To this end, a novel wave tank facility was fabricated to study the dispersion of crude oil under regular non-breaking and irregular breaking wave conditions. This wave tank facility was designed for operation in a flow-through mode to simulate both wave- and current-driven hydrodynamic conditions. We report here an evaluation of the effectiveness of chemical dispersants (Corexit EC9500A and SPC 1000) on two crude oils (Medium South American [MESA] and Alaska North Slope [ANS]) under two different wave conditions (regular non-breaking and plunging breaking waves) in this wave tank. The dispersant effectiveness was assessed by measuring the water column oil concentration and dispersed oil droplet size distribution. In the absence of dispersants, nearly 8-19% of the test crude oils were dispersed and diluted under regular wave and breaking wave conditions. In the presence of dispersants, about 21-36% of the crude oils were dispersed and diluted under regular waves, and 42-62% under breaking waves. Consistently, physical dispersion under regular waves produced large oil droplets (volumetric mean diameter or VMD > or = 300 microm), whereas chemical dispersion under breaking waves created small droplets (VMD < or = 50 microm). The data can provide useful information for developing better operational guidelines for dispersant use and improved predictive models on dispersant effectiveness in the field.

Mechanisms driving the global and seasonal structure of the 16-day planetary wave

NASA Astrophysics Data System (ADS)

Nguyen, V.; Chang, L. C.; Liu, H.; Palo, S. E.

2013-12-01

Past observations have shown that the effects of the quasi 16-day planetary wave, representing the second symmetric Rossby normal mode, are prevalent throughout the middle atmosphere and occasionally, some portions of the upper atmosphere. In the presented work, we investigate the mechanisms driving the propagation of the quasi 16-day planetary wave from a source in the lower atmosphere to higher altitudes by using the NCAR Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM). The quasi 16-day planetary wave is simulated in the model by introducing perturbations in geopotential height at the lower boundary of the model and comparing it to a control run. Analysis of the model runs over the course of a year show that the background zonal winds play an important role in driving seasonal changes in the quasi 16-day planetary wave structure. Derived quasi-geostrophic potential vorticity gradient and Eliassen-Palm flux from the model output also show that the penetration of the wave into regions of mean wind instability can drive wave amplification in certain regions. The model results are compared to the quasi 16-day wave structure derived from TIMED-SABER observations to identify similarities/differences between the model and observations, and provide further insight into the mechanisms driving the wave propagation.

The correlation of VLF propagation variations with atmospheric planetary-scale waves

NASA Technical Reports Server (NTRS)

Cavalieri, D. J.; Deland, R. J.; Potemra, T. A.; Gavin, R. F.

1973-01-01

Variations in the received daytime phase of long distance, cesium-controlled, VLF transmission were compared to the height variations of the 10-mb isobaric surface during the first three months of 1965 and 1969. The VLF phase values are also compared to height variations of constant electron densities in the E-region and to variations of f-min which have been shown to be well correlated with planetary-scale variations in the stratosphere by Deland and Cavalieri (1973). The VLF phase variations show good correlation with these previous ionospheric measurements and with the 10-mb surfaces. The planetary scale waves in the stratosphere are shown to be travelling on the average eastward in 1965 and westward in 1969. These correlations are interpreted as due to the propagation of travelling planetary scale waves with westward tilted wave fronts. Upward energy transport due to the vertical structure of those waves is also discussed. These correlations provide further evidence for the coupling between the lower ionosphere at about 70 km altitude (the daytime VLF reflection height and the stratosphere, and they demonstrate the importance of planetary wave phenomena to VLF propagation.

Remote Sensing Characterization of Two-dimensional Wave Forcing in the Surf Zone

NASA Astrophysics Data System (ADS)

Carini, R. J.; Chickadel, C. C.; Jessup, A. T.

2016-02-01

In the surf zone, breaking waves drive longshore currents, transport sediment, shape bathymetry, and enhance air-sea gas and particle exchange. Furthermore, wave group forcing influences the generation and duration of rip currents. Wave breaking exhibits large gradients in space and time, making it challenging to measure in situ. Remote sensing technologies, specifically thermal infrared (IR) imagery, can provide detailed spatial and temporal measurements of wave breaking at the water surface. We construct two-dimensional maps of active wave breaking from IR imagery collected during the Surf Zone Optics Experiment in September 2010 at the US Army Corps of Engineers' Field Research Facility in Duck, NC. For each breaker identified in the camera's field of view, the crest-perpendicular length of the aerated breaking region (roller length) and wave direction are estimated and used to compute the wave energy dissipation rate. The resultant dissipation rate maps are analyzed over different time scales: peak wave period, infragravity wave period, and tidal wave period. For each time scale, spatial maps of wave breaking are used to characterize wave forcing in the surf zone for a variety of wave conditions. The following phenomena are examined: (1) wave dissipation rates over the bar (location of most intense breaking) have increased variance in infragravity wave frequencies, which are different from the peak frequency of the incoming wave field and different from the wave forcing variability at the shoreline, and (2) wave forcing has a wider spatial distribution during low tide than during high tide due to depth-limited breaking over the barred bathymetry. Future work will investigate the response of the variability in wave setup, longshore currents and rip currents, to the variability in wave forcing in the surf zone.

Rayleigh lidar observations of enhanced stratopause temperature over Gadanki (13.5° N, 79.2° E) during major stratospheric warming in 2006

NASA Astrophysics Data System (ADS)

Sridharan, S.; Sathishkumar, S.; Raghunath, K.

2009-01-01

Rayleigh lidar observations of temperature structure and gravity wave activity were carried out at Gadanki (13.5° N, 79.2° E) during January-February 2006. A major stratospheric warming event occurred at high latitude during the end of January and early February. There was a sudden enhancement in the stratopause temperature over Gadanki coinciding with the date of onset of the major stratospheric warming event which occurred at high latitudes. The temperature enhancement persisted even after the end of the high latitude major warming event. During the same time, the UKMO (United Kingdom Meteorological Office) zonal mean temperature showed a similar warming episode at 10° N and cooling episode at 60° N around the region of stratopause. This could be due to ascending (descending) motions at high (low) latitudes above the critical level of planetary waves, where there was no planetary wave flux. The time variation of the gravity wave potential energy computed from the temperature perturbations over Gadanki shows variabilities at planetary wave periods, suggesting a non-linear interaction between gravity waves and planetary waves. The space-time analysis of UKMO temperature data at high and low latitudes shows the presence of similar periodicities of planetary wave of zonal wavenumber 1.

Solar-Cycle Variability of Magnetosheath Fluctuations at Earth and Venus

NASA Astrophysics Data System (ADS)

Dwivedi, N. K.; Narita, Y.; Kovacs, P.

2014-12-01

The magnetosheath is a region between the bow-shock and magnetopause and the magnetosheath plasma is mostly in the turbulent state. In the present investigation we put an effort to closely examine the magnetosheath fluctuations dependency on the solar-cycles (solar-maximum and solar minimum) at the magnetized planetary body (Earth) and their comparison with the un-magnetized planetary body (Venus) for the solar minimum. We use the CLUSTER FGM data for the solar-maximum (2001-2002), solar-minimum (2006-2008) and Venus fluxgate magnetometer data for the solar-minimum (2006-2008) to perform a comparative statistical study on the energy spectra and probability density function (PDF) and asses the spectral features of the magnetic fluctuations of the both planetary bodies. In the comparison we study the relation between the inertial ranges of the spectra and the temporal scales of non-Gaussian magnetic fluctuations derived from PDF analyses. The first can refer to turbulent cascade dynamics, while the latter may indicate intermittency. We first transformed the magnetic field data into mean field aligned coordinate system with respect to the large-scale magnetic field direction and then after we compute the power spectral density with the help of Welch algorithm. The computed energy spectra of Earth's magnetosheath show a moderate variability with the solar-cycles and have a broader inertial range. However the estimated energy spectra for the solar-minimum at Venus give the clear evidence of the existence of the break point in the vicinity of the ion gyroradius. After the break-point the energy spectra become steeper and show a distinctive spectral scales which is interpreted as the realization of the begging of the energy cascade. We also briefly address the influence of turbulence on the plasma transport and wave dynamics responsible for the spectral break and predict spectral features of the energy spectra for the solar-maximum at Venus based on the results obtained for the solar-minimum. The research leading to these results has received funding from the European Community's Seventh Framework Programme ([FP7/2007-2013]) under grant agreement number 313038/STORM.

Validation of whitecap fraction and breaking wave parameters from WAVEWATCH-III using in situ and remote-sensing data

NASA Astrophysics Data System (ADS)

Leckler, F.; Hanafin, J. A.; Ardhuin, F.; Filipot, J.; Anguelova, M. D.; Moat, B. I.; Yelland, M.; Prytherch, J.

2012-12-01

Whitecaps are the main sink of wave energy. Although the exact processes are still unknown, it is clear that they play a significant role in momentum exchange between atmosphere and ocean, and also influence gas and aerosol exchange. Recently, modeling of whitecap properties was implemented in the spectral wave model WAVEWATCH-III ®. This modeling takes place in the context of the Oceanflux-Greenhouse Gas project, to provide a climatology of breaking waves for gas transfer studies. We present here a validation study for two different wave breaking parameterizations implemented in the spectral wave model WAVEWATCH-III ®. The model parameterizations use different approaches related to the steepness of the carrying waves to estimate breaking wave probabilities. That of Ardhuin et al. (2010) is based on the hypothesis that breaking probabilities become significant when the saturation spectrum exceeds a threshold, and includes a modification to allow for greater breaking in the mean wave direction, to agree with observations. It also includes suppression of shorter waves by longer breaking waves. In the second, (Filipot and Ardhuin, 2012) breaking probabilities are defined at different scales using wave steepness, then the breaking wave height distribution is integrated over all scales. We also propose an adaptation of the latter to make it self-consistent. The breaking probabilities parameterized by Filipot and Ardhuin (2012) are much larger for dominant waves than those from the other parameterization, and show better agreement with modeled statistics of breaking crest lengths measured during the FAIRS experiment. This stronger breaking also has an impact on the shorter waves due to the parameterization of short wave damping associated with large breakers, and results in a different distribution of the breaking crest lengths. Converted to whitecap coverage using Reul and Chapron (2003), both parameterizations agree reasonably well with commonly-used empirical fits of whitecap coverage against wind speed (Monahan and Woolf, 1989) and with the global whitecap coverage of Anguelova and Webster (2006), derived from space-borne radiometry. This is mainly due to the fact that the breaking of larger waves in the parametrization by Filipot and Ardhuin (2012) is compensated for by the intense breaking of smaller waves in that of Ardhuin et al. (2010). Comparison with in situ data collected during research ship cruises in the North and South Atlantic (SEASAW, DOGEE and WAGES), and the Norwegian Sea (HiWASE) between 2006 and 2011 also shows good agreement. However, as large scale breakers produce a thicker foam layer, modeled mean foam thickness clearly depends on the scale of the breakers. Foam thickness is thus a more interesting parameter for calibrating and validating breaking wave parameterizations, as the differences in scale can be determined. With this in mind, we present the initial results of validation using an estimation of mean foam thickness using multiple radiometric bands from satellites SMOS and AMSR-E.

Wave Breaking Dissipation in Fetch-Limited Seas

NASA Astrophysics Data System (ADS)

Schwendeman, M.; Thomson, J. M.; Gemmrich, J.

2012-12-01

Breaking waves on the ocean surface control wave growth and enhance air-sea interaction, yet field measurements of breaking are limited. A promising technique for field measurements of wave breaking uses the breaking crest length distribution Λ(c), introduced by Phillips (1985). However, calculating dynamic quantities from Λ(c) requires knowledge of the breaking strength parameter, b. Estimates of a b have varied over many orders of magnitude, and recent studies have attempted to model b in terms of sea state, such as wave steepness or saturation. We present comprehensive observations of breaking in fetch-limited conditions from Juan de Fuca Strait, WA. The wave evolution along fetch is explained by an observed energy budget using the radiative transfer equation (RTE), and the evolution is consistent with existing empirical fetch laws. Estimates of Λ(c) increase along fetch and are consistent with directly measured breaking rates. Using novel in situ measures of dissipation, as well as a residual term from the RTE budget, we obtain robust estimates of the wave breaking strength b. Results suggest that b decreases with wave steepness and saturation, in contrast with recent laboratory results (Drazen et al, 2008). This trend is discussed in terms of the fetch evolution and associated broadening of the equilibrium range in the wave spectra.Map of drifter tracks colored by wave height for two days in Juan de Fuca Strait, WA.

Upper atmospheric planetary-wave and gravity-wave observations

NASA Technical Reports Server (NTRS)

Justus, C. G.; Woodrum, A.

1973-01-01

Previously collected data on atmospheric pressure, density, temperature and winds between 25 and 200 km from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others were analyzed by a daily-difference method, and results on the magnitude of atmospheric perturbations interpreted as gravity waves and planetary waves are presented. Traveling planetary-wave contributions in the 25-85 km range were found to have significant height and latitudinal variation. It was found that observed gravity-wave density perturbations and wind are related to one another in the manner predicted by gravity-wave theory. It was determined that, on the average, gravity-wave energy deposition or reflection occurs at all altitudes except the 55-75 km region of the mesosphere.

Improving Short Wave Breaking Behavior In Surfbeat Models

NASA Astrophysics Data System (ADS)

Roelvink, J.; Daly, C.; Vandongeren, A. R.; van Thiel de Vries, J.; McCall, R.

2009-12-01

In present surfzone modeling three approaches are widely applied: short-wave resolving models, ‘surfbeat’ models, which resolve wave energy modulations on the time-scale of wave groups and their associated infragravity waves, and wave averaged models. In all three approaches, wave breaking is a process that is highly schematized and governed by several empirical coefficients. In this presentation we will focus on the breaking process in ‘surfbeat’ models, such as XBeach (Roelvink et al, 2009). These models need to describe the short wave dissipation by breaking as a function of the slowly-varying short wave energy or wave height. The model usually applied is that by Roelvink (1993), which combines a probability that waves are breaking as function of wave heigth over water depth ratio H/h with a bore-type dissipation formulation similar to that by Battjes and Janssen (1978). A drawback of such a formulation is that there is no ‘memory’ in the breaking process, and the amount of breaking instantly varies with the water depth (though the wave height itself does have a memory). For cases with bichromatic waves, or for long-period swell, this does not reflect reality enough: waves that start breaking do not instantly stop breaking once the water depth increases, but continue until some lower threshold is reached. This concept was captured in Dally’s (1992) wave-by-wave approach, where individual waves are tracked in a probabilistic setting. We have now implemented a similar formulation in XBeach, where the property that waves are breaking is tracked; it is switched on when H/h exceeds a first criterion; this property is propagated using an advection equation and when H/h gets below a second criterion breaking is switched off. This formulation can do two things the previous one can’t: maintain groupiness inside the surf zone and have a maximum of wave breaking in the trough after a steep bar, as was observed for instance in Arcilla et al’s (1994) test 1C. Obviously this has important consequences for the forcing of both long waves and mean currents. In our presentation we will show results of comparisons of both formulations. References. Arcilla, A.S., Roelvink, J.A., O'Connor, B.A. Reniers, A., and Jimenez. J.A. The Delta Flume '93 Experiment. Coastal Dynamics '94. Arcilla, Stive and Kraus (eds), ASCE, New York, pp. 488-502. Battjes, J.A. and J.P.F.M. Janssen, (1978), Energy loss and set-up due to breaking in random waves, Proc. 16th Int. Coastal Eng. Conf., Hamburg, vol. 1: 569-587. Dally, W.R. (1992) Random breaking waves: Field verification of a wave-by-wave algorithm for engineering application. Coastal Engineering, Volume 16, Issue 4, March 1992, Pages 369-397. Roelvink, Dano, Ad Reniers, Ap van Dongeren, Jaap van Thiel de Vries, Robert McCall, Jamie Lescinski. Modelling storm impacts on beaches, dunes and barrier islands, Coast. Eng. (2009), doi:10.1016/j.coastaleng.2009.08.006 Roelvink, J.A. Dissipation in random wave groups incident on a beach. Coastal Eng., 19 (1993) pp. 127-150.

Wind growth and wave breaking in higher-order spectral phase resolved wave models

NASA Astrophysics Data System (ADS)

Leighton, R.; Walker, D. T.

2016-02-01

Wind growth and wave breaking are a integral parts of the wave evolution. Higher-OrderSpectral models (HoS) describing the non-linear evolution require empirical models for these effects. In particular, the assimilation of phase-resolved remotesensing data will require the prediction and modeling of wave breaking events.The HoS formulation used in this effort is based on fully nonlinear model of O. Nwogu (2009). The model for wave growth due to wind is based on the early normal and tangential stress model of Munk (1947). The model for wave breaking contains two parts. The first part initiates the breaking events based on the local wave geometry and the second part is a model for the pressure field, which acting against the surface normal velocity extracts energy from the wave. The models are tuned to balance the wind energy input with the breaking wave losses and to be similarfield observations of breaking wave coverage. The initial wave field, based on a Pierson-Moskowitz spectrum for 10 meter wind speed of 5-15 m/s, defined over a region of up to approximate 2.5 km on a side with the simulation running for several hundreds of peak wave periods. Results will be presented describing the evolution of the wave field.Sponsored by Office of Naval Research, Code 322

Propagation and Breaking at High Altitudes of Gravity Waves Excited by Tropospheric Forcing

NASA Technical Reports Server (NTRS)

Prusa, Joseph M.; Smolarkiewicz, Piotr K.; Garcia, Rolando R.

1996-01-01

An anelastic approximation is used with a time-variable coordinate transformation to formulate a two-dimensional numerical model that describes the evolution of gravity waves. The model is solved using a semi-Lagrangian method with monotone (nonoscillatory) interpolation of all advected fields. The time-variable transformation is used to generate disturbances at the lower boundary that approximate the effect of a traveling line of thunderstorms (a squall line) or of flow over a broad topographic obstacle. The vertical propagation and breaking of the gravity wave field (under conditions typical of summer solstice) is illustrated for each of these cases. It is shown that the wave field at high altitudes is dominated by a single horizontal wavelength; which is not always related simply to the horizontal dimension of the source. The morphology of wave breaking depends on the horizontal wavelength; for sufficiently short waves, breaking involves roughly one half of the wavelength. In common with other studies, it is found that the breaking waves undergo "self-acceleration," such that the zonal-mean intrinsic frequency remains approximately constant in spite of large changes in the background wind. It is also shown that many of the features obtained in the calculations can be understood in terms of linear wave theory. In particular, linear theory provides insights into the wavelength of the waves that break at high altitudes, the onset and evolution of breaking. the horizontal extent of the breaking region and its position relative to the forcing, and the minimum and maximum altitudes where breaking occurs. Wave breaking ceases at the altitude where the background dissipation rate (which in our model is a proxy for molecular diffusion) becomes greater than the rate of dissipation due to wave breaking, This altitude, in effect, the model turbopause, is shown to depend on a relatively small number of parameters that characterize the waves and the background state.

Convective wave breaking in the KdV equation

NASA Astrophysics Data System (ADS)

Brun, Mats K.; Kalisch, Henrik

2018-03-01

The KdV equation is a model equation for waves at the surface of an inviscid incompressible fluid, and it is well known that the equation describes the evolution of unidirectional waves of small amplitude and long wavelength fairly accurately if the waves fall into the Boussinesq regime. The KdV equation allows a balance of nonlinear steepening effects and dispersive spreading which leads to the formation of steady wave profiles in the form of solitary waves and cnoidal waves. While these wave profiles are solutions of the KdV equation for any amplitude, it is shown here that there for both the solitary and the cnoidal waves, there are critical amplitudes for which the horizontal component of the particle velocity matches the phase velocity of the wave. Solitary or cnoidal solutions of the KdV equation which surpass these amplitudes feature incipient wave breaking as the particle velocity exceeds the phase velocity near the crest of the wave, and the model breaks down due to violation of the kinematic surface boundary condition. The condition for breaking can be conveniently formulated as a convective breaking criterion based on the local Froude number at the wave crest. This breaking criterion can also be applied to time-dependent situations, and one case of interest is the development of an undular bore created by an influx at a lateral boundary. It is shown that this boundary forcing leads to wave breaking in the leading wave behind the bore if a certain threshold is surpassed.

Experimental study on the bed shear stress under breaking waves

NASA Astrophysics Data System (ADS)

Hao, Si-yu; Xia, Yun-feng; Xu, Hua

2017-06-01

The object of present study is to investigate the bed shear stress on a slope under regular breaking waves by a novel instrument named Micro-Electro-Mechanical System (MEMS) flexible hot-film shear stress sensor. The sensors were calibrated before application, and then a wave flume experiment was conducted to study the bed shear stress for the case of regular waves spilling and plunging on a 1:15 smooth PVC slope. The experiment shows that the sensor is feasible for the measurement of the bed shear stress under breaking waves. For regular incident waves, the bed shear stress is mainly periodic in both outside and inside the breaking point. The fluctuations of the bed shear stress increase significantly after waves breaking due to the turbulence and vortexes generated by breaking waves. For plunging breaker, the extreme value of the mean maximum bed shear stress appears after the plunging point, and the more violent the wave breaks, the more dramatic increase of the maximum bed shear stress will occur. For spilling breaker, the increase of the maximum bed shear stress along the slope is gradual compared with the plunging breaker. At last, an empirical equation about the relationship between the maximum bed shear stress and the surf similarity parameter is given, which can be used to estimate the maximum bed shear stress under breaking waves in practice.

Middle Atmosphere Dynamics with Gravity Wave Interactions in the Numerical Spectral Model: Tides and Planetary Waves

NASA Technical Reports Server (NTRS)

Mayr, Hans G.; Mengel, J. G.; Chan, K. L.; Huang, F. T.

2010-01-01

As Lindzen (1981) had shown, small-scale gravity waves (GW) produce the observed reversals of the zonal-mean circulation and temperature variations in the upper mesosphere. The waves also play a major role in modulating and amplifying the diurnal tides (DT) (e.g., Waltersheid, 1981; Fritts and Vincent, 1987; Fritts, 1995a). We summarize here the modeling studies with the mechanistic numerical spectral model (NSM) with Doppler spread parameterization for GW (Hines, 1997a, b), which describes in the middle atmosphere: (a) migrating and non-migrating DT, (b) planetary waves (PW), and (c) global-scale inertio gravity waves. Numerical experiments are discussed that illuminate the influence of GW filtering and nonlinear interactions between DT, PW, and zonal mean variations. Keywords: Theoretical modeling, Middle atmosphere dynamics, Gravity wave interactions, Migrating and non-migrating tides, Planetary waves, Global-scale inertio gravity waves.

Turbulence and wave breaking effects on air-water gas exchange

PubMed

Boettcher; Fineberg; Lathrop

2000-08-28

We present an experimental characterization of the effects of turbulence and breaking gravity waves on air-water gas exchange in standing waves. We identify two regimes that govern aeration rates: turbulent transport when no wave breaking occurs and bubble dominated transport when wave breaking occurs. In both regimes, we correlate the qualitative changes in the aeration rate with corresponding changes in the wave dynamics. In the latter regime, the strongly enhanced aeration rate is correlated with measured acoustic emissions, indicating that bubble creation and dynamics dominate air-water exchange.

A numerical model of gravity wave breaking and stress in the mesosphere

NASA Technical Reports Server (NTRS)

Schoeberl, M. R.; Strobel, D. F.; Apruzese, J. P.

1983-01-01

The goal of the study is to calculate numerically the deceleration and heating caused by breaking gravity waves. The effect of the radiative dissipation of the wave is included as vertical-wavelength-dependent Newtonian cooling. The parameterization for zonal deceleration is extended by breaking gravity waves (Lindzen, 1981) to include the turbulent diffusion of heat and momentum. After describing the numerical model, the numerical results are presented and compared with the parameterizations in a noninteractive model of the mean zonal wind. Attention is then given to the transport of constituents by gravity waves and the attendant turbulent zone. It is noted that if gravity wave breaking were not an intermittent process, gravity wave stresses would produce an adiabatic mesosphere with a zonal mean velocity close to the phase speed of the breaking wave.

On the upper ocean turbulent dissipation rate due to microscale breakers and small whitecaps

NASA Astrophysics Data System (ADS)

Banner, Michael L.; Morison, Russel P.

2018-06-01

In ocean wave modelling, accurately computing the evolution of the wind-wave spectrum depends on the source terms and the spectral bandwidth used. The wave dissipation rate source term which spectrally quantifies wave breaking and other dissipative processes remains poorly understood, including the spectral bandwidth needed to capture the essential model physics. The observational study of Sutherland and Melville (2015a) investigated the relative dissipation rate contributions of breaking waves, from large-scale whitecaps to microbreakers. They concluded that a large fraction of wave energy was dissipated by microbreakers. However, in strong contrast with their findings, our analysis of their data and other recent data sets shows that for young seas, microbreakers and small whitecaps contribute only a small fraction of the total breaking wave dissipation rate. For older seas, we find microbreakers and small whitecaps contribute a large fraction of the breaking wave dissipation rate, but this is only a small fraction of the total dissipation rate, which is now dominated by non-breaking contributions. Hence, for all the wave age conditions observed, microbreakers make an insignificant contribution to the total wave dissipation rate in the wave boundary layer. We tested the sensitivity of the results to the SM15a whitecap analysis methodology by transforming the SM15a breaking data using our breaking crest processing methodology. This resulted in the small-scale breaking waves making an even smaller contribution to the total wave dissipation rate, and so the result is independent of the breaker processing methodology. Comparison with other near-surface total TKE dissipation rate observations also support this conclusion. These contributions to the spectral dissipation rate in ocean wave models are small and need not be explicitly resolved.

The Major Stratospheric Sudden Warming of January 2013: Analyses and Forecasts in the GEOS-5 Data Assimilation System

NASA Technical Reports Server (NTRS)

Coy, Lawrence; Pawson, Steven

2014-01-01

We examine the major stratosphere sudden warming (SSW) that occurred on 6 January 2013, using output from the NASA Global Modeling and Assimilation Office (GMAO) GEOS-5 (Goddard Earth Observing System) near-real-time data assimilation system (DAS). Results show that the major SSW of January 2013 falls into the vortex splitting type of SSW, with the initial planetary wave breaking occurring near 10 hPa. The vertical flux of wave activity at the tropopause responsible for the SSW occurred mainly in the Pacific Hemisphere, including the a pulse associated with the preconditioning of the polar vortex by wave 1 identified on 23 December 2012. While most of the vertical wave activity flux was in the Pacific Hemisphere, a rapidly developing tropospheric weather system over the North Atlantic on 28 December is shown to have produced a strong transient upward wave activity flux into the lower stratosphere coinciding with the peak of the SSW event. In addition, the GEOS-5 5-day forecasts accurately predicted the major SSW of January 2013 as well as the upper tropospheric disturbances responsible for the warming. The overall success of the 5-day forecasts provides motivation to produce regular 10-day forecasts with GEOS-5, to better support studies of stratosphere-troposphere interaction.

Nonlinear density waves in planetary rings

NASA Technical Reports Server (NTRS)

Borderies, Nicole; Goldreich, Peter; Tremaine, Scott

1986-01-01

The steady-state structure of planetary rings in the presence of density waves at the Lindblad resonances of a satellite is indicated. The study is based on the dispersion relation and damping rate for nonlinear density waves, derived by Shu et al. (1985) and by Borderies, Goldreich, and Tremaine (1985). It is shown that strong density waves lead to an enhancement of the background surface density in the wave zone.

Water level effects on breaking wave setup for Pacific Island fringing reefs

NASA Astrophysics Data System (ADS)

Becker, J. M.; Merrifield, M. A.; Ford, M.

2014-02-01

The effects of water level variations on breaking wave setup over fringing reefs are assessed using field measurements obtained at three study sites in the Republic of the Marshall Islands and the Mariana Islands in the western tropical Pacific Ocean. At each site, reef flat setup varies over the tidal range with weaker setup at high tide and stronger setup at low tide for a given incident wave height. The observed water level dependence is interpreted in the context of radiation stress gradients specified by an idealized point break model generalized for nonnormally incident waves. The tidally varying setup is due in part to depth-limited wave heights on the reef flat, as anticipated from previous reef studies, but also to tidally dependent breaking on the reef face. The tidal dependence of the breaking is interpreted in the context of the point break model in terms of a tidally varying wave height to water depth ratio at breaking. Implications for predictions of wave-driven setup at reef-fringed island shorelines are discussed.

Short-crested waves in the surf zone

NASA Astrophysics Data System (ADS)

Wei, Zhangping; Dalrymple, Robert A.; Xu, Munan; Garnier, Roland; Derakhti, Morteza

2017-05-01

This study investigates short-crested waves in the surf zone by using the mesh-free Smoothed Particle Hydrodynamics model, GPUSPH. The short-crested waves are created by generating intersecting wave trains in a numerical wave basin with a beach. We first validate the numerical model for short-crested waves by comparison with large-scale laboratory measurements. Then short-crested wave breaking over a planar beach is studied comprehensively. We observe rip currents as discussed in Dalrymple (1975) and undertow created by synchronous intersecting waves. The wave breaking of the short-crested wavefield created by the nonlinear superposition of intersecting waves and wave-current interaction result in the formation of isolated breakers at the ends of breaking wave crests. Wave amplitude diffraction at these isolated breakers gives rise to an increase in the alongshore wave number in the inner surf zone. Moreover, 3-D vortices and multiple circulation cells with a rotation frequency much lower than the incident wave frequency are observed across the outer surf zone to the beach. Finally, we investigate vertical vorticity generation under short-crested wave breaking and find that breaking of short-crested waves generates vorticity as pointed out by Peregrine (1998). Vorticity generation is not only observed under short-crested waves with a limited number of wave components but also under directional wave spectra.

Numerical modelling of wind effects on breaking waves in the surf zone

NASA Astrophysics Data System (ADS)

Xie, Zhihua

2017-10-01

Wind effects on periodic breaking waves in the surf zone have been investigated in this study using a two-phase flow model. The model solves the Reynolds-averaged Navier-Stokes equations with the k - 𝜖 turbulence model simultaneously for the flows both in the air and water. Both spilling and plunging breakers over a 1:35 sloping beach have been studied under the influence of wind, with a focus during wave breaking. Detailed information of the distribution of wave amplitudes and mean water level, wave-height-to-water-depth ratio, the water surface profiles, velocity, vorticity, and turbulence fields have been presented and discussed. The inclusion of wind alters the air flow structure above water waves, increases the generation of vorticity, and affects the wave shoaling, breaking, overturning, and splash-up processes. Wind increases the water particle velocities and causes water waves to break earlier and seaward, which agrees with the previous experiment.

Effect of current on spectrum of breaking waves in water of finite depth

NASA Technical Reports Server (NTRS)

Tung, C. C.; Huang, N. E.

1987-01-01

This paper presents an approximate method to compute the mean value, the mean square value and the spectrum of waves in water of finite depth taking into account the effect of wave breaking with or without the presence of current. It is assumed that there exists a linear and Gaussian ideal wave train whose spectrum is first obtained using the wave energy flux balance equation without considering wave breaking. The Miche wave breaking criterion for waves in finite water depth is used to limit the wave elevation and establish an expression for the breaking wave elevation in terms of the elevation and its second time derivative of the ideal waves. Simple expressions for the mean value, the mean square value and the spectrum are obtained. These results are applied to the case in which a deep water unidirectional wave train, propagating normally towards a straight shoreline over gently varying sea bottom of parallel and straight contours, encounters an adverse steady current whose velocity is assumed to be uniformly distributed with depth. Numerical results are obtained and presented in graphical form.

Effects of surface wave breaking on the oceanic boundary layer

NASA Astrophysics Data System (ADS)

He, Hailun; Chen, Dake

2011-04-01

Existing laboratory studies suggest that surface wave breaking may exert a significant impact on the formation and evolution of oceanic surface boundary layer, which plays an important role in the ocean-atmosphere coupled system. However, present climate models either neglect the effects of wave breaking or treat them implicitly through some crude parameterization. Here we use a one-dimensional ocean model (General Ocean Turbulence Model, GOTM) to investigate the effects of wave breaking on the oceanic boundary layer on diurnal to seasonal time scales. First a set of idealized experiments are carried out to demonstrate the basic physics and the necessity to include wave breaking. Then the model is applied to simulating observations at the northern North Sea and the Ocean Weather Station Papa, which shows that properly accounting for wave breaking effects can improve model performance and help it to successfully capture the observed upper ocean variability.

Mapping wave breaking and residual foam using infrared remote sensing

NASA Astrophysics Data System (ADS)

Carini, R. J.; Jessup, A. T.; Chickadel, C.

2012-12-01

Quantifying wave breaking in the surfzone is important for the advancement of models that seek to accurately predict energy dissipation, near-shore circulation, wave-current interactions, and air-sea gas transfer. Electro-optical remote sensing has been used to try to identify breaking waves. However, the residual foam, left over after the wave has broken, is indistinguishable from active foam in the visible band, which makes identification of active breaking difficult. Here, we explore infrared remote sensing of breaking waves at near-grazing incidence angles to differentiate between active and residual foam in the surfzone. Measurements were made at two field sites: Duck, NC, in September 2010 (Surf Zone Optics) and New River Inlet, NC, in May 2012 (RIVET). At both sites, multiple IR cameras were mounted to a tower onshore, viewing the surfzone at near-grazing incidence angles. For near-grazing incidence angles, small changes in viewing angle, such as those produced by the slope of a wave face, cause large modulations of the infrared signal. Therefore, the passage of waves can be seen in IR imagery. Wave breaking, however, is identified by the resulting foam. Foam has a higher emissivity than undisturbed water and thus appears warmer in an IR image. Residual foam cools quickly [Marmorino and Smith, 2005], thereby making its signal distinct from that of foam produced during active wave breaking. We will use these properties to develop a technique to produce spatial and temporal maps of active breaking and residual foam. These products can then be used to validate current models of surfzone bubbles and foam coverage. From the maps, we can also estimate energy dissipation due to wave breaking in the surfzone and compare this to estimates made with in situ data.; Infrared image of the surfzone at Duck, NC. Examples of actively breaking foam and cool residual foam are labeled.

A unified spectral,parameterization for wave breaking: from the deep ocean to the surf zone

NASA Astrophysics Data System (ADS)

Filipot, J.

2010-12-01

A new wave-breaking dissipation parameterization designed for spectral wave models is presented. It combines wave breaking basic physical quantities, namely, the breaking probability and the dissipation rate per unit area. The energy lost by waves is fi[|#12#|]rst calculated in the physical space before being distributed over the relevant spectral components. This parameterization allows a seamless numerical model from the deep ocean into the surf zone. This transition from deep to shallow water is made possible by a dissipation rate per unit area of breaking waves that varies with the wave height, wavelength and water depth.The parameterization is further tested in the WAVEWATCH III TM code, from the global ocean to the beach scale. Model errors are smaller than with most specialized deep or shallow water parameterizations.

Some observations on the role of planetary waves in determining the spring time ozone distribution in the Antarctic

NASA Technical Reports Server (NTRS)

Chandra, S.; Mcpeters, R. D.

1986-01-01

Ozone measurements from 1970 to 1984 from the Nimbus 4 backscattered ultraviolet and the Nimbus 7 solar backscattered ultraviolet spectrometers show significant decrease in total ozone only after 1979. The downward trend is most apparent in October south of 70 deg S in the longitude zone 0 to 30 deg W where planetary wave activity is weak. Outside this longitude region, the trend in total ozone is much smaller due to strong interannual variability of wave activity. This paper gives a phenomenological description of ozone depletion in the Antarctic region based on vertical advection and transient planetary waves.

Remote Sensing Characteristics of Wave Breaking Rollers

NASA Astrophysics Data System (ADS)

Haller, M. C.; Catalan, P.

2006-12-01

The wave roller has a primary influence on the balances of mass and momentum in the surf zone (e.g. Svendsen, 1984; Dally and Brown, 1995; Ruessink et al., 2001). In addition, the roller area and its angle of inclination on the wave front are important quantities governing the dissipation rates in breaking waves (e.g Madsen et al., 1997). Yet, there have been very few measurements published of individual breaking wave roller geometries in shallow water. A number of investigators have focused on observations of the initial jet-like motion at the onset of breaking before the establishment of the wave roller (e.g. Basco, 1985; Jansen, 1986), while Govender et al. (2002) provide observations of wave roller vertical cross-sections and angles of inclination for a pair of laboratory wave conditions. Nonetheless, presently very little is known about the growth, evolution, and decay of this aerated region of white water as it propagates through the surf zone; mostly due to the inherent difficulties in making the relevant observations. The present work is focused on analyzing observations of the time and space scales of individual shallow water breaking wave rollers as derived from remote sensing systems. Using a high-resolution video system in a large-scale laboratory facility, we have obtained detailed measurements of the growth and evolution of the wave breaking roller. In addition, by synchronizing the remote video with in-situ wave gages, we are able to directly relate the video intensity signal to the underlying wave shape. Results indicate that the horizontal length scale of breaking wave rollers differs significantly from the previous observations of Duncan (1981), which has been a traditional basis for roller model parameterizations. The overall approach to the video analysis is new in the sense that we concentrate on individual breaking waves, as opposed to the more commonly used time-exposure technique. In addition, a new parameter of interest, denoted Imax, is introduced based on the envelope of the intensity signal. The parameter is shown to be much less sensitive to trailing wave breaking foam, which typically corrupts time-exposure data. In the present work this parameter is shown to provide high-resolution information regarding the onset of wave breaking and the spatial evolution of the wave roller. Ongoing work will attempt to relate the shoreward transformation of the intensity maximum and the geometric characteristics of the wave roller to the spatial distribution of wave breaking dissipation. Finally, we will compare wave breaking characteristics as imaged by two separate remote sensors. Synoptic images from both video and microwave radar remote sensors were obtained in September of 2005 at Duck, NC. This combination of the two observing systems will allow direct quantitative comparisons between the two imaging mechanisms and lead to a better understanding of the strengths and weaknesses of both for nearshore research and observational remote sensing.

A multidisciplinary study of planetary, solar and astrophysical radio emissions

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Calvert, W.; Fielder, R.; Goertz, C.; Grabbe, C.; Kurth, W.; Mutel, R.; Sheerin, J.; Mellott, M.; Spangler, S.

1986-01-01

Combination of the related fields of planetary, solar, and astrophysical radio emissions was attempted in order to more fully understand the radio emission processes. Topics addressed include: remote sensing of astrophysical plasma turbulence; Alfven waves; astrophysical shock waves; surface waves; very long base interferometry results; very large array observations; solar magnetic flux; and magnetohydrodynamic waves as a tool for solar corona diagnostics.

Application of shock wave data to earth and planetary science

NASA Technical Reports Server (NTRS)

Ahrens, T. J.

1985-01-01

It is pointed out that shock wave data for: (1) low temperature condensable gases H2 and He, (2) H2O, CH4, NH3, CO, CO2, and N2 ices, and (3) silicates, metals, oxides and sulfides have many applications in geophysics and planetary science. The present paper is concerned with such applications. The composition of planetary interiors is discussed, taking into account the division of the major constituent of the planets in three groups on the basis of 'cosmic abundance' arguments, the H-He mixtures in the case of Jupiter and Saturn, shock wave data for hydrogen, and constraints on the internal structure of Uranus and Neptune. Attention is also given to the earth's mantle, shock wave data for mantle materials, the earth's core, impacts on planetary surfaces, elastic wave velocities as a function of pressure along the Hugoniot of iron, and reactions which yield the CO2 bearing atmospheres for Venus, earth, and Mars.

Refined Source Terms in Wave Watch 3 with Wave Breaking and Sea Spray Forecasts

DTIC Science & Technology

2016-08-05

Farmer at IOS Canada involved a novel scale analysis of breaking waves. This was motivated by the results of the model study of wave breaking onset by...timely development that needs careful examination. 4.11 Highlights of the SPANDEX study SPANDEX, the Spray Production and Dynamics Experiment, is...speed alone. To accomplish this goal, a parallel laboratory study (SPANDEX II) was undertaken to parameterize sea spray flux dependences on breaking

Origin of the 2016 QBO Disruption and Its Relationship to Extreme El Niño Events

NASA Astrophysics Data System (ADS)

Barton, C. A.; McCormack, J. P.

2017-11-01

The descent of the westerly phase of the quasi-biennial oscillation (QBO) in equatorial stratospheric zonal wind was interrupted by the development of easterlies near 40 hPa ( 23 km altitude) in early 2016. We use tropical meteorological analyses of wind and temperature to describe in detail the special circumstances by which equatorward-propagating planetary waves produced this unprecedented disruption in the QBO. Our findings show that the subtropical easterly jet in the winter lower stratosphere during the 2015-2016 winter was anomalously weak owing to (1) the timing of the QBO relative to the annual cycle and (2) an extreme El Niño event. The weak jet allowed an unusually large flux of westward momentum to propagate from the extratropical Northern Hemisphere to the equator near the 40 hPa level. Consequently, the QBO westerlies at that level experienced sustained easterly acceleration from extratropical wave breaking, leading to the observed wind reversal.

On the structure of climate variability near the tropopause and its relationship to equatorial planetary waves

NASA Astrophysics Data System (ADS)

Grise, Kevin M.

The tropopause is an important interface in the climate system, separating the unique dynamical, chemical, and radiative regimes of the troposphere and stratosphere. Previous studies have demonstrated that the long-term mean structure and variability of the tropopause results from a complex interaction of stratospheric and tropospheric processes. This project provides new insight into the processes involved in the global tropopause region through two perspectives: (1) a high vertical resolution climatology of static stability and (2) an observational analysis of equatorial planetary waves. High vertical resolution global positioning system radio occultation profiles are used to document fine-scale features of the global static stability field near the tropopause. Consistent with previous studies, a region of enhanced static stability, known as the tropopause inversion layer (TIL), exists in a narrow layer above the extratropical tropopause and is strongest over polar regions during summer. However, in the tropics, the TIL possesses a unique horizontally and vertically varying structure with maxima located at ˜17 and ˜19 km. The upper feature peaks during boreal winter and has its largest magnitude between 10º and 15º latitude in both hemispheres; the lower feature exhibits a weaker seasonal cycle and is centered at the Equator. The spatial structure of both features resembles the equatorial planetary wave response to the climatological distribution of deep convection. Equatorial planetary waves not only dominate the climatological-mean general circulation near the tropical tropopause but also play an important role in its intraseasonal and interannual variability. The structure of the equatorial planetary waves emerges as the leading pattern of variability of the zonally asymmetric tropical atmospheric circulation. Regressions on an index of the equatorial planetary waves reveal that they are associated with a distinct pattern of equatorially symmetric climate variability characterized by variations in: (1) the distribution of convection in the deep tropics; (2) the eddy momentum flux convergence and the zonal-mean zonal wind in the tropical upper troposphere; (3) the mean meridional circulation of the tropical and subtropical troposphere; (4) temperatures in the tropical upper troposphere, the tropical lower stratosphere, and the subtropical troposphere of both hemispheres; and (5) the amplitude of the upper tropospheric anticyclones that straddle the Equator over the western tropical Pacific Ocean. The pulsation of the equatorial planetary waves in time provides a framework for interpreting a broad range of climate phenomena. Variability in the equatorial planetary waves is associated with variability in the tropical TIL and is linked to both the El Nino-Southern Oscillation and the Madden-Julian Oscillation (MJO). Evidence is presented that suggests that the MJO can be viewed as the linear superposition of: (1) the pulsation of the equatorial planetary waves at a fixed location and (2) a propagating component. Variability in the equatorial planetary waves may also contribute to variability in troposphere/stratosphere exchange and the width of the tropical belt.

Atmospheric planetary-wave response to external forcing

NASA Technical Reports Server (NTRS)

Stevens, D. E.; Reiter, E. R.

1983-01-01

A summary of the progress report is given, covering the following areas: atmospheric circulation, planetary waves, adaption of the model to the Cyber 205, continental heat flux anomalies, and nonlinear evolution of inertial instabilities in the tropics.

Effects of the planetary-scale waves on the temporal variations of the O2-1.27μm nightglow in the Venusian upper atmosphere

NASA Astrophysics Data System (ADS)

Hoshino, N.; Fujiwara, H.; Takagi, M.; Kasaba, Y.; Takahashi, Y.

2009-12-01

The O2-1.27 μm nightglow distribution, which has the peak intensity in the depression region of the day-to-night flow, gives us information of the wind field at about 95 km in Venus. The past nightglow observations [Crisp et al., 1996] showed that the intensity of the nightglow in the brightness region changed by 20 % in about one hour, and the brightness region disappeared in less than one day. The observation results obtained by Venus Express (VEX) also showed the temporal variations of the nightglow emission. Some simulation studies suggested contributions of gravity waves generated in the cloud deck (50-70 km) to the temporal variations. However, the causes of the temporal variations are still unknown. In recent years, the importance of planetary-scale waves for the dynamics of the Venusian atmosphere has been recognized. For example, Takagi and Matsuda [2006] suggested that the atmospheric superrotation was driven by the momentum transport due to the vertical propagation of the thermal tides generated in the Venus cloud deck. In order to estimate effects of the planetary-scale waves on the temporal variations of the nightglow, we have performed numerical simulations with a general circulation model (GCM), which includes the altitude region of 80 - about 200 km. The planetary-scale waves (thermal tides, Kelvin wave and Rosbby wave) are imposed at the lower boundary. The amplitudes and phase velocities of the waves are assumed from the study by Del Genio and Rossow [1990]. The nightglow intensity and its global distribution are calculated from the GCM results assuming the chemical equilibration. In this study, we investigate contributions of the planetary-scale waves on the temporal variations of the nightglow shown by past observations. In addition, we show the characteristics of the wave propagation and the interactions between the waves in the Venusian upper atmosphere. Venus Climate Orbiter (VCO), which will be launched in 2010 as the second Japanese planetary mission, is expected to provide precious information about the atmospheric waves at the cloud top (about 70 km) and the nightglow distributions in the thermosphere. We can understand effects of the atmospheric waves on the Venusian thermosphere quantitatively by performing simulations with new information about the atmospheric waves obtained from the detailed nightglow observations.

Spitzer Observations of OGLE-2015-BLG-1212 Reveal a New Path toward Breaking Strong Microlens Degeneracies

NASA Technical Reports Server (NTRS)

Bozza, V.; Shvartzvald, Y.; Udalski, A.; Novati, S.Calchi; Bond, I. A.; Han, C.; Hundertmark, M.; Poleski, R.; Pawlak, M.; Szymanski, M. K.;

A unified spectral parameterization for wave breaking: From the deep ocean to the surf zone

NASA Astrophysics Data System (ADS)

Filipot, J.-F.; Ardhuin, F.

2012-11-01

A new wave-breaking dissipation parameterization designed for phase-averaged spectral wave models is presented. It combines wave breaking basic physical quantities, namely, the breaking probability and the dissipation rate per unit area. The energy lost by waves is first explicitly calculated in physical space before being distributed over the relevant spectral components. The transition from deep to shallow water is made possible by using a dissipation rate per unit area of breaking waves that varies with the wave height, wavelength and water depth. This parameterization is implemented in the WAVEWATCH III modeling framework, which is applied to a wide range of conditions and scales, from the global ocean to the beach scale. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Model errors are comparable to those of other specialized deep or shallow water parameterizations. This work shows that it is possible to have a seamless parameterization from the deep ocean to the surf zone.

Regarding tracer transport in Mars' winter atmosphere in the presence of nearly stationary, forced planetary waves

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffrey L.; Haberle, R. M.; Houben, Howard C.

1993-01-01

Large-scale transport of volatiles and condensates on Mars, as well as atmospheric dust, is ultimately driven by the planet's global-scale atmospheric circulation. This circulation arises in part from the so-called mean meridional (Hadley) circulation that is associated with rising/poleward motion in low latitudes and sinking/equatorward motion in middle and high latitudes. Intimately connected to the mean circulation is an eddy-driven component due to large-scale wave activity in the planet's atmosphere. During winter this wave activity arises both from traveling weather systems (i.e., barotropic and baroclinic disturbances) and from 'forced' disturbances (e.g., the thermal tides and surface-forced planetary waves). Possible contributions to the effective (net) transport circulation from forced planetary waves are investigated.

The response of stationary planetary waves to tropospheric forcing

NASA Technical Reports Server (NTRS)

Alpert, J. C.; Geller, M. A.; Avery, S. K.

1983-01-01

The lower boundary forcing of airflow over topography, and the internal forcing that results from the geographical distribution of diabatic heating, are studied in light of a steady state, linear, quasi-geostrophic model of stationary waves on a sphere. The lower boundary vertical motions forced by airflow over topography depend on whether the horizontal deflection of airflow around topographic features is taken into account, the level of the wind profile at which flow over topography is assumed to take place, and the topographic data set that was used in the forcing formulation. The lower boundary forcing is taken to be given by the observed stationary planetary wave in lower boundary geopotential height, and the internal forcing is computed using the planetary wave propagation equation on the observed wave structure.

Laboratory Investigation of Wave Breaking. Part 2. Deep Water Waves

DTIC Science & Technology

1975-06-01

respectively, phase velocity is given implicitly by: C3 = [ + (f )2] ( Levi - Civita , 1925) (2a)C3 CS = F (1 + (c_-_)2 + (fH)4 (Beach Erosion Board, 1941...In view of the above, one is led to wonder why almost all wave- 4 oriented research within the past two decades has been directed towards wave growth...mechanisms, as opposed to wave breaking. There seem to be ’’ at least two reasors. Wave breaking--aidefined by turbulent energy loss- -is a non

Probability function of breaking-limited surface elevation. [wind generated waves of ocean

NASA Technical Reports Server (NTRS)

Tung, C. C.; Huang, N. E.; Yuan, Y.; Long, S. R.

1989-01-01

The effect of wave breaking on the probability function of surface elevation is examined. The surface elevation limited by wave breaking zeta sub b(t) is first related to the original wave elevation zeta(t) and its second derivative. An approximate, second-order, nonlinear, non-Gaussian model for zeta(t) of arbitrary but moderate bandwidth is presented, and an expression for the probability density function zeta sub b(t) is derived. The results show clearly that the effect of wave breaking on the probability density function of surface elevation is to introduce a secondary hump on the positive side of the probability density function, a phenomenon also observed in wind wave tank experiments.

Mesoscale Simulations of Gravity Waves During the 2008-2009 Major Stratospheric Sudden Warming

NASA Technical Reports Server (NTRS)

Limpasuvan, Varavut; Alexander, M. Joan; Orsolini, Yvan J.; Wu, Dong L.; Xue, Ming; Richter, Jadwiga H.; Yamashita, Chihoko

2011-01-01

A series of 24 h mesoscale simulations (of 10 km horizontal and 400 m vertical resolution) are performed to examine the characteristics and forcing of gravity waves (GWs) relative to planetary waves (PWs) during the 2008-2009 major stratospheric sudden wam1ing (SSW). Just prior to SSW occurrence, widespread westward propagating GWs are found along the vortex's edge and associated predominantly with major topographical features and strong near-surface winds. Momentum forcing due to GWs surpasses PW forcing in the upper stratosphere and tends to decelerate the polar westerly jet in excess of 30 m/s/d. With SSW onset, PWs dominate the momentum forcing, providing decelerative effects in excess of 50 m/s/d throughout the upper polar stratosphere. GWs related to topography become less widespread largely due to incipient wind reversal as the vortex starts to elongate. During the SSW maturation and early recovery, the polar vortex eventually splits and both wave signatures and forcing greatly subside. Nonetheless, during SSW, westward and eastward propagating GWs are found in the polar region and may be generated in situ by flow adjustment processes in the stratosphere or by secondary GW breaking. The simulated large-scale features agree well with those resolved in satellite observations and analysis products.

An Experimental Study Comparing Droplet Production by a Strong Plunging and a Weak Spilling Breaking Water Waves

NASA Astrophysics Data System (ADS)

Erinin, Martin; Wang, Dan; Towle, David; Liu, Xinan; Duncan, James

2017-11-01

In this study, the production of droplets by two mechanically generated breaking water waves is investigated in a wave tank. A strong plunging breaker and weak spilling breaker are generated repeatedly with a programmable wave maker by using two dispersively focused wave packets with the same wave maker motion profile shape (average frequency 1.15 Hz) and two overall amplitude factors. The profile histories of the breaking wave crests along the center plane of the tank are measured using cinematic laser-induced fluorescence. The droplets are measured using a high speed (650 Hz) cinematic digital in-line holographic system positioned at various locations along a horizontal plane that is 1 cm above the maximum wave crest height. The measurement plane covers the entire region in the tank where the wave breaks. The holographic system is used to obtain the droplet diameters (d, for d >100 microns) and the three components of the droplet velocities. From these measurements and counting only the droplets that are moving up, the spatio-temporal distribution of droplet generation by the two breaking waves is obtained. The main features of the droplet generation are correlated with the features and phases of the breaking process. The support of the National Science Foundation under Grant OCE0751853 from the Division of Ocean Sciences is gratefully acknowledged.

Assessment of the Breakup of the Antarctic Polar Vortex in Two New Chemistry-Climate Models

NASA Technical Reports Server (NTRS)

Hurwitz, M. M.; Newman, P. A.; Oman, L. D.; Li, F.; Morgenstern, O.; Braesicke, P.; Pyle, J. A.

2010-01-01

Successful simulation of the breakup of the Antarctic polar vortex depends on the representation of tropospheric stationary waves at Southern Hemisphere middle latitudes. This paper assesses the vortex breakup in two new chemistry-climate models (CCMs). The stratospheric version of the UK Chemistry and Aerosols model is able to reproduce the observed timing of the vortex breakup. Version 2 of the Goddard Earth Observing System (GEOS V2) model is typical of CCMs in that the Antarctic polar vortex breaks up too late; at 10 hPa, the mean transition to easterlies at 60 S is delayed by 12-13 days as compared with the ERA-40 and National Centers for Environmental Prediction reanalyses. The two models' skill in simulating planetary wave driving during the October-November period accounts for differences in their simulation of the vortex breakup, with GEOS V2 unable to simulate the magnitude and tilt of geopotential height anomalies in the troposphere and thus underestimating the wave driving. In the GEOS V2 CCM the delayed breakup of the Antarctic vortex biases polar temperatures and trace gas distributions in the upper stratosphere in November and December.

A coherent nonlinear theory of auroral Langmuir-Alfven-whistler (LAW) events in the planetary magnetosphere.

NASA Astrophysics Data System (ADS)

Lopes, S. R.; Chian, A. C.-L.

1996-01-01

A coherent nonlinear theory of three-wave coupling involving Langmuir, Alfven and whistler waves is formulated and applied to the observation of auroral LAW events in the planetary magnetosphere. The effects of pump depletion, dissipation and frequency mismatch in the nonlinear wave dynamics are analyzed. The relevance of this theory for understanding the fine structures of auroral whistler-mode emissions and amplitude modulations of auroral Langmuir waves is discussed.

Jovian Planetary Waves

NASA Astrophysics Data System (ADS)

Harrington, J.; Deming, D.

1997-07-01

We have found over two dozen discrete, linearly-propagating, periodic features in 5-{\\micron} images of Jovian cloud opacities (J. Harrington et al. 1996, Icarus 124, 32--44). Numerous spatially-sinusoidal temperature oscillations also appear in several passbands between 7 and 19 {\\microns} (D. Deming et al. 1997, Icarus 126, 301--312). Both types of Jovian planetary-scale features are zonally-oriented. They have always been detected when sought (1989, '91, '92, '93), and some individual features persist 100 Earth days or longer. These features are superficially consistent with Rossby waves, but they do not follow a simplistic dispersion relation based on cloud-top wind speeds. Planetary wavenumbers are never larger than 15, consistent with predictions based on the Rhines scale for Jupiter. There are many outstanding phenomenological questions: Where and how are the waves driven? How are waves at different atmospheric levels related? What are their true dispersion properties? How long do they last? We are continuing observations and will conduct a search of the Hubble Space Telescope archive for the \\sim 1{°ee} meridional cloud-belt deviations expected for Rossby waves. We are in the process of correlating wave detections of various types, times, and wavelengths with each other. Our goal is to constrain atmospheric stratification and vertical energy transport. Because Rossby waves propagate vertically, these features may probe conditions at the interface between the meteorological atmosphere and the planetary interior. Work supported by NASA Planetary Astronomy RTOP 196-41-54. Work performed while J. H. held a National Research Council - NASA Goddard Space Flight Center Research Associateship.

Hybrid Eulerian and Lagrangian Simulation of Steep and Breaking Waves and Surface Fluxes in High Winds

DTIC Science & Technology

2012-09-30

Lagrangian methods for free - surface turbulence and wave simulation . In the far field, coupled wind and wave simulations are used to obtain wind...to conserve the mass precisely. When the wave breaks, the flow at the free surface may become very violent, air and water may be highly mixed...fluids free - surface flows that can be used to study the fundamental physics of wave breaking. The research will improve the understanding of air-sea

Current Scientific Issues in Large Scale Atmospheric Dynamics

NASA Technical Reports Server (NTRS)

Miller, T. L. (Compiler)

1986-01-01

Topics in large scale atmospheric dynamics are discussed. Aspects of atmospheric blocking, the influence of transient baroclinic eddies on planetary-scale waves, cyclogenesis, the effects of orography on planetary scale flow, small scale frontal structure, and simulations of gravity waves in frontal zones are discussed.

-> Air entrainment and bubble statistics in three-dimensional breaking waves

NASA Astrophysics Data System (ADS)

Deike, L.; Popinet, S.; Melville, W. K.

2016-02-01

Wave breaking in the ocean is of fundamental importance for quantifying wave dissipation and air-sea interaction, including gas and momentum exchange, and for improving air-sea flux parametrizations for weather and climate models. Here we investigate air entrainment and bubble statistics in three-dimensional breaking waves through direct numerical simulations of the two-phase air-water flow using the Open Source solver Gerris. As in previous 2D simulations, the dissipation due to breaking is found to be in good agreement with previous experimental observations and inertial-scaling arguments. For radii larger than the Hinze scale, the bubble size distribution is found to follow a power law of the radius, r-10/3 and to scale linearly with the time dependent turbulent dissipation rate during the active breaking stage. The time-averaged bubble size distribution is found to follow the same power law of the radius and to scale linearly with the wave dissipation rate per unit length of breaking crest. We propose a phenomenological turbulent bubble break-up model that describes the numerical results and existing experimental results.

Mesosphere Dynamics with Gravity Wave Forcing. 1; Diurnal and Semi-Diurnal Tides

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Mengel, J. G.; Chan, K. L.; Porter, H. S.; Einaudi, Franco (Technical Monitor)

2000-01-01

We present results from a nonlinear, 3D, time dependent numerical spectral model (NSM), which extends from the ground up into the thermosphere and incorporates Hines' Doppler Spread Parameterization for small-scale gravity waves (GW). Our focal point is the mesosphere that is dominated by wave interactions. We discuss diurnal and semi-diurnal tides ill the present paper (Part 1) and planetary waves in the companion paper (Part 2). To provide an understanding of the seasonal variations of tides, in particular with regard to gravity wave processes, numerical experiments are performed that lead to the following conclusions: 1. The large semiannual variations in tile diurnal tide (DT), with peak amplitudes observed around equinox, are produced primarily by GW interactions that involve, in part, planetary waves. 2. The DT, like planetary waves, tends to be amplified by GW momentum deposition, which reduces also the vertical wavelength. 3.Variations in eddy viscosity associated with GW interactions tend to peak in late spring and early fall and call also influence the DT. 4. The semidiurnal semidiurnal tide (SDT), and its phase in particular, is strongly influenced by the mean zonal circulation. 5. The SDT, individually, is amplified by GW's. But the DT filters out GW's such that the wave interaction effectively reduces the amplitude of the SDT, effectively producing a strong nonlinear interaction between the DT and SDT. 6.) Planetary waves generated internally by baroclinic instability and GW interaction produce large amplitude modulations of the DT and SDT.

Long-time Dynamics of Stochastic Wave Breaking

NASA Astrophysics Data System (ADS)

Restrepo, J. M.; Ramirez, J. M.; Deike, L.; Melville, K.

2017-12-01

A stochastic parametrization is proposed for the dynamics of wave breaking of progressive water waves. The model is shown to agree with transport estimates, derived from the Lagrangian path of fluid parcels. These trajectories are obtained numerically and are shown to agree well with theory in the non-breaking regime. Of special interest is the impact of wave breaking on transport, momentum exchanges and energy dissipation, as well as dispersion of trajectories. The proposed model, ensemble averaged to larger time scales, is compared to ensemble averages of the numerically generated parcel dynamics, and is then used to capture energy dissipation and path dispersion.

Short and long periodic atmospheric variations between 25 and 200 km

NASA Technical Reports Server (NTRS)

Justus, C. G.; Woodrum, A.

1973-01-01

Previously collected data on atmospheric pressure, density, temperature and winds between 25 and 200 km from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others were analyzed by a daily difference method and results on the distribution statistics, magnitude, and spatial structure of gravity wave and planetary wave atmospheric variations are presented. Time structure of the gravity wave variations were determined by the analysis of residuals from harmonic analysis of time series data. Planetary wave contributions in the 25-85 km range were discovered and found to have significant height and latitudinal variation. Long period planetary waves, and seasonal variations were also computed by harmonic analysis. Revised height variations of the gravity wave contributions in the 25 to 85 km height range were computed. An engineering method and design values for gravity wave magnitudes and wave lengths are given to be used for such tasks as evaluating the effects on the dynamical heating, stability and control of spacecraft such as the space shuttle vehicle in launch or reentry trajectories.

Large-wave simulation of spilling breaking and undertow current over constant slope beach

NASA Astrophysics Data System (ADS)

Dimas, Athanassios; Kolokythas, Gerasimos; Dimakopoulos, Aggelos

2011-11-01

The three-dimensional, free-surface flow, developing by the propagation of nonlinear breaking waves over a constant slope bed, is numerically simulated. The main objective is to investigate the effect of spilling breaking on the characteristics of the induced undertow current by performing large-wave simulations (LWS) based on the numerical solution of the Navier-Stokes equations subject to the fully nonlinear free-surface boundary conditions and the appropriate bottom, inflow and outflow boundary conditions. The equations are properly transformed so that the computational domain becomes time-independent. In the present study, the case of incoming waves with wavelength to inflow depth ratio λ/ d ~ 6.6 and wave steepness H/ λ ~0.025, over bed of slope tan β = 1/35, is investigated. The LWS predicts satisfactorily breaking parameters - height and depth - and wave dissipation in the surf zone, in comparison to experimental data. In the corresponding LES, breaking height and depth are smaller and wave dissipation in the surf zone is weaker. For the undertow current, it is found that it is induced by the breaking process at the free surface, while its strength is controlled by the bed shear stress. Finally, the amplitude of the bed shear stress increases substantially in the breaking zone, becoming up to six times larger than the respective amplitude at the outer region.

Radiative effects of ozone waves on the Northern Hemisphere polar vortex and its modulation by the QBO

NASA Astrophysics Data System (ADS)

Silverman, Vered; Harnik, Nili; Matthes, Katja; Lubis, Sandro W.; Wahl, Sebastian

2018-05-01

The radiative effects induced by the zonally asymmetric part of the ozone field have been shown to significantly change the temperature of the NH winter polar cap, and correspondingly the strength of the polar vortex. In this paper, we aim to understand the physical processes behind these effects using the National Center for Atmospheric Research (NCAR)'s Whole Atmosphere Community Climate Model, run with 1960s ozone-depleting substances and greenhouse gases. We find a mid-winter polar vortex influence only when considering the quasi-biennial oscillation (QBO) phases separately, since ozone waves affect the vortex in an opposite manner. Specifically, the emergence of a midlatitude QBO signal is delayed by 1-2 months when radiative ozone-wave effects are removed. The influence of ozone waves on the winter polar vortex, via their modulation of shortwave heating, is not obvious, given that shortwave heating is largest during fall, when planetary stratospheric waves are weakest. Using a novel diagnostic of wave 1 temperature amplitude tendencies and a synoptic analysis of upward planetary wave pulses, we are able to show the chain of events that lead from a direct radiative effect on weak early fall upward-propagating planetary waves to a winter polar vortex modulation. We show that an important stage of this amplification is the modulation of individual wave life cycles, which accumulate during fall and early winter, before being amplified by wave-mean flow feedbacks. We find that the evolution of these early winter upward planetary wave pulses and their induced stratospheric zonal mean flow deceleration is qualitatively different between QBO phases, providing a new mechanistic view of the extratropical QBO signal. We further show how these differences result in opposite radiative ozone-wave effects between east and west QBOs.

An assessment of thermal, wind, and planetary wave changes in the middle and lower atmosphere due to 11-year UV flux variations

NASA Technical Reports Server (NTRS)

Callis, L. B.; Alpert, J. C.; Geller, M. A.

1985-01-01

Hines (1974) speculated that solar-induced modifications of the middle and upper atmosphere may alter the transmissivity of the stratosphere to upwardly propagating atmospheric waves. It was suggested that subsequent constructive or destructive interference may result in a change of phase or amplitude of these waves in the troposphere leading to weather or climate changes. The present investigation has the objective to bring together both radiative transfer and planetary wave studies in an effort to assess specifically whether Hines mechanism can be initiated by the solar ultraviolet flux variability assumed to be associated with the 11-year solar cycle. The obtained results suggest that the presently studied mechanism, which links solar-induced zonal wind changes in the stratosphere and mesosphere to planetary wave changes in the troposphere, is not strong enough to cause substantive changes in the troposphere.

Nonlocal symmetries, solitary waves and cnoidal periodic waves of the (2+1)-dimensional breaking soliton equation

NASA Astrophysics Data System (ADS)

Zou, Li; Tian, Shou-Fu; Feng, Lian-Li

2017-12-01

In this paper, we consider the (2+1)-dimensional breaking soliton equation, which describes the interaction of a Riemann wave propagating along the y-axis with a long wave along the x-axis. By virtue of the truncated Painlevé expansion method, we obtain the nonlocal symmetry, Bäcklund transformation and Schwarzian form of the equation. Furthermore, by using the consistent Riccati expansion (CRE), we prove that the breaking soliton equation is solvable. Based on the consistent tan-function expansion, we explicitly derive the interaction solutions between solitary waves and cnoidal periodic waves.

Planetary wave-like oscillations in the ionosphere retrieved with a longitudinal chain of ionosondes at high northern latitudes

NASA Astrophysics Data System (ADS)

Stray, Nora H.; Espy, Patrick J.

2018-06-01

This paper examines the influence of neutral dynamics on the high latitude ionosphere. Using a longitudinal chain of ionosondes at high northern latitudes (52°-65° N), planetary wave-like structures were observed in the spatial structure of the peak electron density in the ionosphere. Longitudinal wavenumbers S0, S1 and S2 have been extracted from these variations of the F layer. The observed wave activity in wavenumber one and two does not show any significant correlation with indices of magnetic activity, suggesting that this is not the primary driver. In addition, the motion of the S1 ionospheric wave structures parallels that of the S1 planetary waves observed in the winds of the mesosphere-lower-thermosphere derived from a longitudinal array of SuperDARN meteor-radar wind measurements. The time delay between the motions of the wave structures would indicate a indirect coupling, commensurate with the diffusion to the ionosphere of mesospheric atomic oxygen perturbations.

The effects of blocking in the subtropics on the phase speed of the MJO

NASA Astrophysics Data System (ADS)

Roundy, P. E.

2016-12-01

The phase speed of the MJO might be regulated by many different factors. Previous works have suggested that moist processes govern the phase speed, and our results show that intensification of convection is associated with reduction of phase speed down to about 5 ms-1. However, convection and rainfall decline with declining phase speeds below 5 ms-1. This presentation shows that increased Rossby wave breaking and blocking east of MJO deep convection is associated with reduced phase speed below about 6 ms-1. A wavelet filter is applied to extract time series characterized by selected zonal wavenumbers and frequencies at select equatorial base longitudes over the Indian and West Pacific Oceans. Results show that anomalies of active convection characterized by wavenumber 2 (the dominant scale of MJO convection over the warm pool) are associated with meridional potential vorticity (PV) gradients across the tropics to the east of the active convection that are near climatology for events moving east at 5 ms-1. These gradients are much weaker for slower events. The slowest phase speed events have almost no meridional PV gradients across the tropics between the mean latitudes of the subtropical jet streams, suggesting that jet exit regions occur immediately east of the deep convection, dumping mass in the upper troposphere over the region of suppressed convection. In the absence of PV gradients, synoptic to planetary scale waves moving into that environment break or cease to propagate linearly.

An Experimental Study of Droplets Produced by a Plunging Breakers

NASA Astrophysics Data System (ADS)

Erinin, Martin; Wang, Dan; Towle, David; Liu, Xinan; Duncan, James

2016-11-01

In this study, the production of droplets by a mechanically generated plunging breaking water wave is investigated in a wave tank. The breaker, with an amplitude of 0.070 m, is generated repeatedly with a programmable wave maker by using a dispersively focused wave packet (average frequency 1.15 Hz). The profile histories of the breaking wave crests along the center plane of the tank are measured using cinematic laser-induced fluorescence. The droplets are measured using a cinematic digital in-line holographic system positioned at 30 locations along a horizontal plane that is 1 cm above the maximum wave crest height. This measurement plane covers the entire region in the tank where the wave breaks. The holographic system is used to obtain the droplet diameters (d, for d >100 microns) and the three components of the droplet velocities. From these measurements and counting only the droplets that are moving up, the spatio-temporal distribution of droplet generation by the breaking wave is obtained. The main features of the droplet generation are correlated with the features and phases of the breaking process. The support of the National Science Foundation under Grant OCE0751853 from the Division of Ocean Sciences is gratefully acknowledged.

The effect of latent heat release on synoptic-to-planetary wave interactions and its implication for satellite observations: Theoretical modeling

NASA Technical Reports Server (NTRS)

Branscome, Lee E.; Bleck, Rainer; Obrien, Enda

1990-01-01

The project objectives are to develop process models to investigate the interaction of planetary and synoptic-scale waves including the effects of latent heat release (precipitation), nonlinear dynamics, physical and boundary-layer processes, and large-scale topography; to determine the importance of latent heat release for temporal variability and time-mean behavior of planetary and synoptic-scale waves; to compare the model results with available observations of planetary and synoptic wave variability; and to assess the implications of the results for monitoring precipitation in oceanic-storm tracks by satellite observing systems. Researchers have utilized two different models for this project: a two-level quasi-geostrophic model to study intraseasonal variability, anomalous circulations and the seasonal cycle, and a 10-level, multi-wave primitive equation model to validate the two-level Q-G model and examine effects of convection, surface processes, and spherical geometry. It explicitly resolves several planetary and synoptic waves and includes specific humidity (as a predicted variable), moist convection, and large-scale precipitation. In the past year researchers have concentrated on experiments with the multi-level primitive equation model. The dynamical part of that model is similar to the spectral model used by the National Meteorological Center for medium-range forecasts. The model includes parameterizations of large-scale condensation and moist convection. To test the validity of results regarding the influence of convective precipitation, researchers can use either one of two different convective schemes in the model, a Kuo convective scheme or a modified Arakawa-Schubert scheme which includes downdrafts. By choosing one or the other scheme, they can evaluate the impact of the convective parameterization on the circulation. In the past year researchers performed a variety of initial-value experiments with the primitive-equation model. Using initial conditions typical of climatological winter conditions, they examined the behavior of synoptic and planetary waves growing in moist and dry environments. Surface conditions were representative of a zonally averaged ocean. They found that moist convection associated with baroclinic wave development was confined to the subtropics.

Dependence of Wave-Breaking Statistics on Wind Stress and Wave Development

NASA Technical Reports Server (NTRS)

Katsaros, Kristina B.; Atakturk, Serhad S.

1992-01-01

Incidence of wave breaking for pure wind driven waves has been studied on Lake Washington at wind speeds up to 8 m/s. Video recordings were employed to identify and categorize the breaking events in terms of micro-scale, spilling and plunging breakers. These events were correlated with the magnitude of the wave spectrum measured with a resistance wire wave gauge and band pass filtered between 6 and 10 Hz. An equivalent percentage of breaking crests were found for spilling and plunging events. Wave forcing as measured by wind stress (or friction velocity, u(sub *), squared) and by inverse wave age, u(sub *)/Cp where Cp is the phase velocity of the waves at the peak of the frequency spectrum, were found to be good prerictors of percentage of breaking crests. When combined in a two parameter regression, those two variables gave small standard deviation and had a high correlation coefficient (66 percent). The combination of u(sub *)(exp 2) and u(sub *)/Cp can be understood in physical terms. Furthermore, for the larger values of u(sub *)(exp 2) the dependence of wave braking and wave age was stronger than at the low end of the values u(sub *)(exp 2) and u(sub *)/Cp. Thus, both the level of wave development as determined by inverse wave age, which we may term relative wind effectiveness for wave forcing and the wind forcing on the water surface determine the incidence of wave breaking. Substituting U(sub 10)(sup 3.75) (which is the dependence of whitecap cover found by Monahan and coworkers) an equivalent correlation was found to the prediction by u(sub *)(exp 2). Slightly better standard deviation value and higher correlation coefficient were found by using a Reynolds number as predictor. A two-parameter regression involving u(sub *)(exp 2) and a Reynold's number proposed by Toba and his colleagues which relates u(sub *)(exp 2) and peak wave frequency, improves the correlation even more but is less easy to interpret in physical terms. The equivalent percentage of breaking crests obtained in our previous study was reported at 8.6 percent for a short record obtained at U(sub 10N) of about 6 m/s. Typical values in the current study for similar conditions are 6 percent, which is consistent with the previous study in view of the scatter. In that study we did not have a video recording system, so the observed breaking may include more of the micro-scaic breaking events, and the value, 8.6 percent, is well within the range of highly probable sampling variability.

Nearshore Current Model Workshop Summary.

DTIC Science & Technology

1983-09-01

dissipation , and wave-current interaction. b. Incorporation into models of wave-breaking. c. Parameterization of turbulence in models. d. Incorporation...into models of surf zone energy dissipation . e. Methods to specify waves and currents on the boundaries of the grid. f. Incorporation into models of...also recommended. Improvements should include nonlinear and irregular wave effects and improved models of wave-breaking and wave energy dissipation in

Migrating diurnal tide variability induced by propagating planetary waves

NASA Astrophysics Data System (ADS)

Chang, Loren C.

The migrating diurnal tide is one of the dominant dynamical features in the low latitudes of the Earth's Mesosphere and Lower Thermosphere (MLT) region, representing the atmospheric response to the largest component of solar forcing, propagating upwards from excitation regions in the lower atmosphere. Ground-based observations of the tide have resolved short term variations attributed to nonlinear interactions between the tide and planetary waves also in the region. However, the conditions, effects, and mechanisms of a planetary wave - tidal interaction are still unclear. These questions are addressed using the NCAR Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM) to examine two types of planetary waves, known to attain significant amplitudes in the low latitude and equatorial region where the migrating diurnal tide is dominant. The quasi-two day wave (QTDW) can rapidly amplify to large amplitudes from the summer hemisphere during post-solstice periods, while ultra fast Kelvin (UFK) waves occur sporadically in the temperature and zonal wind fields of the equatorial lower thermosphere. While child waves resulting from a nonlinear interaction are resolved in both cases, the response of the tidal structure and amplitudes to the two planetary waves differs significantly. In the case of the QTDW, the migrating diurnal tide displays a general amplitude decrease of 20 - 40%, as well as a shortening of vertical wavelength by roughly 4 km. Nonlinear advection is found to result in energy transfer to and from the tide, resulting in latitudinal smoothing of the tidal structure. The QTDW also produces significant changes to the mean zonal winds in the equator and at summer mid to high latitudes that can also account for changes in tidal amplitude and vertical wavelength. Filtering of gravity waves by the altered mean winds can also result in changes to the zonal mean zonal winds in the tropics. However, gravity wave momentum forcing on the tide is smaller than the advective tendencies throughout most of the MLT region, and cannot iv directly account for the changes in the tide during the QTDW model simulation. In the case of the UFK wave, baseline tidal amplitudes are found to show much smaller changes of 10% or less, despite the larger amplitudes of the UFK wave in the lower thermosphere region compared to the QTDW. Analysis of the nonlinear advective tendencies shows smaller magnitudes than those in the the case of the QTDW, with interaction regions limited primarily to a smaller region in latitude and altitude. Increased tidal convergence in the tropical lower thermosphere is attributed to eastward forcing of the background zonal mean winds by the UFK wave. Increasing the UFK wave forcing by an order of magnitude, although unrealistic, results in changes to the tide comparable in magnitude to the case of the QTDW. While child waves generated by nonlinear advection are present with both of the propagating planetary waves examined, the QTDW produces much greater tidal variability through both nonlinear and linear advection due to its broader horizontal and vertical structure, compared to the UFK wave. Planetary wave induced background atmosphere changes can also drive tidal variability, suggesting that changes to the tidal response in the MLT can also result from this indirect coupling mechanism, in addition to nonlinear advection.

Assessment of chemical dispersant effectiveness in a wave tank under regular non-breaking and breaking wave conditions.

PubMed

Li, Zhengkai; Lee, Kenneth; King, Thomas; Boufadel, Michel C; Venosa, Albert D

2008-05-01

Current chemical dispersant effectiveness tests for product selection are commonly performed with bench-scale testing apparatus. However, for the assessment of oil dispersant effectiveness under real sea state conditions, test protocols are required to have hydrodynamic conditions closer to the natural environment, including transport and dilution effects. To achieve this goal, Fisheries and Oceans Canada and the US Environmental Protection Agency (EPA) designed and constructed a wave tank system to study chemical dispersant effectiveness under controlled mixing energy conditions (regular non-breaking, spilling breaking, and plunging breaking waves). Quantification of oil dispersant effectiveness was based on observed changes in dispersed oil concentrations and oil-droplet size distribution. The study results quantitatively demonstrated that total dispersed oil concentration and breakup kinetics of oil droplets in the water column were strongly dependent on the presence of chemical dispersants and the influence of breaking waves. These data on the effectiveness of dispersants as a function of sea state will have significant implications in the drafting of future operational guidelines for dispersant use at sea.

What Controls the Temperature of the Arctic Stratosphere during the Spring?

NASA Technical Reports Server (NTRS)

Newman, Paul A.; Nash, Eric R.; Rosenfield, Joan E.; Einaudi, Franco (Technical Monitor)

2000-01-01

Understanding the mechanisms that control the temperature of the polar lower stratosphere during spring is key to understanding ozone loss in the Arctic polar vortex. Spring ozone loss rates are directly tied to polar stratospheric temperatures by the formation of polar stratospheric clouds, and the conversion of chlorine species to reactive forms on these cloud particle surfaces. In this paper, we study those factors that control temperatures in the polar lower stratosphere. We use the National Centers for Environmental Prediction (NCEP)/NCAR reanalysis data covering the last two decades to investigate how planetary wave driving of the stratosphere is connected to polar temperatures. In particular, we show that planetary waves forced in the troposphere in mid- to late winter (January-February) are principally responsible for the mean polar temperature during the March period. These planetary waves are forced by both thermal and orographic processes in the troposphere, and propagate into the stratosphere in the mid and high latitudes. Strong mid-winter planetary wave forcing leads to a warmer Arctic lower stratosphere in early spring, while weak mid-winter forcing leads to cooler Arctic temperatures.

Propagation of Stationary Planetary Waves in the Upper Atmosphere under Different Solar Activity

NASA Astrophysics Data System (ADS)

Koval, A. V.; Gavrilov, N. M.; Pogoreltsev, A. I.; Shevchuk, N. O.

2018-03-01

Numerical modeling of changes in the zonal circulation and amplitudes of stationary planetary waves are performed with an accounting for the impact of solar activity variations on the thermosphere. A thermospheric version of the Middle/Upper Atmosphere Model (MUAM) is used to calculate the circulation in the middle and upper atmosphere at altitudes up to 300 km from the Earth's surface. Different values of the solar radio emission flux in the thermosphere are specified at a wavelength of 10.7 cm to take into account the solar activity variations. The ionospheric conductivities and their variations in latitude, longitude, and time are taken into account. The calculations are done for the January-February period and the conditions of low, medium, and high solar activity. It was shown that, during high-activity periods, the zonal wind velocities increases at altitudes exceeding 150 km and decreases in the lower layers. The amplitudes of planetary waves at high solar activity with respect to the altitude above 120 km or below 100 km, respectively, are smaller or larger than those at low activity. These differences correspond to the calculated changes in the refractive index of the atmosphere for stationary planetary waves and the Eliassen-Palm flux. Changes in the conditions for the propagation and reflection of stationary planetary waves in the thermosphere may influence the variations in their amplitudes and the atmospheric circulation, including the lower altitudes of the middle atmosphere.

Numerical Simulations of Upstream Propagating Solitary Waves and Wave Breaking In A Stratified Fjord

NASA Astrophysics Data System (ADS)

Stastna, M.; Peltier, W. R.

In this talk we will discuss ongoing numerical modeling of the flow of a stratified fluid over large scale topography motivated by observations in Knight Inlet, a fjord in British Columbia, Canada. After briefly surveying the work done on the topic in the past we will discuss our latest set of simulations in which we have observed the gener- ation and breaking of three different types of nonlinear internal waves in the lee of the sill topography. The first type of wave observed is a large lee wave in the weakly strat- ified main portion of the water column, The second is an upward propagating internal wave forced by topography that breaks in the strong, near-surface pycnocline. The third is a train of upstream propagating solitary waves that, in certain circumstances, form as breaking waves consisting of a nearly solitary wave envelope and a highly unsteady core near the surface. Time premitting, we will comment on the implications of these results for our long term goal of quantifying tidally driven mixing in Knight Inlet.

Classification of regimes of internal solitary waves transformation over a shelf-slope topography

NASA Astrophysics Data System (ADS)

Terletska, Kateryna; Maderich, Vladimir; Talipova, Tatiana; Brovchenko, Igor; Jung, Kyung Tae

2015-04-01

The internal waves shoal and dissipate as they cross abrupt changes of the topography in the coastal ocean, estuaries and in the enclosed water bodies. They can form near the coast internal bores propagating into the shallows and re-suspend seabed pollutants that may have serious ecological consequences. Internal solitary waves (ISW) with trapped core can transport masses of water and marine organisms for some distance. The transport of cold, low-oxygen waters results in nutrient pumping. These facts require development of classification of regimes of the ISWs transformation over a shelf-slope topography to recognize 'hot spots' of wave energy dissipation on the continental shelf. A new classification of regimes of internal solitary wave interaction with the shelf-slope topography in the framework of two-layer fluid is proposed. We introduce a new three-dimensional diagram based on parameters α ,β , γ. Here α is the nondimensional wave amplitude normalized on the thermocline thickness α = ain/h1 (α > 0), β is the blocking parameter introduced in (Talipova et al., 2013) that is the ratio of the height of the bottom layer on the the shelf step h2+ to the incident wave amplitude ain, β = h2+/ain (β > -3), and γ is the parameter inverse to the slope inclination (γ > 0.01). Two mechanisms are important during wave shoaling: (i) wave breaking resulting in mixing and (ii) changing of the polarity of the initial wave of depression on the slope. Range of the parameters at which wave breaking occurs can be defined using the criteria, obtained empirically (Vlasenko and Hutter, 2002). In the three-dimensional diagram this criteria is represented by the surface f1(β,γ) = 0 that separates the region of parameters where breaking takes place from the region without breaking. The polarity change surface f2(α,β) = 0 is obtained from the condition of equality of the depth of upper layer h1 to the depth of the lower layer h2. In the two-layer stratification waves of depression may be converted to wave of elevation at the 'turning point' (h2 = h1) as they propagate from deep water onto a shallow shelf. Thus intersecting surfaces f1 and f2 divide three-dimensional diagram into four zones. Zone I located above two surfaces and corresponds to the non breaking regime. Zone II lies above 'breaking' surfaces but below the surface of changing polarity and corresponds to regime of changing polarity without breaking. Zone III lies above surface of changing polarity but below 'breaking' surfaces and corresponds to regime of wave breaking without changing polarity. Zone IV that located below two surfaces and corresponds to the regime of wave breaking with changing polarity. Regimes predicted by diagram agree with results of numerical modelling, laboratory and observation data. Based on the proposed diagram the regions in α, β, γ space with a high energy dissipation of ISW passed over the shelf-slope topography are distinguished. References Talipova T., Terletska K., Maderich V, Brovchenko I., Jung K.T., Pelinovsky E. and Grimshaw R. 2013. Internal solitary wave transformation over the bottom step: loss of energy. Phys. Fluids, 25, 032110 Vlasenko V., Hutter K. 2002. Numerical Experiments on the Breaking of Solitary Internal Waves over a Slope-Shelf Topography. J. Phys. Oceanogr., 32 (6), 1779-1793

Interannual and Decadal Variations of Planetary Wave Activity, Stratospheric Cooling, and Northern Hemisphere Annular Mode.

NASA Astrophysics Data System (ADS)

Hu, Yongyun; Kit Tung, Ka

2002-07-01

Using NCEP-NCAR 51-yr reanalysis data, the interannual and decadal variations of planetary wave activity and its relationship to stratospheric cooling, and the Northern Hemisphere Annular mode (NAM), are studied. It is found that winter stratospheric polar temperature is highly correlated on a year-to-year basis with the Eliassen-Palm (E-P) wave flux from the troposphere, implying a dynamical control of the former by the latter, as often suggested. Greater (lower) wave activity from the troposphere implies larger (smaller) poleward heat flux into the polar region, which leads to warmer (colder) polar temperature. A similar highly correlated antiphase relationship holds for E-P flux divergence and the strength of the polar vortex in the stratosphere. It is tempting to extrapolate these relationships found for interannual timescales to explain the recent stratospheric polar cooling trend in the past few decades as caused by decreased wave activity in the polar region. This speculation is not supported by the data. On timescales of decades the cooling trend is not correlated with the trend in planetary wave activity. In fact, it is found that planetary wave amplitude, E-P flux, and E-P flux convergence all show little statistical evidence of decrease in the past 51 yr, while the stratosphere is experiencing a cooling trend and the NAM index has a positive trend during the past 30 yr. This suggests that the trends in the winter polar temperature and the NAM index can reasonably be attributed to the radiative cooling of the stratosphere, due possibly to increasing greenhouse gases and ozone depletion. It is further shown that the positive trend of the NAM index in the past few decades is not through the inhibition of upward planetary wave propagation from the troposphere to the stratosphere, as previously suggested.

Wave-Particle Dynamics of Wave Breaking in the Self-Excited Dust Acoustic Wave

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teng, L.-W.; Chang, M.-C.; Tseng, Y.-P.

2009-12-11

The wave-particle microdynamics in the breaking of the self-excited dust acoustic wave growing in a dusty plasma liquid is investigated through directly tracking dust micromotion. It is found that the nonlinear wave growth and steepening stop as the mean oscillating amplitude of dust displacement reaches about 1/k (k is the wave number), where the vertical neighboring dust trajectories start to crossover and the resonant wave heating with uncertain crest trapping onsets. The dephased dust oscillations cause the abrupt dropping and broadening of the wave crest after breaking, accompanied by the transition from the liquid phase with coherent dust oscillation tomore » the gas phase with chaotic dust oscillation. Corkscrew-shaped phase-space distributions measured at the fixed phases of the wave oscillation cycle clearly indicate how dusts move in and constitute the evolving waveform through dust-wave interaction.« less

Wave-Particle Dynamics of Wave Breaking in the Self-Excited Dust Acoustic Wave

NASA Astrophysics Data System (ADS)

Teng, Lee-Wen; Chang, Mei-Chu; Tseng, Yu-Ping; I, Lin

2009-12-01

The wave-particle microdynamics in the breaking of the self-excited dust acoustic wave growing in a dusty plasma liquid is investigated through directly tracking dust micromotion. It is found that the nonlinear wave growth and steepening stop as the mean oscillating amplitude of dust displacement reaches about 1/k (k is the wave number), where the vertical neighboring dust trajectories start to crossover and the resonant wave heating with uncertain crest trapping onsets. The dephased dust oscillations cause the abrupt dropping and broadening of the wave crest after breaking, accompanied by the transition from the liquid phase with coherent dust oscillation to the gas phase with chaotic dust oscillation. Corkscrew-shaped phase-space distributions measured at the fixed phases of the wave oscillation cycle clearly indicate how dusts move in and constitute the evolving waveform through dust-wave interaction.

Experimental investigation of change of energy of infragavity waves in dependence on spectral characteristics of an irregular wind waves in coastal zone

NASA Astrophysics Data System (ADS)

Saprykina, Yana; Divinskii, Boris

2013-04-01

An infragravity waves are long waves with periods of 20 - 300 s. Most essential influence of infragarvity waves on dynamic processes is in a coastal zone, where its energy can exceed the energy of wind waves. From practical point of view, the infragravity waves are important, firstly, due to their influence on sand transport processes in a coastal zone. For example, interacting with group structure of wind waves the infragravity waves can define position of underwater bars on sandy coast. Secondly, they are responsible on formation of long waves in harbors. Main source of infragravity waves is wave group structure defined by sub-nonlinear interactions of wind waves (Longuet-Higgins, Stewart, 1962). These infragravity waves are bound with groups of wind waves and propagate with wave group velocity. Another type of infragravity waves are formed in a surf zone as a result of migration a wave breaking point (Symonds, et al., 1982). What from described above mechanisms of formation of infragravity waves prevails, till now it is unknown. It is also unknown how energy of infragravity waves depends on energy of input wind waves and how it changes during nonlinear wave transformation in coastal zone. In our work on the basis of the analysis of data of field experiment and numerical simulation a contribution of infragravity waves in total wave energy in depending on integral characteristics of an irregular wave field in the conditions of a real bathymetry was investigated. For analysis the data of field experiment "Shkorpilovtsy-2007" (Black sea) and data of numerical modeling of Boussinesq type equation with extended dispersion characteristics (Madsen et al., 1997) were used. It was revealed that infragravity waves in a coastal zone are defined mainly by local group structure of waves, which permanently changes due to nonlinearity, shoaling and breaking processes. Free infragravity waves appearing after wave breaking exist together with bound infragravity waves. There are no clear total dependences of energy of infrragravity waves from energy of wind waves and mean period of infragravity waves from mean period of wind waves. But significant wave height of infragravity waves depends on relative water depth (wave height of wind waves divided on water depth). There are different types of this dependence for breaking and non-breaking waves. The influence of peak period, significant wave height and directional spreading of initial wave spectrum on these dependences are discussed. The peculiarities of spectra of infragravity waves for non-breaking, breaking and multibreaking wind waves are shown. This work is supported by the RFBR, project 12-05-00965. References: Longuet-Higgins, M. S., R. W. Stewart, 1962. Radiation stress and mass transport in gravity waves, with an application to surf beats. J. Fluid Mech., 13, pp. 481-504. Symonds G., D.A. Huntley, A.J. Bowen, 1982. Two dimensional surf beat: long wave generation by a time-varying breakpoint. J. of Geoph. Res., 87(C), pp.492-498. Madsen P.A., Sorensen O.R., Shaffer H.A. 1997. Surf zone dynamics simulated by a Boussinesq type model. Coastal Engineering, 32, p. 255-287.

Wave tilt sounding of multilayered structures. [for probing of stratified planetary surface electrical properties and thickness

NASA Technical Reports Server (NTRS)

Warne, L.; Jaggard, D. L.; Elachi, C.

1979-01-01

The relationship between the wave tilt and the electrical parameters of a multilayered structure is investigated. Particular emphasis is placed on the inverse problem associated with the sounding planetary surfaces. An inversion technique, based on multifrequency wave tilt, is proposed and demonstrated with several computer models. It is determined that there is close agreement between the electrical parameters used in the models and those in the inversion values.

Numerical study of wind over breaking waves and generation of spume droplets

NASA Astrophysics Data System (ADS)

Yang, Zixuan; Tang, Shuai; Dong, Yu-Hong; Shen, Lian

2017-11-01

We present direct numerical simulation (DNS) results on wind over breaking waves. The air and water are simulated as a coherent system. The air-water interface is captured using a coupled level-set and volume-of-fluid method. The initial condition for the simulation is fully-developed wind turbulence over strongly-forced steep waves. Because wave breaking is an unsteady process, we use ensemble averaging of a large number of runs to obtain turbulence statistics. The generation and transport of spume droplets during wave breaking is also simulated. The trajectories of sea spray droplets are tracked using a Lagrangian particle tracking method. The generation of droplets is captured using a kinematic criterion based on the relative velocity of fluid particles of water with respect to the wave phase speed. From the simulation, we observe that the wave plunging generates a large vortex in air, which makes an important contribution to the suspension of sea spray droplets.

A depth-averaged 2-D shallow water model for breaking and non-breaking long waves affected by rigid vegetation

USDA-ARS?s Scientific Manuscript database

This paper presents a depth-averaged two-dimensional shallow water model for simulating long waves in vegetated water bodies under breaking and non-breaking conditions. The effects of rigid vegetation are modelled in the form of drag and inertia forces as sink terms in the momentum equations. The dr...

Nonlinear Wave-Particle Interaction: Implications for Newborn Planetary and Backstreaming Proton Velocity Distribution Functions

NASA Astrophysics Data System (ADS)

Romanelli, N.; Mazelle, C.; Meziane, K.

2018-02-01

Seen from the solar wind (SW) reference frame, the presence of newborn planetary protons upstream from the Martian and Venusian bow shocks and SW protons reflected from each of them constitutes two sources of nonthermal proton populations. In both cases, the resulting proton velocity distribution function is highly unstable and capable of giving rise to ultralow frequency quasi-monochromatic electromagnetic plasma waves. When these instabilities take place, the resulting nonlinear waves are convected by the SW and interact with nonthermal protons located downstream from the wave generation region (upstream from the bow shock), playing a predominant role in their dynamics. To improve our understanding of these phenomena, we study the interaction between a charged particle and a large-amplitude monochromatic circularly polarized electromagnetic wave propagating parallel to a background magnetic field, from first principles. We determine the number of fix points in velocity space, their stability, and their dependence on different wave-particle parameters. Particularly, we determine the temporal evolution of a charged particle in the pitch angle-gyrophase velocity plane under nominal conditions expected for backstreaming protons in planetary foreshocks and for newborn planetary protons in the upstream regions of Venus and Mars. In addition, the inclusion of wave ellipticity effects provides an explanation for pitch angle distributions of suprathermal protons observed at the Earth's foreshock, reported in previous studies. These analyses constitute a mean to evaluate if nonthermal proton velocity distribution functions observed at these plasma environments present signatures that can be understood in terms of nonlinear wave-particle processes.

Mesospheric Non-Migrating Tides Generated With Planetary Waves. 1; Characteristics

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Mengel, J. G.; Talaat, E. L.; Porter, H. S.; Chan, K. L.

2003-01-01

We discuss results from a modeling study with our Numerical Spectral Model (NSM) that specifically deals with the non-migrating tides generated in the mesosphere. The NSM extends from the ground to the thermosphere, incorporates Hines' Doppler Spread Parameterization for small-scale gravity waves (GWs), and it describes the major dynamical features of the atmosphere including the wave driven equatorial oscillations (QBO and SAO), and the seasonal variations of tides and planetary waves. Accounting solely for the excitation sources of the solar migrating tides, the NSM generates through dynamical interactions also non-migrating tides in the mesosphere that are comparable in magnitude to those observed. Large non-migrating tides are produced in the diurnal and semi-diurnal oscillations for the zonal mean (m = 0) and in the semidiurnal oscillation for m = 1. In general, significant eastward and westward propagating tides are generated for all the zonal wave numbers m = 1 to 4. To identify the cause, the NSM is run without the solar heating for the zonal mean (m = 0), and the amplitudes of the resulting non-migrating tides are then negligibly small. In this case, the planetary waves are artificially suppressed, which are generated in the NSM through instabilities. This leads to the conclusion that the non-migrating tides are generated through non-linear interactions between planetary waves and migrating tides, as Forbes et al. and Talaat and Liberman had proposed. In an accompanying paper, we present results from numerical experiments, which indicate that gravity wave filtering contributes significantly to produce the non-linear coupling that is involved.

Large-scale laboratory study of breaking wave hydrodynamics over a fixed bar

NASA Astrophysics Data System (ADS)

van der A, Dominic A.; van der Zanden, Joep; O'Donoghue, Tom; Hurther, David; Cáceres, Iván.; McLelland, Stuart J.; Ribberink, Jan S.

2017-04-01

A large-scale wave flume experiment has been carried out involving a T = 4 s regular wave with H = 0.85 m wave height plunging over a fixed barred beach profile. Velocity profiles were measured at 12 locations along the breaker bar using LDA and ADV. A strong undertow is generated reaching magnitudes of 0.8 m/s on the shoreward side of the breaker bar. A circulation pattern occurs between the breaking area and the inner surf zone. Time-averaged turbulent kinetic energy (TKE) is largest in the breaking area on the shoreward side of the bar where the plunging jet penetrates the water column. At this location, and on the bar crest, TKE generated at the water surface in the breaking process reaches the bottom boundary layer. In the breaking area, TKE does not reduce to zero within a wave cycle which leads to a high level of "residual" turbulence and therefore lower temporal variation in TKE compared to previous studies of breaking waves on plane beach slopes. It is argued that this residual turbulence results from the breaker bar-trough geometry, which enables larger length scales and time scales of breaking-generated vortices and which enhances turbulence production within the water column compared to plane beaches. Transport of TKE is dominated by the undertow-related flux, whereas the wave-related and turbulent fluxes are approximately an order of magnitude smaller. Turbulence production and dissipation are largest in the breaker zone and of similar magnitude, but in the shoaling zone and inner surf zone production is negligible and dissipation dominates.

Balance models for equatorial planetary-scale dynamics

NASA Astrophysics Data System (ADS)

Chan, Ian Hiu-Fung

This thesis aims at advancing our understanding of large-scale dynamics in the tropics, specifically the characterization of slow planetary-scale motions through a balance theory; current balance theories in the tropics are unsatisfactory as they filter out Kelvin waves, which are an important component of variability, along with fast inertia-gravity (IG) waves. (Abstract shortened by UMI.).

Wave-induced stress and breaking of sea ice in a coupled hydrodynamic discrete-element wave-ice model

NASA Astrophysics Data System (ADS)

Herman, Agnieszka

2017-11-01

In this paper, a coupled sea ice-wave model is developed and used to analyze wave-induced stress and breaking in sea ice for a range of wave and ice conditions. The sea ice module is a discrete-element bonded-particle model, in which ice is represented as cuboid grains floating on the water surface that can be connected to their neighbors by elastic joints. The joints may break if instantaneous stresses acting on them exceed their strength. The wave module is based on an open-source version of the Non-Hydrostatic WAVE model (NHWAVE). The two modules are coupled with proper boundary conditions for pressure and velocity, exchanged at every wave model time step. In the present version, the model operates in two dimensions (one vertical and one horizontal) and is suitable for simulating compact ice in which heave and pitch motion dominates over surge. In a series of simulations with varying sea ice properties and incoming wavelength it is shown that wave-induced stress reaches maximum values at a certain distance from the ice edge. The value of maximum stress depends on both ice properties and characteristics of incoming waves, but, crucially for ice breaking, the location at which the maximum occurs does not change with the incoming wavelength. Consequently, both regular and random (Jonswap spectrum) waves break the ice into floes with almost identical sizes. The width of the zone of broken ice depends on ice strength and wave attenuation rates in the ice.

Evaluating Crude Oil Chemical Dispersion Efficacy In A Flow-Through Wave Tank Under Regular Non-Breaking Wave And Breaking Wave Conditions

EPA Science Inventory

Testing dispersant effectiveness under conditions similar to that of the open environment is required for improvements in operational procedures and the formulation of regulatory guidelines. To this end, a novel wave tank facility was fabricated to study the dispersion of crude ...

Quasi-biweekly oscillations of the South Asian monsoon and its co-evolution in the upper and lower troposphere

NASA Astrophysics Data System (ADS)

Ortega, Sebastián; Webster, Peter J.; Toma, Violeta; Chang, Hai-Ru

2017-11-01

The Upper Tropospheric Quasi-Biweekly Oscillation (UQBW) of the South Asian monsoon is studied using the potential vorticity field on the 370 K isentrope. The UQBW is shown to be a common occurrence in the upper troposphere during the monsoon, and its typical evolution is described. We suggest that the UQBW is a phenomenon of both the middle and tropical latitudes, owing its existence to the presence of the planetary-scale upper-tropospheric monsoon anticyclone. The UQBW is first identified as Rossby waves originating in the northern flank of the monsoon anticyclone. These Rossby waves break when reaching the Pacific Ocean, and their associated cyclonic PV anomalies move southward to the east of Asia and then westward across the Indian Ocean and Africa advected by the monsoon anticyclone. A strong correlation, or co-evolution, between the UQBW and quasi-biweekly oscillations in the lower troposphere (QBW) is also found. In particular, analysis of vertically-integrated horizontal moisture transport, 850 hPa geopotential, and outgoing long-wave radiation show that the UQBW is usually observed at the same time as, and co-evolves with, the lower tropospheric QBW over South Asia. We discuss the nature of the UQBW, and its possible physical link with the QBW.

Analysis of the Interactions of Planetary Waves with the Mean Flow of the Stratosphere

NASA Technical Reports Server (NTRS)

Newman, Paul A.

2007-01-01

During the winter period, large scale waves (planetary waves) are observed to propagate from the troposphere into the stratosphere. Such wave events have been recognized since the 1 950s. The very largest wave events result in major stratospheric warmings. These large scale wave events have typical durations of a few days to 2 weeks. The wave events deposit easterly momentum in the stratosphere, decelerating the polar night jet and warming the polar region. In this presentation we show the typical characteristics of these events via a compositing analysis. We will show the typical periods and scales of motion and the associated decelerations and warmings. We will illustrate some of the differences between major and minor warming wave events. We will further illustrate the feedback by the mean flow on subsequent wave events.

Temporal variability of gravity wave drag - vertical coupling and possible climate links

NASA Astrophysics Data System (ADS)

Miksovsky, Jiri; Sacha, Petr; Kuchar, Ales; Pisoft, Petr

2017-04-01

In the atmosphere, the internal gravity waves (IGW) are one of the fastest ways of natural information transfer in the vertical direction. Tropospheric changes that result in modification of sourcing, propagation or breaking conditions for IGWs almost immediately influence the distribution of gravity wave drag in the stratosphere. So far most of the related studies deal with IGW impacts higher in the upper stratospheric/mesospheric region and with the modulation of IGWs by planetary waves. This is most likely due to the fact that IGWs induce highest accelerations in the mesosphere and lower thermosphere region. However, the imposed drag force is much bigger in the stratosphere. In the presented analysis, we have assessed the relationship between the gravity wave activity in the stratosphere and other climatic phenomena through statistical techniques. Multivariable regression has been applied to investigate the IGW-related eastward and northward wind tendencies in the CMAM30-SD data, subject to the explanatory variables involving local circulation characteristics (derived from regional configuration of the thermobaric field) as well as the phases of the large-scale internal climate variability modes (ENSO, NAO, QBO). Our tests have highlighted several geographical areas with statistically significant responses of the orographic gravity waves effect to each of the variability modes under investigation; additional experiments have also indicated distinct signs of nonlinearity in some of the links uncovered. Furthermore, we have also applied composite analysis of displaced and split stratospheric polar vortex events (SPV) from CMAM30-SD to focus on how the strength and occurrence of the IGW hotspots can play a role in SPV occurrence and frequency.

Equatorial waves simulated by the NCAR community climate model

NASA Technical Reports Server (NTRS)

Cheng, Xinhua; Chen, Tsing-Chang

1988-01-01

The equatorial planetary waves simulated by the NCAR CCM1 general circulation model were investigated in terms of space-time spectral analysis (Kao, 1968; Hayashi, 1971, 1973) and energetic analysis (Hayashi, 1980). These analyses are particularly applied to grid-point data on latitude circles. In order to test some physical factors which may affect the generation of tropical transient planetary waves, three different model simulations with the CCM1 (the control, the no-mountain, and the no-cloud experiments) were analyzed.

The influence of planetary-wave transience on horizontal air motions in the stratosphere

NASA Technical Reports Server (NTRS)

Salby, Murry L.

1992-01-01

The influence of transience of the planetary-wave field on the horizontal air motions and tracer distributions in the stratosphere was investigated in equivalent barotropic calculations. Two classes of transience are considered: a monochromatic traveling wave, representative of discrete components such as the 5- and 16-day waves, and a second-order stochastic process representative of broadband variability. The response to each of these forms of unsteady forcing is investigated in terms of the characteristic time scale of the transience. Results are presented, and the implications these results have on stratospheric behavior are discussed.

Near-Bed Turbulent Kinetic Energy Budget Under a Large-Scale Plunging Breaking Wave Over a Fixed Bar

NASA Astrophysics Data System (ADS)

van der Zanden, Joep; van der A, Dominic A.; Cáceres, Iván.; Hurther, David; McLelland, Stuart J.; Ribberink, Jan S.; O'Donoghue, Tom

2018-02-01

Hydrodynamics under regular plunging breaking waves over a fixed breaker bar were studied in a large-scale wave flume. A previous paper reported on the outer flow hydrodynamics; the present paper focuses on the turbulence dynamics near the bed (up to 0.10 m from the bed). Velocities were measured with high spatial and temporal resolution using a two component laser Doppler anemometer. The results show that even at close distance from the bed (1 mm), the turbulent kinetic energy (TKE) increases by a factor five between the shoaling, and breaking regions because of invasion of wave breaking turbulence. The sign and phase behavior of the time-dependent Reynolds shear stresses at elevations up to approximately 0.02 m from the bed (roughly twice the elevation of the boundary layer overshoot) are mainly controlled by local bed-shear-generated turbulence, but at higher elevations Reynolds stresses are controlled by wave breaking turbulence. The measurements are subsequently analyzed to investigate the TKE budget at wave-averaged and intrawave time scales. Horizontal and vertical turbulence advection, production, and dissipation are the major terms. A two-dimensional wave-averaged circulation drives advection of wave breaking turbulence through the near-bed layer, resulting in a net downward influx in the bar trough region, followed by seaward advection along the bar's shoreward slope, and an upward outflux above the bar crest. The strongly nonuniform flow across the bar combined with the presence of anisotropic turbulence enhances turbulent production rates near the bed.

A numerical investigation of wave-breaking-induced turbulent coherent structure under a solitary wave

NASA Astrophysics Data System (ADS)

Zhou, Zheyu; Sangermano, Jacob; Hsu, Tian-Jian; Ting, Francis C. K.

2014-10-01

To better understand the effect of wave-breaking-induced turbulence on the bed, we report a 3-D large-eddy simulation (LES) study of a breaking solitary wave in spilling condition. Using a turbulence-resolving approach, we study the generation and the fate of wave-breaking-induced turbulent coherent structures, commonly known as obliquely descending eddies (ODEs). Specifically, we focus on how these eddies may impinge onto bed. The numerical model is implemented using an open-source CFD library of solvers, called OpenFOAM, where the incompressible 3-D filtered Navier-Stokes equations for the water and the air phases are solved with a finite volume scheme. The evolution of the water-air interfaces is approximated with a volume of fluid method. Using the dynamic Smagorinsky closure, the numerical model has been validated with wave flume experiments of solitary wave breaking over a 1/50 sloping beach. Simulation results show that during the initial overturning of the breaking wave, 2-D horizontal rollers are generated, accelerated, and further evolve into a couple of 3-D hairpin vortices. Some of these vortices are sufficiently intense to impinge onto the bed. These hairpin vortices possess counter-rotating and downburst features, which are key characteristics of ODEs observed by earlier laboratory studies using Particle Image Velocimetry. Model results also suggest that those ODEs that impinge onto bed can induce strong near-bed turbulence and bottom stress. The intensity and locations of these near-bed turbulent events could not be parameterized by near-surface (or depth integrated) turbulence unless in very shallow depth.

Vacillations induced by interference of stationary and traveling planetary waves

NASA Technical Reports Server (NTRS)

Salby, Murry L.; Garcia, Rolando R.

1987-01-01

The interference pattern produced when a traveling planetary wave propagates over a stationary forced wave is explored, examining the interference signature in a variety of diagnostics. The wave field is first restricted to a diatomic spectrum consisting of two components: a single stationary wave and a single monochromatic traveling wave. A simple barotropic normal mode propagating over a simple stationary plane wave is considered, and closed form solutions are obtained. The wave fields are then restricted spatially, providing more realistic structures without sacrificing the advantages of an analytical solution. Both stationary and traveling wave fields are calculated numerically with the linearized Primitive Equations in a realistic basic state. The mean flow reaction to the fluctuating eddy forcing which results from interference is derived. Synoptic geopotential behavior corresponding to the combined wave and mean flow fields is presented, and the synoptic signature in potential vorticity on isentropic surfaces is examined.

Scaling depth-induced wave-breaking in two-dimensional spectral wave models

NASA Astrophysics Data System (ADS)

Salmon, J. E.; Holthuijsen, L. H.; Zijlema, M.; van Vledder, G. Ph.; Pietrzak, J. D.

2015-03-01

Wave breaking in shallow water is still poorly understood and needs to be better parameterized in 2D spectral wave models. Significant wave heights over horizontal bathymetries are typically under-predicted in locally generated wave conditions and over-predicted in non-locally generated conditions. A joint scaling dependent on both local bottom slope and normalized wave number is presented and is shown to resolve these issues. Compared to the 12 wave breaking parameterizations considered in this study, this joint scaling demonstrates significant improvements, up to ∼50% error reduction, over 1D horizontal bathymetries for both locally and non-locally generated waves. In order to account for the inherent differences between uni-directional (1D) and directionally spread (2D) wave conditions, an extension of the wave breaking dissipation models is presented. By including the effects of wave directionality, rms-errors for the significant wave height are reduced for the best performing parameterizations in conditions with strong directional spreading. With this extension, our joint scaling improves modeling skill for significant wave heights over a verification data set of 11 different 1D laboratory bathymetries, 3 shallow lakes and 4 coastal sites. The corresponding averaged normalized rms-error for significant wave height in the 2D cases varied between 8% and 27%. In comparison, using the default setting with a constant scaling, as used in most presently operating 2D spectral wave models, gave equivalent errors between 15% and 38%.

Modeling Tides, Planetary Waves, and Equatorial Oscillations in the MLT

NASA Technical Reports Server (NTRS)

Mengel, J. G.; Mayr, H. G.; Drob, D. P.; Porter, H. S.; Bhartia, P. K. (Technical Monitor)

2001-01-01

Applying Hines Doppler Spread Parameterization for gravity waves (GW), our 3D model reproduces some essential features that characterize the observed seasonal variations of tides and planetary waves in the upper mesosphere. In 2D, our model also reproduces the large Semi-Annual Oscillation (SAO) and Quasi Biennial Oscillation (QBO) observed in this region at low latitudes. It is more challenging to describe these features combined in a more comprehensive self consistent model, and we give a progress report that outlines the difficulties and reports some success. In 3D, the GW's are partially absorbed by tides and planetary waves to amplify them. Thus the waves are less efficient in generating the QBO and SAO at equatorial latitudes. Some of this deficiency is compensated by the fact that the GW activity is observed to be enhanced at low latitudes. Increasing the GW source has the desired effect to boost the QBO, but the effect is confined primarily to the stratosphere. With increasing altitude, the meridional circulation becomes more important in redistributing the momentum deposited in the background flow by the GW's. Another factor involved is the altitude at which the GW's originate, which we had originally chosen to be the surface. Numerical experiments show that moving this source altitude to the top of the troposphere significantly increases the efficiency for generating the QBO without affecting much the tides and planetary waves in the model. Attention to the details in which the GW source comes into play thus appears to be of critical importance in modeling the phenomenology of the MLT. Among the suite of numerical experiments reported, we present a simulation that produced significant variations of tides and planetary waves in the upper mesosphere. The effect is related to the QBO generated in the model, and GW filtering is the likely cause.

On the dispersionless Kadomtsev-Petviashvili equation with arbitrary nonlinearity and dimensionality: exact solutions, longtime asymptotics of the Cauchy problem, wave breaking and shocks

NASA Astrophysics Data System (ADS)

Santucci, F.; Santini, P. M.

2016-10-01

We study the generalization of the dispersionless Kadomtsev-Petviashvili (dKP) equation in n+1 dimensions and with nonlinearity of degree m+1, a model equation describing the propagation of weakly nonlinear, quasi one-dimensional waves in the absence of dispersion and dissipation, and arising in several physical contexts, like acoustics, plasma physics, hydrodynamics and nonlinear optics. In 2 + 1 dimensions and with quadratic nonlinearity, this equation is integrable through a novel inverse scattering transform, and it has been recently shown to be a prototype model equation in the description of the two-dimensional wave breaking of localized initial data. In higher dimensions and with higher nonlinearity, the generalized dKP equations are not integrable, but their invariance under motions on the paraboloid allows one to construct in this paper a family of exact solutions describing waves constant on their paraboloidal wave front and breaking simultaneously in all points of it, developing after breaking either multivaluedness or single-valued discontinuous profiles (shocks). Then such exact solutions are used to build the longtime behavior of the solutions of the Cauchy problem, for small and localized initial data, showing that wave breaking of small initial data takes place in the longtime regime if and only if m(n-1)≤slant 2. Lastly, the analytic aspects of such wave breaking are investigated in detail in terms of the small initial data, in both cases in which the solution becomes multivalued after breaking or it develops a shock. These results, contained in the 2012 master’s thesis of one of the authors (FS) [1], generalize those obtained in [2] for the dKP equation in n+1 dimensions with quadratic nonlinearity, and are obtained following the same strategy.

REVIEWS OF TOPICAL PROBLEMS: The physics of planetary rings

NASA Astrophysics Data System (ADS)

Gor'kavyĭ, N. N.; Fridman, Aleksei M.

1990-02-01

A review of the collisional, collective, and resonance phenomena in planetary rings is presented. The following questions are examined: the reasons for the existence of planetary rings and the properties of a typical particle, the collisional breaking of loose bodies, and the azimuthal asymmetry effect for the rings of Saturn. A transfer theory is being developed for differentially rotating disks of inelastic particles, and the collective instabilities of planetary rings and a protoplanetary disk are discussed. A model for the resonance origin for the rings of Uranus is described, which enabled one to predict unknown satellites of Uranus that were later discovered by "Voyager-2". The problem of the stability of the rings of Uranus is examined.

MGS Radio Science Measurements of Atmospheric Dynamics on Mars

NASA Astrophysics Data System (ADS)

Hinson, D. P.

2001-12-01

The Sun-synchronous, polar orbit of Mars Global Surveyor (MGS) provides frequent opportunities for radio occultation sounding of the neutral atmosphere. The basic result of each experiment is a profile of pressure and temperature versus planetocentric radius and geopotential. More than 4000 profiles were obtained during the 687-day mapping phase of the mission, and additional observations are underway. These measurements allow detailed characterization of planetary-scale dynamics, including stationary planetary (or Rossby) waves and transient waves produced by instability. For example, both types of dynamics were observed near 67° S during midwinter of the southern hemisphere (Ls=134° --160° ). Planetary waves are the most prominent dynamical feature in this subset of data. At zonal wave number s=1, both the temperature and geopotential fields tilt westward with increasing height, as expected for vertically-propagating planetary waves forced at the surface. The wave-2 structure is more nearly barotropic. The amplitude in geopotential height at Ls=150° increases from ~200 m near the surface to ~700 m at 10 Pa. The corresponding meridional wind speed increases from ~5 m s-1 near the surface to ~20 m s-1 at 10 Pa. Traveling ``baroclinic'' waves also appear intermittently during this interval. The dominant mode has a period of ~2 sols, s=3, and a peak amplitude of ~7 K at 300 Pa. Stong zonal variations in eddy amplitude signal the presence of a possible ``storm zone'' at 150° --330° E longitude. This talk will include other examples of these phenomena as well as comparisons with computer simulations by a Martian general circulation model (MGCM).

Nearshore Tsunami Inundation Model Validation: Toward Sediment Transport Applications

USGS Publications Warehouse

Apotsos, Alex; Buckley, Mark; Gelfenbaum, Guy; Jaffe, Bruce; Vatvani, Deepak

2011-01-01

Model predictions from a numerical model, Delft3D, based on the nonlinear shallow water equations are compared with analytical results and laboratory observations from seven tsunami-like benchmark experiments, and with field observations from the 26 December 2004 Indian Ocean tsunami. The model accurately predicts the magnitude and timing of the measured water levels and flow velocities, as well as the magnitude of the maximum inundation distance and run-up, for both breaking and non-breaking waves. The shock-capturing numerical scheme employed describes well the total decrease in wave height due to breaking, but does not reproduce the observed shoaling near the break point. The maximum water levels observed onshore near Kuala Meurisi, Sumatra, following the 26 December 2004 tsunami are well predicted given the uncertainty in the model setup. The good agreement between the model predictions and the analytical results and observations demonstrates that the numerical solution and wetting and drying methods employed are appropriate for modeling tsunami inundation for breaking and non-breaking long waves. Extension of the model to include sediment transport may be appropriate for long, non-breaking tsunami waves. Using available sediment transport formulations, the sediment deposit thickness at Kuala Meurisi is predicted generally within a factor of 2.

A high-performance wave guide cryogenic thermal break

NASA Astrophysics Data System (ADS)

Melhuish, S. J.; McCulloch, M. A.; Piccirillo, L.; Stott, C.

2016-10-01

We describe a high-performance wave guide cryogenic thermal break. This has been constructed both for Ka band, using WR28 wave guide, and Q band, using WR22 wave guide. The mechanical structure consists of a hexapod (Stewart platform) made from pultruded carbon fibre tubing. We present a tentative examination of the cryogenic Young's modulus of this material. The thermal conductivity is measured at temperatures above the range explored by Runyan and Jones, resulting in predicted conductive loads through our thermal breaks of 3.7 mW to 3 K and 17 μK to 1 K.

Atmospheric planetary wave response to external forcing

NASA Technical Reports Server (NTRS)

Stevens, D. E.; Reiter, E. R.

1985-01-01

The tools of observational analysis, complex general circulation modeling, and simpler modeling approaches were combined in order to attack problems on the largest spatial scales of the earth's atmosphere. Two different models were developed and applied. The first is a two level, global spectral model which was designed primarily to test the effects of north-south sea surface temperature anomaly (SSTA) gradients between the equatorial and midlatitude north Pacific. The model is nonlinear, contains both radiation and a moisture budget with associated precipitation and surface evaporation, and utilizes a linear balance dynamical framework. Supporting observational analysis of atmospheric planetary waves is briefly summarized. More extensive general circulation models have also been used to consider the problem of the atmosphere's response, especially in the horizontal propagation of planetary scale waves, to SSTA.

Proceedings, Nonlinear Water Waves Workshop Held at the University of Bristol on October 22-25, 1991

DTIC Science & Technology

1991-01-01

far as I understand, you have studied the case of one -dimensional spectrum of waves. I think that taking into account non- one -dimensional triplets...2b Evolving shoi waves (T- 1.0s). 13 components even became larger than that of the primary wave itself. The short waves (ff= 1.0 Hz), on the...breaking waves. This allows one to study statistics of breaking waves as rare events of high level excursion by a (three-dimensional) field of the wave

Observations and estimates of wave-driven water level extremes at the Marshall Islands

NASA Astrophysics Data System (ADS)

Merrifield, M. A.; Becker, J. M.; Ford, M.; Yao, Y.

2014-10-01

Wave-driven extreme water levels are examined for coastlines protected by fringing reefs using field observations obtained in the Republic of the Marshall Islands. The 2% exceedence water level near the shoreline due to waves is estimated empirically for the study sites from breaking wave height at the outer reef and by combining separate contributions from setup, sea and swell, and infragravity waves, which are estimated based on breaking wave height and water level over the reef flat. Although each component exhibits a tidal dependence, they sum to yield a 2% exceedence level that does not. A hindcast based on the breaking wave height parameterization is used to assess factors leading to flooding at Roi-Namur caused by an energetic swell event during December 2008. Extreme water levels similar to December 2008 are projected to increase significantly with rising sea level as more wave and tide events combine to exceed inundation threshold levels.

Study on ambient noise generated from breaking waves simulated by a wave maker in a tank

NASA Astrophysics Data System (ADS)

Wei, Ruey-Chang; Chan, Hsiang-Chih

2002-11-01

This paper studies ambient noise in the surf zone that was simulated by a piston-type wave maker in a tank. The experiment analyzed the bubbles of a breaking wave by using a hydrophone to receive the acoustic signal, and the images of bubbles were recorded by a digital video camera to observe the distribution of the bubbles. The slope of the simulated seabed is 1:5, and the dimensions of the water tank are 35 m x1 m x1.2 m. The studied parameters of ambient noise generated by breaking wave bubbles were wave height, period, and water depth. Short-time Fourier transform was applied to obtain the acoustic spectrum of bubbles, MATLAB programs were used to calculate mean sound pressure level, and determine the number of bubbles. Bubbles with resonant frequency from 0.5 to 10 kHz were studied, counted from peaks in the spectrum. The number of bubbles generated by breaking waves could be estimated by the bubbles energy distributions. The sound pressure level of ambient noise was highly related to the wave height and period, with correlation coefficient 0.7.

Measuring the accelerating effect of the planetary-scale waves on Venus observed with UVI/AKATSUKI and ground-based telescopes

NASA Astrophysics Data System (ADS)

Imai, M.; Kouyama, T.; Takahashi, Y.; Watanabe, S.; Yamazaki, A.; Yamada, M.; Nakamura, M.; Satoh, T.; Imamura, T.; Nakaoka, T.; Kawabata, M.; Yamanaka, M.; Kawabata, K. S.

2017-12-01

Venus has a global cloud layer, and the atmosphere rotates with the speed over 100 m/s. The scattering of solar radiance and absorber in clouds cause the strong dark and bright contrast in 365 nm unknown absorption bands. The Japanese Venus orbiter AKATSUKI and the onboard instrument UVI capture 100 km mesoscale cloud features over the entire visible dayside area. In contrast, planetary-scale features are observed when the orbiter is at the moderate distance from Venus and when the Sun-Venus-orbiter phase angle is smaller than 45 deg. Cloud top wind velocity was measured with the mesoscale cloud tracking technique, however, observations of the propagation velocity and its variation of the planetary-scale feature are not well conducted because of the limitation of the observable area. The purpose of the study is measuring the effect of wind acceleration by planetary-scale waves. Each cloud motion can be represented as the wind and phase velocity of the planetary-scale waves, respectively. We conducted simultaneous observations of the zonal motion of both mesoscale and planetary-scale feature using UVI/AKATSUKI and ground-based Pirka and Kanata telescopes in Japan. Our previous ground-based observation revealed the periodicity change of planetary-scale waves with a time scale of a couple of months. For the initial analysis of UVI images, we used the time-consecutive images taken in the orbit #32. During this orbit (from Nov. 13 to 20, 2016), 7 images were obtained with 2 hr time-interval in a day whose spatial resolution ranged from 10-35 km. To investigate the typical mesoscale cloud motion, the Gaussian-filters with sigma = 3 deg. were used to smooth geometrically mapped images with 0.25 deg. resolution. Then the amount of zonal shift for each 5 deg. latitudinal bands between the pairs of two time-consecutive images were estimated by searching the 2D cross-correlation maximum. The final wind velocity (or rotation period) for mesoscale features were determined with a small error about +/- 0.1-day period in equatorial region (Figure 2). The same method will be applied for planetary-scale features captured by UVI, and ground-based observations compensate the discontinuity in UVI data. At the presentation, the variability in winds and wave propagation velocity with the time scale of a couple of months will be shown.

Assessment of Reinforced Concrete Surface Breaking Crack Using Rayleigh Wave Measurement.

PubMed

Lee, Foo Wei; Chai, Hwa Kian; Lim, Kok Sing

2016-03-05

An improved single sided Rayleigh wave (R-wave) measurement was suggested to characterize surface breaking crack in steel reinforced concrete structures. Numerical simulations were performed to clarify the behavior of R-waves interacting with surface breaking crack with different depths and degrees of inclinations. Through analysis of simulation results, correlations between R-wave parameters of interest and crack characteristics (depth and degree of inclination) were obtained, which were then validated by experimental measurement of concrete specimens instigated with vertical and inclined artificial cracks of different depths. Wave parameters including velocity and amplitude attenuation for each case were studied. The correlations allowed us to estimate the depth and inclination of cracks measured experimentally with acceptable discrepancies, particularly for cracks which are relatively shallow and when the crack depth is smaller than the wavelength.

Assessing the performance of wave breaking parameterizations in shallow waters in spectral wave models

NASA Astrophysics Data System (ADS)

Lin, Shangfei; Sheng, Jinyu

2017-12-01

Depth-induced wave breaking is the primary dissipation mechanism for ocean surface waves in shallow waters. Different parametrizations were developed for parameterizing depth-induced wave breaking process in ocean surface wave models. The performance of six commonly-used parameterizations in simulating significant wave heights (SWHs) is assessed in this study. The main differences between these six parameterizations are representations of the breaker index and the fraction of breaking waves. Laboratory and field observations consisting of 882 cases from 14 sources of published observational data are used in the assessment. We demonstrate that the six parameterizations have reasonable performance in parameterizing depth-induced wave breaking in shallow waters, but with their own limitations and drawbacks. The widely-used parameterization suggested by Battjes and Janssen (1978, BJ78) has a drawback of underpredicting the SWHs in the locally-generated wave conditions and overpredicting in the remotely-generated wave conditions over flat bottoms. The drawback of BJ78 was addressed by a parameterization suggested by Salmon et al. (2015, SA15). But SA15 had relatively larger errors in SWHs over sloping bottoms than BJ78. We follow SA15 and propose a new parameterization with a dependence of the breaker index on the normalized water depth in deep waters similar to SA15. In shallow waters, the breaker index of the new parameterization has a nonlinear dependence on the local bottom slope rather than the linear dependence used in SA15. Overall, this new parameterization has the best performance with an average scatter index of ∼8.2% in comparison with the three best performing existing parameterizations with the average scatter index between 9.2% and 13.6%.

Non-Migrating Diurnal Tides Generated with Planetary Waves in the Mesosphere

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Mengel, J. G.; Talaat, E. R.; Porter, H. S.; Chan, K. L.

2003-01-01

We report here the results from a modeling study with our Numerical Spectral Model (NSM) that extends from the ground into thermosphere. The NSM incorporates Hines Doppler Spread Parameterization for small-scale gravity waves (GWs) and describes the major dynamical features of the atmosphere, including the wave driven equatorial oscillations (QBO and SAO), and the seasonal variations of tides and planetary waves. Accounting solely for the solar migrating tidal excitation sources, the NSM generates through dynamical interactions also non-migrating tides in the mesosphere that have amplitudes comparable to those observed. The model produces the diurnal (and semidiurnal) oscillations of the zonal mean (m = 0), and eastward and westward propagating tides for zonal wave numbers m = 1 to 4. To identify the mechanism of excitation for these tides, a numerical experiment is performed. The NSM is run without the heat source for the zonal-mean circulation and temperature variation, and the amplitudes of the resulting nonmigrating tides are then negligibly small. This leads to the conclusion that the planetary waves, which normally are excited in the NSM by instabilities but are suppressed in this case, generate the nonmigrating tides through nonlinear interactions with the migrating tides.

Air motions accompanying the development of a planetary wave critical layer

NASA Technical Reports Server (NTRS)

Salby, Murry L.; O'Sullivan, Donal; Callaghan, Patrick; Garcia, Rolando R.

1990-01-01

The horizontal air motions accompanying the development of a planetary wave critical layer are presently investigated on the sphere, in terms of wave amplitude, the characteristics of the zonal flow, and dissipation. While attention is given to adiabatic motions, which should furnish an upper bound on the redistribution of conserved quantities by eddy stirring, nonconservative processes may be important in determining how large a role eddy stirring actually plays in the redistribution of atmospheric constituents. Nonconservative processes may also influence tracer distributions by directly affecting dynamics.

Resonant ion acceleration by plasma jets: Effects of jet breaking and the magnetic-field curvature.

PubMed

Artemyev, A V; Vasiliev, A A

2015-05-01

In this paper we consider resonant ion acceleration by a plasma jet originating from the magnetic reconnection region. Such jets propagate in the background magnetic field with significantly curved magnetic-field lines. Decoupling of ion and electron motions at the leading edge of the jet results in generation of strong electrostatic fields. Ions can be trapped by this field and get accelerated along the jet front. This mechanism of resonant acceleration resembles surfing acceleration of charged particles at a shock wave. To describe resonant acceleration of ions, we use adiabatic theory of resonant phenomena. We show that particle motion along the curved field lines significantly influences the acceleration rate. The maximum gain of energy is determined by the particle's escape from the system due to this motion. Applications of the proposed mechanism to charged-particle acceleration in the planetary magnetospheres and the solar corona are discussed.

Air Entrainment in Steady Breaking Waves

NASA Astrophysics Data System (ADS)

Li, C. Y.; Duncan, J. H.; Wenz, A.; Full, O. E.

1997-11-01

Air entrainment due to steady breaking waves generated by fully submerged hydrofoils moving at constant speed and angle of attack is investigated experimentally. Three hydrofoils with the same shape (NACA 0012) but different chords (15, 20 and 30 cm) are used with Froude scaled operating conditions to generate the breaking waves. In this way, the effect of scale due to the combined influence of surface tension and viscosity on the bubble entrainment process is investigated. The bubbles are measured from plan-view and side-view 35-mm photographs of the wake. It is found that the number and average size of the bubbles increases dramatically with scale. High-speed movies of the turbulent breaking region that rides on the forward face of the wave are also used to observe bubble entrainment events. It is found that the bubbles are entrained periodically when the leading edge of the breaking region rushes forward and plunges over a pocket of air. This plunging process appears to become more frequent and more violent as the scale of the breaker increases.

A Conjugate Study of Mean Winds and Planetary Waves Employing Enhanced Meteor Radars at Rio Grande, Argentina (53.8degS) and Juliusruh, Germany (54.6degN)

NASA Technical Reports Server (NTRS)

Fritts, D. C.; Imura, H.; Lieberman, R.; Janches, D.; Singer, W.

2011-01-01

Two meteor radars with enhanced power and sensitivity and located at closely conjugate latitudes (54.6degN and 53.8degS) are employed for inter-hemispheric comparisons of mean winds and planetary wave structures. Our study uses data from June 2008 through May 2010 during which both radars provided nearly continuous wind measurements from approx.80 to 100 km. Monthly mean winds at 53.8degS exhibit a somewhat stronger westward mean zonal jet in spring and early summer at lower altitudes and no westward monthly mean winds at higher altitudes. In contrast, westward mean winds of approx.5-10 m/s at 54.6degN extend to above 96 km during late winter and early spring each year. Equatorward monthly mean winds extend approximately from spring to fall equinox at both latitudes, with amplitudes of approx.5-10 m/s and more rapid decreases in amplitude at 54.6degN at higher altitudes. Meridional mean winds are more variable at both latitudes during fall and winter, with both poleward and equatorward monthly means indicating longer-period variability. Planetary waves seen in the 2-day mean data are episodic and variable at both sites, exhibit dominant periodicities of approx.8-10 and 16-20 days and are more confined to late fall and winter at 54.6degN. At both latitudes, planetary waves in the two period bands coincide closely in time and exhibit similar horizontal velocity covariances that are positive (negative) at 54.6degN (53.8degS) during peak planetary wave responses.

Internal Gravity Waves: Generation and Breaking Mechanisms by Laboratory Experiments

NASA Astrophysics Data System (ADS)

la Forgia, Giovanni; Adduce, Claudia; Falcini, Federico

2016-04-01

Internal gravity waves (IGWs), occurring within estuaries and the coastal oceans, are manifest as large amplitude undulations of the pycnocline. IGWs propagating horizontally in a two layer stratified fluid are studied. The breaking of an IGW of depression shoaling upon a uniformly sloping boundary is investigated experimentally. Breaking dynamics beneath the shoaling waves causes both mixing and wave-induced near-bottom vortices suspending and redistributing the bed material. Laboratory experiments are conducted in a Perspex tank through the standard lock-release method, following the technique described in Sutherland et al. (2013). Each experiment is analysed and the instantaneous pycnocline position is measured, in order to obtain both geometric and kinematic features of the IGW: amplitude, wavelength and celerity. IGWs main features depend on the geometrical parameters that define the initial experimental setting: the density difference between the layers, the total depth, the layers depth ratio, the aspect ratio, and the displacement between the pycnoclines. Relations between IGWs geometric and kinematic features and the initial setting parameters are analysed. The approach of the IGWs toward a uniform slope is investigated in the present experiments. Depending on wave and slope characteristics, different breaking and mixing processes are observed. Sediments are sprinkled on the slope to visualize boundary layer separation in order to analyze the suspension e redistribution mechanisms due to the wave breaking.

Spacecraft Radio Scintillation and Solar System Exploration

NASA Technical Reports Server (NTRS)

Woo, Richard

1993-01-01

When a wave propagates through a turbulent medium, scattering by the random refractive index inhomogeneities can lead to a wide variety of phenomena that have been the subject of extensive study. The observed scattering effects include amplitude or intensity scintillation, phase scintillation, angular broadening, and spectral broadening, among others. In this paper, I will refer to these scattering effects collectively as scintillation. Although the most familiar example is probably the twinkling of stars (light wave intensity scintillation by turbulence in the Earth's atmosphere), scintillation has been encountered and investigated in such diverse fields as ionospheric physics, oceanography, radio astronomy, and radio and optical communications. Ever since planetary spacecraft began exploring the solar system, scintillation has appeared during the propagation of spacecraft radio signals through planetary atmospheres, planetary ionospheres, and the solar wind. Early studies of these phenomena were motivated by the potential adverse effects on communications and navigation, and on experiments that use the radio link to conduct scientific investigations. Examples of the latter are radio occultation measurements (described below) of planetary atmospheres to deduce temperature profiles, and the search for gravitational waves. However,these concerns soon gave way to the emergence of spacecraft radio scintillation as a new scientific tool for exploring small-scale dynamics in planetary atmospheres and structure in the solar wind, complementing in situ and other remote sensing spacecraft measurements, as well as scintillation measurements using natural (celestial) radio sources. The purpose of this paper is to briefly describe and review the solar system spacecraft radio scintillation observations, to summarize the salient features of wave propagation analyses employed in interpreting them, to underscore the unique remote sensing capabilities and scientific relevance of the scintillation measurements, and to highlight some of the scientific results obtained to date. Special emphasis is placed on comparing the remote sensing features of planetary and terrestrial scintillation measurements, and on contrasting spacecraft and natural radio source scintillation measurements. I will first discuss planetary atmospheres and ionospheres, and then the solar wind.

Coherent structures in the Es layer and neutral middle atmosphere

NASA Astrophysics Data System (ADS)

Mošna, Zbyšek; Knížová, Petra Koucká; Potužníková, Kateřina

2015-12-01

The present paper shows results from the summer campaign performed during geomagnetically quiet period from June 1 to August 31, 2009. Within time-series of stratospheric and mesospheric temperatures at pressure levels 10-0.1 hPa, mesospheric winds measured in Collm, Germany, and the sporadic E-layer parameters foEs and hEs measured at the Pruhonice station we detected specific coherent wave-bursts in planetary wave domain. Permanent wave-like activity is observed in all analyzed data sets. However, the number of wave-like structures persistent in large range of height from the stratosphere to lower ionosphere is limited. The only coherent modes that are detected on consequent levels of the atmosphere are those corresponding to eigenmodes of planetary waves.

Destructive tsunami-like wave generated by surf beat over a coral reef during Typhoon Haiyan.

PubMed

Roeber, Volker; Bricker, Jeremy D

2015-08-06

Storm surges cause coastal inundation due to setup of the water surface resulting from atmospheric pressure, surface winds and breaking waves. Here we show that during Typhoon Haiyan, the setup generated by breaking waves near the fringing-reef-protected town of Hernani, the Philippines, oscillated with the incidence of large and small wave groups, and steepened into a tsunami-like wave that caused extensive damage and casualties. Though fringing reefs usually protect coastal communities from moderate storms, they can exacerbate flooding during strong events with energetic waves. Typical for reef-type bathymetries, a very short wave-breaking zone over the steep reef face facilitates the freeing of infragravity-period fluctuations (surf beat) with little energy loss. Since coastal flood planning relies on phase-averaged wave modelling, infragravity surges are not being accounted for. This highlights the necessity for a policy change and the adoption of phase-resolving wave models for hazard assessment in regions with fringing reefs.

Destructive tsunami-like wave generated by surf beat over a coral reef during Typhoon Haiyan

PubMed Central

Roeber, Volker; Bricker, Jeremy D.

2015-01-01

Storm surges cause coastal inundation due to setup of the water surface resulting from atmospheric pressure, surface winds and breaking waves. Here we show that during Typhoon Haiyan, the setup generated by breaking waves near the fringing-reef-protected town of Hernani, the Philippines, oscillated with the incidence of large and small wave groups, and steepened into a tsunami-like wave that caused extensive damage and casualties. Though fringing reefs usually protect coastal communities from moderate storms, they can exacerbate flooding during strong events with energetic waves. Typical for reef-type bathymetries, a very short wave-breaking zone over the steep reef face facilitates the freeing of infragravity-period fluctuations (surf beat) with little energy loss. Since coastal flood planning relies on phase-averaged wave modelling, infragravity surges are not being accounted for. This highlights the necessity for a policy change and the adoption of phase-resolving wave models for hazard assessment in regions with fringing reefs. PMID:26245839

The Temperature of the Arctic and Antarctic Lower Stratosphere

NASA Technical Reports Server (NTRS)

Newman, Paul A.; Nash, Eric R.; Bhartia, P. K. (Technical Monitor)

2002-01-01

The temperature of the polar lower stratosphere during spring is the key factor in changing the magnitude of ozone loss in the polar vortices. In this talk, we will review the results of Newman et al. [2000] that quantitatively demonstrate that the polar lower stratospheric temperature is primarily controlled by planetary-scale waves. In particular, the tropospheric eddy heat flux in middle to late winter (January--February) is highly correlated with the mean polar stratospheric temperature during March. Strong midwinter planetary wave forcing leads to a warmer spring Arctic lower stratosphere in early spring, while weak midwinter forcing leads to cooler spring Arctic temperatures. In addition, this planetary wave driving also has a strong impact on the strength of the polar vortex. These results from the Northern Hemisphere will be contrasted with the Southern Hemisphere.

Constraints on Wave Drag Parameterization Schemes for Simulating the Quasi-Biennial Oscillation. Part I: Gravity Wave Forcing.

NASA Astrophysics Data System (ADS)

Campbell, Lucy J.; Shepherd, Theodore G.

2005-12-01

Parameterization schemes for the drag due to atmospheric gravity waves are discussed and compared in the context of a simple one-dimensional model of the quasi-biennial oscillation (QBO). A number of fundamental issues are examined in detail, with the goal of providing a better understanding of the mechanism by which gravity wave drag can produce an equatorial zonal wind oscillation. The gravity wave driven QBOs are compared with those obtained from a parameterization of equatorial planetary waves. In all gravity wave cases, it is seen that the inclusion of vertical diffusion is crucial for the descent of the shear zones and the development of the QBO. An important difference between the schemes for the two types of waves is that in the case of equatorial planetary waves, vertical diffusion is needed only at the lowest levels, while for the gravity wave drag schemes it must be included at all levels. The question of whether there is downward propagation of influence in the simulated QBOs is addressed. In the gravity wave drag schemes, the evolution of the wind at a given level depends on the wind above, as well as on the wind below. This is in contrast to the parameterization for the equatorial planetary waves in which there is downward propagation of phase only. The stability of a zero-wind initial state is examined, and it is determined that a small perturbation to such a state will amplify with time to the extent that a zonal wind oscillation is permitted.

Atmospheric Rivers across Multi-scales of the Hydrologic cycle

NASA Astrophysics Data System (ADS)

Hu, H.

2017-12-01

Atmospheric Rivers (ARs) are defined as filamentary structures with strong water vapor transport in the atmosphere, moving as much water as is discharged by the Amazon River. As a large-scale phenomenon, ARs are embedded in the planetary-scale Rossby waves and account for the majority of poleward moisture transport in the midlatitudes. On the other hand, AR is the fundamental physical mechanism leading to extreme basin-scale precipitation and flooding over the U.S. West Coast in the winter season. The moisture transported by ARs is forced to rise and generate precipitation when it impinges on the mountainous coastal lands. My goal is to build the connection between the multi-scale features associated with ARs with their impacts on local hydrology, with particular focus on the U.S. West Coast. Moving across the different scales I have: (1) examined the planetary-scale dynamics in the upper-troposphere, and established a robust relationship between the two regimes of Rossby wave breaking and AR-precipitation and streamflow along the West Coast; (2) quantified the contribution from the tropics/subtropics to AR-related precipitation intensity and found a significant modulation from the large-scale thermodynamics; (3) developed a water tracer tool in a land surface model to track the lifecycle of the water collected from AR precipitation over the terrestrial system, so that the role of catchment-scale factors in modulating ARs' hydrological consequences could be examined. Ultimately, the information gather from these studies will indicate how the dynamic and thermodynamic changes as a response to climate change could affect the local flooding and water resource, which would be helpful in decision making.

On the kinematic criterion for the inception of breaking in surface gravity waves: Fully nonlinear numerical simulations and experimental verification

NASA Astrophysics Data System (ADS)

Khait, A.; Shemer, L.

2018-05-01

The evolution of unidirectional wave trains containing a wave that gradually becomes steep is evaluated experimentally and numerically using the Boundary Element Method (BEM). The boundary conditions for the nonlinear numerical simulations corresponded to the actual movements of the wavemaker paddle as recorded in the physical experiments, allowing direct comparison between the measured in experiments' characteristics of the wave train and the numerical predictions. The high level of qualitative and quantitative agreement between the measurements and simulations validated the kinematic criterion for the inception of breaking and the location of the spilling breaker, on the basis of the BEM computations and associated experiments. The breaking inception is associated with the fluid particle at the crest of the steep wave that has been accelerated to match and surpass the crest velocity. The previously observed significant slow-down of the crest while approaching breaking is verified numerically; both narrow-/broad-banded wave trains are considered. Finally, the relative importance of linear and nonlinear contributions is analyzed.

Dynamics of 2013 Sudden Stratospheric Warming event and its impact on cold weather over Eurasia: Role of planetary wave reflection

PubMed Central

Nath, Debashis; Chen, Wen; Zelin, Cai; Pogoreltsev, Alexander Ivanovich; Wei, Ke

2016-01-01

In the present study, we investigate the impact of stratospheric planetary wave reflection on tropospheric weather over Central Eurasia during the 2013 Sudden Stratospheric Warming (SSW) event. We analyze EP fluxes and Plumb wave activity fluxes to study the two and three dimensional aspects of wave propagation, respectively. The 2013 SSW event is excited by the combined influence of wavenumber 1 (WN1) and wavenumber 2 (WN2) planetary waves, which makes the event an unusual one and seems to have significant impact on tropospheric weather regime. We observe an extraordinary development of a ridge over the Siberian Tundra and the North Pacific during first development stage (last week of December 2012) and later from the North Atlantic in the second development stage (first week of January 2013), and these waves appear to be responsible for the excitation of the WN2 pattern during the SSW. The wave packets propagated upward and were then reflected back down to central Eurasia due to strong negative wind shear in the upper stratospheric polar jet, caused by the SSW event. Waves that propagated downward led to the formation of a deep trough over Eurasia and brought extreme cold weather over Kazakhstan, the Southern part of Russia and the Northwestern part of China during mid-January 2013. PMID:27051997

Dynamics of 2013 Sudden Stratospheric Warming event and its impact on cold weather over Eurasia: Role of planetary wave reflection.

PubMed

Nath, Debashis; Chen, Wen; Zelin, Cai; Pogoreltsev, Alexander Ivanovich; Wei, Ke

2016-04-07

In the present study, we investigate the impact of stratospheric planetary wave reflection on tropospheric weather over Central Eurasia during the 2013 Sudden Stratospheric Warming (SSW) event. We analyze EP fluxes and Plumb wave activity fluxes to study the two and three dimensional aspects of wave propagation, respectively. The 2013 SSW event is excited by the combined influence of wavenumber 1 (WN1) and wavenumber 2 (WN2) planetary waves, which makes the event an unusual one and seems to have significant impact on tropospheric weather regime. We observe an extraordinary development of a ridge over the Siberian Tundra and the North Pacific during first development stage (last week of December 2012) and later from the North Atlantic in the second development stage (first week of January 2013), and these waves appear to be responsible for the excitation of the WN2 pattern during the SSW. The wave packets propagated upward and were then reflected back down to central Eurasia due to strong negative wind shear in the upper stratospheric polar jet, caused by the SSW event. Waves that propagated downward led to the formation of a deep trough over Eurasia and brought extreme cold weather over Kazakhstan, the Southern part of Russia and the Northwestern part of China during mid-January 2013.

Apparent relationship between solar-sector boundaries and 300-mb vorticity: Possible explanation in terms of upward propagation of planetary-scale waves

NASA Technical Reports Server (NTRS)

Deland, R. J.

1974-01-01

The selection process for sector structure boundary crossings used in vorticity correlation studies is examined and the possible influence of ascending planetary scale waves is assessed. It is proposed that some of the observed correlations between geomagnetic and meteorological variations may be due to meteorological effects on the geometric variables, rather than due to common solar origin.

REVIEWS OF TOPICAL PROBLEMS: Generation of large-scale eddies and zonal winds in planetary atmospheres

NASA Astrophysics Data System (ADS)

Onishchenko, O. G.; Pokhotelov, O. A.; Astafieva, N. M.

2008-06-01

The review deals with a theoretical description of the generation of zonal winds and vortices in a turbulent barotropic atmosphere. These large-scale structures largely determine the dynamics and transport processes in planetary atmospheres. The role of nonlinear effects on the formation of mesoscale vortical structures (cyclones and anticyclones) is examined. A new mechanism for zonal wind generation in planetary atmospheres is discussed. It is based on the parametric generation of convective cells by finite-amplitude Rossby waves. Weakly turbulent spectra of Rossby waves are considered. The theoretical results are compared to the results of satellite microwave monitoring of the Earth's atmosphere.

Past and future of radio occultation studies of planetary atmospheres

NASA Technical Reports Server (NTRS)

Eshleman, Von R.; Hinson, David P.; Tyler, G. Leonard; Lindal, Gunnar F.

1987-01-01

Measurements of radio waves that have propagated through planetary atmospheres have provided exploratory results on atmospheric constituents, structure, dynamics, and ionization for Venus, Mars, Titan, Jupiter, Saturn, and Uranus. Highlights of past results are reviewed in order to define and illustrate the potential of occultation and related radio studies in future planetary missions.

An Asymptotic and Stochastic Theory for the Effects of Surface Gravity Waves on Currents and Infragravity Waves

NASA Astrophysics Data System (ADS)

McWilliams, J. C.; Lane, E.; Melville, K.; Restrepo, J.; Sullivan, P.

2004-12-01

Oceanic surface gravity waves are approximately irrotational, weakly nonlinear, and conservative, and they have a much shorter time scale than oceanic currents and longer waves (e.g., infragravity waves) --- except where the primary surface waves break. This provides a framework for an asymptotic theory, based on separation of time (and space) scales, of wave-averaged effects associated with the conservative primary wave dynamics combined with a stochastic representation of the momentum transfer and induced mixing associated with non-conservative wave breaking. Such a theory requires only modest information about the primary wave field from measurements or operational model forecasts and thus avoids the enormous burden of calculating the waves on their intrinsically small space and time scales. For the conservative effects, the result is a vortex force associated with the primary wave's Stokes drift; a wave-averaged Bernoulli head and sea-level set-up; and an incremental material advection by the Stokes drift. This can be compared to the "radiation stress" formalism of Longuet-Higgins, Stewart, and Hasselmann; it is shown to be a preferable representation since the radiation stress is trivial at its apparent leading order. For the non-conservative breaking effects, a population of stochastic impulses is added to the current and infragravity momentum equations with distribution functions taken from measurements. In offshore wind-wave equilibria, these impulses replace the conventional surface wind stress and cause significant differences in the surface boundary layer currents and entrainment rate, particularly when acting in combination with the conservative vortex force. In the surf zone, where breaking associated with shoaling removes nearly all of the primary wave momentum and energy, the stochastic forcing plays an analogous role as the widely used nearshore radiation stress parameterizations. This talk describes the theoretical framework and presents some preliminary solutions using it. McWilliams, J.C., J.M. Restrepo, & E.M. Lane, 2004: An asymptotic theory for the interaction of waves and currents in coastal waters. J. Fluid Mech. 511, 135-178. Sullivan, P.P., J.C. McWilliams, & W.K. Melville, 2004: The oceanic boundary layer driven by wave breaking with stochastic variability. J. Fluid Mech. 507, 143-174.

Nearshore bars and the break-point hypothesis

USGS Publications Warehouse

Sallenger, A.H.; Howd, P.A.

1989-01-01

The set of hypotheses calling for bar formation at the break point was tested with field data. During two different experiments, waves were measured across the surf zone coincident with the development of a nearshore bar. We use a criterion, based on the wave height to depth ratio, to determine the offshore limit of the inner surf zone. During the first experiment, the bar became better developed and migrated offshore while remaining well within the inner surf zone. During the second experiment, the surf zone was narrower and we cannot rule out the possibility of break point processes contributing to bar development. We conclude that bars are not necessarily coupled with the break point and can become better developed and migrate offshore while being in the inner surf zone landward from initial wave breaking in the outer surf zone. ?? 1989.

Dynamical Influence and Operational Impacts of an Extreme Mediterranean Cold Surge

DTIC Science & Technology

2013-06-01

over 45 cm of snowfall in Souda Bay, Crete, which significantly impacted operations at Naval Support Activity Souda Bay. The extratropical wave...cold surge event and its dependence on the upstream synoptic scale events. 14. SUBJECT TERMS Extratropical Cyclone, Souda Bay...Activity Souda Bay. The extratropical wave associated with the cold surge could be classified as a classic life-cycle 1 wave break. The wave-breaking

Arctic Climate and Atmospheric Planetary Waves

NASA Technical Reports Server (NTRS)

Cavalieri, D. J.; Haekkinen, S.

2000-01-01

Analysis of a fifty-year record (1946-1995) of monthly-averaged sea level pressure data provides a link between the phases of planetary-scale sea level pressure waves and Arctic Ocean and ice variability. Results of this analysis show: (1) a breakdown of the dominant wave I pattern in the late 1960's, (2) shifts in the mean phase of waves 1 and 2 since this breakdown, (3) an eastward shift in the phases of both waves 1 and 2 during the years of simulated cyclonic Arctic Ocean circulation relative to their phases during the years of anticyclonic circulation, (4) a strong decadal variability of wave phase associated with simulated Arctic Ocean circulation changes. Finally, the Arctic atmospheric circulation patterns that emerge when waves 1 and 2 are in their extreme eastern and western positions suggest an alternative approach to determine significant forcing patterns of sea ice and high-latitude variability.

The GISS global climate-middle atmosphere model. II - Model variability due to interactions between planetary waves, the mean circulation and gravity wave drag

NASA Technical Reports Server (NTRS)

Rind, D.; Suozzo, R.; Balachandran, N. K.

1988-01-01

The variability which arises in the GISS Global Climate-Middle Atmosphere Model on two time scales is reviewed: interannual standard deviations, derived from the five-year control run, and intraseasonal variability as exemplified by statospheric warnings. The model's extratropical variability for both mean fields and eddy statistics appears reasonable when compared with observations, while the tropical wind variability near the stratopause may be excessive possibly, due to inertial oscillations. Both wave 1 and wave 2 warmings develop, with connections to tropospheric forcing. Variability on both time scales results from a complex set of interactions among planetary waves, the mean circulation, and gravity wave drag. Specific examples of these interactions are presented, which imply that variability in gravity wave forcing and drag may be an important component of the variability of the middle atmosphere.

Breaking Waves on the Ocean Surface

NASA Astrophysics Data System (ADS)

Schwendeman, Michael S.

In the open ocean, breaking waves are a critical mechanism for the transfer of energy, momentum, and mass between the atmosphere and the ocean. Despite much study, fundamental questions about wave breaking, such as what determines whether a wave will break, remain unresolved. Measurements of oceanic breakers, or "whitecaps," are often used to validate the hypotheses derived in simplified theoretical, numerical, or experimental studies. Real-world measurements are also used to improve the parameterizations of wave-breaking in large global models, such as those forecasting climate change. Here, measurements of whitecaps are presented using ship-based cameras, from two experiments in the North Pacific Ocean. First, a method for georectifying the camera imagery is described using the distant horizon, without additional instrumentation. Over the course of the experiment, this algorithm correctly identifies the horizon in 92% of images in which it is visible. In such cases, the calculation of camera pitch and roll is accurate to within 1 degree. The main sources of error in the final georectification are from mislabeled horizons due to clouds, rain, or poor lighting, and from vertical "heave" motions of the camera, which cannot be calculated with the horizon method. This method is used for correcting the imagery from the first experiment, and synchronizing the imagery from the second experiment to an onboard inertial motion package. Next, measurements of the whitecap coverage, W, are shown from both experiments. Although W is often used in models to represent whitecapping, large uncertainty remains in the existing parameterizations. The data show good agreement with recent measurements using the wind speed. Although wave steepness and dissipation are hypothesized to be more robust predictors of W, this is shown to not always be the case. Wave steepness shows comparable success to the wind parameterizations only when using a mean-square slope variable calculated over the equilibrium range waves and normalizing by the wave directional spread. Meanwhile, correlation of W with turbulent dissipation measurements is significantly worse, which may be due to uncertainty in the measurements or bias related to micro-breaking waves. Finally, phase-resolved, three-dimensional, measurements of the whitecaps were made from a new ship-based stereo video system. Comparison with concurrent buoy measurements indicate that the stereo data accurately reproduces the wave statistics, including the frequency spectra. The whitecaps are characterized by transient and spatially localized regions of extreme surface gradients, rather than large crest-to-trough steepnesses. It was found that whitecaps were around 10 times more likely to have extreme slopes, and 50% of the observed extreme surface slopes were in the vicinity of the breaking waves. The maximum whitecap slopes show good agreement with the Stokes 120 degree limiting crest geometry, and the whitecap crest loses much of its maximum steepness shortly after the onset of breaking. The whitecap phase speeds are consistently less than the linear or weakly nonlinear predicted phase speed, which indicate the effect of narrow-band wave groups, despite the broad-band wave spectra.

PMP-2 Report: Equatorial Wave Dynamics

NASA Technical Reports Server (NTRS)

Hirota, I.

1982-01-01

The activities of the pre-MAP project 2 (PMP-2) from 1978 through 1981 are described. The following topics relating to the equatorial middle atmosphere are discussed briefly: (1) the semi-annual oscillation and Kelvin waves; (2) planetary Rossby waves; (3) upper mesospheric waves; and (4) gravity waves.

Observations of planetary mixed Rossby-gravity waves in the upper stratosphere

NASA Technical Reports Server (NTRS)

Randel, William J.; Boville, Byron A.; Gille, John C.

1990-01-01

Observational evidence is presented for planetary scale (zonal wave number 1-2) mixed Rossby-gravity (MRG) waves in the equatorial upper stratosphere (35-50 km). These waves are detected in LIMS measurements as coherently propagating temperature maxima of amplitude 0.1-0.3 K, which are antisymmetric (out of phase) about the equator, centered near 10-15 deg north and south latitude. These features have vertical wavelengths of order 10-15 km, periods near 2-3 days, and zonal phase velocities close to 200 m/s. Both eastward and westward propagating waves are found, and the observed vertical wavelengths and meridional structures are in good agreement with the MRG dispersion relation. Theoretical estimates of the zonal accelerations attributable to these waves suggest they do not contribute substantially to the zonal momentum balance in the middle atmosphere.

Studies of Tidal and Planetary Wave Variability in the Middle Atmosphere using UARS and Correlative MF Radar Data

NASA Technical Reports Server (NTRS)

Fritts, David C.

1996-01-01

The goals of this research effort have been to use MF radar and UARS/HRDI wind measurements for correlative studies of large-scale atmospheric dynamics, focusing specifically on the tidal and various planetary wave structures occurring in the middle atmosphere. We believed that the two data sets together would provide the potential for much more comprehensive studies than either by itself, since they jointly would allow the removal of ambiguities in wave structure that are difficult to resolve with either data set alone. The joint data were to be used for studies of wave structure, variability, and the coupling of these motions to mean and higher-frequency motions.

Solar system plasma waves

NASA Technical Reports Server (NTRS)

Gurnett, Donald A.

1995-01-01

An overview is given of spacecraft observations of plasma waves in the solar system. In situ measurements of plasma phenomena have now been obtained at all of the planets except Mercury and Pluto, and in the interplanetary medium at heliocentric radial distances ranging from 0.29 to 58 AU. To illustrate the range of phenomena involved, we discuss plasma waves in three regions of physical interest: (1) planetary radiation belts, (2) planetary auroral acceleration regions and (3) the solar wind. In each region we describe examples of plasma waves that are of some importance, either due to the role they play in determining the physical properties of the plasma, or to the unique mechanism involved in their generation.

Dynamics of the middle atmosphere as observed by the ARISE project

NASA Astrophysics Data System (ADS)

Blanc, Elisabeth

2015-04-01

The atmosphere is a complex system submitted to disturbances in a wide range of scales, including high frequency sources as volcanoes, thunderstorms, tornadoes and at larger scales, gravity waves from deep convection or wind over mountains, atmospheric tides and planetary waves. These waves affect the different atmospheric layers submitted to different temperature and wind systems which strongly control the general atmospheric circulation. The full description of gravity and planetary waves constitutes a challenge for the development of future models of atmosphere and climate. The objective of this paper is to present a review of recent advances obtained in this topic, especially in the framework of the ARISE (Atmospheric dynamics Research InfraStructure in Europe) project

Modeling the Dynamics of the Middle Atmosphere and Lower Thermosphere Under the Influence of Gravity Waves

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Mengel, J. G.; Chan, K. L.; Porter, H. S.; Einaudi, Franco (Technical Monitor)

2000-01-01

Our Numerical Spectral Model (NSM), which extends from the ground up into the thermosphere, is non-linear, time-dependent and has been employed for 2D and 3D applications. The standard version of the NSM incorporates Hines' Doppler Spread Parameterization for small scale gravity waves (GW), but planetary waves generated in the troposphere have also been incorporated. The NSM has been applied to describe: (1) the anomalous seasonal variations of the zonal circulation and temperature in the upper mesosphere, (2) the equatorial oscillations (quasi-biennial and semi-annual oscillations (QBO and SAO)) extending from the stratosphere into the upper mesosphere, (3) the diurnal and semi-diurnal tides, and (4) the planetary waves that are excited in the mesosphere. With the emphasis to provide understanding, we present here results from numerical experiments with the NSM that shed light on the GW processes that are of central importance in the mesosphere and lower thermosphere. These are our conclusions: (1) The large semiannual variations in the diurnal tide (DT), with peak amplitudes observed around equinox, are produced primarily by GW interactions that involve, in part, planetary waves. The DT, like planetary waves, tends to be amplified by GW momentum deposition, which reduces also the vertical wavelength, but variations in eddy viscosity associated with GW interactions are also important. (2) The semidiurnal tide (SDT) and its phase in particular, is strongly influenced by the mean zonal circulation. The SDT, individually, is also amplified by GW. But the DT filters out GW such that the GW interaction effectively reduces the amplitude of the SDT, producing a strong nonlinear interaction between the DT and SDT. (3) Without external time dependent energy or momentum sources, planetary waves (PW) are generated in the model for zonal wavenumbers 1 to 4, which have amplitudes in the mesosphere above 50 km as large as 40 m/s and periods between 50 and 2 days. The waves are generated primarily during solstice conditions, which indicates that the baroclinic instability (associated with the GW induced reversal in the latitudinal temperature gradient) is playing an important role. Numerical experiment show that GW, directly, also greatly amplify the PW. A common feature of the PW generated in summer and winter is that their vertical wavelengths throughout the mesosphere are large, which indicates that the waves are not propagating freely but are generated throughout the region. Another common feature is that the PW propagate preferentially westward in summer and eastward in winter, being launched from the westward and eastward zonal winds that prevail respectively in summer and winter at altitudes below 80 km. (4) Planetary waves generated internally by baroclinic instability and GW interaction produce large amplitude modulations of the DT and SDT. In summary we conclude that GW play major roles in generating and amplifying the dynamical components in the MLT region and, acting principally through wave filtering, produce important non-linear interactions between the components.

Laboratory measurements of microwave and millimeter-wave properties of planetary atmospheric constituents

NASA Technical Reports Server (NTRS)

Steffes, Paul G.

1989-01-01

Accurate data on microwave and millimeter-wave properties of potential planetary atmospheric constituents is critical for the proper interpretation of radio occultation measurements, and of radio astronomical observations of both continuum and spectral line emissions. Such data is also needed to correct for atmospheric effects on radar studies of surface reflectivity. Since the refractive and absorptive properties of atmospheric constituents often vary drastically from theoretically-predicted profiles, especially under the extreme conditions characteristic of the planetary atmosphere, laboratory measurements under simulated planetary conditions are required. This paper reviews the instrumentation and techniques used for laboratory measurement of the refractivity and absorptivity of atmospheric constituents at wavelengths longward of 1 mm, under simulated planetary conditions (temperature, pressure, and broadening gases). Techniques for measuring both gases and condensates are considered. Also reviewed are the relative accuracies of the various techniques. Laboratory measurements are reviewed which have already been made, and additional measurements which are needed for interpretation of data from Venus and the outer planets, are highlighted.

Sensitivity of Middle Atmospheric Temperature and Circulation in the UIUC Mesosphere-Stratosphere-Troposphere GCM to the Treatment of Subgrid-Scale Gravity-Wave Breaking

NASA Technical Reports Server (NTRS)

Yang, Fanglin; Schlesinger, Michael E.; Andranova, Natasha; Zubov, Vladimir A.; Rozanov, Eugene V.; Callis, Lin B.

2003-01-01

The sensitivity of the middle atmospheric temperature and circulation to the treatment of mean- flow forcing due to breaking gravity waves was investigated using the University of Illinois at Urbana-Champaign 40-layer Mesosphere-Stratosphere-Troposphere General Circulation Model (MST-GCM). Three GCM experiments were performed. The gravity-wave forcing was represented first by Rayleigh friction, and then by the Alexander and Dunkerton (AD) parameterization with weak and strong breaking effects of gravity waves. In all experiments, the Palmer et al. parameterization was included to treat the breaking of topographic gravity waves in the troposphere and lower stratosphere. Overall, the experiment with the strong breaking effect simulates best the middle atmospheric temperature and circulation. With Rayleigh friction and the weak breaking effect, a large warm bias of up to 60 C was found in the summer upper mesosphere and lower thermosphere. This warm bias was linked to the inability of the GCM to simulate the reversal of the zonal winds from easterly to westerly crossing the mesopause in the summer hemisphere. With the strong breaking effect, the GCM was able to simulate this reversal, and essentially eliminated the warm bias. This improvement was the result of a much stronger meridional transport circulation that possesses a strong vertical ascending branch in the summer upper mesosphere, and hence large adiabatic cooling. Budget analysis indicates that 'in the middle atmosphere the forces that act to maintain a steady zonal-mean zonal wind are primarily those associated with the meridional transport circulation and breaking gravity waves. Contributions from the interaction of the model-resolved eddies with the mean flow are small. To obtain a transport circulation in the mesosphere of the UIUC MST-GCM that is strong enough to produce the observed cold summer mesopause, gravity-wave forcing larger than 100 m/s/day in magnitude is required near the summer mesopause. In the tropics, only with the AD parameterization can the model produce realistic semiannual oscillations.

Nonlinear interaction and wave breaking with a submerged porous structure

NASA Astrophysics Data System (ADS)

Hsieh, Chih-Min; Sau, Amalendu; Hwang, Robert R.; Yang, W. C.

2016-12-01

Numerical simulations are performed to investigate interactive velocity, streamline, turbulent kinetic energy, and vorticity perturbations in the near-field of a submerged offshore porous triangular structure, as Stokes waves of different heights pass through. The wave-structure interaction and free-surface breaking for the investigated flow situations are established based on solutions of 2D Reynolds Averaged Navier-Stokes equations in a Cartesian grid in combination with K-ɛ turbulent closure and the volume of fluid methodology. The accuracy and stability of the adopted model are ascertained by extensive comparisons of computed data with the existing experimental and theoretical findings and through efficient predictions of the internal physical kinetics. Simulations unfold "clockwise" and "anticlockwise" rotation of fluid below the trough and the crest of the viscous waves, and the penetrated wave energy creates systematic flow perturbation in the porous body. The interfacial growths of the turbulent kinetic energy and the vorticity appear phenomenal, around the apex of the immersed structure, and enhanced significantly following wave breaking. Different values of porosity parameter and two non-porous cases have been examined in combination with varied incident wave height to reveal/analyze the nonlinear flow behavior in regard to local spectral amplification and phase-plane signatures. The evolution of leading harmonics of the undulating free-surface and the vertical velocity exhibits dominating roles of the first and the second modes in inducing the nonlinearity in the post-breaking near-field that penetrates well below the surface layer. The study further suggests the existence of a critical porosity that can substantially enhance the wave-shoaling and interface breaking.

Physical measurements of breaking wave impact on a floating wave energy converter

NASA Astrophysics Data System (ADS)

Hann, Martyn R.; Greaves, Deborah M.; Raby, Alison

2013-04-01

Marine energy converter must both efficiently extract energy in small to moderate seas and also successfully survive storms and potential collisions. Extreme loads on devices are therefore an important consideration in their design process. X-MED is a SuperGen UKCMER project and is a collaboration between the Universities of Manchester, Edinburgh and Plymouth and the Scottish Association for Marine Sciences. Its objective is to extend the knowledge of extreme loads due to waves, currents, flotsam and mammal impacts. Plymouth Universities contribution to the X-MED project involves measuring the loading and response of a taut moored floating body due to steep and breaking wave impacts, in both long crested and directional sea states. These measurements are then to be reproduced in STAR-CCM+, a commercial volume of fluid CFD solver, so as to develop techniques to predict the wave loading on wave energy converters. The measurements presented here were conducted in Plymouth Universities newly opened COAST laboratories 35m long, 15.5m wide and 3m deep ocean basin. A 0.5m diameter taut moored hemispherical buoy was used to represent a floating wave energy device or support structure. The changes in the buoys 6 degree of freedom motion and mooring loads are presented due to focused breaking wave impacts, with the breaking point of the wave changed relative to the buoy.

Altimeter Observations of Baroclinic Oceanic Inertia-Gravity Wave Turbulence

NASA Technical Reports Server (NTRS)

Glazman, R. E.; Cheng, B.

1996-01-01

For a wide range of nonlinear wave processes - from capillary to planetary waves - theory predicts the existence of Kolmogorov-type spectral cascades of energy and other conserved quantities occuring via nonlinear resonant wave-wave interactions. So far, observations of wave turbulence (WT) have been limited to small-scale processes such as surface gravity and capillary-gravity waves.

Langmuir-like waves and radiation in planetary foreshocks

NASA Technical Reports Server (NTRS)

Cairns, Iver H.; Robinson, P. A.; Anderson, R. R.; Gurnett, D. A.; Kurth, W. S.

1995-01-01

The basic objectives of this NASA Grant are to develop theoretical understandings (tested with spacecraft data) of the generation and characteristics of electron plasma waves, commonly known as Langmuir-like waves, and associated radiation near f(sub p) and 2f(sub p) in planetary foreshocks. (Here f(sub p) is plasma frequency.) Related waves and radiation in the source regions of interplanetary type III solar radio bursts provide a simpler observational and theoretical context for developing and testing such understandings. Accordingly, applications to type III bursts constitute a significant fraction of the research effort. The testing of the new Stochastic Growth Theory (SGT) for type III bursts, and its extension and testing for foreshock waves and radiation, constitutes a major longterm strategic goal of the research effort.

Maximum Langmuir Fields in Planetary Foreshocks Determined from the Electrostatic Decay Threshold

NASA Technical Reports Server (NTRS)

Robinson, P. A.; Cairns, Iver H.

1995-01-01

Maximum electric fields of Langmuir waves at planetary foreshocks are estimated from the threshold for electrostatic decay, assuming it saturates beam driven growth, and incorporating heliospheric variation of plasma density and temperature. Comparisons with spacecraft observations yields good quantitative agreement. Observations in type 3 radio sources are also in accord with this interpretation. A single mechanism can thus account for the highest fields of beam driven waves in both contexts.

Analysis of bubble plume spacing produced by regular breaking waves

NASA Astrophysics Data System (ADS)

Phaksopa, J.; Haller, M. C.

2012-12-01

The breaking wave process in the ocean is a significant mechanism for energy dissipation, splash, and entrainment of air. The relationship between breaking waves and bubble plume characteristics is still a mystery because of the complexity of the breaking wave mechanism. This study takes a unique approach to quantitatively analyze bubble plumes produced by regular breaking waves. Various previous studies have investigated the formation and the characteristics of bubble plumes using either field observations, laboratory experiments, or numerical modeling However, in most observational work the plume characteristics have been studied from the underneath the water surface. In addition, though numerical simulations are able to include much of the important physics, the computational costs are high and bubble plume events are only simulated for short times. Hence, bubble plume evolution and generation throughout the surf zone is not yet computationally feasible. In the present work we take a unique approach to analyzing bubble plumes. These data may be of use for model/data comparisons as numerical simulations become more tractable. The remotely sensed video data from freshwater breaking waves in the OSU Large Wave Flume (Catalan and Haller, 2008) are analyzed. The data set contains six different regular wave conditions and the video intensity data are used to estimate the spacing of plume events (wavenumber spectrum), to calculate the spectral width (i.e. the range of plume spacing), and to relate these with the wave conditions. The video intensity data capture the evolution of the wave passage over a fixed bed arranged in a bar-trough morphology. Bright regions represent the moving path or trajectory coincident with bubble plume of each wave. It also shows the bubble foam were generated and released from wave crest shown in the form of bubble tails with almost regular spacing for each wave. The bubble tails show that most bubbles did not move along with wave. For the estimation of wavenumber spectrum, the density is high at low wavenumber and it decreases toward high wavenumber. The average spectrum bandwidth was estimated and represented as the bubble event spacing for each run. It is found that its magnitude varies with wave conditions range from 8.81 - 11.82 and is related to the waveheight. Additionally, the calculated wavenumbers from power density function vary in the range of 0.80 - 1.58 meters-1. It is found that the bubble wavenumbers are mostly higher than the wavenumbers calculated from the linear wave theory between 0.2L-0.7L. In other words, the bubble plume length does not exceed the progressive wavelength.

Rapid Assessment of Wave Height Transformation through a Tidal Inlet via Radar Remote Sensing

NASA Astrophysics Data System (ADS)

Díaz Méndez, G.; Haller, M. C.; Raubenheimer, B.; Elgar, S.; Honegger, D.

2014-12-01

Radar has the potential to enable temporally and spatially dense, continuous monitoring of waves and currents in nearshore environments. If quantitative relationships between the remote sensing signals and the hydrodynamic parameters of interest can be found, remote sensing techniques can mitigate the challenges of continuous in situ sampling and possibly enable a better understanding of wave transformation in areas with strongly inhomogeneous along and across-shore bathymetry, currents, and dissipation. As part of the DARLA experiment (New River Inlet, NC), the accuracy of a rapid assessment of wave height transformation via radar remote sensing is tested. Wave breaking events are identified in the radar image time series (Catalán et al. 2011). Once the total number of breaking waves (per radar collection) is mapped throughout the imaging domain, radar-derived bathymetry and wave frequency are used to compute wave breaking dissipation (Janssen and Battjes 2007). Given the wave breaking dissipation, the wave height transformation is calculated by finding an inverse solution to the 1D cross-shore energy flux equation (including the effect of refraction). The predicted wave height transformation is consistent (correlation R > 0.9 and rmse as low as 0.1 m) with the transformation observed with in situ sensors in an area of complex morphology and strong (> 1 m/s) tidal currents over a nine-day period. The wave forcing (i.e., radiation stress gradients) determined from the remote sensing methodology will be compared with values estimated with in situ sensors. Funded by ONR and ASD(R&E)

A case study of the energy dissipation of the gravity wave field based on satellite altimeter measurements

NASA Technical Reports Server (NTRS)

Huang, N. E.; Parsons, C. L.; Long, S. R.; Bliven, L. F.

1983-01-01

Wave breaking is proposed as the primary energy dissipation mechanism for the gravity wave field. The energy dissipation rate is calculated based on the statistical model proposed by Longuet-Higgins (1969) with a modification of the breaking criterion incorporating the surface stress according to Phillips and Banner (1974). From this modified model, an analytic expression is found for the wave attenuation rate and the half-life time of the wave field which depend only on the significant slope of the wave field and the ratio of friction velocity to initial wave phase velocity. These expressions explain why the freshly generated wave field does not last long, but why swells are capable of propagating long distances without substantial change in energy density. It is shown that breaking is many orders of magnitude more effective in dissipating wave energy than the molecular viscosity, if the significant slope is higher than 0.01. Limited observational data from satellite and laboratory are used to compare with the analytic results, and show good agreement.

Do tidal or swing waves roughen planetary surfaces?

NASA Astrophysics Data System (ADS)

Kochemasov, Gennady G.

2010-05-01

Surfaces of the terrestrial planets and their moons are far from being smooth. They are warped by several wavelengths and show a remarkable regularity: their roughness increases with the solar distance. Thus, if for Mercury the surface relief range does not exceed several km, for Mars it is already about 30 km. Earth's range is 20 km, Venus' one 14 km. Recently it was shown that this row of ranges reflects ratios of the tectonic granules radii of terrestrial planets [1, 2]. These radii related to unity of reduced planetary globes (in a geometrical model all planets are represented by even circles [2]) are as follows: Mercury πR/16, Venus πR/6, Earth πR/4, Mars πR/2. It means that in the great planetary circles (equators) there are 32, 12, 8, and 4 tectonic granules (now they all are mapped by remote methods) and their numbers are inversely proportional to the orbital frequencies of the planets: higher frequency - smaller granule, and, vice versa, lower frequency - larger granule. In this planetary law is a firm confirmation of the main conceptual point of the wave planetology: "Orbits make structures" [3]. But how this happens? A basic reason lies in the keplerian elliptical orbits implying periodical changes of planetary bodies accelerations. Periodical slowing down and speeding up produce inertia-gravity waves warping any celestial body. In rotating bodies this wave warping is divided in four directions: two orthogonal and two diagonal. An interference of these directions produces tectonic blocks of three kinds: uplifting, subsiding, and neutral. Sizes and amplitudes of the blocks (granules) depend on the warping wavelengths and increase with the solar distance. Thus, a relief-forming potential and the actual relief range observed on the planets increase in this direction [1, 2, 4]. But the tidal forces diminish in this direction. That is why they cannot be a reason for the relief-forming potential. Having in mind a swinging action of planetary orbits on heavenly bodies one might think of swing forces and swing waves (contrary to the tidal waves) producing the wave warping surfaces and the deeper planetary spheres [1]. Three observations in relation with this revelation might be mentioned. 1. An increasing surface roughness of the icy satellites of Saturn with increasing distances from the planet [5]. 2. Atmospheric masses of terrestrial planets increase with the diminishing solar distance as a sequence of more frequent wave oscillations - a sweeping out making atmospheres volatiles from planetary depths is facilitated by more frequent oscillations. 3. The inner rapidly orbiting satellites of Jupiter (Io), Saturn (Enceladus), and Neptun (Triton) are still emitting volatiles as a result of more thorough sweeping out their volatile stock. Mercury also has traces of some metals in its exosphere (MESSENGER data). References: [1] Kochemasov G.G. (2009) A regular row of planetary relief ranges connected with tectonic granulations of celestial bodies // New Concepts in Global Tectonics Newsletter, # 51, 58-61. [2] Kochemasov G.G. (2009) A quantitative geometric model of relief-forming potential in terrestrial planets // EPSC Abstracts, Vol. 4, EPSC2009-16-1. [3] Kochemasov G.G. (1998) Tectonic dichotomy, sectoring and granulation of Earth and other celestial bodies // Proceedings of the International Symposium on New Concepts in Global Tectonics, "NCGT-98 TSUKUBA", Geological Survey of Japan, Tsukuba, Nov 20-23, 1998, 144-147. [4] Kochemasov G.G. (1993) Relief-forming potential of planets // 18th Russian-American microsymposium on planetology, Abstracts, Oct. 9-10, 1993, Moscow, Vernadsky Inst. (GEOKHI), 27-28. [5] Thomas, P.C., Veverka, J., Helfenstein, P., Porco, C. et al. (2006) Shapes of the saturnian icy satellites // Lunar and Planetary Science Conference XXXVII, Houston, USA, Abstract 1639 pdf. CD-ROM.

The oceanic boundary layer driven by wave breaking with stochastic variability. Part 1. Direct numerical simulations

NASA Astrophysics Data System (ADS)

Sullivan, Peter P.; McWilliams, James C.; Melville, W. Kendall

2004-05-01

We devise a stochastic model for the effects of breaking waves and fit its distribution functions to laboratory and field data. This is used to represent the space time structure of momentum and energy forcing of the oceanic boundary layer in turbulence-resolving simulations. The aptness of this breaker model is evaluated in a direct numerical simulation (DNS) of an otherwise quiescent fluid driven by an isolated breaking wave, and the results are in good agreement with laboratory measurements. The breaker model faithfully reproduces the bulk features of a breaking event: the mean kinetic energy decays at a rate approaching t(-1) , and a long-lived vortex (eddy) is generated close to the water surface. The long lifetime of this vortex (more than 50 wave periods) makes it effective in energizing the surface region of oceanic boundary layers. Next, a comparison of several different DNS of idealized oceanic boundary layers driven by different surface forcing (i.e. constant current (as in Couette flow), constant stress, or a mixture of constant stress plus stochastic breakers) elucidates the importance of intermittent stress transmission to the underlying currents. A small amount of active breaking, about 1.6% of the total water surface area at any instant in time, significantly alters the instantaneous flow patterns as well as the ensemble statistics. Near the water surface a vigorous downwelling upwelling pattern develops at the head and tail of each three-dimensional breaker. This enhances the vertical velocity variance and generates both negative- and positive-signed vertical momentum flux. Analysis of the mean velocity and scalar profiles shows that breaking effectively increases the surface roughness z_o by more than a factor of 30; for our simulations z_o/lambda {≈} 0.04 to 0.06, where lambda is the wavelength of the breaking wave. Compared to a flow driven by a constant current, the extra mixing from breakers increases the mean eddy viscosity by more than a factor of 10 near the water surface. Breaking waves alter the usual balance of production and dissipation in the turbulent kinetic energy (TKE) budget; turbulent and pressure transports and breaker work are important sources and sinks in the budget. We also show that turbulent boundary layers driven by constant current and constant stress (i.e. with no breaking) differ in fundamental ways. The additional freedom provided by a constant-stress boundary condition permits finite velocity variances at the water surface, so that flows driven by constant stress mimic flows with weakly and statistically homogeneous breaking waves.

Study of Linear and Nonlinear Waves in Plasma Crystals Using the Box_Tree Code

NASA Astrophysics Data System (ADS)

Qiao, K.; Hyde, T.; Barge, L.

Dusty plasma systems play an important role in both astrophysical and planetary environments (protostellar clouds, planetary ring systems and magnetospheres, cometary environments) and laboratory settings (plasma processing or nanofabrication). Recent research has focussed on defining (both theoretically and experimentally) the different types of wave mode propagations, which are possible within plasma crystals. This is an important topic since several of the fundamental quantities for characterizing such crystals can be obtained directly from an analysis of the wave propagation/dispersion. This paper will discuss a num rical model fore 2D-monolayer plasma crystals, which was established using a modified box tree code. Different wave modes were examined by adding a time dependent potential to the code designed to simulate a laser radiation perturbation as has been applied in many experiments. Both linear waves (for example, longitudinal and transverse dust lattice waves) and nonlinear waves (solitary waves) are examined. The output data will also be compared with the results of corresponding experiments and discussed.

Dense Gravity Currents with Breaking Internal Waves

NASA Astrophysics Data System (ADS)

Tanimoto, Yukinobu; Hogg, Charlie; Ouellette, Nicholas; Koseff, Jeffrey

2017-11-01

Shoaling and breaking internal waves along a pycnocline may lead to mixing and dilution of dense gravity currents, such as cold river inflows into lakes or brine effluent from desalination plants in near-coastal environments. In order to explore the interaction between gravity currents and breaking interfacial waves a series of laboratory experiments was performed in which a sequence of internal waves impinge upon a shelf-slope gravity current. The waves are generated in a two-layer thin-interface ambient water column under a variety of conditions characterizing both the waves and the gravity currents. The mixing of the gravity current is measured through both intrusive (CTD probe) and nonintrusive (Planar-laser inducted fluorescence) techniques. We will present results over a full range of Froude number (characterizing the waves) and Richardson number (characterizing the gravity current) conditions, and will discuss the mechanisms by which the gravity current is mixed into the ambient environment including the role of turbulence in the process. National Science Foundation.

Equatorial Dynamics Observed by Rocket, Radar, and Satellite During the CADRE/MALTED Campaign. 1; Programmatics and small-scale fluctuations

NASA Technical Reports Server (NTRS)

Goldberg, Richard A.; Lehmacher, Gerald A.; Schmidlin, Frank J.; Fritts, David C.; Mitchell, J. D.; Croskey, C. L.; Friedrich, M.; Swartz, W. E.

1997-01-01

In August 1994, the Mesospheric and Lower Thermospheric Equatorial Dynamics (MALTED) Program was conducted from the Alcantara rocket site in northeastern Brazil as part of the International Guard Rocket Campaign to study equatorial dynamics, irregularities, and instabilities in the ionosphere. This site was selected because of its proximity to the geographic (2.3 deg S) and magnetic (approx. 0.5 deg S) equators. MALTED was concerned with planetary wave modulation of the diurnal tidal amplitude, which exhibits considerable amplitude variability at equatorial and subtropical latitudes. Our goals were to study this global modulation of the tidal motions where tidal influences on the thermal structure are maximum, to study the interaction of these tidal structures with gravity waves and turbulence at mesopause altitudes, and to gain a better understanding of dynamic influences and variability on the equatorial middle atmosphere. Four (two daytime and two nighttime) identical Nike-Orion payloads designed to investigate small-scale turbulence and irregularities were coordinated with 20 meteorological falling-sphere rockets designed to measure temperature and wind fields during a 10-day period. These in situ measurements were coordinated with observations of global-scale mesospheric motions that were provided by various ground based radars and the Upper Atmosphere Research Satellite (UARS) through the Coupling and Dynamics of Regions Equatorial (CADRE) campaign. The ground-based observatories included the Jicamarca radar observatory near Lima, Peru, and medium frequency (MF) radars in Hawaii, Christmas Island, and Adelaide. Since all four Nike-Orion flights penetrated and overflew the electrojet with apogees near 125 km, these flights provided additional information about the electrodynamics and irregularities in the equatorial ionospheric E region and may provide information on wave coupling between the mesosphere and the electrojet. Simultaneous with these flights, the CUPRI 50-MHz radar (Cornell University) provided local sounding of the electrojet region. A description of the campaign logistics and the measurements performed with the Nike-Orion instrumentation and their implications for turbulence due to gravity waves and tidal instability in the mesosphere and lower thermosphere (MLT) are presented here. From a study of electron density fluctuations measured by rocket probes, we have found evidence for equatorial mesospheric neutral-atmospheric turbulence between 85 and 90 km. Furthermore, falling-sphere data imply that gravity wave breaking was a source for this turbulence. Mean motions and the various planetary, tidal, and gravity wave structures and their coherence and variability are the subjects of a companion paper.

Equatorial dynamics observed by rocket, radar, and satellite during the CADRE/MALTED campaign 1. Programmatics and small-scale fluctuations

NASA Astrophysics Data System (ADS)

Goldberg, Richard A.; Lehmacher, Gerald A.; Schmidlin, Frank J.; Fritts, David C.; Mitchell, J. D.; Croskey, C. L.; Friedrich, M.; Swartz, W. E.

1997-11-01

In August 1994, the Mesospheric and Lower Thermospheric Equatorial Dynamics (MALTED) Program was conducted from the Alca‸ntara rocket site in northeastern Brazil as part of the International Guará Rocket Campaign to study equatorial dynamics, irregularities, and instabilities in the ionosphere. This site was selected because of its proximity to the geographic (2.3°S) and magnetic (~0.5°S) equators. MALTED was concerned with planetary wave modulation of the diurnal tidal amplitude, which exhibits considerable amplitude variability at equatorial and subtropical latitudes. Our goals were to study this global modulation of the tidal motions where tidal influences on the thermal structure are maximum, to study the interaction of these tidal structures with gravity waves and turbulence at mesopause altitudes, and to gain a better understanding of dynamic influences and variability on the equatorial middle atmosphere. Four (two daytime and two nighttime) identical Nike-Orion payloads designed to investigate small-scale turbulence and irregularities were coordinated with 20 meteorological falling-sphere rockets designed to measure temperature and wind fields during a 10-day period. These in situ measurements were coordinated with observations of global-scale mesospheric motions that were provided by various ground based radars and the Upper Atmosphere Research Satellite (UARS) through the Coupling and Dynamics of Regions Equatorial (CADRE) campaign. The ground-based observatories included the Jicamarca radar observatory near Lima, Peru, and medium frequency (MF) radars in Hawaii, Christmas Island, and Adelaide. Since all four Nike-Orion flights penetrated and overflew the electrojet with apogees near 125 km, these flights provided additional information about the electrodynamics and irregularities in the equatorial ionospheric E region and may provide information on wave coupling between the mesosphere and the electrojet. Simultaneous with these flights, the CUPRI 50-MHz radar (Cornell University) provided local sounding of the electrojet region. A description of the campaign logistics and the measurements performed with the Nike-Orion instrumentation and their implications for turbulence due to gravity waves and tidal instability in the mesosphere and lower thermosphere (MLT) are presented here. From a study of electron density fluctuations measured by rocket probes, we have found evidence for equatorial mesospheric neutral-atmospheric turbulence between 85 and 90 km. Furthermore, falling-sphere data imply that gravity wave breaking was a source for this turbulence. Mean motions and the various planetary, tidal, and gravity wave structures and their coherence and variability are the subjects of a companion paper.

Gas transfer under high wind and its dependence on wave breaking and sea state

NASA Astrophysics Data System (ADS)

Brumer, Sophia; Zappa, Christopher; Fairall, Christopher; Blomquist, Byron; Brooks, Ian; Yang, Mingxi

2016-04-01

Quantifying greenhouse gas fluxes on regional and global scales relies on parameterizations of the gas transfer velocity K. To first order, K is dictated by wind speed (U) and is typically parameterized as a non-linear functions of U. There is however a large spread in K predicted by the traditional parameterizations at high wind speed. This is because a large variety of environmental forcing and processes (Wind, Currents, Rain, Waves, Breaking, Surfactants, Fetch) actually influence K and wind speed alone cannot capture the variability of air-water gas exchange. At high wind speed especially, breaking waves become a key factor to take into account when estimating gas fluxes. The High Wind Gas exchange Study (HiWinGS) presents the unique opportunity to gain new insights on this poorly understood aspects of air-sea interaction under high winds. The HiWinGS cruise took place in the North Atlantic during October and November 2013. Wind speeds exceeded 15 m s-1 25% of the time, including 48 hrs with U10 > 20 m s-1. Continuous measurements of turbulent fluxes of heat, momentum, and gas (CO2, DMS, acetone and methanol) were taken from the bow of the R/V Knorr. The wave field was sampled by a wave rider buoy and breaking events were tracked in visible imagery was acquired from the port and starboard side of the flying bridge during daylight hours at 20Hz. Taking advantage of the range of physical forcing and wave conditions sampled during HiWinGS, we test existing parameterizations and explore ways of better constraining K based on whitecap coverage, sea state and breaking statistics contrasting pure windseas to swell dominated periods. We distinguish between windseas and swell based on a separation algorithm applied to directional wave spectra for mixed seas, system alignment is considered when interpreting results. The four gases sampled during HiWinGS ranged from being mostly waterside controlled to almost entirely airside controlled. While bubble-mediated transfer appears to be small for moderately soluble gases like DMS, the importance of wave breaking turbulence transport has yet to be determined for all gases regardless of their solubility. This will be addressed by correlating measured K to estimates of active whitecap fraction (WA) and turbulent kinetic energy dissipation rate (ɛ). WA and ɛ are estimated from moments of the breaking crest length distribution derived from the imagery, focusing on young seas, when it is likely that large-scale breaking waves (i.e., whitecapping) will dominate the ɛ.

Vortex-induced suspension of sediment in the surf zone

NASA Astrophysics Data System (ADS)

Otsuka, Junichi; Saruwatari, Ayumi; Watanabe, Yasunori

2017-12-01

A major mechanism of sediment suspension by organized vortices produced under violent breaking waves in the surf zone was identified through physical and computational experiments. Counter-rotating flows within obliquely descending eddies produced between adjacent primary roller vortices induce transverse convergent near-bed flows, driving bed load transport to form regular patterns of transverse depositions. The deposited sediment is then rapidly ejected by upward carrier flows induced between the vortices. This mechanism of vortex-induced suspension is supported by experimental evidence that coherent sediment clouds are ejected where the obliquely descending eddies reach the sea bed after the breaking wave front has passed. In addition to the effects of settling and turbulent diffusion caused by breaking waves, the effect of the vortex-induced flows was incorporated into a suspension model on the basis of vorticity dynamics and parametric characteristics of transverse flows in breaking waves. The model proposed here reasonably predicts an exponential attenuation of the measured sediment concentration due to violent plunging waves and significantly improves the underprediction of the concentration produced by previous models.

Rip currents and alongshore flows in single channels dredged in the surf zone

NASA Astrophysics Data System (ADS)

Moulton, Melissa; Elgar, Steve; Raubenheimer, Britt; Warner, John C.; Kumar, Nirnimesh

2017-05-01

To investigate the dynamics of flows near nonuniform bathymetry, single channels (on average 30 m wide and 1.5 m deep) were dredged across the surf zone at five different times, and the subsequent evolution of currents and morphology was observed for a range of wave and tidal conditions. In addition, circulation was simulated with the numerical modeling system COAWST, initialized with the observed incident waves and channel bathymetry, and with an extended set of wave conditions and channel geometries. The simulated flows are consistent with alongshore flows and rip-current circulation patterns observed in the surf zone. Near the offshore-directed flows that develop in the channel, the dominant terms in modeled momentum balances are wave-breaking accelerations, pressure gradients, advection, and the vortex force. The balances vary spatially, and are sensitive to wave conditions and the channel geometry. The observed and modeled maximum offshore-directed flow speeds are correlated with a parameter based on the alongshore gradient in breaking-wave-driven-setup across the nonuniform bathymetry (a function of wave height and angle, water depths in the channel and on the sandbar, and a breaking threshold) and the breaking-wave-driven alongshore flow speed. The offshore-directed flow speed increases with dissipation on the bar and reaches a maximum (when the surf zone is saturated) set by the vertical scale of the bathymetric variability.

Rip currents and alongshore flows in single channels dredged in the surf zone

USGS Publications Warehouse

Moulton, Melissa; Elgar, Steve; Raubenheimer, Britt; Warner, John C.; Kumar, Nirnimesh

2017-01-01

To investigate the dynamics of flows near nonuniform bathymetry, single channels (on average 30 m wide and 1.5 m deep) were dredged across the surf zone at five different times, and the subsequent evolution of currents and morphology was observed for a range of wave and tidal conditions. In addition, circulation was simulated with the numerical modeling system COAWST, initialized with the observed incident waves and channel bathymetry, and with an extended set of wave conditions and channel geometries. The simulated flows are consistent with alongshore flows and rip-current circulation patterns observed in the surf zone. Near the offshore-directed flows that develop in the channel, the dominant terms in modeled momentum balances are wave-breaking accelerations, pressure gradients, advection, and the vortex force. The balances vary spatially, and are sensitive to wave conditions and the channel geometry. The observed and modeled maximum offshore-directed flow speeds are correlated with a parameter based on the alongshore gradient in breaking-wave-driven-setup across the nonuniform bathymetry (a function of wave height and angle, water depths in the channel and on the sandbar, and a breaking threshold) and the breaking-wave-driven alongshore flow speed. The offshore-directed flow speed increases with dissipation on the bar and reaches a maximum (when the surf zone is saturated) set by the vertical scale of the bathymetric variability.

Hemispheric asymmetries in the quasibiennial oscillation signature on the mid- to high-latitude circulation of the stratosphere.

PubMed

Peña-Ortiz, C; García-Herrera, R; Ribera, P; Calvo, N

2008-12-01

The quasibiennial oscillation (QBO) dominates the variability of the equatorial stratosphere and also affects the circulation and temperature of the extratropical region. In this paper we review previous work showing that the mid- to high-latitude circulation is weaker (stronger) when QBO easterlies (westerlies) dominate in the low equatorial stratosphere. The accepted explanation for the extratropical QBO signature is based on the QBO modulation of upward propagating planetary Rossby waves. This mechanism is consistent with the strong seasonality observed in the extratropical QBO. The largest QBO signature in the northern extratropical stratosphere occurs during winter when the dominating westerly wind allows the penetration of planetary waves in the northern stratosphere. However, during the southern winter, planetary waves do not disrupt the southern stratospheric vortex and the largest QBO signature is found during the late spring (November). To further illustrate these mechanisms, we analyze the QBO signature on the mid- to high-latitude circulation of the stratosphere using data from the ERA-40 reanalysis. The extratropical signature in both hemispheres is evaluated as a function of the latitude-height structure of the zonal wind in the tropical region in order to determine how the extratropical response depends on the vertical phase structure of the tropical QBO. We also analyze the QBO impact on planetary wave activity in order to determine how this modulation can explain the observed extratropical QBO signal.

Wave transport in the South Australian Basin

NASA Astrophysics Data System (ADS)

Bye, John A. T.; James, Charles

2018-02-01

The specification of the dynamics of the air-sea boundary layer is of fundamental importance to oceanography. There is a voluminous literature on the subject, however a strong link between the velocity profile due to waves and that due to turbulent processes in the wave boundary layer does not appear to have been established. Here we specify the velocity profile due to the wave field using the Toba spectrum, and the velocity profile due to turbulence at the sea surface by the net effect of slip and wave breaking in which slip is the dominant process. Under this specification, the inertial coupling of the two fluids for a constant viscosity Ekman layer yields two independent estimates for the frictional parameter (which is a function of the 10 m drag coefficient and the peak wave period) of the coupled system, one of which is due to the surface Ekman current and the other to the peak wave period. We show that the median values of these two estimates, evaluated from a ROMS simulation over the period 2011-2012 at a station on the Southern Shelf in the South Australian Basin, are similar in strong support of the air-sea boundary layer model. On integrating over the planetary boundary layer we obtain the Ekman transport (w*2/f) and the wave transport due to a truncated Toba spectrum (w*zB/κ) where w* is the friction velocity in water, f is the Coriolis parameter, κ is von Karman's constant and zB = g T2/8 π2 is the depth of wave influence in which g is the acceleration of gravity and T is the peak wave period. A comparison of daily estimates shows that the wave transports from the truncated Toba spectrum and from the SWAN spectral model are highly correlated (r = 0.82) and that on average the Toba estimates are about 86% of the SWAN estimates due to the omission of low frequency tails of the spectra, although for wave transports less than about 0.5 m2 s-1 the estimates are almost equal. In the South Australian Basin the Toba wave transport is on average about 42% of the Ekman transport.

A New Multiscale Model for the Madden-Julian Oscillation.

NASA Astrophysics Data System (ADS)

Biello, Joseph A.; Majda, Andrew J.

2005-06-01

A multiscale model of the MJO is developed here that accounts, in a simplified fashion, for both the upscale transfer from synoptic to planetary scales of momentum and temperature from wave trains of thermally driven equatorial synoptic-scale circulations in a moving convective envelope as well as direct mean heating on planetary scales. This model involves idealized thermally driven congestus synoptic-scale fluctuations in the eastern part of the moving wave envelope and convective superclusters in the western part of the envelope. The model self-consistently reproduces qualitatively many of the detailed structural features of the planetary circulation in the observations of the MJO, including the vertical structure in both the westerly onset region and the strong westerly wind burst region, as well as the horizontal quadrupole planetary vortex structure. The westerly midlevel inflow in the strong westerly region and the quadrupole vortex are largely produced in the model by the upscale transport of momentum to the planetary scales, while the midlevel easterly jet in the westerly onset region is substantially strengthened by this process. The role of wave trains of tilted organized synoptic-scale circulations is crucial for this fidelity with observations. The appeal of the multiscale models developed below is their firm mathematical underpinnings, simplicity, and analytic tractability while remaining self-consistent with many of the features of the observational record.

Planetary Wave-Tide Interactions in Atmosphere-Ionosphere Coupling, Xiaoli Zhang, Jeffrey M. Forbes, Astrid Maute, and Maura E. Hagan

NASA Astrophysics Data System (ADS)

Zhang, X.; Forbes, J. M.; Maute, A. I.

2017-12-01

Planetary Wave-Tide Interactions in Atmosphere-Ionosphere Coupling Xiaoli Zhang, Jeffrey M. Forbes, Astrid Maute, and Maura E. Hagan The existence of secondary waves in the mesosphere and thermosphere due to nonlinear interactions between atmospheric tides and longer-period waves have been revealed in both satellite data and in the National Center for Atmospheric Research (NCAR) Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM). The longer-period waves include the quasi-2-day and 6-day westward-propagating "normal modes" of the atmosphere, and eastward-propagating ultra-fast Kelvin waves with periods between 2 and 4 days. The secondary waves add to both the temporal and longitude variability of the atmosphere beyond that associated with the linear superposition of the interacting waves, thus adding "complexity" to the system. Based on our knowledge of the processes governing atmosphere-ionosphere interactions, similar revelations are expected to occur in electric fields, vertical plasma drifts and F-region electron densities. Towards this end, examples of such ionospheric manifestations of wave-wave interactions in TIE-GCM simulations will be presented.

Stellar, remnant, planetary, and dark-object masses from astrometric microlensing

NASA Technical Reports Server (NTRS)

Boden, A.; Gould, A. P.; Bennett, D. P.; Depoy, D. L.; Gaudi, S. B.; Griest, K.; Han, C.; Paczynski, B.; Reid, I. N.

2002-01-01

With SIM, we will break the microlensing degeneracy, and allow detailed interpretation of individual microlensing events. We will thus develop a detailed census of the dark and luminous stellar population of the Galaxy.

Model for predicting mountain wave field uncertainties

NASA Astrophysics Data System (ADS)

Damiens, Florentin; Lott, François; Millet, Christophe; Plougonven, Riwal

2017-04-01

Studying the propagation of acoustic waves throughout troposphere requires knowledge of wind speed and temperature gradients from the ground up to about 10-20 km. Typical planetary boundary layers flows are known to present vertical low level shears that can interact with mountain waves, thereby triggering small-scale disturbances. Resolving these fluctuations for long-range propagation problems is, however, not feasible because of computer memory/time restrictions and thus, they need to be parameterized. When the disturbances are small enough, these fluctuations can be described by linear equations. Previous works by co-authors have shown that the critical layer dynamics that occur near the ground produces large horizontal flows and buoyancy disturbances that result in intense downslope winds and gravity wave breaking. While these phenomena manifest almost systematically for high Richardson numbers and when the boundary layer depth is relatively small compare to the mountain height, the process by which static stability affects downslope winds remains unclear. In the present work, new linear mountain gravity wave solutions are tested against numerical predictions obtained with the Weather Research and Forecasting (WRF) model. For Richardson numbers typically larger than unity, the mesoscale model is used to quantify the effect of neglected nonlinear terms on downslope winds and mountain wave patterns. At these regimes, the large downslope winds transport warm air, a so called "Foehn" effect than can impact sound propagation properties. The sensitivity of small-scale disturbances to Richardson number is quantified using two-dimensional spectral analysis. It is shown through a pilot study of subgrid scale fluctuations of boundary layer flows over realistic mountains that the cross-spectrum of mountain wave field is made up of the same components found in WRF simulations. The impact of each individual component on acoustic wave propagation is discussed in terms of absorption and dispersion and a stochastic model is constructed for ground-based acoustic signals in mountain environments.

Analysis of wave-like oscillations in parameters of sporadic E layer and neutral atmosphere

NASA Astrophysics Data System (ADS)

Mošna, Z.; Koucká Knížová, P.

2012-12-01

The present study mainly concerns the wave-like activity in the ionospheric sporadic E layer (Es) and in the lower lying stratosphere. The proposed analysis involves parameters describing the state of plasma in the sporadic E layer. Critical frequencies foEs and layer heights hEs were measured at the Pruhonice station (50°N, 14.5°E) during summer campaigns 2004, 2006 and 2008. Further, we use neutral atmosphere (temperature data at 10 hPa) data from the same time interval. The analysis concentrates on vertically propagating wave-like structures within distant atmospheric regions. By means of continuous wavelet transform (CWT) we have detected significant wave-like oscillation at periods covering tidal and planetary oscillation domains both in the Es layer parameters (some of them were reported earlier, for instance in works of Abdu et al., 2003; Pancheva and Mitchel, 2004; Pancheva et al., 2003; Šauli and Bourdillon, 2008) and in stratospheric temperature variations. Further analyses using cross wavelet transform (XWT) and wavelet coherence analysis (WTC) show that despite high wave-like activity in a wide period range, there are only limited coherent wave-like bursts present in both spectra. Such common coherent wave bursts occur on periods close to eigen-periods of the terrestrial atmosphere. We suppose that vertical coupling between atmospheric regions realized by vertically propagating planetary waves occurs predominantly on periods close to those of Rossby modes. Analysis of the phase shift between data from distant atmospheric regions reveals high variability and very likely supports the non-linear scenario of the vertical coupling provided by planetary waves.

Hybrid Eulerian and Lagrangian Simulation of Steep and Breaking Waves and Surface Fluxes in High Winds

DTIC Science & Technology

2010-09-30

simulating violent free - surface flows , and show the importance of wave breaking in energy transport...using Eulerian simulation . 3 IMPACT/APPLICATION This project aims at developing an advanced simulation tool for multi-fluids free - surface flows that...several Eulerian and Lagrangian methods for free - surface turbulence and wave simulation . The WIND–SNOW is used to simulate 1 Report

Investigation of the small-scale structure and dynamics of Uranus' atmosphere

NASA Technical Reports Server (NTRS)

Eshleman, Von R.; Hinson, David P.

1991-01-01

This document constitutes the final technical report of the Uranus Analysis Program. Papers and/or abstracts resulting from this research are presented. The following topics are covered: (1) past and future of radio occultation studies of planetary atmospheres; (2) equatorial waves in the stratosphere of Uranus; (3) the atmosphere of Uranus- results of radio occultation measurements with Voyager 2; (4) Uranus' atmospheric dynamics and circulation; (5) small-scale structure and dynamics in the atmosphere of Uranus; (6) evidence for inertia-gravity waves in the stratosphere of Uranus derived from Voyager 2 radio occultation data; and (7) planetary waves in the equatorial stratosphere of Uranus.

Probability of US Heat Waves Affected by a Subseasonal Planetary Wave Pattern

NASA Technical Reports Server (NTRS)

Teng, Haiyan; Branstator, Grant; Wang, Hailan; Meehl, Gerald A.; Washington, Warren M.

2013-01-01

Heat waves are thought to result from subseasonal atmospheric variability. Atmospheric phenomena driven by tropical convection, such as the Asian monsoon, have been considered potential sources of predictability on subseasonal timescales. Mid-latitude atmospheric dynamics have been considered too chaotic to allow significant prediction skill of lead times beyond the typical 10-day range of weather forecasts. Here we use a 12,000-year integration of an atmospheric general circulation model to identify a pattern of subseasonal atmospheric variability that can help improve forecast skill for heat waves in the United States. We find that heat waves tend to be preceded by 15-20 days by a pattern of anomalous atmospheric planetary waves with a wavenumber of 5. This circulation pattern can arise as a result of internal atmospheric dynamics and is not necessarily linked to tropical heating.We conclude that some mid-latitude circulation anomalies that increase the probability of heat waves are predictable beyond the typical weather forecast range.

The aurora as a source of planetary-scale waves in the middle atmosphere. [atmospheric turbulence caused by auroral energy absorption

NASA Technical Reports Server (NTRS)

Chiu, Y. T.; Straus, J. M.

1974-01-01

Photographs of global scale auroral forms taken by scanning radiometers onboard weather satellites in 1972 show that auroral bands exhibit well organized wave motion with typical zonal wave number of 5 or so. The scale size of these waves is in agreement with that of well organized neutral wind fields in the 150- to 200-km region during the geomagnetic storm of May 27, 1967. Further, the horizontal scale size revealed by these observations are in agreement with that of high altitude traveling ionospheric disturbances. It is conjectured that the geomagnetic storm is a source of planetary and synoptic scale neutral atmospheric waves in the middle atmosphere. Although there is, at present, no observation of substorm related waves of this scale size at mesospheric and stratospheric altitudes, the possible existence of a new source of waves of the proper scale size to trigger instabilities in middle atmospheric circulation systems may be significant in the study of lower atmospheric response to geomagnetic activity.

Ocean wave generation by collapsing ice shelves

NASA Astrophysics Data System (ADS)

Macayeal, D. R.; Bassis, J. N.; Okal, E. A.; Aster, R. C.; Cathles, L. M.

2008-12-01

The 28-29 February, 2008, break-up of the Wilkins Ice Shelf, Antarctica, exemplifies the now-familiar, yet largely unexplained pattern of explosive ice-shelf break-up. While environmental warming is a likely ultimate cause of explosive break-up, several key aspects of their short-term behavior need to be explained: (1) The abrupt, near-simultaneous onset of iceberg calving across long spans of the ice front margin; (2) High outward drift velocity (about 0.3 m/s) of a leading phalanx of tabular icebergs that originate from the seaward edge of the intact ice shelf prior to break-up; (3) Rapid coverage of the ocean surface in the wake of this leading phalanx by small, capsized and dismembered tabular icebergs; (4) Extremely large gravitational potential energy release rates, e.g., up to 3 × 1010 W; (5) Lack of proximal iceberg-calving triggers that control the timing of break-up onset and that maintain the high break-up calving rates through to the conclusion of the event. Motivated by seismic records obtained from icebergs and the Ross Ice Shelf that show hundreds of micro- tsunamis emanating from near the ice shelf front, we re-examine the basic dynamic features of ice- shelf/ocean-wave interaction and, in particular, examine the possibility that collapsing ice shelves themselves are a source of waves that stimulate the disintegration process. We propose that ice-shelf generated surface-gravity waves associated with initial calving at an arbitrary seed location produce stress perturbations capable of triggering the onset of calving on the entire ice front. Waves generated by parting detachment rifts, iceberg capsize and break-up act next to stimulate an inverted submarine landslide (ice- slide) process, where gravitational potential energy released by upward movement of buoyant ice is radiated as surface gravity waves in the wake of the advancing phalanx of tabular icebergs. We conclude by describing how field research and remote sensing can be used to test the various conjectures about ice- shelf/wave interaction that appear to be at play during ice-shelf disintegration.

Global Observation of Planetary-Scale Waves in UARS HRDI and WINDII MLT Winds

NASA Technical Reports Server (NTRS)

Lieberman, Ruth

1999-01-01

The purpose of this study is to use examine planetary-scale motions in the UARS mesosphere and lower thermospheric data. The actual study was confined to HRDI winds and temperatures, since these observations were more continuous, and spanned the 60-120 km range. Three classes of waves were studied: fast equatorial Kelvin waves, nonmigrating tides, and the midlatitude 2-day wave. The purpose of the Kelvin wave and the 2-day wave studies was to test whether the waves significantly affect the mean flow. Such studies require high-quality spectral definitions in order to derive the wave heat and momentum flux divergence which can act in comination to drive the mean flow. Accordingly, HRDI winds from several special observing campaigns were used for analyses of fast (periods under 5 days) waves. The campaigns are characterized by continuous viewing by HRDI in 2 viewing directions, for periods of 10-12 days. Data sampled in this manner lend themselves quite well to "asynoptic spectral analysis", from which motions with periods as low as one day can be retrieved with relatively minimal aliasing.

Coupling of the quasi-biennial oscillation and the extratropical circulation in the stratosphere through planetary wave transport

NASA Technical Reports Server (NTRS)

O'Sullivan, Donal; Salby, Murry L.

1990-01-01

The effects of tropical winds on the extratropical circulation are examined using calculations of eddy transport with tropical flow that is representative of the easterly and westerly phases of the quasi-biennial oscillation (QBO). A dependence of extratropical circulation on tropical winds and the QBO is shown to originate in planetary wave transport. Also, the effects of low latitude flow on high latitude circulation and the behavior of the vortex in opposite phases of the QBO are examined.

Quantifying Wave Breaking Shape and Type in the Surf-Zone Using LiDAR

NASA Astrophysics Data System (ADS)

Albright, A.; Brodie, K. L.; Hartzell, P. J.; Glennie, C. L.

2017-12-01

Waves change shape as they shoal and break across the surf-zone, ultimately dissipating and transferring their energy into turbulence by either spilling or plunging. This injection of turbulence and changes in wave shape can affect the direction of sediment transport at the seafloor, and ultimately lead to morphological evolution. Typical methods for collecting wave data in the surf-zone include in-situ pressure gauges, velocimeters, ultrasonic sensors, and video imagery. Drawbacks to these data collection methods are low spatial resolution of point measurements, reliance on linear theory to calculate sea-surface elevations, and intensive computations required to extract wave properties from stereo 2D imagery. As a result, few field measurements of the shapes of plunging and/or spilling breakers exist, and existing knowledge is confined to results of laboratory studies. We therefore examine the use of a multi-beam scanning Light Detection and Ranging (LiDAR) remote sensing instrument with the goal of classifying the breaking type of propagating waves in the surf-zone and quantitatively determining wave morphometric properties. Data were collected with a Velodyne HDL-32E LiDAR scanner (360° vertical field of view) mounted on an arm of the Coastal Research Amphibious Buggy (CRAB) at the U.S. Army Corps of Engineers Field Research Facility in Duck, North Carolina. Processed laser scan data are used to visualize the lifecycle of a wave (shoaling, breaking, broken) and identify wave types (spilling, plunging, non-breaking) as they pass beneath the scanner. For each rotation of the LiDAR scanner, the point cloud data are filtered, smoothed, and detrended in order to identify individual waves and measure their properties, such as speed, height, period, upward/downward slope, asymmetry, and skewness. The 3D nature of point cloud data is advantageous for research, because it enables viewing from any angle. In our analysis, plan views are used to separate individual waves, and cross-shore profiles are used to extract wave properties. Combined with accurate georeferencing information, LiDAR has the potential to be a powerful remote sensing tool for coastal monitoring systems and the study of nearshore processes.

The Response of the Southern Hemisphere Middle Atmosphere to the Madden-Julian oscillation during Austral Winter Using the Specified-Dynamics Whole Atmosphere Community Climate Model

NASA Astrophysics Data System (ADS)

Yang, C.; Li, T.; Smith, A. K.; Dou, X.

2017-12-01

Using the Specified-Dynamic (SD) Whole Atmosphere Community Climate Model (WACCM), we investigated the effects of the Madden-Julian oscillation (MJO) on the mid-winter stratosphere and mesosphere in the southern hemisphere (SH). The most significant responses of the SH polar cap temperature to the MJO are found 30 days after MJO Phase 1 (P1) and 10 days after the MJO Phase 5 (P5) in both the ERA-interim reanalysis and the SD-WACCM simulation. The 200 and 500 hPa geopotential height anomalies in the SH reveal that wave trains emanate from the Indian and Pacific Oceans when the MJO convection is enhanced in the eastern Indian Ocean and the western Pacific. As a result, the upward propagation and dissipation of planetary waves (PWs) in the mid- and high- latitude of the SH stratosphere is significantly enhanced, the Brewer-Dobson (BD) circulation in the SH stratosphere strengthens, and temperatures in the SH polar stratosphere increase. Wavenumber 1 in the stratosphere is the dominant component of the PW perturbation induced by the MJO convection. Filtering by the modified SH stratospheric winds alters the gravity waves (GWs) that propagate to the mesosphere. The dissipation and breaking of these waves causes anomalous downwelling in the mid- and high- latitudes of the mesosphere. The circulation changes, in turn, result in significant anomalous cooling in the mesosphere in response to MJO P1 and P5 at lags of 10 days and 30 days, respectively.

Scaling properties of conduction velocity in heterogeneous excitable media

NASA Astrophysics Data System (ADS)

Shajahan, T. K.; Borek, Bartłomiej; Shrier, Alvin; Glass, Leon

2011-10-01

Waves of excitation through excitable media, such as cardiac tissue, can propagate as plane waves or break up to form reentrant spiral waves. In diseased hearts reentrant waves can be associated with fatal cardiac arrhythmias. In this paper we investigate the conditions that lead to wave break, reentry, and propagation failure in mathematical models of heterogeneous excitable media. Two types of heterogeneities are considered: sinks are regions in space in which the voltage is fixed at its rest value, and breaks are nonconducting regions with no-flux boundary conditions. We find that randomly distributed heterogeneities in the medium have a decremental effect on the velocity, and above a critical density of such heterogeneities the conduction fails. Using numerical and analytical methods we derive the general relationship among the conduction velocity, density of heterogeneities, diffusion coefficient, and the rise time of the excitation in both two and three dimensions. This work helps us understand the factors leading to reduced propagation velocity and the formation of spiral waves in heterogeneous excitable media.

Factorization breaking of A d T for polarized deuteron targets in a relativistic framework

DOE PAGES

Jeschonnek, Sabine; Van Orden, J. W.

2017-04-17

We discuss the possible factorization of the tensor asymmetrymore » $$A^T_d$$ measured for polarized deuteron targets within a relativistic framework. We define a reduced asymmetry and find that factorization holds only in plane wave impulse approximation and if $p$-waves are neglected. Our numerical results show a strong factorization breaking once final state interactions are included. We also compare the $d$-wave content of the wave functions with the size of the factored, reduced asymmetry and find that there is no systematic relationship of this quantity to the d-wave probability of the various wave functions.« less

Criteria for Evaluating Coastal Flood-Protection Structures

DTIC Science & Technology

1989-12-01

Hotta, S., and Marui , N. 1976. "Local Scour and Current Around a Porous Breakwater," Chapter 93, Proceedings, 15th Coastal Engineering Conference, 11- 17...breaking waves consistent with FEMA depth-limited breaking wave approach to design. 7. Hotta and Marui (1976) testing permeable and impermeable shore

Assessment Of Chemical Dispersant Effectiveness In A Wave Tank Under Regular Non-Breaking And Breaking Wave Conditions

EPA Science Inventory

Current chemical dispersant effectiveness tests for product selection are commonly performed with bench-scale testing apparatus. However, for the assessment of oil dispersant effectiveness under real sea state conditions, test protocols are required to have hydrodynamic conditio...

Application of nonlinear deterministic decomposition to the prediction and energy dissipation of long-crested irregular ocean surface waves

NASA Astrophysics Data System (ADS)

Meza Conde, Eustorgio

The Hybrid Wave Model (HWM) is a deterministic nonlinear wave model developed for the computation of wave properties in the vicinity of ocean wave measurements. The HWM employs both Mode-Coupling and Phase Modulation Methods to model the wave-wave interactions in an ocean wave field. Different from other nonlinear wave models, the HWM decouples the nonlinear wave interactions from ocean wave field measurements and decomposes the wave field into a set of free-wave components. In this dissertation the HWM is applied to the prediction of wave elevation from pressure measurements and to the quantification of energy during breaking of long-crested irregular surface waves. 1.A transient wave train was formed in a two-dimensional wave flume by sequentially generating a series of waves from high to low frequencies that superposed at a downstream location. The predicted wave elevation using the HWM based on the pressure measurement of a very steep transient wave train is in excellent agreement with the corresponding elevation measurement, while that using Linear Wave Theory (LWT) has relatively large discrepancies. Furthermore, the predicted elevation using the HWM is not sensitive to the choice of the cutoff frequency, while that using LWT is very sensitive. 2.Several transient wave trains containing an isolated plunging or spilling breaker at a prescribed location were generated in a two-dimensional wave flume using the same superposition technique. Surface elevation measurements of each transient wave train were made at locations before and after breaking. Applying the HWM nonlinear deterministic decomposition to the measured elevation, the free-wave components comprising the transient wave train were derived. By comparing the free-wave spectra before and after breaking it is found that energy loss was almost exclusively from wave components at frequencies higher than the spectral peak frequency. Even though the wave components near the peak frequency are the largest, they do not significantly gain or lose energy after breaking. It was also observed that wave components of frequencies significantly below or near the peak frequency gain a small portion of energy lost by the high-frequency waves. These findings may have important implications to the ocean wave energy budget.

The response of plasma density to breaking inertial gravity wave in the lower regions of ionosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Wenbo, E-mail: Wenbo.Tang@asu.edu; Mahalov, Alex, E-mail: Alex.Mahalov@asu.edu

2014-04-15

We present a three-dimensional numerical study for the E and lower F region ionosphere coupled with the neutral atmosphere dynamics. This model is developed based on a previous ionospheric model that examines the transport patterns of plasma density given a prescribed neutral atmospheric flow. Inclusion of neutral dynamics in the model allows us to examine the charge-neutral interactions over the full evolution cycle of an inertial gravity wave when the background flow spins up from rest, saturates and eventually breaks. Using Lagrangian analyses, we show the mixing patterns of the ionospheric responses and the formation of ionospheric layers. The correspondingmore » plasma density in this flow develops complex wave structures and small-scale patches during the gravity wave breaking event.« less

A two-dimensional analysis of the sensitivity of a pulse first break to wave speed contrast on a scale below the resolution length of ray tomography.

PubMed

Willey, Carson L; Simonetti, Francesco

2016-06-01

Mapping the speed of mechanical waves traveling inside a medium is a topic of great interest across many fields from geoscience to medical diagnostics. Much work has been done to characterize the fidelity with which the geometrical features of the medium can be reconstructed and multiple resolution criteria have been proposed depending on the wave-matter interaction model used to decode the wave speed map from scattering measurements. However, these criteria do not define the accuracy with which the wave speed values can be reconstructed. Using two-dimensional simulations, it is shown that the first-arrival traveltime predicted by ray theory can be an accurate representation of the arrival of a pulse first break even in the presence of diffraction and other phenomena that are not accounted for by ray theory. As a result, ray-based tomographic inversions can yield accurate wave speed estimations also when the size of a sound speed anomaly is smaller than the resolution length of the inversion method provided that traveltimes are estimated from the signal first break. This increased sensitivity however renders the inversion more susceptible to noise since the amplitude of the signal around the first break is typically low especially when three-dimensional anomalies are considered.

Equatorial Oscillation and Planetary Wave Activity in Saturn's Stratosphere Through the Cassini Epoch

NASA Astrophysics Data System (ADS)

Guerlet, S.; Fouchet, T.; Spiga, A.; Flasar, F. M.; Fletcher, L. N.; Hesman, B. E.; Gorius, N.

2018-01-01

Thermal infrared spectra acquired by Cassini/Composite InfraRed Spectrometer (CIRS) in limb-viewing geometry in 2015 are used to derive 2-D latitude-pressure temperature and thermal wind maps. These maps are used to study the vertical structure and evolution of Saturn's equatorial oscillation (SEO), a dynamical phenomenon presenting similarities with the Earth's quasi-biennal oscillation (QBO) and semi-annual oscillation (SAO). We report that a new local wind maximum has appeared in 2015 in the upper stratosphere and derive the descent rates of other wind extrema through time. The phase of the oscillation observed in 2015, as compared to 2005 and 2010, remains consistent with a ˜15 year period. The SEO does not propagate downward at a regular rate but exhibits faster descent rate in the upper stratosphere, combined with a greater vertical wind shear, compared to the lower stratosphere. Within the framework of a QBO-type oscillation, we estimate the absorbed wave momentum flux in the stratosphere to be on the order of ˜7 × 10-6 N m-2. On Earth, interactions between vertically propagating waves (both planetary and mesoscale) and the mean zonal flow drive the QBO and SAO. To broaden our knowledge on waves potentially driving Saturn's equatorial oscillation, we searched for thermal signatures of planetary waves in the tropical stratosphere using CIRS nadir spectra. Temperature anomalies of amplitude 1-4 K and zonal wave numbers 1 to 9 are frequently observed, and an equatorial Rossby (n = 1) wave of zonal wave number 3 is tentatively identified in November 2009.

Wave breaking induced surface wakes and jets observed during a bora event

NASA Astrophysics Data System (ADS)

Jiang, Qingfang; Doyle, James D.

2005-09-01

An observational and modeling study of a bora event that occurred during the field phase of the Mesoscale Alpine Programme is presented. Research aircraft in-situ measurements and airborne remote-sensing observations indicate the presence of strong low-level wave breaking and alternating surface wakes and jets along the Croatian coastline over the Adriatic Sea. The observed features are well captured by a high-resolution COAMPS simulation. Analysis of the observations and modeling results indicate that the long-extending wakes above the boundary layer are induced by dissipation associated with the low-level wave breaking, which locally tends to accelerate the boundary layer flow beneath the breaking. Farther downstream of the high peaks, a hydraulic jump occurs in the boundary layer, which creates surface wakes. Downstream of lower-terrain (passes), the boundary layer flow stays strong, resembling supercritical flow.

Wave modulation of the extratropical tropopause inversion layer

NASA Astrophysics Data System (ADS)

Pilch Kedzierski, Robin; Matthes, Katja; Bumke, Karl

2017-03-01

This study aims to quantify how much of the observed strength and variability in the zonal-mean extratropical tropopause inversion layer (TIL) comes from the modulation of the temperature field and its gradients around the tropopause by planetary- and synoptic-scale waves. By analyzing high-resolution observations, it also puts other TIL enhancing mechanisms into context.Using gridded Global Positioning System radio occultation (GPS-RO) temperature profiles from the COSMIC mission (2007-2013), we are able to extract the extratropical wave signal by a simplified wavenumber-frequency domain filtering method and quantify the resulting TIL enhancement. By subtracting the extratropical wave signal, we show how much of the TIL is associated with other processes, at mid- and high latitudes, for both hemispheres and all seasons.The transient and reversible modulation by planetary- and synoptic-scale waves is almost entirely responsible for the TIL in midlatitudes. This means that wave-mean flow interactions, inertia-gravity waves and the residual circulation are of minor importance for the strength and variability in the midlatitude TIL.At polar regions, the extratropical wave modulation is dominant for the TIL strength as well, but there is also a clear fingerprint from sudden stratospheric warmings (SSWs) and final warmings in both hemispheres. Therefore, polar vortex breakups are partially responsible for the observed polar TIL strength in winter (if SSWs occur) and spring. Also, part of the polar summer TIL strength cannot be explained by extratropical wave modulation.We suggest that our wave modulation mechanism integrates several TIL enhancing mechanisms proposed in previous literature while robustly disclosing the overall outcome of the different processes involved. By analyzing observations only, our study identifies which mechanisms dominate the extratropical TIL strength and their relative contribution. It remains to be determined, however, which roles the different planetary- and synoptic-scale wave types play within the total extratropical wave modulation of the TIL, as well as what causes the observed amplification of extratropical waves near the tropopause.

Simplified method for the calculation of irregular waves in the coastal zone

NASA Astrophysics Data System (ADS)

Leont'ev, I. O.

2011-04-01

A method applicable for the estimation of the wave parameters along a set bottom profile is suggested. It takes into account the principal processes having an influence on the waves in the coastal zone: the transformation, refraction, bottom friction, and breaking. The ability to use a constant mean value of the friction coefficient under conditions of sandy shores is implied. The wave breaking is interpreted from the viewpoint of the concept of the limiting wave height at a given depth. The mean and root-mean-square wave heights are determined by the height distribution function, which transforms under the effect of the breaking. The verification of the method on the basis of the natural data shows that the calculation results reproduce the observed variations of the wave heights in a wide range of conditions, including profiles with underwater bars. The deviations from the calculated values mostly do not exceed 25%, and the mean square error is 11%. The method does not require a preliminary setting and can be implemented in the form of a relatively simple calculator accessible even for an inexperienced user.

Atmospheric waves on Venus as seen by the Venus Express Radio Science Experiment VeRa

NASA Astrophysics Data System (ADS)

Tellmann, S.; Häusler, B.; Hinson, D. P.; Tyler, G. L.; Andert, T. P.; Bird, M. K.; Imamura, T.; Pätzold, M.; Remus, S.

2013-09-01

Next to quasi-horizontal waves and eddies on near planetary scales, diurnally forced eddies and thermal tides, small-scale gravity waves and turbulence play a significant role in the development and maintenance of atmospheric super rotation.

Universal planetary tectonics (supertectonics)

NASA Astrophysics Data System (ADS)

Kochemasov, G. G.

2009-04-01

Universal planetary tectonics (supertectonics) G. Kochemasov IGEM of the Russian Academy of Sciences, Moscow, Russia, kochem.36@mail.ru The wave planetology [1-3 & others] proceeds from the following: "planetary structures are made by orbits and rotations". A uniform reason makes uniform structures. Inertia-gravity waves arising in planetary bodies due to their movements in Keplerian elliptical orbits with periodically changing accelerations warp these bodies in such way that they acquire polyhedron shapes (after interference of standing waves of four directions). Strong Newtonian gravity makes bodies larger than ~400 to 500 km in diameter globular and polyhedra are rarely seen. Only geomorphologic, geologic and geophysical mapping can develop these hidden structures. But small bodies, normally less than ~ 300 to 400 km in diameter, often show parts of the polyhedra, rarely fully developed forms (the asteroid Steins and satellite Amalthea present rather perfect forms of "diamond"). Depending on warping wavelengths (they make harmonics) various Plato's figures superimposed on each other can be distinguished. The fundamental wave 1 produces a tetrahedron, intrinsically dichotomic figure in which a vertex (contraction) always is opposed to a face (expansion). From the recent examples the best is the saturnian northern hexagon (a face) opposed to the southern hurricane (a vertex). The first overtone wave 2 is responsible for creation of structural octahedra. Whole ‘diamonds" and their parts are known [4, 5]. Other overtones produce less developed (because of smaller wave amplitudes) planetary shapes complicating main forms. Thus, the first common structural peculiarity of planetary bodies is their polyhedron nature. Not less important is the second common structural peculiarity. As all globular or smaller more or less isometric bodies rotate, they have an angular momentum. It is inevitably different in tropic and extra-tropic belts having uneven radii or distances to the rotation axe. But this unevenness is undesirable because it creates tectonic stresses and increases energetic status that is against the natural tendency to minimize these physical characteristics. So, a body tends to lower angular momentum of tropics and increase it in extra-tropics. With the same angular velocity it remains only mass and radius to play in this tendency. Tropical belt is destructed (for an example, the lithosphere disintegration in solid bodies), extra-tropical belts add dense material (plumes), expand - the constructive tendency [6]. Both tectonic peculiarities-polyhedrons and constructive - destructive tendencies - are common for celestial bodies of various classes. They are characteristic for our star, planets, satellites and small bodies. That is why a term "supertectonics" seems rather suitable. References: [1] Kochemasov G.G. Concerted wave supergranulation of the solar system bodies // 16th Russian-American microsymposium on planetology, Abstracts, Moscow, Vernadsky Inst. (GEOKHI), 1992, 36-37. [2] Kochemasov G.G. Tectonic dichotomy, sectoring and granulation of Earth and other celestial bodies // Proceedings of the International Symposium on New Concepts in Global Tectonics, "NCGT-98 TSUKUBA", Geological Survey of Japan, Tsukuba, Nov 20-23, 1998, p. 144-147. [3] Kochemasov G.G. Theorems of wave planetary tectonics // Geophys. Res. Abstr., 1999, V.1, №3, 700. [4] Kochemasov G.G. Plato' polyhedra as shapes of small icy satellites // Geophys. Res. Abstracts, Vol. 10, 2008, EGU2008-A-01271, CD-ROM; [5] Kochemasov G.G. (1999) "Diamond" and "dumb-bells"-like shapes of celestial bodies induced by inertia-gravity waves // 30th Vernadsky-Brown microsymposium on comparative planetology, Abstracts, Moscow, Vernadsky Inst.,, 49-50; [6] Kochemasov G.G. Tectonics of rotating celestial globes // Vernadsky-Brown microsymposium 48, 20-22 Oct. 2008, Moscow, Abstr. m48_20.

Remote sensing signatures of oceanic whitecap at different wavelengths

NASA Astrophysics Data System (ADS)

Anguelova, M. D.; Dowgiallo, D. J.; Smith, G. B.; Means, S. L.; Savelyev, I.; Frick, G. M.; Snow, C. M.; Schindall, J. A.; Bobak, J. P.

2012-12-01

Oceanic whitecaps are the most direct surface expression of breaking wind waves in the ocean. Whitecap fraction quantifies the breaking events and is thus a suitable forcing variable for parameterizing and predicting various air-sea interaction processes. To this end, we have compiled a database of whitecap fraction W from satellites-borne microwave radiometric observations. These observations provide the total W including foam generated during active breaking of wind-driven waves and residual foam left behind by these breaking waves. However, the whitecap fraction associated with the actively breaking waves WA is needed for dynamic air-sea processes in the upper ocean such as turbulent mixing, gas exchange, ocean ambient noise, and spray-mediated intensification of tropical storms. To parameterize such processes, a database of WA separate from W is needed. We pursue this separation of WA from W by combining the Phillips concept of breaking wave statistics which connects WA with the energy dissipation rate of breaking waves and parametric estimates of energy dissipation from wave spectra measured from buoys. We seek additional physical understanding of, and experimental support for, this separation with a multi-instrumental field campaign. The instrumentation deployed includes a suite of sensors recording the whitecaps and breaking waves on the surface over wide range of the electromagnetic spectrum: visible (video cameras), infrared (IR camera), and microwave (radiometers at two frequencies, 10 GHz and 37 GHz). An acoustic array with three nested-aperture array at frequencies up to 2.4 kHz and aerosol/particle counter provide data for the bubbles generated beneath and sea spray produced above the whitecaps. We also deployed a transmitter horn to collect data useful to asses Radio Frequency Interference (RFI), which affects the collection and accuracy of satellite-based data. Various auxiliary data such as wind speed, air temperature, humidity, wave field, and water temperature profile characterize the experimental conditions. The goal of this field campaign is to provide experimental data for determining WA and W independently from the Phillips concept for energy dissipation. In these measurements, we rely on the good separation between WA and W in the IR region of the electromagnetic spectrum. We use the IR data to identify a separation criterion which then can be applied to time series of microwave and acoustic data. Obtaining WA via this separation criterion and comparing the results with those from the Phillips concept, we will have additional possibility to constrain WA obtained using energy dissipation. The measurements are made in April-May, 2012, on the Floating Instrument Platform (FLIP) drifting along the coast of California from Monterey Bay south toward Point Conception. We describe the experiment, characterize the study site, and present first data collected during this campaign.

On the construction of a direct numerical simulation of a breaking inertia-gravity wave in the upper mesosphere

NASA Astrophysics Data System (ADS)

Fruman, Mark D.; Remmler, Sebastian; Achatz, Ulrich; Hickel, Stefan

2014-10-01

A systematic approach to the direct numerical simulation (DNS) of breaking upper mesospheric inertia-gravity waves of amplitude close to or above the threshold for static instability is presented. Normal mode or singular vector analysis applied in a frame of reference moving with the phase velocity of the wave (in which the wave is a steady solution) is used to determine the most likely scale and structure of the primary instability and to initialize nonlinear "2.5-D" simulations (with three-dimensional velocity and vorticity fields but depending only on two spatial coordinates). Singular vector analysis is then applied to the time-dependent 2.5-D solution to predict the transition of the breaking event to three-dimensional turbulence and to initialize three-dimensional DNS. The careful choice of the computational domain and the relatively low Reynolds numbers, on the order of 25,000, relevant to breaking waves in the upper mesosphere, makes the three-dimensional DNS tractable with present-day computing clusters. Three test cases are presented: a statically unstable low-frequency inertia-gravity wave, a statically and dynamically stable inertia-gravity wave, and a statically unstable high-frequency gravity wave. The three-dimensional DNS are compared to ensembles of 2.5-D simulations. In general, the decay of the wave and generation of turbulence is faster in three dimensions, but the results are otherwise qualitatively and quantitatively similar, suggesting that results of 2.5-D simulations are meaningful if the domain and initial condition are chosen properly.

Observations of coarse sediment movements on the mixed beach of the Elwha Delta, Washington

USGS Publications Warehouse

Miller, I.M.; Warrick, J.A.; Morgan, C.

2011-01-01

Mixed beaches, with poorly sorted grains of multiple sizes, are a common and globally distributed shoreline type. Despite this, rates and mechanisms of sediment transport on mixed beaches are poorly understood. A series of tracer deployments using native clasts implanted with Radio Frequency Identifier (RFID) tags was used to develop a better understanding of sediment transport directions and magnitudes on the mixed grain-size beach of the Elwha River delta. Using tracer samples selected to match the distribution of the coarse fraction on the beach we find that all grain sizes, up to large cobbles (128-256 mm), were mobile under most measured wave conditions and move in relationship to the direction of the alongshore component of wave energy as estimated by incident breaking wave angles. In locations where the breaking wave is normal to the shoreline we find that tracers move in both alongshore directions with approximately equal frequency. In locations where breaking waves are oblique to the shoreline we find that alongshore transport is more unidirectional and tracers can approach average velocities of 100. m/day under winter wave conditions. We use the tracer cloud to estimate the beach active width, the mobile layer depth and sediment velocity. Our results suggest that, while sediment velocity increases under increased incident wave angles, the active layer depth and width decrease, reducing sediment flux at the site with the more oblique breaking waves. This result is contrary to what is suggested by traditional wave energy transport models of alongshore sediment transport. ?? 2011 Elsevier B.V.

Atmospheric Transport and Mixing linked to Rossby Wave Breaking in GFDL Dynamical Core

NASA Astrophysics Data System (ADS)

Liu, C.; Barnes, E. A.

2015-12-01

Atmospheric transport and mixing plays an important role in the global energy balance and the distribution of health-related chemical constituents. Previous studies suggest a close linkage between large-scale transport and Rossby wave breaking (RWB). In this work, we use the GFDL spectral dynamical core to investigate this relationship and study the response of RWB-related transport in different climate scenarios. In a standard control run, we quantify the contribution of RWB to the total transport and mixing of an idealized tracer. In addition, we divide the contribution further into the two types of RWB - anticyclonic wave breaking (AWB) and cyclonic wave breaking (CWB) -- and contrast their efficiency at transport and mixing. Our results are compared to a previous study in which the transport ability of the two types of RWB is studied for individual baroclinic wave life-cycles. In a series of sensitivity runs, we study the response of RWB-related transport and mixing to various states of the jet streams. The responses of the mean strength, frequency, and the efficiency of RWB-related transport are documented and the implications for the transport and mixing in a warmer climate are discussed.

Virtual reality and planetary exploration

NASA Technical Reports Server (NTRS)

Mcgreevy, Michael W.

1992-01-01

Exploring planetary environments is central to NASA's missions and goals. A new computing technology called Virtual Reality has much to offer in support of planetary exploration. This technology augments and extends human presence within computer-generated and remote spatial environments. Historically, NASA has been a leader in many of the fundamental concepts and technologies that comprise Virtual Reality. Indeed, Ames Research Center has a central role in the development of this rapidly emerging approach to using computers. This ground breaking work has inspired researchers in academia, industry, and the military. Further, NASA's leadership in this technology has spun off new businesses, has caught the attention of the international business community, and has generated several years of positive international media coverage. In the future, Virtual Reality technology will enable greatly improved human-machine interactions for more productive planetary surface exploration. Perhaps more importantly, Virtual Reality technology will democratize the experience of planetary exploration and thereby broaden understanding of, and support for, this historic enterprise.

Virtual reality and planetary exploration

NASA Astrophysics Data System (ADS)

McGreevy, Michael W.

Exploring planetary environments is central to NASA's missions and goals. A new computing technology called Virtual Reality has much to offer in support of planetary exploration. This technology augments and extends human presence within computer-generated and remote spatial environments. Historically, NASA has been a leader in many of the fundamental concepts and technologies that comprise Virtual Reality. Indeed, Ames Research Center has a central role in the development of this rapidly emerging approach to using computers. This ground breaking work has inspired researchers in academia, industry, and the military. Further, NASA's leadership in this technology has spun off new businesses, has caught the attention of the international business community, and has generated several years of positive international media coverage. In the future, Virtual Reality technology will enable greatly improved human-machine interactions for more productive planetary surface exploration. Perhaps more importantly, Virtual Reality technology will democratize the experience of planetary exploration and thereby broaden understanding of, and support for, this historic enterprise.

Experimental and Numerical Studies on Wave Breaking Characteristics over a Fringing Reef under Monochromatic Wave Conditions

PubMed Central

2014-01-01

Fringing reefs play an important role in protecting the coastal area by inducing wave breaking and wave energy dissipation. However, modeling of wave transformation and energy dissipation on this topography is still difficult due to the unique structure. In the present study, two-dimensional laboratory experiments were conducted to investigate the cross-shore variations of wave transformation, setup, and breaking phenomena over an idealized fringing reef with the 1/40 reef slope and to verify the Boussinesq model under monochromatic wave conditions. One-layer and two-layer model configurations of the Boussinesq model were used to figure out the model capability. Both models predicted well (r 2 > 0.8) the cross-shore variation of the wave heights, crests, troughs, and setups when the nonlinearity is not too high (A 0/h 0 < 0.07 in this study). However, as the wave nonlinearity and steepness increase, the one-layer model showed problems in prediction and stability due to the error on the vertical profile of fluid velocity. The results in this study revealed that one-layer model is not suitable in the highly nonlinear wave condition over a fringing reef bathymetry. This data set can contribute to the numerical model verification. PMID:25276853

Experimental and numerical studies on wave breaking characteristics over a fringing reef under monochromatic wave conditions.

PubMed

Lee, Jong-In; Shin, Sungwon; Kim, Young-Taek

2014-01-01

Fringing reefs play an important role in protecting the coastal area by inducing wave breaking and wave energy dissipation. However, modeling of wave transformation and energy dissipation on this topography is still difficult due to the unique structure. In the present study, two-dimensional laboratory experiments were conducted to investigate the cross-shore variations of wave transformation, setup, and breaking phenomena over an idealized fringing reef with the 1/40 reef slope and to verify the Boussinesq model under monochromatic wave conditions. One-layer and two-layer model configurations of the Boussinesq model were used to figure out the model capability. Both models predicted well (r (2) > 0.8) the cross-shore variation of the wave heights, crests, troughs, and setups when the nonlinearity is not too high (A 0/h 0 < 0.07 in this study). However, as the wave nonlinearity and steepness increase, the one-layer model showed problems in prediction and stability due to the error on the vertical profile of fluid velocity. The results in this study revealed that one-layer model is not suitable in the highly nonlinear wave condition over a fringing reef bathymetry. This data set can contribute to the numerical model verification.

Use of satellite data and modeling to asses the influence of stratospheric processes on the troposphere

NASA Technical Reports Server (NTRS)

Nathan, Terrence R.; Yarger, Douglas N.

1989-01-01

The research is comprised of the following tasks: use of simple analytical and numerical models of a coupled troposphere-stratosphere system to examine the effects of radiation and ozone on planetary wave dynamics and the tropospheric circulation; use of satellite data obtained from the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) instrument and Solar Backscattered Ultraviolet (SBUV) experiment, in conjunction with National Meteorological Center (NMC) data, to determine the planetary wave vertical structures, dominant wave spectra, ozone spectra, and time variations in diabatic heating rate; and synthesis of the modeling and observational results to provide a better understanding of the effects that stratospheric processes have on tropospheric dynamics.

Planetary and synoptic-scale interactions during the life cycle of a mid-latitude blocking anticyclone over the North Atlantic

NASA Technical Reports Server (NTRS)

Smith, Phillip J.

1995-01-01

The formation of a blocking anticyclone over the North Atlantic has been examined over its entire life-CyCle using the Zwack-Okossi (Z-O) equation as the diagnostic tool. This blocking anticyclone occurred in late October and early November of 1985. The data used were provided by the NASA Goddard Laboratory for Atmospheres on a global 2.O degree latitude by 2.5 degree longitudinal grid. The horizontal distribution of the atmospheric forcing mechanisms that were important to 500 mb block formation, maintenance and decay were examined. A scale-partitioned form of the Z-O equation was then used to examine the relative importance of forcing on the planetary and synoptic scales, and their interactions. As seen in previous studies, the results presented here show that upper tropospheric anticyclonic vorticity advection was the most important contributor to block formation and maintenance. However, adiabatic warming, and vorticity tilting were also important at various times during the block lifetime. In association with precursor surface cyclogenesis, the 300 mb jet streak in the downstream (upstream) from a long-wave trough (ridge) amplified significantly. This strengthening of the jet streak enhanced the anti-cyclonic vorticity advection field that aided the amplification of a 500 mb short-wave ridge. Tile partitioned height tendency results demonstrate that the interactions between the planetary and sn,noptic-scale through vorticity advection was the most important contributor to block formation. Planetary-scale, synoptic-scale. and their interactions contributed weakly to the maintenance of the blocking anticyclone with the advection of synoptic-scale vorticity by the planetary-scale flow playing a more important role. Planetary-scale decay ofthe long-wave ridge contributed to the demise of this blocking event.

3D DNS and LES of Breaking Inertia-Gravity Waves

NASA Astrophysics Data System (ADS)

Remmler, S.; Fruman, M. D.; Hickel, S.; Achatz, U.

2012-04-01

As inertia-gravity waves we refer to gravity waves that have a sufficiently low frequency and correspondingly large horizontal wavelength to be strongly influenced by the Coriolis force. Inertia-gravity waves are very active in the middle atmosphere and their breaking is potentially an important influence on the circulation in this region. The parametrization of this process requires a good theoretical understanding, which we want to enhance with the present study. Primary linear instabilities of an inertia-gravity wave and "2.5-dimensional" nonlinear simulations (where the spatial dependence is two dimensional but the velocity and vorticity fields are three-dimensional) with the wave perturbed by its leading primary instabilities by Achatz [1] have shown that the breaking differs significantly from that of high-frequency gravity waves due to the strongly sheared component of velocity perpendicular to the plane of wave-propagation. Fruman & Achatz [2] investigated the three-dimensionalization of the breaking by computing the secondary linear instabilities of the same waves using singular vector analysis. These secondary instabilities are variations perpendicular to the direction of the primary perturbation and the wave itself, and their wavelengths are an order of magnitude shorter than both. In continuation of this work, we carried out fully three-dimensional nonlinear simulations of inertia-gravity waves perturbed by their leading primary and secondary instabilities. The direct numerical simulation (DNS) was made tractable by restricting the domain size to the dominant scales selected by the linear analyses. The study includes both convectively stable and unstable waves. To the best of our knowledge, this is the first fully three-dimensional nonlinear direct numerical simulation of inertia-gravity waves at realistic Reynolds numbers with complete resolution of the smallest turbulence scales. Previous simulations either were restricted to high frequency gravity waves (e. g. Fritts et al. [3]), or the ratio N/f was artificially reduced (e. g. Lelong & Dunkerton [4]). The present simulations give us insight into the three-dimensional breaking process as well as the emerging turbulence. We assess the possibility of reducing the computational costs of three-dimensional simulations by using an implicit turbulence subgrid-scale parametrization based on the Adaptive Local Deconvolution Method (ALDM) for stratified turbulence [5]. In addition, we have performed ensembles of nonlinear 2.5-dimensional DNS, like those in Achatz [1] but with a small amount of noise superposed to the initial state, and compared the results with coarse-resolution simulations using either ALDM as well as with standard LES schemes. We found that the results of the models with parametrized turbulence, which are orders of magnitude more computationally economical than the DNS, compare favorably with the DNS in terms of the decay of the wave amplitude with time (the quantity most important for application to gravity-wave drag parametrization) suggesting that they may be trusted in future simulations of gravity wave breaking.

Stereo Refractive Imaging of Breaking Free-Surface Waves in the Surf Zone

NASA Astrophysics Data System (ADS)

Mandel, Tracy; Weitzman, Joel; Koseff, Jeffrey; Environmental Fluid Mechanics Laboratory Team

2014-11-01

Ocean waves drive the evolution of coastlines across the globe. Wave breaking suspends sediments, while wave run-up, run-down, and the undertow transport this sediment across the shore. Complex bathymetric features and natural biotic communities can influence all of these dynamics, and provide protection against erosion and flooding. However, our knowledge of the exact mechanisms by which this occurs, and how they can be modeled and parameterized, is limited. We have conducted a series of controlled laboratory experiments with the goal of elucidating these details. These have focused on quantifying the spatially-varying characteristics of breaking waves and developing more accurate techniques for measuring and predicting wave setup, setdown, and run-up. Using dynamic refraction stereo imaging, data on free-surface slope and height can be obtained over an entire plane. Wave evolution is thus obtained with high spatial precision. These surface features are compared with measures of instantaneous turbulence and mean currents within the water column. We then use this newly-developed ability to resolve three-dimensional surface features over a canopy of seagrass mimics, in order to validate theoretical formulations of wave-vegetation interactions in the surf zone.

Wave Dissipation over Nearshore Beach Morphology: Insights from High-Resolution LIDAR Observations and the SWASH Wave Model

NASA Astrophysics Data System (ADS)

Mulligan, R. P.; Gomes, E.; McNinch, J.; Brodie, K. L.

2016-02-01

Numerical modelling of the nearshore zone can be computationally intensive due to the complexity of wave breaking, and the need for high temporal and spatial resolution. In this study we apply the SWASH non-hydrostatic wave-flow model that phase-resolves the free surface and fluid motions in the water column at high resolution. The model is forced using observed directional energy spectra, and results are compared to wave observations during moderate storm events. Observations are collected outside the surf zone using acoustic wave and currents sensors, and inside the surf zone over a 100 m transect using high-resolution LIDAR measurements of the sea surface from a sensor mounted on a tower on the beach dune at the Field Research Facility in Duck, NC. The model is applied to four cases with different wave conditions and bathymetry, and used to predict the spatial variability in wave breaking, and correlation between energy dissipation and morphologic features. Model results compare well with observations of spectral evolution outside the surf zone, and with the remotely sensed observations of wave transformation inside the surf zone. The results indicate the importance of nearshore bars, rip-channels, and larger features (major scour depression under the pier following large waves from Hurricane Irene) on the location of wave breaking and alongshore variability in wave energy dissipation.

Impacts of wave-induced circulation in the surf zone on wave setup

NASA Astrophysics Data System (ADS)

Guérin, Thomas; Bertin, Xavier; Coulombier, Thibault; de Bakker, Anouk

2018-03-01

Wave setup corresponds to the increase in mean water level along the coast associated with the breaking of short-waves and is of key importance for coastal dynamics, as it contributes to storm surges and the generation of undertows. Although overall well explained by the divergence of the momentum flux associated with short waves in the surf zone, several studies reported substantial underestimations along the coastline. This paper investigates the impacts of the wave-induced circulation that takes place in the surf zone on wave setup, based on the analysis of 3D modelling results. A 3D phase-averaged modelling system using a vortex force formalism is applied to hindcast an unpublished field experiment, carried out at a dissipative beach under moderate to very energetic wave conditions (Hm 0 = 6m at breaking and Tp = 22s). When using an adaptive wave breaking parameterisation based on the beach slope, model predictions for water levels, short waves and undertows improved by about 30%, with errors reducing to 0.10 m, 0.10 m and 0.09 m/s, respectively. The analysis of model results suggests a very limited impact of the vertical circulation on wave setup at this dissipative beach. When extending this analysis to idealized simulations for different beach slopes ranging from 0.01 to 0.05, it shows that the contribution of the vertical circulation (horizontal and vertical advection and vertical viscosity terms) becomes more and more relevant as the beach slope increases. In contrast, for a given beach slope, the wave height at the breaking point has a limited impact on the relative contribution of the vertical circulation on the wave setup. For a slope of 0.05, the contribution of the terms associated with the vertical circulation accounts for up to 17% (i.e. a 20% increase) of the total setup at the shoreline, which provides a new explanation for the underestimations reported in previously published studies.

Characteristics of the solitary waves and rogue waves with interaction phenomena in a (2 + 1)-dimensional Breaking Soliton equation

NASA Astrophysics Data System (ADS)

Hossen, Md. Belal; Roshid, Harun-Or; Ali, M. Zulfikar

2018-05-01

Under inquisition in this paper is a (2 + 1)-dimensional Breaking Soliton equation, which can describe various nonlinear scenarios in fluid dynamics. Using the Bell polynomials, some proficient auxiliary functions are offered to apparently construct its bilinear form and corresponding soliton solutions which are different from the previous literatures. Moreover, a direct method is used to construct its rogue wave and solitary wave solutions using particular auxiliary function with the assist of bilinear formalism. Finally, the interactions between solitary waves and rogue waves are offered with a complete derivation. These results enhance the variety of the dynamics of higher dimensional nonlinear wave fields related to mathematical physics and engineering.

The opportunities and realities of doing science in an alternative research environment

NASA Astrophysics Data System (ADS)

Newman, Claire E.

2018-01-01

A planetary scientist describes how she left the traditional corridors of academia to help found her own company, thereby continuing her research program and interests. The flexibility afforded by this break-away has been life-changing.

Breaking Kelvin-Helmholtz waves and cloud-top entrainment as revealed by K-band Doppler radar

NASA Technical Reports Server (NTRS)

Martner, Brooks E.; Ralph, F. Martin

1993-01-01

Radars have occasionally detected breaking Kelvin-Helmholtz (KH) waves under clear-air conditions in the atmospheric boundary layer and in the free troposphere. However, very few direct measurements of such waves within clouds have previously been reported and those have not clearly documented wave breaking. In this article, we present some of the most detailed and striking radar observations to date of breaking KH waves within clouds and at cloud top and discuss their relevance to the issue of cloud-top entrainment, which is believed to be important in convective and stratiform clouds. Aircraft observations reported by Stith suggest that vortex-like circulations near cloud top are an entrainment mechanism in cumuliform clouds. Laboratory and modeling studies have examined possibility that KH instability may be responsible for mixing at cloud top, but direct observations have not yet been presented. Preliminary analyses shown here may help fill this gap. The data presented in this paper were obtained during two field projects in 1991 that included observations from the NOAA Wave Propagation Laboratory's K-band Doppler radar (wavelength = 8.7 mm) and special rawinsonde ascents. The sensitivity (-30 dBZ at 10 km range), fine spatial resolution (375-m pulse length and 0.5 degrees beamwidth), velocity measurement precision (5-10 cm s-1), scanning capability, and relative immunity to ground clutter make it sensitive to non-precipitating and weakly precipitating clouds, and make it an excellent instrument to study gravity waves in clouds. In particular, the narrow beam width and short pulse length create scattering volumes that are cylinders 37.5 m long and 45 m (90 m) in diameter at 5 km (10 km) range. These characteristics allow the radar to resolve the detailed structure in breaking KH waves such as have been seen in photographic cloud images.

Planetary-Scale Inertio Gravity Waves in the Numerical Spectral Model

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Mengel, J. R.; Talaat, E. R.; Porter, H. S.

2004-01-01

In the polar region of the upper mesosphere, horizontal wind oscillations have been observed with periods around 10 hours. Waves with such a period are generated in our Numerical Spectral Model (NSM), and they are identified as planetary-scale inertio gravity waves (IGW). These IGWs have periods between 9 and 11 hours and appear above 60 km in the zonal mean (m = 0), as well as in zonal wavenumbers m = 1 to 4. The waves can propagate eastward and westward and have vertical wavelengths around 25 km. The amplitudes in the wind field are typically between 10 and 20 m/s and can reach 30 m/s in the westward propagating component for m = 1 at the poles. In the temperature perturbations, the wave amplitudes above 100 km are typically 5 K and as large as 10 K for m = 0 at the poles. The IGWs are intermittent but reveal systematic seasonal variations, with the largest amplitudes occurring generally in late winter and spring. In the NSM, the IGW are generated like the planetary waves (PW). They are produced apparently by the instabilities that arise in the zonal mean circulation. Relative to the PWs, however, the IGWs propagate zonally with much larger velocities, such that they are not affected much by interactions with the background zonal winds. Since the IGWs can propagate through the mesosphere without much interaction, except for viscous dissipation, one should then expect that they reach the thermosphere with significant and measurable amplitudes.

Influence of tides and planetary waves on E sporadic layer at mid latitudes

NASA Astrophysics Data System (ADS)

Pezzopane, Michael; Pignalberi, Alessio; Zuccheretti, Enrico

This paper describes the influence that tides and planetary waves have on the variability shown by the main characteristics of the E sporadic (Es) layer, that is the top frequency (ftEs) and the lowest virtual height (h’Es). The study is based on ionograms recorded during the summertime of 2013, a year falling in the maximum of solar activity of cycle 24, and precisely in June, July, August and September, by the Advanced Ionospheric Sounder by Istituto Nazionale di Geofisica e Vulcanologia (AIS-INGV) ionosondes installed at Rome (41.8°N, 12.5°E) and Gibilmanna (37.9°N, 14.0°E), Italy. We applied the height-time-intensity (HTI) methodology proposed by Haldoupis et al. (2006) to investigate how tides control the Es dynamics. As a whole, the HTI analysis showed that a well-defined semidiurnal periodicity characterizes the Es layer descent and occurrence for all the considered months, although in September some cases which showed a prevailing diurnal periodicity were recorded. Through the application of the wavelet analysis it was also found that the tidal oscillations shown by ftEs and h’Es are affected by a strong amplitude modulation with periods of several days but with important differences between the two parameters. This amplitude modulation is a proof that Es layers are indirectly affected by planetary waves through their nonlinear interaction with tides at lower altitudes; this nonlinear interaction produces the presence of secondary waves with frequencies that are the sum and difference of the primary waves frequencies involved in the interaction as proposed by Teitelbaum and Vial [1991]. This work adds to those that were already done by Haldoupis et al. (2004, 2006), and confirms that ionosonde data, especially those registered in summertime, can be used as a powerful tool for studying tidal and planetary waves properties, as well as their climatology, in the mesosphere-low-termosphere region.

Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

USGS Publications Warehouse

Kumar, Nirnimesh; Voulgaris, George; Warner, John C.; Olabarrieta, Maitane

2012-01-01

Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK' 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from and . Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using non-dimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction, bottom stress, breaking acceleration, horizontal advection and horizontal vortex forces dominate the momentum balance. The simulation results for the bar/rip channel morphology case clearly show the ability of the modeling system to reproduce horizontal and vertical circulation patterns similar to those found in laboratory studies and to numerical simulations using the radiation stress representation. The vortex force term is found to be more important at locations where strong flow vorticity interacts with the wave-induced Stokes flow field. Outside the surf zone, the three-dimensional model simulations of wave-induced flows for non-breaking waves closely agree with flow observations from MVCO, with the vertical structure of the simulated flow varying as a function of the vertical viscosity as demonstrated by Lentz et al. (2008).

Large-scale Vortex Generation and Evolution in Short-crested Isolated Wave Breaking

NASA Astrophysics Data System (ADS)

Derakhti, M.; Kirby, J. T., Jr.

2016-12-01

Peregrine (1999), in discussing the effect of localization of wave energy dissipation as a generation mechanism for vorticity at the scale of individual waves, spurred a wave of study of vorticity dynamics and mixing processes in the wave-driven ocean. In deep water, the limited depth of penetration of breaking effects leads to the conceptual forcing of a "smoke-ring" resulting from the localized cross-section of impulsive forcing (Pizzo and Melville, 2013). In shallow water, depth limitations favor the generation of a quasi-two-dimensional field of vertical vortex structures, with a resulting inverse cascade of energy to low wavenumbers and the evolution of flows such as transient rip currents (Johnson and Pattiaratchi, 2006). In this study, we are examining a more detailed picture of the vorticity field evolving during a localized breaking event, with particular interest in the span from deep water to shallow water, with special attention to the transition from weak to strong bottom control. Using an LES/VOF model (Derakhti and Kirby, 2014), we examine the evolution of coherent vortex structures whose initial scales are determined by the width of the breaking region, and are much larger than the locally-controlled reverse horseshoe structures seen in typical studies of along-crest uniform breaking. We study the persistence of three-dimensionality of these structures and their contribution to the development of depth-integrated vertical vorticity, and comment on the suitability of 2D or quasi-3D models to represent nearshore flow fields.

Observation of 1-D time dependent non-propagating laser plasma structures using fluid and PIC codes

NASA Astrophysics Data System (ADS)

Verma, Deepa; Bera, Ratan Kumar; Kumar, Atul; Patel, Bhavesh; Das, Amita

2017-12-01

The manuscript reports the observation of time dependent localized and non-propagating structures in the coupled laser plasma system through 1-D fluid and Particle-In-Cell (PIC) simulations. It is reported that such structures form spontaneously as a result of collision amongst certain exact solitonic solutions. They are seen to survive as coherent entities for a long time up to several hundreds of plasma periods. Furthermore, it is shown that such time dependence can also be artificially recreated by significantly disturbing the delicate balance between the radiation and the density fields required for the exact non-propagating solution obtained by Esirkepov et al., JETP 68(1), 36-41 (1998). The ensuing time evolution is an interesting interplay between kinetic and field energies of the system. The electrostatic plasma oscillations are coupled with oscillations in the electromagnetic field. The inhomogeneity of the background and the relativistic nature, however, invariably produces large amplitude density perturbations leading to its wave breaking. In the fluid simulations, the signature of wave breaking can be discerned by a drop in the total energy which evidently gets lost to the grid. The PIC simulations are observed to closely follow the fluid simulations till the point of wave breaking. However, the total energy in the case of PIC simulations is seen to remain conserved throughout the simulations. At the wave breaking, the particles are observed to acquire thermal kinetic energy in the case of PIC. Interestingly, even after wave breaking, compact coherent structures with trapped radiation inside high-density peaks continue to exist both in PIC and fluid simulations. Although the time evolution does not exactly match in the two simulations as it does prior to the process of wave breaking, the time-dependent features exhibited by the remnant structures are characteristically similar.

Investigating the impact of surface wave breaking on modeling the trajectories of drifters in the northern Adriatic Sea during a wind-storm event

USGS Publications Warehouse

Carniel, S.; Warner, J.C.; Chiggiato, J.; Sclavo, M.

2009-01-01

An accurate numerical prediction of the oceanic upper layer velocity is a demanding requirement for many applications at sea and is a function of several near-surface processes that need to be incorporated in a numerical model. Among them, we assess the effects of vertical resolution, different vertical mixing parameterization (the so-called Generic Length Scale -GLS- set of k-??, k-??, gen, and the Mellor-Yamada), and surface roughness values on turbulent kinetic energy (k) injection from breaking waves. First, we modified the GLS turbulence closure formulation in the Regional Ocean Modeling System (ROMS) to incorporate the surface flux of turbulent kinetic energy due to wave breaking. Then, we applied the model to idealized test cases, exploring the sensitivity to the above mentioned factors. Last, the model was applied to a realistic situation in the Adriatic Sea driven by numerical meteorological forcings and river discharges. In this case, numerical drifters were released during an intense episode of Bora winds that occurred in mid-February 2003, and their trajectories compared to the displacement of satellite-tracked drifters deployed during the ADRIA02-03 sea-truth campaign. Results indicted that the inclusion of the wave breaking process helps improve the accuracy of the numerical simulations, subject to an increase in the typical value of the surface roughness z0. Specifically, the best performance was obtained using ??CH = 56,000 in the Charnok formula, the wave breaking parameterization activated, k-?? as the turbulence closure model. With these options, the relative error with respect to the average distance of the drifter was about 25% (5.5 km/day). The most sensitive factors in the model were found to be the value of ??CH enhanced with respect to a standard value, followed by the adoption of wave breaking parameterization and the particular turbulence closure model selected. ?? 2009 Elsevier Ltd.

Stickney Crater on Phobos and some other outstanding planetary depressions as features of crustal wave interference origin

NASA Astrophysics Data System (ADS)

Kochemasov, G. G.

2011-10-01

Some not fully understood (enigmatic) large planetary depressions and geoid minima on planets and satellites are better understood as regular wave woven features, not random large impacts [1]. A main reason for this is their similar tectonic position in a regular sectoral network produced by interfering crossing standing waves warping any celestial body. These waves arise in the bodies due to their movements in keplerian elliptical orbits with changing accelerations. The fundamental wave1 produces universal tectonic dichotomy, its first overtone wave2 superposes on it sectoring - a regular network of risen and fallen blocks [2, 3]. Thus, deeply subsided sectoral blocks are formed on uplifted highland segments -hemispheres [1]. Examples of this pattern are shown in Fig. 1 to 8 on various globes and irregular bodies. The Moon - the SPA basin, Earth - Indian geoid min imum, Phobos - Stickney Crater, Miranda - an ovoid, Phoebe - a sector, Mars - Hellas Planitia, Lutetia - a deep sector indentation. Fig. 9 - a geometrical model of dichotomy and sectors format ion by wave interference.

A numerical analysis of transient planetary waves and the vertical structure in a meso-strato-troposphere model, part 1.4A

NASA Technical Reports Server (NTRS)

Zhang, K. S.; Sasamori, T.

1984-01-01

The structure of unstable planetary waves is computed by a quasi-geostrophic model extending from the surface up to 80 km by means of eigenvalue-eigenfunction techniques in spherical coordinates. Three kinds of unstable modes of distinct phase speeds and vertical structures are identified in the winter climate state: (1) the deep Green mode with its maximum amplitude in the stratosphere; (2) the deep Charney mode with its maximum amplitude in the troposphere: and (3) the shallow Charney mode which is largely confined to the troposphere. Both the Green mode and the deep Charney mode are characterized by very slow phase speeds. They are mainly supported by upward wave energy fluxes, but the local baroclinic energy conversion within the stratosphere also contributes in supporting these deep modes. The mesosphere and the troposphere are dynamically independent in the summer season decoupled by the deep stratospheric easterly. The summer mesosphere supports the easterly unstable waves 1-4. Waves 3 and 4 are identified with the observed mesospheric 2-day wave and 1.7-day wave, respectively.

Hydrodynamic modeling of tsunamis from the Currituck landslide

USGS Publications Warehouse

Geist, E.L.; Lynett, P.J.; Chaytor, J.D.

2009-01-01

Tsunami generation from the Currituck landslide offshore North Carolina and propagation of waves toward the U.S. coastline are modeled based on recent geotechnical analysis of slide movement. A long and intermediate wave modeling package (COULWAVE) based on the non-linear Boussinesq equations are used to simulate the tsunami. This model includes procedures to incorporate bottom friction, wave breaking, and overland flow during runup. Potential tsunamis generated from the Currituck landslide are analyzed using four approaches: (1) tsunami wave history is calculated from several different scenarios indicated by geotechnical stability and mobility analyses; (2) a sensitivity analysis is conducted to determine the effects of both landslide failure duration during generation and bottom friction along the continental shelf during propagation; (3) wave history is calculated over a regional area to determine the propagation of energy oblique to the slide axis; and (4) a high-resolution 1D model is developed to accurately model wave breaking and the combined influence of nonlinearity and dispersion during nearshore propagation and runup. The primary source parameter that affects tsunami severity for this case study is landslide volume, with failure duration having a secondary influence. Bottom friction during propagation across the continental shelf has a strong influence on the attenuation of the tsunami during propagation. The high-resolution 1D model also indicates that the tsunami undergoes nonlinear fission prior to wave breaking, generating independent, short-period waves. Wave breaking occurs approximately 40-50??km offshore where a tsunami bore is formed that persists during runup. These analyses illustrate the complex nature of landslide tsunamis, necessitating the use of detailed landslide stability/mobility models and higher-order hydrodynamic models to determine their hazard.

Plasma and radio waves from Neptune: Source mechanisms and propagation

NASA Astrophysics Data System (ADS)

Wong, H. K.

1994-03-01

This report summarizes results obtained through the support of NASA Grant NAGW-2412. The objective of this project is to conduct a comprehensive investigation of the radio wave emission observed by the planetary radio astronomy (PRA) instrument on board Voyager 2 as if flew by Neptune. This study has included data analysis, theoretical and numerical calculations, ray tracing, and modeling to determine the possible source mechanism(s) and locations of the Neptune radio emissions. We have completed four papers, which are included in the appendix. The paper 'Modeling of Whistler Ray Paths in the Magnetosphere of Neptune' investigated the propagation and dispersion of lighting-generated whistler in the magnetosphere of Neptune by using three dimensional ray tracing. The two papers 'Numerical Simulations of Bursty Radio Emissions from Planetary Magnetospheres' and 'Numerical Simulations of Bursty Planetary Radio Emissions' employed numerical simulations to investigate an alternate source mechanism of bursty radio emissions in addition to the cyclotron maser instability. We have also studied the possible generation of Z and whistler mode waves by the temperature anisotropic beam instability and the result was published in 'Electron Cyclotron Wave Generation by Relativistic Electrons.' Besides the aforementioned studies, we have also collaborated with members of the PRA team to investigate various aspects of the radio wave data. Two papers have been submitted for publication and the abstracts of these papers are also listed in the appendix.

Plasma and radio waves from Neptune: Source mechanisms and propagation

NASA Technical Reports Server (NTRS)

Wong, H. K.

1994-01-01

This report summarizes results obtained through the support of NASA Grant NAGW-2412. The objective of this project is to conduct a comprehensive investigation of the radio wave emission observed by the planetary radio astronomy (PRA) instrument on board Voyager 2 as if flew by Neptune. This study has included data analysis, theoretical and numerical calculations, ray tracing, and modeling to determine the possible source mechanism(s) and locations of the Neptune radio emissions. We have completed four papers, which are included in the appendix. The paper 'Modeling of Whistler Ray Paths in the Magnetosphere of Neptune' investigated the propagation and dispersion of lighting-generated whistler in the magnetosphere of Neptune by using three dimensional ray tracing. The two papers 'Numerical Simulations of Bursty Radio Emissions from Planetary Magnetospheres' and 'Numerical Simulations of Bursty Planetary Radio Emissions' employed numerical simulations to investigate an alternate source mechanism of bursty radio emissions in addition to the cyclotron maser instability. We have also studied the possible generation of Z and whistler mode waves by the temperature anisotropic beam instability and the result was published in 'Electron Cyclotron Wave Generation by Relativistic Electrons.' Besides the aforementioned studies, we have also collaborated with members of the PRA team to investigate various aspects of the radio wave data. Two papers have been submitted for publication and the abstracts of these papers are also listed in the appendix.

The Fate and Impact of Internal Waves in Nearshore Ecosystems

NASA Astrophysics Data System (ADS)

Woodson, C. B.

2018-01-01

Internal waves are widespread features of global oceans that play critical roles in mixing and thermohaline circulation. Similarly to surface waves, internal waves can travel long distances, ultimately breaking along continental margins. These breaking waves can transport deep ocean water and associated constituents (nutrients, larvae, and acidic low-oxygen waters) onto the shelf and locally enhance turbulence and mixing, with important effects on nearshore ecosystems. We are only beginning to understand the role internal waves play in shaping nearshore ecosystems. Here, I review the physics of internal waves in shallow waters and identify two commonalities among internal waves in the nearshore: exposure to deep offshore waters and enhanced turbulence and mixing. I relate these phenomena to important ecosystem processes ranging from extreme events to fertilization success to draw general conclusions about the influence of internal waves on ecosystems and the effects of internal waves in a changing climate.

The Fate and Impact of Internal Waves in Nearshore Ecosystems.

PubMed

Woodson, C B

2018-01-03

Internal waves are widespread features of global oceans that play critical roles in mixing and thermohaline circulation. Similarly to surface waves, internal waves can travel long distances, ultimately breaking along continental margins. These breaking waves can transport deep ocean water and associated constituents (nutrients, larvae, and acidic low-oxygen waters) onto the shelf and locally enhance turbulence and mixing, with important effects on nearshore ecosystems. We are only beginning to understand the role internal waves play in shaping nearshore ecosystems. Here, I review the physics of internal waves in shallow waters and identify two commonalities among internal waves in the nearshore: exposure to deep offshore waters and enhanced turbulence and mixing. I relate these phenomena to important ecosystem processes ranging from extreme events to fertilization success to draw general conclusions about the influence of internal waves on ecosystems and the effects of internal waves in a changing climate.

A spectral study of the mid-latitude sporadic E layer characteristic oscillations comparable to those of the tidal and the planetary waves

NASA Astrophysics Data System (ADS)

Pignalberi, A.; Pezzopane, M.; Zuccheretti, E.

2015-01-01

In this paper different spectral analyses are employed to investigate the tidal and planetary wave periodicities imprinted in the following two main characteristics of the sporadic E (Es) layer: the top frequency (ftEs) and the lowest virtual height (h‧Es). The study is based on ionograms recorded during the summertime of 2013, and precisely in June, July, August and September, by the Advanced Ionospheric Sounder by Istituto Nazionale di Geofisica e Vulcanologia (AIS-INGV) ionosondes installed at Rome (41.8°N, 12.5°E) and Gibilmanna (37.9°N, 14.0°E), Italy. It was confirmed that the diurnal and semidiurnal atmospheric tides play a fundamental role in the formation of the mid-latitude Es layers, acting through their vertical wind-shear forcing of the long-living metallic ions in the lower thermosphere, and at the same time it was found that the planetary atmospheric waves might affect the Es layers acting through their horizontal wind-shear forcing with periods close to the normal Rossby modes, that is 2, 5, 10 and 16 days. The wavelet analysis shows also that the ftEs and h‧Es tidal oscillations undergo a strong amplitude modulation with periods of several days and with important differences between the two parameters. This amplitude modulation, characterizing markedly the first thirty days of the ftEs spectrogram, suggests that Es layers are affected indirectly by planetary waves through their nonlinear interaction with the atmospheric tides at lower altitudes. This study wants to be a continuation of the Haldoupis et al. (2004) work in order to verify their results for the foEs characteristic and on the other hand to extend the study also to the h‧Es characteristic not yet shown so far. Anyhow, the study confirms that ionosonde data, especially those registered in summertime, represent a powerful tool for studying tidal and planetary waves properties and their climatology in the mesosphere-low-thermosphere region.

A model study of sediment transport across the shelf break

NASA Astrophysics Data System (ADS)

Marchal, Olivier

2017-04-01

A variety of dynamical processes can contribute to the transport of material (e.g., particulate matter) across the shelf break - the region separating the continental shelf from the continental slope. Among these processes are (i) the reflection of internal waves on the outer shelf and upper slope, and (ii) the instability of hydrographic fronts, roughly aligned with isobaths, that are often present at the shelf break. On the one hand, internal waves reflecting on a sloping boundary can produce bottom shear stresses that are large enough to resuspend non-cohesive sediments into the water column. On the other hand, eddies shed from unstable shelf break fronts can incorporate into their core particle-rich waters from the outer shelf and upper slope, and transport these waters offshore. Here we present numerical experiments with a three-dimensional numerical model of ocean circulation and sediment transport, which illustrate the joint effect of internal waves and eddies on sediment transport across the shelf break. The model is based on the primitive equations and terrain-following coordinates. The model domain is square and idealized, comprising a flat continental shelf, a constant continental slope, and a flat abyssal basin. The model grid has O(1 km) horizontal resolution, so that (sub)mesoscale eddies observed in the vicinity of shelf breaks, such as south of New England, can be represented in detail. Internal waves are excited through the specification of a periodic variation in the across-slope component of velocity at the offshore boundary of the domain, and eddies are generated from the baroclinic instability of a shelf break jet that is initially in strict thermal wind balance. Numerical experiments are conducted that are characterized by (i) different slopes of internal wave characteristics relative to the continental slope, representing sub-critical, critical, and super-critical regimes, and (ii) different values for the dimensionless ratios that emerge from the linear stability analysis of shelf break fronts. Emphasis is placed on the physical conditions that are conducive to the formation and maintenance of bottom and intermediate nepheloid layers - the particle-rich layers that are often observed near oceanic margins in the traces of optical instruments.

Ground-based observation of the cyclic nature and temporal variability of planetary-scale UV features at the Venus cloud top level

NASA Astrophysics Data System (ADS)

Imai, Masataka; Takahashi, Yukihiro; Watanabe, Makoto; Kouyama, Toru; Watanabe, Shigeto; Gouda, Shuhei; Gouda, Yuya

2016-11-01

A planetary-scale bright and dark UV feature, known as the ;Y-feature,; rotates around Venus with a period of 4-5 days and has been long-time interpreted as planetary waves. When assuming this, its rotation period and spatial structure might help to understand the propagation of the planetary-scale waves and find out their role in the acceleration-deceleration of the zonal wind speed, which is essential for understanding the super-rotation of the planet. The rotation period of the UV feature varied over the course of observation by the Pioneer Venus orbiter. However, in previous explorations of Venus such as Pioneer Venus and Venus Express, the spacecraft were operated in nearly fixed inertial space. As a result, the periodicity variations on sub-yearly timescales (one Venusian year is ∼224 Earth days) were obscured by the limitations of continuous dayside observations. We newly conducted six periods of ground-based Venus imaging observations at 365 nm from mid-August 2013 to the end of June 2014. Each observation period spanned over half or one month, enabling long-term monitoring of Venus' atmosphere above the equator region. Distributions of the relative brightness were obtained from the equatorial (EQ) to mid-latitudinal regions in both hemispheres, and from the cyclical variations of these distributions we deduced the rotation periods of the UV features of the cloud tops brightness. The relative brightness exhibited periods of 5.2 and 3.5 days above 90% of significance. The relative intensities of these two significant components also seemed subject to temporal variations. Although the 3.5-day component considered persists throughout the observation periods, its dominance over the longer period varied in a cyclic fashion. The prevailing first significant mode seems to change from 5.2-day waves to 3.5-day waves in about nine months, which is clearly inconsistent with the Venusian year. Clear periodic perturbations, indicating stability of the planetary-scale UV-feature, were observed only in the presence of single longer or shorter periodic waves. During the transition periods of dominant-wave changing, the amplitude of the relative brightness was largely changed. This can be explained by the deformation of the Y-shaped UV feature as observed by Pioneer Venus in 1979.

Semester and Event-Specific Motives for Alcohol Use During Spring Break: Associated Protective Strategies and Negative Consequences

PubMed Central

Patrick, Megan E.; Lewis, Melissa A.; Lee, Christine M.; Maggs, Jennifer L.

2012-01-01

Motives surrounding alcohol use behavior are important for understanding college student drinking. However, no previous research has addressed how motives for and against drinking during specific events associated with high-risk drinking, such as Spring Break, may differ from motives for and against drinking during the regular semester. Further, we examine the extent to which semester and Spring Break motives are associated with alcohol use, protective behavioral strategies (PBS), and consequences. Participants were college students (N = 261; 55% women) who provided data both immediately prior to (Wave 1) and after (Wave 2) Spring Break. Fun/Social motives for drinking were greater for Spring Break, and Driving motives against drinking were lower for Spring Break, compared to semester drinking. Relax and Image motives for drinking and Physical/Behavioral motives for not drinking during Spring Break did not differ from semester motives. Spring Break motives for and against drinking were associated with total drinks, maximum drinks, PBS, and experienced negative consequences during Spring Break. Students’ specific motives regarding drinking during Spring Break predict high-risk drinking and may be utilized in creating salient event-specific interventions. PMID:23384451

Transverse particle acceleration and diffusion in a planetary magnetic field

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1994-01-01

A general model of particle acceleration by plasma waves coupled with adiabatic radial diffusion in a planetary magnetic field is developed. The model assumes that a spectrum of lower hybird waves is present to resonantly accelerate ions transverse to the magnetic field. The steady state Green's function for the combined radial diffusion and wave acceleration equation is found in terms of a series expansion. The results provide a rigorous demonstration of how a quasi-Maxwellian distribution function is formed in the absence of particle collisons and elucidate the nature of turbulent heating of magnetospheric plasmas. The solution is applied to the magnetosphere of Neptune for which a number of examples are given illustrating how the spectrum of pickup N(+) ions from Triton evolves.

Detection and Characterization of Deep Water Wave Breaking Using Moderate Incidence Angle Microwave Backscatter from the Sea Surface

DTIC Science & Technology

1990-06-01

interaction and wave breaking. The ocean surface can be modelled as a two-scale or composite surface - 21 - made up of short wind-generated ripples... composite or two-scale rough surface (Barrick and Peake, 1968). For radar wavelengths on the order of a few centimeters, the resonant scatterers are...short wind ripples which ride on top of long gravity waves, and a - 46 - composite model is used to describe the two-scale nature of the sea surface

Wave Activity (Planetary, Tidal) throughout the Middle Atmoshere (25-100 km) over the CUJO Network: Satellite and Medium Frequency (MF) Radar Observations

NASA Astrophysics Data System (ADS)

Manson, A.; Meek, C.; Chshyolkova, T.; Avery, S.; Thorsen, D.; MacDougall, J.; Hocking, W.; Murayama, Y.; Igarashi, K.

Planetary and tidal wave activity in the mesosphere-lower thermosphere (MLT), and assessment of wave activity sources in the lower atmosphere, are studied using combinations of ground based (GB) and satellite instruments (2000-2002). CUJO (Canada U.S. Japan Opportunity) comprises MF radar (MFR) systems at London (43°N, 81°W), Platteville (40°N, 105°W), Saskatoon (52°N, 107°W), Wakkanai (45°N, 142°E) and Yamagawa (31°N, 131°E). It offers a significant mid-latitude 7,000 km longitudinal sector in the North American-Pacific region, and a useful range of latitudes (12-14°) at two longitudes. CUJO provides winds and tides 70-100km. Satellite data include the daily values of the total ozone column measured by the Earth Probe (EP) TOMS (Total Ozone Mapping Spectrometer) and provides a measure of tropopause-lower stratospheric planetary wave activity as well as ozone variability. The so-called UKMO data (an assimilation system) are used for correlative purposes with the TOMS data. Climatologies of ozone and winds/tides involving frequency versus time (wavelet) contour plots for periods from 2-d to 30-d and the interval from mid 2000 to 2002, show that the changes with altitude, longitude and latitude are very significant and distinctive. Geometric-mean wavelets for the region of the 40°N MFRs demonstrate occasions during the autumn, winter and spring months when there are similarities in the spectral features of the lower atmosphere and at mesopause (85km) heights. Both direct planetary wave (PW) propagation into the MLT, non-linear PW-tide interactions, and disturbances in MLT tides associated with fluctuations in the ozone forcing are considered to be possible coupling processes. The complex horizontal wave numbers of the longer period oscillations are provided in frequency contour plots for the TOMS and UKMO data to demonstrate the differences between lower atmospheric and MLT wave motions and their directions of propagation.

Assessing the performance of formulations for nonlinear feedback of surface gravity waves on ocean currents over coastal waters

NASA Astrophysics Data System (ADS)

Wang, Pengcheng; Sheng, Jinyu; Hannah, Charles

2017-08-01

This study presents applications of a two-way coupled wave-circulation modelling system over coastal waters, with a special emphasis of performance assessments of two different methods for nonlinear feedback of ocean surface gravity waves on three-dimensional (3D) ocean currents. These two methods are the vortex force (VF) formulation suggested by Bennis et al. (2011) and the latest version of radiation stress (RS) formulation suggested by Mellor (2015). The coupled modelling system is first applied to two idealized test cases of surf-zone scales to validate implementations of these two methods in the coupled wave-circulation system. Model results show that the latest version of RS has difficulties in producing the undertow over the surf zone. The coupled system is then applied to Lunenburg Bay (LB) of Nova Scotia during Hurricane Juan in 2003. The coupled system using both the VF and RS formulations generates much stronger and more realistic 3D circulation in the Bay during Hurricane Juan than the circulation-only model, demonstrating the importance of surface wave forces to the 3D ocean circulation over coastal waters. However, the RS formulation generates some weak unphysical currents outside the wave breaking zone due to a less reasonable representation for the vertical distribution of the RS gradients over a slopping bottom. These weak unphysical currents are significantly magnified in a two-way coupled system when interacting with large surface waves, degrading the model performance in simulating currents at one observation site. Our results demonstrate that the VF formulation with an appropriate parameterization of wave breaking effects is able to produce reasonable results for applications over coastal waters during extreme weather events. The RS formulation requires a complex wave theory rather than the linear wave theory for the approximation of a vertical RS term to improve its performance under both breaking and non-breaking wave conditions.

The Solsticial Pause on Mars. Part 1; A Planetary Wave Reanalysis

NASA Technical Reports Server (NTRS)

Lewis, Stephen R.; Mulholland, David P.; Read, Peter L.; Montabone, Luca; Wilson, R. John; Smith, Michael D.

2015-01-01

Large-scale planetary waves are diagnosed from an analysis of profiles retrieved from the Thermal Emission Spectrometer aboard the Mars Global Surveyor spacecraft during its scientific mapping phase. The analysis is conducted by assimilating thermal profiles and total dust opacity retrievals into a Mars global circulation model. Transient waves are largest throughout the northern hemisphere autumn, winter and spring period and almost absent during the summer. The southern hemisphere exhibits generally weaker transient wave behavior. A striking feature of the low-altitude transient waves in the analysis is that they show a broad subsidiary minimum in amplitude centred on the winter solstice, a period when the thermal contrast between the summer hemisphere and the winter pole is strongest and baroclinic wave activity might be expected to be strong. This behavior, here called the 'solsticial pause,' is present in every year of the analysis. This strong pause is under-represented in many independent model experiments, which tend to produce relatively uniform baroclinic wave activity throughout the winter. This paper documents and diagnoses the transient wave solsticial pause found in the analysis; a companion paper investigates the origin of the phenomenon in a series of model experiments.

Quasi-biennial modulation of planetary-wave fluxes in the Northern Hemisphere winter

NASA Technical Reports Server (NTRS)

Dunkerton, Timothy J.; Baldwin, Mark P.

1991-01-01

Using 25 years of National Meteorological Center (NMC) data for 1964-88 the relation between tropical and extratropical quasi-biennial oscillations (QBOs) was examined for zonally averaged quantities and planetary-wave Eliassen-Palm fluxes in the Northern Hemisphere winter. The extratropical QBO discussed by Holton and Tan (1980) existed in both temporal halves of the dataset. Autocorrelation analysis demonstrated that it was an important mode of interannual variability in the extratropical winter stratosphere. Correlation with the tropics was strongest when 40-mb equatorial winds were used to define the tropical QBO. Easterly phase at 40 mb implied a weaker than normal polar night jet and warmer than normal polar temperature and vice versa. An opposite relationship was obtained using 10-mb equatorial winds. The association between tropical and extratropical QBOs was observed in about 90 percent of the winters and was statistically significant. It is shown that planetary-wave Eliassen-Palm fluxes were generally consistent with the extratropical QBO. These fluxes were more (less) convergent in the midlatitude (subtropical) upper stratosphere in the 40-mb east (= easterly) phase category relative to the west category.

A Link between Variability of the Semidiurnal Tide and Planetary Waves in the Opposite Hemisphere

NASA Technical Reports Server (NTRS)

Smith, Anne K.; Pancheva, Dora V.; Mitchell, Nicholas J.; Marsh, Daniel R.; Russell, James M., III; Mlynczak, Martin G.

2007-01-01

Horizontal wind observations over four years from the meteor radar at Esrange (68 deg N) are analyzed to determine the variability of the semidiurnal tide. Simultaneous global observations of temperature and geopotential from the SABER satellite instrument are used to construct time series of planetary wave amplitudes and geostrophic mean zonal wind. During NH summer and fall, the temporal variability of the semidiurnal tide at Esrange is found to be well correlated with the amplitude of planetary wavenumber 1 in the stratosphere in high southern latitudes (i.e., in the opposite hemisphere). The correlations indicate that a significant part of the tidal variations at Esrange is due to dynamical interactions in the Southern Hemisphere. Other times of the year do not indicate a corresponding robust correlation pattern for the Esrange tides over multiple years.

Sedimentary structures formed under water surface waves: examples from a sediment-laden flash flood observed by remote camer

NASA Astrophysics Data System (ADS)

Froude, Melanie; Alexander, Jan; Cole, Paul; Barclay, Jenni

2014-05-01

On 13-14 October 2012, Tropical Storm Rafael triggered sediment-laden flash floods in the Belham Valley on Montserrat, West Indies. Rainfall was continuous for ~38 hours and intensity peaked at 48 mm/hr. Flow was strongly unsteady, turbulent with sediment concentrations varying up to hyperconcentrated. Time-lapse images captured at >1 frame per second by remote camera overlooking a surveyed valley section show the development of trains of water surface waves at multiple channel locations during different flow stages. Waves grew and diminished in height and remained stationary or migrated upstream. Trains of waves persisted for <5 minutes, until a single wave broke, sometimes initiating the breaking of adjacent waves within the train. Channel-wide surges (bores) propagating downstream with distinct turbulent flow fronts, were observed at irregular intervals during and up to 7 hours after peak stage. These bores are mechanically similar to breaking front tidal bores and arid flood bores, and resulted in a sudden increase in flow depth and velocity. When a bore front came into close proximity (within ~10 m) upstream of a train of water surface waves, the waves appeared to break simultaneously generating a localised surge of water upstream, that was covered by the bore travelling downstream. Those trains in which waves did not break during the passage of a bore temporarily reduced in height. In both cases, water surface waves reformed immediately after the surge in the same location. Deposits from the event, were examined in <4 m deep trenches ~0.5 km downstream of the remote camera. These contained laterally extensive lenticular and sheet-like units comprised of varying admixtures of sand and gravel that are attributed to antidunes, and associated transitions from upper-stage-plane-beds. Some of the structures are organised within concave upward sequences which contain downflow shifts between foreset and backset laminae; interpreted as trough fills from chute-and-pools or water surface wave breaking. At least 90% of the deposit is interpreted upper flow regime origin. The sequence, geometry and lamina-scale texture of the sedimentary structures will be discussed with reference to remote camera images of rapidly varying, unsteady and pulsatory flow behaviour.

Breaking Bat

ERIC Educational Resources Information Center

Aguilar, Isaac-Cesar; Kagan, David

2013-01-01

The sight of a broken bat in Major League Baseball can produce anything from a humorous dribbler in the infield to a frightening pointed projectile headed for the stands. Bats usually break at the weakest point, typically in the handle. Breaking happens because the wood gets bent beyond the breaking point due to the wave sent down the bat created…

NEWTON - NEW portable multi-sensor scienTific instrument for non-invasive ON-site characterization of rock from planetary surface and sub-surfaces

NASA Astrophysics Data System (ADS)

Díaz-Michelena, M.; de Frutos, J.; Ordóñez, A. A.; Rivero, M. A.; Mesa, J. L.; González, L.; Lavín, C.; Aroca, C.; Sanz, M.; Maicas, M.; Prieto, J. L.; Cobos, P.; Pérez, M.; Kilian, R.; Baeza, O.; Langlais, B.; Thébault, E.; Grösser, J.; Pappusch, M.

2017-09-01

In space instrumentation, there is currently no instrument dedicated to susceptibly or complete magnetization measurements of rocks. Magnetic field instrument suites are generally vector (or scalar) magnetometers, which locally measure the magnetic field. When mounted on board rovers, the electromagnetic perturbations associated with motors and other elements make it difficult to reap the benefits from the inclusion of such instruments. However, magnetic characterization is essential to understand key aspects of the present and past history of planetary objects. The work presented here overcomes the limitations currently existing in space instrumentation by developing a new portable and compact multi-sensor instrument for ground breaking high-resolution magnetic characterization of planetary surfaces and sub-surfaces. This new technology introduces for the first time magnetic susceptometry (real and imaginary parts) as a complement to existing compact vector magnetometers for planetary exploration. This work aims to solve the limitations currently existing in space instrumentation by means of providing a new portable and compact multi-sensor instrument for use in space, science and planetary exploration to solve some of the open questions on the crustal and more generally planetary evolution within the Solar System.

On the Connection Between Microbursts and Nonlinear Electronic Structures in Planetary Radiation Belts

NASA Technical Reports Server (NTRS)

Osmane, Adnane; Wilson, Lynn B., III; Blum, Lauren; Pulkkinen, Tuija I.

2016-01-01

Using a dynamical-system approach, we have investigated the efficiency of large-amplitude whistler waves for causing microburst precipitation in planetary radiation belts by modeling the microburst energy and particle fluxes produced as a result of nonlinear wave-particle interactions. We show that wave parameters, consistent with large amplitude oblique whistlers, can commonly generate microbursts of electrons with hundreds of keV-energies as a result of Landau trapping. Relativistic microbursts (greater than 1 MeV) can also be generated by a similar mechanism, but require waves with large propagation angles Theta (sub k)B greater than 50 degrees and phase-speeds v(sub phi) greater than or equal to c/9. Using our result for precipitating density and energy fluxes, we argue that holes in the distribution function of electrons near the magnetic mirror point can result in the generation of double layers and electron solitary holes consistent in scales (of the order of Debye lengths) to nonlinear structures observed in the radiation belts by the Van Allen Probes. Our results indicate a relationship between nonlinear electrostatic and electromagnetic structures in the dynamics of planetary radiation belts and their role in the cyclical production of energetic electrons (E greater than or equal to 100 keV) on kinetic timescales, which is much faster than previously inferred.

Ozone perturbations in the Arctic summer lower stratosphere as a reflection of NOX chemistry and planetary scale wave activity

NASA Astrophysics Data System (ADS)

Akiyoshi, H.; Sugita, T.; Kanzawa, H.; Kawamoto, N.

2004-02-01

Ozone concentration perturbations in the high-latitude lower stratosphere in the Northern Hemisphere were observed by Improved Limb Atmospheric Spectrometer (ILAS) after the polar vortex breakdown at the beginning of May 1997 and until the end of June of that same year. Simulations and a passive tracer experiment using the Center for Climate System Research/National Institute for Environmental Studies (CCSR/NIES) nudging chemical transport model (CTM) show that the low-ozone perturbations observed in May were caused by the Arctic polar vortex debris, while those after the end of May resulted from a dynamical elongation due to zonal wave number 2 planetary waves of the low-ozone region in the summer polar stratosphere, which had been developed by the catalytic ozone destruction cycle of NOX. These low-O3 air masses of different origin were advected or elongated from the polar region to the ILAS measurement points. An episodic event of a dynamical O3 perturbation in June 1997 on a chemically induced meridional O3 gradient is described. These results show that a timing of the polar vortex breakdown and activity of planetary waves after the breakdown may affect the O3 background gradient in the summer lower stratosphere at middle and high latitudes.

Orbitally shaken shallow fluid layers. I. Regime classification

NASA Astrophysics Data System (ADS)

Alpresa, Paola; Sherwin, Spencer; Weinberg, Peter; van Reeuwijk, Maarten

2018-03-01

Orbital shakers are simple devices that provide mixing, aeration, and shear stress at multiple scales and high throughput. For this reason, they are extensively used in a wide range of applications from protein production to bacterial biofilms and endothelial cell experiments. This study focuses on the behaviour of orbitally shaken shallow fluid layers in cylindrical containers. In order to investigate the behaviour over a wide range of different conditions, a significant number of numerical simulations are carried out under different configuration parameters. We demonstrate that potential theory—despite the relatively low Reynolds number of the system—describes the free-surface amplitude well and the velocity field reasonably well, except when the forcing frequency is close to a natural frequency and resonance occurs. By classifying the simulations into non-breaking, breaking, and breaking with part of the bottom uncovered, it is shown that the onset of wave breaking is well described by Δh/(2R) = 0.7Γ, where Δh is the free-surface amplitude, R is the container radius, and Γ is the container aspect ratio; Δh can be well approximated using the potential theory. This result is in agreement with standard wave breaking theories although the significant inertial forcing causes wave breaking at lower amplitudes.

Wave setup over a Pacific Island fringing reef

NASA Astrophysics Data System (ADS)

Vetter, O.; Becker, J. M.; Merrifield, M. A.; Pequignet, A.-C.; Aucan, J.; Boc, S. J.; Pollock, C. E.

2010-12-01

Measurements obtained across a shore-attached, fringing reef on the southeast coast of the island of Guam are examined to determine the relationship between incident waves and wave-driven setup during storm and nonstorm conditions. Wave setup on the reef flat correlates well (r > 0.95) and scales near the shore as approximately 35% of the incident root mean square wave height in 8 m water depth. Waves generated by tropical storm Man-Yi result in a 1.3 m setup during the peak of the storm. Predictions based on traditional setup theory (steady state, inviscid cross-shore momentum and depth-limited wave breaking) and an idealized model of localized wave breaking at the fore reef are in agreement with the observations. The reef flat setup is used to estimate a similarity parameter at breaking that is in agreement with observations from a steeply sloping sandy beach. A weak (˜10%) increase in setup is observed across the reef flat during wave events. The inclusion of bottom stress in the cross-shore momentum balance may account for a portion of this signal, but this assessment is inconclusive as the reef flat currents in some cases are in the wrong direction to account for the increase. An independent check of fringing reef setup dynamics is carried out for measurements at the neighboring island of Saipan with good agreement.

Fully three-dimensional direct numerical simulation of a plunging breaker

NASA Astrophysics Data System (ADS)

Lubin, Pierre; Vincent, Stéphane; Caltagirone, Jean-Paul; Abadie, Stéphane

2003-07-01

The scope of this paper is to show the results obtained for simulating three-dimensional breaking waves by solving the Navier-Stokes equations in air and water. The interface tracking is achieved by a Lax-Wendroff TVD scheme (Total Variation Diminishing), which is able to handle interface reconnections. We first present the equations and the numerical methods used in this work. We then proceed to the study of a three-dimensional plunging breaking wave, using initial conditions corresponding to unstable periodic sinusoidal waves of large amplitudes. We compare the results obtained for two simulations, a longshore depth perturbation has been introduced in the solution of the flow equations in order to see the transition from a two-dimensional velocity field to a fully three-dimensional one after plunging. Breaking processes including overturning, splash-up and breaking induced vortex-like motion beneath the surface are presented and discussed. To cite this article: P. Lubin et al., C. R. Mecanique 331 (2003).

Deep Orographic Gravity Wave Dynamics over Subantarctic Islands as Observed and Modeled during the Deep Propagating Gravity Wave Experiment (DEEPWAVE)

NASA Astrophysics Data System (ADS)

Eckermann, S. D.; Broutman, D.; Ma, J.; Doyle, J. D.; Pautet, P. D.; Taylor, M. J.; Bossert, K.; Williams, B. P.; Fritts, D. C.; Smith, R. B.; Kuhl, D.; Hoppel, K.; McCormack, J. P.; Ruston, B. C.; Baker, N. L.; Viner, K.; Whitcomb, T.; Hogan, T. F.; Peng, M.

2016-12-01

The Deep Propagating Gravity Wave Experiment (DEEPWAVE) was an international aircraft-based field program to observe and study the end-to-end dynamics of atmospheric gravity waves from 0-100 km altitude and the effects on atmospheric circulations. On 14 July 2014, aircraft remote-sensing instruments detected large-amplitude gravity-wave oscillations within mesospheric airglow and sodium layers downstream of the Auckland Islands, located 1000 km south of Christchurch, New Zealand. A high-altitude reanalysis and a three-dimensional Fourier gravity wave model are used to investigate the dynamics of this event from the surface to the mesosphere. At 0700 UTC when first observations were made, surface flow across the islands' terrain generated linear three-dimensional wavefields that propagated rapidly to ˜78 km altitude, where intense breaking occurred in a narrow layer beneath a zero-wind region at ˜83 km altitude. In the following hours, the altitude of weak winds descended under the influence of a large-amplitude migrating semidiurnal tide, leading to intense breaking of these wavefields in subsequent observations starting at 1000 UTC. The linear Fourier model constrained by upstream reanalysis reproduces the salient aspects of observed wavefields, including horizontal wavelengths, phase orientations, temperature and vertical displacement amplitudes, heights and locations of incipient wave breaking, and momentum fluxes. Wave breaking has huge effects on local circulations, with inferred layer-averaged westward mean-flow accelerations of ˜350 m s-1 hour-1 and dynamical heating rates of ˜8 K hour-1, supporting recent speculation of important impacts of orographic gravity waves from subantarctic islands on the mean circulation and climate of the middle atmosphere during austral winter. We also study deep orographic gravity waves from islands during DEEPWAVE more widely using observations from the Atmospheric Infrared Sounder (AIRS) and high-resolution high-altitude numerical weather prediction models.

Size distribution of oceanic air bubbles entrained in sea-water by wave-breaking

NASA Technical Reports Server (NTRS)

Resch, F.; Avellan, F.

1982-01-01

The size of oceanic air bubbles produced by whitecaps and wave-breaking is determined. The production of liquid aerosols at the sea surface is predicted. These liquid aerosols are at the origin of most of the particulate materials exchanged between the ocean and the atmosphere. A prototype was designed and built using an optical technique based on the principle of light scattering at an angle of ninety degrees from the incident light beam. The output voltage is a direct function of the bubble diameter. Calibration of the probe was carried out within a range of 300 microns to 1.2 mm. Bubbles produced by wave-breaking in a large air-sea interaction simulating facility. Experimental results are given in the form of size spectrum.

Generation of Wind Waves in the Persian Gulf: A Numerical Investigation

NASA Astrophysics Data System (ADS)

Liao, Y.; Kaihatu, J. M.

2010-12-01

The Persian Gulf is a long shallow basin located between the Arabian Peninsula and Iran. Wind-wave generation processes in the region are often affected by the shamal, a strong wind caused by the passage of cold fronts over the mountains of Turkey and Kurdistan. This can set up sudden energetic wind seas, hampering marine traffic. It is not immediately clear whether present wind-wave models can predict this intense, short-term growth and evolution under these conditions. Furthermore, few wave measurements or models studies have been performed in this area. In advance of a wind-wave generation experiment to be conducted off the Qatar coast, we performed a climatological study of the wind wave environment in the Persian Gulf. Using the SWAN wave model as a baseline of the state of the art, five years (2004-2008)of wind field model hindcasts from COAMPS are used as forcing.To investigate the sensitivity of the results to bathymetry, the climatological analysis was run twice more, with refraction or wave breaking deactivated, in turn. The results do not show significant differences with and without refraction, which implies the wind-wave process in Persian Gulf is less dominated by the variation of bathymetry. However the results show that a large amount of wave is dissipated by wave breaking. Wide, flat and shallow bathymetry in Persian Gulf results in a long-fetch scenario, particularly for waves arriving from the northwest. It implies that long period wind-generated waves can be fully generated in this region. Wave height is therefore fully grown by the long-fetch condition, so as to lead in higher possibility of wave breaking and energy dissipation.

Impact Processes in the Solar System

NASA Technical Reports Server (NTRS)

Ahrens, Thomas J.

2004-01-01

The three main topics of this program as described initially in our May 2003 proposal are: 1) Shock-induced damage and attenuation in planetary materials. 2 ) Shock-induced melting and phase changes. 3) Impact-induced volatilization and vapor speciation of planetary materials Topic 4 has been the subject of a continuing investigation since approximately 1990. On Topic 5, we have a paper in preparation and have submitted a proposal to Astrobiology. 4) Responses of planetary atmospheres to giant impact, 5) Effects of impact-induced shock waves on microbial life

Limits of applicability of the quasilinear approximation to the electrostatic wave-plasma interaction

NASA Astrophysics Data System (ADS)

Zacharegkas, Georgios; Isliker, Heinz; Vlahos, Loukas

2016-11-01

The limitation of the Quasilinear Theory (QLT) to describe the diffusion of electrons and ions in velocity space when interacting with a spectrum of large amplitude electrostatic Langmuir, Upper and Lower hybrid waves, is analyzed. We analytically and numerically estimate the threshold for the amplitude of the waves above which the QLT breaks down, using a test particle code. The evolution of the velocity distribution, the velocity-space diffusion coefficients, the driven current, and the heating of the particles are investigated, for the interaction with small and large amplitude electrostatic waves, that is, in both regimes, where QLT is valid and where it clearly breaks down.

The effect of breaking gravity waves on the dynamics and chemistry of the mesosphere and lower thermosphere (invited review)

NASA Technical Reports Server (NTRS)

Garcia, R. R.

1986-01-01

The influence of breaking gravity waves on the dynamics and chemical composition of the 60 to 110 km region is investigated with a two dimensional model that includes a parameterization of gravity wave momentum deposition and diffusion. The dynamical model is described by Garcia and Solomon (1983) and Solomon and Garcia (1983) and includes a complete chemical scheme for the mesosphere and lower thermosphere. The parameterization of Lindzen (1981) is used to calculate the momentum deposited and the turbulent diffusion produced by the gravity waves. It is found that wave momentum deposition drives a very vigorous mean meridional circulation, produces a very cold summer mesopause and reverse the zonal wind jets above about 85 km. The seasonal variation of the turbulent diffusion coefficient is consistent with the behavior of mesospheric turbulences inferred from MST radar echoes. The large degree of consistency between model results and various types of dynamical and chemical data supports very strongly the hypothesis that breaking gravity waves play a major role in determining the zonally-averaged dynamical and chemical structure of the 60 to 110 km region of the atmosphere.

Influence of internal waves on the dispersion and transport of inclined gravity currents

NASA Astrophysics Data System (ADS)

Hogg, C. A. R.; Pietrasz, V. B.; Ouellette, N. T.; Koseff, J. R.

2016-02-01

Brine discharge from desalination facilities presents environmental risks, particularly to benthic organisms. High concentrations of salt and chemical additives, which can be toxic to local ecosystems, are typically mitigated by dilution close to the source. Our laboratory experiments investigate how breaking internal tides can help to dilute gravity currents caused by desalination effluents and direct them away from the benthic layer. In laboratory experiments, internal waves at the pycnocline of an ambient stratification were directed towards a sloping shelf, down which ran a gravity current. The breaking internal waves were seen to increase the proportion of the fluid from the gravity current diverted away from the slope into an intrusion along the pycnocline. In a parametric study, increasing the amplitude of the internal wave was seen to increase the amount of dense fluid in the pycnocline intrusion. The amplitude required to divert the gravity current into the intrusion compares well with an analytical theory that equates the incident energy in the internal wave to the potential energy required to dilute the gravity current. These experimental results suggest that sites of breaking internal waves may be good sites for effluent disposal. Effluent diverted into the intrusion avoids the ecologically sensitive benthic layer.

Towards a better understanding of tidal dissipation at corotation layers in differentially rotating stars and planets

NASA Astrophysics Data System (ADS)

Astoul, A.; Mathis, S.; Baruteau, C.; André, Q.

2017-12-01

Star-planet tidal interactions play a significant role in the dynamical evolution of close-in planetary systems. We investigate the propagation and dissipation of tidal inertial waves in a stellar/planetary convective region. We take into account a latitudinal differential rotation for the background flow, similar to what is observed in the envelope of low-mass stars like the Sun. Previous works have shown that differential rotation significantly alters the propagation and dissipation properties of inertial waves. In particular, when the Doppler-shifted tidal frequency vanishes in the fluid, a critical layer forms where tidal dissipation can be greatly enhanced. Our present work develops a local analytic model to better understand the propagation and dissipation properties of tidally forced inertial waves at critical layers.

Transfer and dissipation of energy during wave group propagation on a gentle beach slope

NASA Astrophysics Data System (ADS)

Padilla, Enrique M.; Alsina, José M.

2017-08-01

The propagation of bichromatic wave groups over a constant 1:100 beach slope and the influence of the group modulation is presented. The modulation is controlled by varying the group frequency, fg, which is shown to remarkably affect the energy transfer to high and low frequency components. The growth of the high frequency (hf) wave skewness increases when fg decreases. This is explained by nonlinear coupling between the primary frequencies, which results in a larger growth of hf components as fg decreases, causing the hf waves to break earlier. Due to high spatial resolution, wave tracking has provided an accurate measurement of the varying breakpoint. These breaking locations are very well described (R2>0.91) by the wave-height to effective-depth ratio (γ). However, for any given Iribarren number, this γ is shown to increase with fg. Therefore, a modified Iribarren number is proposed to include the grouping structure, leading to a considerable improvement in reproducing the measured γ-values. Within the surf zone, the behavior of the Incident Long Wave also depends on the group modulation. For low fg conditions, the lf wave decays only slightly by transferring energy back to the hf wave components. However, for high fg wave conditions, strong dissipation of low frequency (lf) components occurs close to the shoreline associated with lf wave breaking. This mechanism is explained by the growth of the lf wave height, induced partly by the self-self interaction of fg, and partly by the nonlinear coupling between the primary frequencies and fg.

Phase-breaking effect on polaron transport in organic conjugated polymers

DOE PAGES

Meng, Ruixuan; Yin, Sun; Zheng, Yujun; ...

2017-06-15

Despite intense investigations and many accepted viewpoints on theory and experiment, the coherent and incoherent carrier transport in organic semiconductors remains an unsettled topic due to the strong electron-phonon coupling. Based on the tight-binding Su-Schrieffer-Heeger (SSH) model combined with a non-adiabatic dynamics method, we study the effect of phase-breaking on polaron transport by introducing a group of phase-breaking factors into π-electron wave-functions in organic conjugated polymers. Two approaches are applied: the modification of the transfer integral and the phase-breaking addition to the wave-function. Within the former, it is found that a single site phase-breaking can trap a polaron. However, withmore » a larger regular phase-breaking a polaron becomes more delocalized and lighter. Additionally, a group of disordered phase-breaking factors can make the polaron disperse in transport process. Within the latter approach, we show that the phase-breaking can render the delocalized state in valence band discrete and the state in the gap more localized. Consequently, the phase-breaking frequency and intensity can reduce the stability of a polaron. Furthermore, the phase-breaking in organic systems is the main factor that degrades the coherent transport and destroys the carrier stability.« less

Phase-breaking effect on polaron transport in organic conjugated polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Ruixuan; Yin, Sun; Zheng, Yujun

Despite intense investigations and many accepted viewpoints on theory and experiment, the coherent and incoherent carrier transport in organic semiconductors remains an unsettled topic due to the strong electron-phonon coupling. Based on the tight-binding Su-Schrieffer-Heeger (SSH) model combined with a non-adiabatic dynamics method, we study the effect of phase-breaking on polaron transport by introducing a group of phase-breaking factors into π-electron wave-functions in organic conjugated polymers. Two approaches are applied: the modification of the transfer integral and the phase-breaking addition to the wave-function. Within the former, it is found that a single site phase-breaking can trap a polaron. However, withmore » a larger regular phase-breaking a polaron becomes more delocalized and lighter. Additionally, a group of disordered phase-breaking factors can make the polaron disperse in transport process. Within the latter approach, we show that the phase-breaking can render the delocalized state in valence band discrete and the state in the gap more localized. Consequently, the phase-breaking frequency and intensity can reduce the stability of a polaron. Furthermore, the phase-breaking in organic systems is the main factor that degrades the coherent transport and destroys the carrier stability.« less

Numerical simulation of evaluation of surface breaking cracks by array-lasers generated narrow-band SAW

NASA Astrophysics Data System (ADS)

Dong, Li-Ming; Ni, Chen-Yin; Shen, Zhong-Hua; Ni, Xiao-Wu

2011-09-01

Most of the factors limiting the extensive application of laser-based ultrasonic for nondestructive evaluation of surface breaking crack are its poor sensitivity, low efficiency relative to conventional contact ultrasonic methods and limit on the dimension of the cracks. For this reason, a new technique that multiplepulse narrow-band ultrasound generated by laser arrays has been proposed. It is found that crack detection dependent on spectrum of narrow-band ultrasound generated by laser arrays can be operated with low amplitude requirements. In this paper, the narrow-band ultrasound generated by pulse laser arrays interacting with surface breaking cracks has been simulated in detail by the finite element method (FEM) according to the thermoelastic theory. The pulsed array lasers were assumed to be transient heat source, and the surface acoustic wave (SAW) which propagating on the top of the plate was computed based on thermoelastic theory. Then the frequency spectrums of both reflected waves by crack and transmission ones through crack were compared with the direct waves. Results demonstrate that multiple-frequency components of the narrow-band ultrasound were varied with change of the depth of surface breaking cracks significantly, which provides the possibility for precise evaluation of surface breaking cracks.

Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

NASA Technical Reports Server (NTRS)

Steffes, Paul G.

1989-01-01

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. Work performed has shown that laboratory measurements of the millimeter-wave opacity of ammonia between 7.5 mm and 9.3 mm and also at the 3.2 mm wavelength require a different lineshape to be used in the theoretical prediction for millimeter-wave ammonia opacity than was previously used. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

Short-Term TEC Perturbations Associated With Planetary Waves Occurrence in the Ionosphere

NASA Astrophysics Data System (ADS)

Shagimuratov, I. I.; Karpov, I.; Krankowski, A.

2008-12-01

Analysis of TEC response to storm showed short-term perturbations which were observed after initial phase of geomagnetic storms. The perturbations demonstrated very well expressed latitudinal structure and were recognized on diurnal variations as surges of TEC enhancement of TEC. Ordinary such storm-time positive effect was associated with TAD. Duration of the perturbations was about 2-4 hours and their amplitude increased toward low latitudes. Such TEC perturbations have the longitudinal dependence. It is important that time location of surges have week dependence on latitude. The observed structure appeared to arrive from high latitudes, but at middle latitudes it was represented as a standing wave. It is assumed that such TEC perturbations can be produced due to superposition of the eastward and westward propagating planetary Poincare waves. The periods of these waves are usually several hours. Poincare waves can be excited at the atmosphere in storm time. At middle latitudes their superposition is as standing wave that forms observing TEC perturbations. In the report, the possibilities of application Poincare waves to the ionosphere dynamics studies are discussed and an explanation of the observed ionospheric effects is given.

Stationary Planetary Waves in the Mars Winter Atmosphere as seen by the Radio Science Experiment MaRS on Mars Express

NASA Astrophysics Data System (ADS)

Tellmann, Silvia; Pätzold, Martin; Häusler, Bernd; Tyler, Leonard G.; Hinson, David P.

2015-11-01

Stationary (Rossby) Waves are excited by the interaction of the zonally varying topography with the strong eastward winter jets. They lead to distinctive longitudinal temperature variations which contribute significantly to the asymmetry of the seasonal polar CO2 ice caps and are also important for the dust redistribution in the planetary atmosphere.Radio Science profiles from the Mars Express Radio Science Experiment MaRS at northern and southern high latitudes are used to gain insight into winter stationary wave structures on both hemispheres.Mars Global Surveyor (MGS) radio occultation measurements from the same season and year with their exceptionally good longitudinal and temporal coverage can be used to estimate the influence of transient eddies. Transient waves are especially important in the northern winter hemisphere.Wave number 2 stationary waves, driven by topography, are dominant in the northern winter latitudes while the wave number 1 wave is the most significant wave number during southern winter. The wave amplitudes peak around winter solstice on both hemispheres.Radio occultation measurements provide the unique opportunity to determine simultaneous measurements of temperature and geopotential height structures. Assuming geostrophic balance, these measurements can be used to determine meridional winds and eddy heat fluxes which provide further insight into the contribution of stationary waves to the heat exchange between the poles and the lower latitudes.

Planetary plasma waves

NASA Technical Reports Server (NTRS)

Gurnett, Donald A.

1993-01-01

The primary types of plasma waves observed in the vicinity of the planets Venus, Mars, Earth, Jupiter, Saturn, Uranus, and Neptune are described. The observations are organized according to the various types of plasma waves observed, ordered according to decreasing distance from the planet, starting from the sunward side of the planet, and ending in the region near the closest approach. The plasma waves observed include: electron plasma oscillations and ion acoustic waves; trapped continuum radiation; electron cyclotron and upper hybrid waves; whistler-mode emissions; electrostatic ion cyclotron waves; and electromagnetic ion cyclotron waves.

Supercontinuum generation in silicon waveguides relying on wave-breaking.

PubMed

Castelló-Lurbe, David; Silvestre, Enrique

2015-10-05

Four-wave-mixing processes enabled during optical wave-breaking (OWB) are exploited in this paper for supercontinuum generation. Unlike conventional approaches based on OWB, phase-matching is achieved here for these nonlinear interactions, and, consequently, new frequency production becomes more efficient. We take advantage of this kind of pulse propagation to obtain numerically a coherent octave-spanning mid-infrared supercontinuum generation in a silicon waveguide pumping at telecom wavelengths in the normal dispersion regime. This scheme shows a feasible path to overcome limits imposed by two-photon absorption on spectral broadening in silicon waveguides.

Acoustic nonreciprocity in Coriolis mean flow systems.

PubMed

Naghdi, Masoud; Farzbod, Farhad

2018-01-01

One way to break acoustic reciprocity is to have a moving wave propagation medium. If the acoustic wave vector and the moving fluid velocity are collinear, the wave vector shift caused by the fluid flow can be used to break. In this paper, an alternative approach is investigated in which the fluid velocity enters the differential equation of the system as a cross product term with the wave vector. A circular field where the fluid velocity increases radially has a Coriolis acceleration term. In such a system, the acoustic wave enters from the central wall and exits from the perimeter wall. In this paper, the differential equation is solved numerically and the effect of fluid velocity on the nonreciprocity factor is examined.

Self-organization of large-scale ULF electromagnetic wave structures in their interaction with nonuniform zonal winds in the ionospheric E region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aburjania, G. D.; Chargazia, Kh. Z.

A study is made of the generation and subsequent linear and nonlinear evolution of ultralow-frequency planetary electromagnetic waves in the E region of a dissipative ionosphere in the presence of a nonuniform zonal wind (a sheared flow). Hall currents flowing in the E region and such permanent global factors as the spatial nonuniformity of the geomagnetic field and of the normal component of the Earth's angular velocity give rise to fast and slow planetary-scale electromagnetic waves. The efficiency of the linear amplification of planetary electromagnetic waves in their interaction with a nonuniform zonal wind is analyzed. When there are shearedmore » flows, the operators of linear problems are non-self-conjugate and the corresponding eigenfunctions are nonorthogonal, so the canonical modal approach is poorly suited for studying such motions and it is necessary to utilize the so-called nonmodal mathematical analysis. It is shown that, in the linear evolutionary stage, planetary electromagnetic waves efficiently extract energy from the sheared flow, thereby substantially increasing their amplitude and, accordingly, energy. The criterion for instability of a sheared flow in an ionospheric medium is derived. As the shear instability develops and the perturbation amplitude grows, a nonlinear self-localization mechanism comes into play and the process ends with the self-organization of nonlinear, highly localized, solitary vortex structures. The system thus acquires a new degree of freedom, thereby providing a new way for the perturbation to evolve in a medium with a sheared flow. Depending on the shape of the sheared flow velocity profile, nonlinear structures can be either purely monopole vortices or vortex streets against the background of the zonal wind. The accumulation of such vortices can lead to a strongly turbulent state in an ionospheric medium.« less

Infragravity wave generation and dynamics over a mild slope beach : Experiments and numerical computations

NASA Astrophysics Data System (ADS)

Cienfuegos, R.; Duarte, L.; Hernandez, E.

2008-12-01

Charasteristic frequencies of gravity waves generated by wind and propagating towards the coast are usually comprised between 0.05Hz and 1Hz. Nevertheless, lower frequecy waves, in the range of 0.001Hz and 0.05Hz, have been observed in the nearshore zone. Those long waves, termed as infragravity waves, are generated by complex nonlinear mechanisms affecting the propagation of irregular waves up to the coast. The groupiness of an incident random wave field may be responsible for producing a slow modulation of the mean water surface thus generating bound long waves travelling at the group speed. Similarly, a quasi- periodic oscillation of the break-point location, will be accompained by a slow modulation of set-up/set-down in the surf zone and generation and release of long waves. If the primary structure of the carrying incident gravity waves is destroyed (e.g. by breaking), forced long waves can be freely released and even reflected at the coast. Infragravity waves can affect port operation through resonating conditions, or strongly affect sediment transport and beach morphodynamics. In the present study we investigate infragravity wave generation mechanisms both, from experiments and numerical computations. Measurements were conducted at the 70-meter long wave tank, located at the Instituto Nacional de Hidraulica (Chile), prepared with a beach of very mild slope of 1/80 in order to produce large surf zone extensions. A random JONSWAP type wave field (h0=0.52m, fp=0.25Hz, Hmo=0.17m) was generated by a piston wave-maker and measurements of the free surface displacements were performed all over its length at high spatial resolution (0.2m to 1m). Velocity profiles were also measured at four verticals inside the surf zone using an ADV. Correlation maps of wave group envelopes and infragravity waves are computed in order to identify long wave generation and dynamics in the experimental set-up. It appears that both mechanisms (groupiness and break-point oscillation) are clearly present in this experiment while spectral analysis evidences the reorganization of energy density from the original narrow spectrum into the infragravity band. This experiment provides an opportunity to test numerical models that would in principle be able to reproduce infragravity wave generation and dynamics. We compare numerical results (free surface and velocities) produced by a fully nonlinear Boussinesq model including breaking and runup to the experimental data and show that the complex infragravity wave dynamics is adequately reproduced by the model.

Impact of northern Eurasian snow cover in autumn on the warm Arctic-cold Eurasia pattern during the following January and its linkage to stationary planetary waves

NASA Astrophysics Data System (ADS)

Xu, Xinping; He, Shengping; Li, Fei; Wang, Huijun

2018-03-01

The connection between Eurasian snow cover (SC) in autumn and Eurasian winter mean surface air temperature (SAT) has been identified by many studies. However, some recent observations indicate that early and late winter climate sometimes shows an out-of-phase relationship, suggesting that the winter mean situation might obscure the important relationships that are relevant for scientific research and applications. This study investigates the relationship between October northern Eurasian SC (NESC; 58°-68°N, 30°-90°E) and Eurasian SAT during the winter months and finds a significant relationship only exists in January. Generally, following reduced October NESC, the East Asian trough and Ural high are intensified in January, and anomalous northeasterly winds prevail in mid-latitudes, causing cold anomalies over Eurasia. Meanwhile, anomalous southwesterly winds along the northern fringe of the Ural high favor warm anomalies in the Arctic. The dynamical mechanism for the connection between NESC in October and the warm Arctic-cold Eurasia (WACE) anomaly in January is further investigated from the perspective of quasi-stationary planetary wave activity. It is found that planetary waves with zonal wavenumber-1 (ZWN1) play a dominant role in this process. Specifically, the ZWN1 pattern of planetary-scale waves concurrent with October NESC anomaly extends from the surface to the upper-stratosphere. It persists in the stratosphere through November-December and propagates downward to the surface by the following January, making the connection between October NESC and January climate possible. Additionally, the influence of October NESC on the January WACE pattern has intensified since the early-2000s.

Coherent Backscattering by Particulate Planetary Media of Nonspherical Particles

NASA Astrophysics Data System (ADS)

Muinonen, Karri; Penttila, Antti; Wilkman, Olli; Videen, Gorden

2014-11-01

The so-called radiative-transfer coherent-backscattering method (RT-CB) has been put forward as a practical Monte Carlo method to compute multiple scattering in discrete random media mimicking planetary regoliths (K. Muinonen, Waves in Random Media 14, p. 365, 2004). In RT-CB, the interaction between the discrete scatterers takes place in the far-field approximation and the wave propagation faces exponential extinction. There is a significant constraint in the RT-CB method: it has to be assumed that the form of the scattering matrix is that of the spherical particle. We aim to extend the RT-CB method to nonspherical single particles showing significant depolarization characteristics. First, ensemble-averaged single-scattering albedos and phase matrices of nonspherical particles are matched using a phenomenological radiative-transfer model within a microscopic volume element. Second, the phenomenologial single-particle model is incorporated into the Monte Carlo RT-CB method. In the ray tracing, the electromagnetic phases within the microscopic volume elements are omitted as having negligible lengths, whereas the phases are duly accounted for in the paths between two or more microscopic volume elements. We assess the computational feasibility of the extended RT-CB method and show preliminary results for particulate media mimicking planetary regoliths. The present work can be utilized in the interpretation of astronomical observations of asteroids and other planetary objects. In particular, the work sheds light on the depolarization characteristics of planetary regoliths at small phase angles near opposition. The research has been partially funded by the ERC Advanced Grant No 320773 entitled “Scattering and Absorption of Electromagnetic Waves in Particulate Media” (SAEMPL), by the Academy of Finland (contract 257966), NASA Outer Planets Research Program (contract NNX10AP93G), and NASA Lunar Advanced Science and Exploration Research Program (contract NNX11AB25G).

Forcing a three-dimensional, hydrostatic, primitive-equation model for application in the surf zone: 2. Application to DUCK94

NASA Astrophysics Data System (ADS)

Newberger, P. A.; Allen, J. S.

2007-08-01

A three-dimensional primitive-equation model for application to the nearshore surf zone has been developed. This model, an extension of the Princeton Ocean Model (POM), predicts the wave-averaged circulation forced by breaking waves. All of the features of the original POM are retained in the extended model so that applications can be made to regions where breaking waves, stratification, rotation, and wind stress make significant contributions to the flow behavior. In this study we examine the effects of breaking waves and wind stress. The nearshore POM circulation model is embedded within the NearCom community model and is coupled with a wave model. This combined modeling system is applied to the nearshore surf zone off Duck, North Carolina, during the DUCK94 field experiment of October 1994. Model results are compared to observations from this experiment, and the effects of parameter choices are examined. A process study examining the effects of tidal depth variation on depth-dependent wave-averaged currents is carried out. With identical offshore wave conditions and model parameters, the strength and spatial structure of the undertow and of the alongshore current vary systematically with water depth. Some three-dimensional solutions show the development of shear instabilities of the alongshore current. Inclusion of wave-current interactions makes an appreciable difference in the characteristics of the instability.

Symmetry Breaking of Counter-Propagating Light in a Nonlinear Resonator.

PubMed

Del Bino, Leonardo; Silver, Jonathan M; Stebbings, Sarah L; Del'Haye, Pascal

2017-02-21

Spontaneous symmetry breaking is a concept of fundamental importance in many areas of physics, underpinning such diverse phenomena as ferromagnetism, superconductivity, superfluidity and the Higgs mechanism. Here we demonstrate nonreciprocity and spontaneous symmetry breaking between counter-propagating light in dielectric microresonators. The symmetry breaking corresponds to a resonance frequency splitting that allows only one of two counter-propagating (but otherwise identical) states of light to circulate in the resonator. Equivalently, this effect can be seen as the collapse of standing waves and transition to travelling waves within the resonator. We present theoretical calculations to show that the symmetry breaking is induced by Kerr-nonlinearity-mediated interaction between the counter-propagating light. Our findings pave the way for a variety of applications including optically controllable circulators and isolators, all-optical switching, nonlinear-enhanced rotation sensing, optical flip-flops for photonic memories as well as exceptionally sensitive power and refractive index sensors.

Symmetry Breaking of Counter-Propagating Light in a Nonlinear Resonator

PubMed Central

Del Bino, Leonardo; Silver, Jonathan M.; Stebbings, Sarah L.; Del'Haye, Pascal

2017-01-01

Spontaneous symmetry breaking is a concept of fundamental importance in many areas of physics, underpinning such diverse phenomena as ferromagnetism, superconductivity, superfluidity and the Higgs mechanism. Here we demonstrate nonreciprocity and spontaneous symmetry breaking between counter-propagating light in dielectric microresonators. The symmetry breaking corresponds to a resonance frequency splitting that allows only one of two counter-propagating (but otherwise identical) states of light to circulate in the resonator. Equivalently, this effect can be seen as the collapse of standing waves and transition to travelling waves within the resonator. We present theoretical calculations to show that the symmetry breaking is induced by Kerr-nonlinearity-mediated interaction between the counter-propagating light. Our findings pave the way for a variety of applications including optically controllable circulators and isolators, all-optical switching, nonlinear-enhanced rotation sensing, optical flip-flops for photonic memories as well as exceptionally sensitive power and refractive index sensors. PMID:28220865

New challenges of the ARISE project

NASA Astrophysics Data System (ADS)

Blanc, Elisabeth

2015-04-01

It has been robustly demonstrated that variations in the circulation of the middle atmosphere influence weather and climate throughout the troposphere all the way to the Earth's surface. A key part of the coupling between the troposphere and stratosphere occurs through the propagation and breaking of planetary-scale Rossby waves and gravity waves. Limited observation of the middle atmosphere and these waves in particular limits the ability to faithfully reproduce the dynamics of the middle atmosphere in numerical weather prediction and climate models. The ARISE project combines for the first time international networks with complementary technologies such as infrasound, lidar and airglow. This joint network provided advanced data products that started to be used as benchmarks for weather forecast models. The ARISE network also allows enhanced and detailed monitoring of other extreme events in the Earth system such as erupting volcanoes, magnetic storms, tornadoes and tropical thunderstorms. In order to improve the ability of the network to monitor atmospheric dynamics, ARISE proposes to extend i) the existing network coverage in Africa and the high latitudes, ii) the altitude range in the stratosphere and mesosphere, iii) the observation duration using routine observation modes, and to use complementary existing infrastructures and innovative instrumentations. Data will be collected over the long term to improve weather forecasting to monthly or seasonal timescales, to monitor atmospheric extreme events and climate change. ARISE focuses on the link between models and observations for future assimilation of data by operational weather forecasting models. Among the applications, ARISE2 proposes infrasound remote volcano monitoring to provide notifications to civil aviation.

The Newton constant and gravitational waves in some vector field adjusting mechanisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santillán, Osvaldo P.; Scornavacche, Marina, E-mail: firenzecita@hotmail.com, E-mail: marina.scorna@hotmail.com

At the present, there exist some Lorentz breaking scenarios which explain the smallness of the cosmological constant at the present era [1]–[2]. An important aspect to analyze is the propagation of gravitational waves and the screening or enhancement of the Newton constant G {sub N} in these models. The problem is that the Lorentz symmetry breaking terms may induce an unacceptable value of the Newton constant G {sub N} or introduce longitudinal modes in the gravitational wave propagation. Furthermore this breaking may spoil the standard dispersion relation ω= ck . In [3] the authors have presented a model suggesting thatmore » the behavior of the gravitational constant is correct for asymptotic times. In the present work, an explicit checking is made and we finally agree with these claims. Furthermore, it is suggested that the gravitational waves are also well behaved for large times. In the process, some new models with the same behavior are obtained, thus enlarging the list of possible adjustment mechanisms.« less

The formation and fate of internal waves in the South China Sea

NASA Astrophysics Data System (ADS)

Alford, Matthew H.; Peacock, Thomas; MacKinnon, Jennifer A.; Nash, Jonathan D.; Buijsman, Maarten C.; Centuroni, Luca R.; Chao, Shenn-Yu; Chang, Ming-Huei; Farmer, David M.; Fringer, Oliver B.; Fu, Ke-Hsien; Gallacher, Patrick C.; Graber, Hans C.; Helfrich, Karl R.; Jachec, Steven M.; Jackson, Christopher R.; Klymak, Jody M.; Ko, Dong S.; Jan, Sen; Johnston, T. M. Shaun; Legg, Sonya; Lee, I.-Huan; Lien, Ren-Chieh; Mercier, Matthieu J.; Moum, James N.; Musgrave, Ruth; Park, Jae-Hun; Pickering, Andrew I.; Pinkel, Robert; Rainville, Luc; Ramp, Steven R.; Rudnick, Daniel L.; Sarkar, Sutanu; Scotti, Alberto; Simmons, Harper L.; St Laurent, Louis C.; Venayagamoorthy, Subhas K.; Wang, Yu-Huai; Wang, Joe; Yang, Yiing J.; Paluszkiewicz, Theresa; (David) Tang, Tswen-Yung

2015-05-01

Internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. Because of their strong vertical and horizontal currents, and the turbulent mixing caused by their breaking, they affect a panoply of ocean processes, such as the supply of nutrients for photosynthesis, sediment and pollutant transport and acoustic transmission; they also pose hazards for man-made structures in the ocean. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking, making it challenging to observe them and to include them in numerical climate models, which are sensitive to their effects. For over a decade, studies have targeted the South China Sea, where the oceans' most powerful known internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their mechanism of generation, variability and energy budget, however, owing to the lack of in situ data from the Luzon Strait, where extreme flow conditions make measurements difficult. Here we use new observations and numerical models to (1) show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, (2) reveal the existence of >200-metre-high breaking internal waves in the region of generation that give rise to turbulence levels >10,000 times that in the open ocean, (3) determine that the Kuroshio western boundary current noticeably refracts the internal wave field emanating from the Luzon Strait, and (4) demonstrate a factor-of-two agreement between modelled and observed energy fluxes, which allows us to produce an observationally supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions.

The formation and fate of internal waves in the South China Sea.

PubMed

Alford, Matthew H; Peacock, Thomas; MacKinnon, Jennifer A; Nash, Jonathan D; Buijsman, Maarten C; Centurioni, Luca R; Centuroni, Luca R; Chao, Shenn-Yu; Chang, Ming-Huei; Farmer, David M; Fringer, Oliver B; Fu, Ke-Hsien; Gallacher, Patrick C; Graber, Hans C; Helfrich, Karl R; Jachec, Steven M; Jackson, Christopher R; Klymak, Jody M; Ko, Dong S; Jan, Sen; Johnston, T M Shaun; Legg, Sonya; Lee, I-Huan; Lien, Ren-Chieh; Mercier, Matthieu J; Moum, James N; Musgrave, Ruth; Park, Jae-Hun; Pickering, Andrew I; Pinkel, Robert; Rainville, Luc; Ramp, Steven R; Rudnick, Daniel L; Sarkar, Sutanu; Scotti, Alberto; Simmons, Harper L; St Laurent, Louis C; Venayagamoorthy, Subhas K; Wang, Yu-Huai; Wang, Joe; Yang, Yiing J; Paluszkiewicz, Theresa; Tang, Tswen-Yung David

2015-05-07

Internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. Because of their strong vertical and horizontal currents, and the turbulent mixing caused by their breaking, they affect a panoply of ocean processes, such as the supply of nutrients for photosynthesis, sediment and pollutant transport and acoustic transmission; they also pose hazards for man-made structures in the ocean. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking, making it challenging to observe them and to include them in numerical climate models, which are sensitive to their effects. For over a decade, studies have targeted the South China Sea, where the oceans' most powerful known internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their mechanism of generation, variability and energy budget, however, owing to the lack of in situ data from the Luzon Strait, where extreme flow conditions make measurements difficult. Here we use new observations and numerical models to (1) show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, (2) reveal the existence of >200-metre-high breaking internal waves in the region of generation that give rise to turbulence levels >10,000 times that in the open ocean, (3) determine that the Kuroshio western boundary current noticeably refracts the internal wave field emanating from the Luzon Strait, and (4) demonstrate a factor-of-two agreement between modelled and observed energy fluxes, which allows us to produce an observationally supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions.

Wave activity (planetary, tidal) throughout the middle atmosphere (20-100km) over the CUJO network: Satellite (TOMS) and Medium Frequency (MF) radar observations

NASA Astrophysics Data System (ADS)

Manson, A. H.; Meek, C. E.; Chshyolkova, T.; Avery, S. K.; Thorsen, D.; MacDougall, J. W.; Hocking, W.; Murayama, Y.; Igarashi, K.

2005-02-01

Planetary and tidal wave activity in the tropopause-lower stratosphere and mesosphere-lower thermosphere (MLT) is studied using combinations of ground-based (GB) and satellite instruments (2000-2002). The relatively new MFR (medium frequency radar) at Platteville (40° N, 105° W) has provided the opportunity to create an operational network of middle-latitude MFRs, stretching from 81° W-142° E, which provides winds and tides 70-100km. CUJO (Canada U.S. Japan Opportunity) comprises systems at London (43° N, 81° W), Platteville (40° N, 105° W), Saskatoon (52° N, 107° W), Wakkanai (45° N, 142° E) and Yamagawa (31° N, 131° E). It offers a significant 7000-km longitudinal sector in the North American-Pacific region, and a useful range of latitudes (12-14°) at two longitudes. Satellite data mainly involve the daily values of the total ozone column measured by the Earth Probe (EP) TOMS (Total Ozone Mapping Spectrometer) and provide a measure of tropopause-lower stratospheric planetary wave activity, as well as ozone variability. Climatologies of ozone and winds/tides involving frequency versus time (wavelet) contour plots for periods from 2-d to 30-d and the interval from mid 2000 to 2002, show that the changes with altitude, longitude and latitude are very significant and distinctive. Geometric-mean wavelets for the region of the 40° N MFRs demonstrate occasions during the autumn, winter and spring months when there are similarities in the spectral features of the lower atmosphere and at mesopause (85km) heights. Both direct planetary wave (PW) propagation into the MLT, nonlinear PW-tide interactions, and disturbances in MLT tides associated with fluctuations in the ozone forcing are considered to be possible coupling processes. The complex horizontal wave numbers of the longer period oscillations are provided in frequency contour plots for the TOMS satellite data to demonstrate the differences between lower atmospheric and MLT wave motions and their directions of propagation.

Numerical modeling of a multiscale gravity wave event and its airglow signatures over Mount Cook, New Zealand, during the DEEPWAVE campaign

NASA Astrophysics Data System (ADS)

Heale, C. J.; Bossert, K.; Snively, J. B.; Fritts, D. C.; Pautet, P.-D.; Taylor, M. J.

2017-01-01

A 2-D nonlinear compressible model is used to simulate a large-amplitude, multiscale mountain wave event over Mount Cook, NZ, observed as part of the Deep Propagating Gravity Wave Experiment (DEEPWAVE) campaign and to investigate its observable signatures in the hydroxyl (OH) layer. The campaign observed the presence of a λx=200 km mountain wave as part of the 22nd research flight with amplitudes of >20 K in the upper stratosphere that decayed rapidly at airglow heights. Advanced Mesospheric Temperature Mapper (AMTM) showed the presence of small-scale (25-28 km) waves within the warm phase of the large mountain wave. The simulation results show rapid breaking above 70 km altitude, with the preferential formation of almost-stationary vortical instabilities within the warm phase front of the mountain wave. An OH airglow model is used to identify the presence of small-scale wave-like structures generated in situ by the breaking of the mountain wave that are consistent with those seen in the observations. While it is easy to interpret these feature as waves in OH airglow data, a considerable fraction of the features are in fact instabilities and vortex structures. Simulations suggest that a combination of a large westward perturbation velocity and shear, in combination with strong perturbation temperature gradients, causes both dynamic and convective instability conditions to be met particularly where the wave wind is maximized and the temperature gradient is simultaneously minimized. This leads to the inevitable breaking and subsequent generation of smaller-scale waves and instabilities which appear most prominent within the warm phase front of the mountain wave.

Breaking phase focused wave group loads on offshore wind turbine monopiles

NASA Astrophysics Data System (ADS)

Ghadirian, A.; Bredmose, H.; Dixen, M.

2016-09-01

The current method for calculating extreme wave loads on offshore wind turbine structures is based on engineering models for non-breaking regular waves. The present article has the aim of validating previously developed models at DTU, namely the OceanWave3D potential flow wave model and a coupled OceanWave3D-OpenFOAM solver, against measurements of focused wave group impacts on a monopile. The focused 2D and 3D wave groups are reproduced and the free surface elevation and the in-line forces are compared to the experimental results. In addition, the pressure distribution on the monopile is examined at the time of maximum force and discussed in terms of shape and magnitude. Relative pressure time series are also compared between the simulations and experiments and detailed pressure fields for a 2D and 3D impact are discussed in terms of impact type. In general a good match for free surface elevation, in-line force and wave-induced pressures is found.

Synoptic Formation of Double Tropopauses

NASA Astrophysics Data System (ADS)

Liu, Chengji; Barnes, Elizabeth

2018-01-01

Double tropopauses are ubiquitous in the midlatitude winter hemisphere and represent the vertical stacking of two stable tropopause layers separated by a less stable layer. By analyzing COSMIC GPS data, reanalysis, and eddy life cycle simulations, we demonstrate that they often occur during Rossby wave breaking and act to increase the stratosphere-to-troposphere exchange of mass. We further investigate the adiabatic formation of double tropopauses and propose two mechanisms by which they can occur. The first mechanism operates at the tropopause break in the subtropics where the higher tropical tropopause sits on one side of the break and the lower extratropical tropopause sits on the other. The double tropopauses are then formed by differential meridional advection of the higher and lower tropopauses on the two sides of the tropopause break. We show that anticyclonic wave breaking can form double tropopauses mainly by providing stronger poleward advection of the higher tropopause in its poleward lobe. Cyclonic wave breaking mainly forms double tropopauses by providing stronger equatorward advection of the lower tropopause in its equatorward lobe. We demonstrate in the COSMIC GPS data and reanalysis that about half of the double tropopauses in the Northern Hemisphere winter can be directly attributed to such differential advection. For the second mechanism, adiabatic destabilization of the air above the tropopause contributes to the formation of a double tropopause. In this case, a tropopause inversion layer is necessary for this destabilization to result in a double tropopause.

A Microscopic View of Oil Slick Break-Up and Emulsion Formation in Breaking Waves

NASA Astrophysics Data System (ADS)

Law, J.; Shahrokhi, H.; Shaw, J. M.

1996-11-01

The hydrodynamic behaviour of oil spills in breaking waves determines the appropriateness and effectiveness of remedial measures during clean-up operations. Oil slicks either disperse as fine drops or form water in oil emulsions when exposed to breaking waves. However, there is little agreement with respect to the controlling variables or mechanisms for emulsification or dispersion and predictions are unreliable. For example, predicted energy dissipation rates in breaking waves are too low to account for the drop sizes encountered experimentally[1]. In this paper, we assess the impact of hydrodynamics and physical properties on the formation of dispersions or emulsions. The maximum stable drop size for dispersions arising from oil slicks and water in oil emulsions are shown to be controlled by Raleigh-Taylor instability or the prevalent local shear stress. Data from four experimental studies[2-5], with a broad range of physical properties were fitted quantitatively. As high shear events are intermittent, stable water in oil emulsions can be formed by dispersion inversion near the water air interface or by water entrained by gas bubbles passing through oil slicks. 1) Li & Garrett, 19th AMOP, Calgary AB, 1, 185-198 (1996). 2) Lin et al., Report CG-D-54-78, U.S. Coast Guard, Washington D.C. (1978). 3) Buist, MASc Thesis, University of Toronto (1979). 4) Wallace et al., 9th AMOP, Edmonton AB, 2, 421-429, June 10-12 (1986). 5) Ross Environmental Research Ltd., Ottawa ON, Report EE-96, (1987).

Detecting Lorentz Violations with Gravitational Waves From Black Hole Binaries

NASA Astrophysics Data System (ADS)

Sotiriou, Thomas P.

2018-01-01

Gravitational wave observations have been used to test Lorentz symmetry by looking for dispersive effects that are caused by higher order corrections to the dispersion relation. In this Letter I argue on general grounds that, when such corrections are present, there will also be a scalar excitation. Hence, a smoking-gun observation of Lorentz symmetry breaking would be the direct detection of scalar waves that travel at a speed other than the speed of the standard gravitational wave polarizations or the speed of light. Interestingly, in known Lorentz-breaking gravity theories the difference between the speeds of scalar and tensor waves is virtually unconstrained, whereas the difference between the latter and the speed of light is already severely constrained by the coincident detection of gravitational waves and gamma rays from a binary neutron star merger.

Non-Hydrostatic Modelling of Waves and Currents over Subtle Bathymetric Features

NASA Astrophysics Data System (ADS)

Gomes, E.; Mulligan, R. P.; McNinch, J.

2014-12-01

Localized areas with high rates of shoreline erosion on beaches, referred to as erosional hotspots, can occur near clusters of relict shore-oblique sandbars. Wave transformation and wave-driven currents over these morphological features could provide an understanding of the hydrodynamic-morphologic coupling mechanism that connects them to the occurrence of erosional hotspots. To investigate this, we use the non-hydrostatic SWASH model that phase-resolves the free surface and fluid motions throughout the water column, allowing for high resolution of wave propagation and breaking processes. In this study we apply a coupled system of nested models including SWAN over a large domain of the North Carolina shelf with smaller nested SWASH domains in areas of interest to determine the hydrodynamic processes occurring over shore oblique bars. In this presentation we focus on a high resolution grid (10 vertical layers, 10 m horizontal resolution) applied to the Duck region with model validation from acoustic wave and current data, and observations from the Coastal Lidar And Radar Imaging System (CLARIS). By altering the bathymetry input for each model run based on bathymetric surveys and comparing the predicted and observed wave heights and current profiles, the effects of subtle bathymetric perturbations have on wave refraction, wave breaking, surf zone currents and vorticity are investigated. The ability to predict wave breaking and hydrodynamics with a non-hydrostatic model may improve our understanding of surf zone dynamics in relation to morphologic conditions.

Characterizing Droplet Formation from Non-Linear Slosh in a Propellant Tank

NASA Technical Reports Server (NTRS)

Brodnick, Jacob; Yang, Hong; West, Jeffrey

2015-01-01

The Fluid Dynamics Branch (ER42) at the Marshall Space Flight Center (MSFC) was tasked with characterizing the formation and evolution of liquid droplets resulting from nonlinear propellant slosh in a storage tank. Lateral excitation of propellant tanks can produce high amplitude nonlinear slosh waves through large amplitude excitations and or excitation frequencies near a resonance frequency of the tank. The high amplitude slosh waves become breaking waves upon attaining a certain amplitude or encountering a contracting geometry such as the upper dome section of a spherical tank. Inherent perturbations in the thinning regions of breaking waves result in alternating regions of high and low pressure within the fluid. Droplets form once the force from the local pressure differential becomes larger than the force maintaining the fluid interface shape due to surface tension. Droplets released from breaking waves in a pressurized tank may lead to ullage collapse given the appropriate conditions due to the increased liquid surface area and thus heat transfer between the fluids. The goal of this project is to create an engineering model that describes droplet formation as a function of propellant slosh for use in the evaluation of ullage collapse during a sloshing event. The Volume of Fluid (VOF) model in the production level Computational Fluid Dynamics (CFD) code Loci-Stream was used to predict droplet formation from breaking waves with realistic surface tension characteristics. Various excitation frequencies and amplitudes were investigated at multiple fill levels for a single storage tank to create the engineering model of droplet formation from lateral propellant slosh.

Temporal characterization of the wave-breaking flash in a laser plasma accelerator

NASA Astrophysics Data System (ADS)

Miao, Bo; Feder, Linus; Goers, Andrew; Hine, George; Salehi, Fatholah; Wahlstrand, Jared; Woodbury, Daniel; Milchberg, Howard

2017-10-01

Wave-breaking injection of electrons into a relativistic plasma wake generated in near-critical density plasma by sub-terawatt laser pulses generates an intense ( 1 μJ) and ultra-broadband (Δλ 300 nm) radiation flash. In this work we demonstrate the spectral coherence of this radiation and measure its temporal width using single-shot supercontinuum spectral interferometry (SSSI). The measured temporal width is limited by measurement resolution to 50 fs. Spectral coherence is corroborated by PIC simulations which show that the spatial extent of the acceleration trajectory at the trapping region is small compared to the radiation center wavelength. To our knowledge, this is the first temporal and coherence characterization of wave-breaking radiation. This work is supported by the US Department of Energy, the National Science Foundation, and the Air Force Office of Scientific Research.

Sheaths: A Comparison of Magnetospheric, ICME, and Heliospheric Sheaths

NASA Technical Reports Server (NTRS)

Sibeck, D. G.; Richardson, J. D.; Liu, W.

2007-01-01

When a supersonic flow encounters an obstacles, shocks form to divert the flow around the obstacle. The region between the shock and the obstacle is the sheath, where the supersonic flow is compressed, heated, decelerated, and deflected. Supersonic flows, obstacles, and thus sheaths are observed on many scales throughout the Universe. We compare three examples seen in the heliosphere, illustrating the interaction of the solar wind with obstacles of three very different scales lengths. Magnetosheaths form behind planetary bow shocks on scales ranging from tens to 100 planetary radii. ICME sheath form behind shocks driven by solar disturbances on scale lengths of a few to tens of AU. The heliosheath forms behind the termination shock due to the obstacle presented by the interstellar medium on scale lengths of tens to a hundred AU. Despite this range in scales some common features have been observed. Magnetic holes, possibly due to mirror mode waves, have been observed in all three of these sheaths. Plasma depletion layers are observed in planetary and ICME sheaths. Other features observed in some sheaths are wave activity (ion cyclotron, plasma), energetic particles, transmission of Alfven waves/shocks, tangential discontinuities turbulence behind quasi-parallel shocks, standing slow mode waves, and reconnection on the obstacle boundary. We compare these sheath regions, discussing similarities and differences and how these may relate to the scale lengths of these regions.

Numerical experiments with a general circulation model concerning the distribution of ozone in the stratosphere

NASA Technical Reports Server (NTRS)

Kurzeja, R. J.; Haggard, K. V.; Grose, W. L.

1984-01-01

The distribution of ozone below 60 km altitude has been simulated in two experiments employing a nine-layer quasi-geostrophic spectral model and linear parameterization of ozone photochemistry, the first of which included thermal and orographic forcing of the planetary scale waves, while the second omitted it. The first experiment exhibited a high latitude winter ozone buildup which was due to a Brewer-Dodson circulation forced by large amplitude (planetary scale) waves in the winter lower stratosphere. Photochemistry was also found to be important down to lower altitudes (20 km) in the summer stratosphere than had previously been supposed.

Observations of Surfzone Albedo

NASA Astrophysics Data System (ADS)

Sinnett, G.; Feddersen, F.

2014-12-01

The surfzone environment (where waves break) contains several unique and previously unconsidered processes that affect the heat budget. Entering short-wave radiation is a dominant term in both shelf and surfzone heat budgets. In contrast to the shelf, however, depth limited wave breaking in the surfzone generates spray, whitewater and suspended sediments, elevating the surface albedo (ratio of reflected to incident short-wave radiation). Elevated albedo reduces the level of solar short-wave radiation entering the water, potentially resulting in less heating. Additionally, surfzone water quality is often impacted by fecal bacteria contamination. As bacteria mortality is related to short-wave solar radiation, elevated surfzone albedo could reduce pathogen mortality, impacting human health. Albedo in the open ocean has been frequently studied and parameterizations often consider solar zenith angle, wind speed and ocean chlorophyll concentration, producing albedo values typically near 0.06. However, surfzone albedo observations have been extremely sparse, yet show depth limited wave breaking may increase the albedo by nearly a factor of 10 up to 0.5. Here, we present findings from a field study at the Scripps Institution of Oceanography pier to observe the affect of waves on surfzone albedo. Concurrent measurements were taken with a four-way radiometer (to measure both downwelling and upwelling short-wave and long wave radiation) mounted above the surfzone. A co-located GoPro camera was used to relate visual aspects of the surfzone to measured reflectance, and wave height and period were observed with a bottom mounted pressure sensor in 5 m water depth just outside the surfzone. Wind speed and direction were observed on the pier 10 m above the water surface. Here, we will examine the surfzone albedo dependence on surfzone parameters, such as wave height.

Surface wave effects on water temperature in the Baltic Sea: simulations with the coupled NEMO-WAM model

NASA Astrophysics Data System (ADS)

Alari, Victor; Staneva, Joanna; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian; Janssen, Peter

2016-08-01

Coupled circulation (NEMO) and wave model (WAM) system was used to study the effects of surface ocean waves on water temperature distribution and heat exchange at regional scale (the Baltic Sea). Four scenarios—including Stokes-Coriolis force, sea-state dependent energy flux (additional turbulent kinetic energy due to breaking waves), sea-state dependent momentum flux and the combination these forcings—were simulated to test the impact of different terms on simulated temperature distribution. The scenario simulations were compared to a control simulation, which included a constant wave-breaking coefficient, but otherwise was without any wave effects. The results indicate a pronounced effect of waves on surface temperature, on the distribution of vertical temperature and on upwelling's. Overall, when all three wave effects were accounted for, did the estimates of temperature improve compared to control simulation. During the summer, the wave-induced water temperature changes were up to 1 °C. In northern parts of the Baltic Sea, a warming of the surface layer occurs in the wave included simulations in summer months. This in turn reduces the cold bias between simulated and measured data, e.g. the control simulation was too cold compared to measurements. The warming is related to sea-state dependent energy flux. This implies that a spatio-temporally varying wave-breaking coefficient is necessary, because it depends on actual sea state. Wave-induced cooling is mostly observed in near-coastal areas and is the result of intensified upwelling in the scenario, when Stokes-Coriolis forcing is accounted for. Accounting for sea-state dependent momentum flux results in modified heat exchange at the water-air boundary which consequently leads to warming of surface water compared to control simulation.

Theoretical aspects of tidal and planetary wave propagation at thermospheric heights

NASA Technical Reports Server (NTRS)

Volland, H.; Mayr, H. G.

1977-01-01

A simple semiquantitative model is presented which allows analytic solutions of tidal and planetary wave propagation at thermospheric heights. This model is based on perturbation approximation and mode separation. The effects of viscosity and heat conduction are parameterized by Rayleigh friction and Newtonian cooling. Because of this simplicity, one gains a clear physical insight into basic features of atmospheric wave propagation. In particular, we discuss the meridional structures of pressure and horizontal wind (the solutions of Laplace's equation) and their modification due to dissipative effects at thermospheric heights. Furthermore, we solve the equations governing the height structure of the wave modes and arrive at a very simple asymptotic solution valid in the upper part of the thermosphere. That 'system transfer function' of the thermosphere allows one to estimate immediately the reaction of the thermospheric wave mode parameters such as pressure, temperature, and winds to an external heat source of arbitrary temporal and spatial distribution. Finally, the diffusion effects of the minor constituents due to the global wind circulation are discussed, and some results of numerical calculations are presented.

Inertial Wave Turbulence Driven by Elliptical Instability.

PubMed

Le Reun, Thomas; Favier, Benjamin; Barker, Adrian J; Le Bars, Michael

2017-07-21

The combination of elliptical deformation of streamlines and vorticity can lead to the destabilization of any rotating flow via the elliptical instability. Such a mechanism has been invoked as a possible source of turbulence in planetary cores subject to tidal deformations. The saturation of the elliptical instability has been shown to generate turbulence composed of nonlinearly interacting waves and strong columnar vortices with varying respective amplitudes, depending on the control parameters and geometry. In this Letter, we present a suite of numerical simulations to investigate the saturation and the transition from vortex-dominated to wave-dominated regimes. This is achieved by simulating the growth and saturation of the elliptical instability in an idealized triply periodic domain, adding a frictional damping to the geostrophic component only, to mimic its interaction with boundaries. We reproduce several experimental observations within one idealized local model and complement them by reaching more extreme flow parameters. In particular, a wave-dominated regime that exhibits many signatures of inertial wave turbulence is characterized for the first time. This regime is expected in planetary interiors.

Inertial Wave Turbulence Driven by Elliptical Instability

NASA Astrophysics Data System (ADS)

Le Reun, Thomas; Favier, Benjamin; Barker, Adrian J.; Le Bars, Michael

2017-07-01

The combination of elliptical deformation of streamlines and vorticity can lead to the destabilization of any rotating flow via the elliptical instability. Such a mechanism has been invoked as a possible source of turbulence in planetary cores subject to tidal deformations. The saturation of the elliptical instability has been shown to generate turbulence composed of nonlinearly interacting waves and strong columnar vortices with varying respective amplitudes, depending on the control parameters and geometry. In this Letter, we present a suite of numerical simulations to investigate the saturation and the transition from vortex-dominated to wave-dominated regimes. This is achieved by simulating the growth and saturation of the elliptical instability in an idealized triply periodic domain, adding a frictional damping to the geostrophic component only, to mimic its interaction with boundaries. We reproduce several experimental observations within one idealized local model and complement them by reaching more extreme flow parameters. In particular, a wave-dominated regime that exhibits many signatures of inertial wave turbulence is characterized for the first time. This regime is expected in planetary interiors.

Magnetohydrodynamic and gasdynamic theories for planetary bow waves

NASA Technical Reports Server (NTRS)

Spreiter, John R.; Stahara, Stephen S.

1985-01-01

A bow wave was previously observed in the solar wind upstream of each of the first six planets. The observed properties of these bow waves and the associated plasma flows are outlined, and those features identified that can be described by a continuum magnetohydrodynamic flow theory. An account of the fundamental concepts and current status of the magnetohydrodynamic and gas dynamic theories for solar wind flow past planetary bodies is provided. This includes a critical examination of: (1) the fundamental assumptions of the theories; (2) the various simplifying approximations introduced to obtain tractable mathematical problems; (3) the limitations they impose on the results; and (4) the relationship between the results of the simpler gas dynamic-frozen field theory and the more accurate but less completely worked out magnetohydrodynamic theory. Representative results of the various theories are presented and compared.

Planetary wave-mean flow interaction in the stratosphere: A comparison between the Northern and Southern Hemispheres

NASA Technical Reports Server (NTRS)

Shiotani, M.; Hirota, I.

1985-01-01

Based on satellite-derived data supplied by the National Meteorological Center (NMC), the dynamical interaction between planetary waves and mean zonal winds in the stratosphere is investigated. Special attention is paid to the differences between the Northern Hemisphere (NH) and the Southern Hemisphere (SH). An analysis is made using Eliassen-Palm (E-P) flux diagnostics for the period from June 1981 to May 1982. In a climatological sense, different seasonal evolutions of large-scale motions between the NH and the SH in the stratosphere are demonstrated. Vertical cross-section analysis is presented to show the day-to-day variation in the mean zonal wind and wave activity, in particular, the following phenomena: (1) the poleward shifting of the westerly jet, and (2) episodes after the shifting of the westerly jet.

Magnetohydrodynamic and gasdynamic theories for planetary bow waves

NASA Technical Reports Server (NTRS)

Spreiter, J. R.; Stahara, S. S.

1983-01-01

A bow wave was previously observed in the solar wind upstream of each of the first six planets. The observed properties of these bow waves and the associated plasma flows are outlined, and those features identified that can be described by a continuum magnetohydrodynamic flow theory. An account of the fundamental concepts and current status of the magnetohydrodynamic and gas dynamic theories for solar wind flow past planetary bodies is provided. This includes a critical examination of: (1) the fundamental assumptions of the theories; (2) the various simplifying approximations introduced to obtain tractable mathematical problems; (3) the limitations they impose on the results; and (4) the relationship between the results of the simpler gas dynamic-frozen field theory and the more accurate but less completely worked out magnetohydrodynamic theory. Representative results of the various theories are presented and compared.

Winds and Waves (4 Min - 11 Yrs) in the Upper Middle Atmosphere (60-110 Km) at Saskatoon, Canada (52 Deg N, 107 Deg W): MF Radar (2.2 Mhz) Soundings 1973 - 1983

NASA Technical Reports Server (NTRS)

Manson, A. H.; Meek, C. E.; Gregory, J. B.

1984-01-01

Examples of gravity waves (GW), tides, planetary waves (PW), and circulation effects in the upper middle atmosphere are presented. Energy densities of GW, tides, and PW are compared. Fourier and spectral analyses are applied to the data.

Observations of Equatorial Kelvin Waves and their Convective Coupling with the Atmosphere/Ocean Surface Layer

NASA Astrophysics Data System (ADS)

Conry, Patrick; Fernando, H. J. S.; Leo, Laura; Blomquist, Byron; Amelie, Vincent; Lalande, Nelson; Creegan, Ed; Hocut, Chris; MacCall, Ben; Wang, Yansen; Jinadasa, S. U. P.; Wang, Chien; Yeo, Lik-Khian

2016-11-01

Intraseasonal disturbances with their genesis in the equatorial Indian Ocean (IO) are an important component of global climate. The disturbances, which include Madden-Julian Oscillation and equatorial Kelvin and Rossby waves in the atmosphere and ocean, carry energy which affects El Niño, cyclogenesis, and monsoons. A recent field experiment in IO (ASIRI-RAWI) observed disturbances at three sites across IO with arrays of instruments probing from surface layer to lower stratosphere. During the field campaign the most pronounced planetary-scale disturbances were Kelvin waves in tropical tropopause layer. In Seychelles, quasi-biweekly westerly wind bursts were documented and linked to the Kelvin waves aloft, which breakdown in the upper troposphere due to internal shear instabilities. Convective coupling between waves' phase in upper troposphere and surface initiates rapid (turbulent) vertical transport and resultant wind bursts at surface. Such phenomena reveal linkages between planetary-scale waves and small-scale turbulence in the surface layer that can affect air-sea property exchanges and should be parameterized in atmosphere-ocean general circulation models. Funded by ONR Grants N00014-14-1-0279 and N00014-13-1-0199.

Imaging across the interface of small-scale breaking waves

NASA Astrophysics Data System (ADS)

Techet, Alexandra H.; Belden, Jesse L.

2007-11-01

Flow characteristics on both the air and water side of small scale spilling and plunging waves are investigated using fully time-resolved particle image velocimetry (PIV). PIV at 1000 frames per second (fps) is used to capture the flow field in both the air and water for waves generated by shoaling. Reynolds number of the waves is on the order of Re = 9x10^4 to 2x10^6, where Re = ρ√g 3̂μ, ρ is fluid density, μ is fluid dynamic viscosity, g is gravity, and λ is the characteristic wavelength of the breaking wave before breaking. Isopropyl alcohol is mixed with the distilled water in the tank to reduce surface tension and thus achieve plunging breakers on this scale. Flow in the water is seeded using conventional silver-coated hollow glass spheres, whereas the quiescent air side (i.e. no wind) is seeded using micro-air balloons with high stokes drag and thus long settling times. Imaging of both the air and water are performed simultaneously and advanced image processing is performed to determine the water surface location and to avoid surface tracking during PIV processing. Repeatable, coherent vortical structures are revealed on the air-side of the waves and are considered mechanisms for energy transfer across the interface.

Magnetospheric radio and plasma wave research - 1987-1990

NASA Technical Reports Server (NTRS)

Kurth, W. S.

1991-01-01

This review covers research performed in the area of magnetospheric plasma waves and wave-particle interactions as well as magnetospheric radio emissions. The report focuses on the near-completion of the discovery phase of radio and plasma wave phenomena in the planetary magnetospheres with the successful completion of the Voyager 2 encounters of Neptune and Uranus. Consideration is given to the advances made in detailed studies and theoretical investigations of radio and plasma wave phenomena in the terrestrial magnetosphere or in magnetospheric plasmas in general.

Dramatic changes of the thermosphere and ionosphere caused by the quasi-two-day wave forcing

NASA Astrophysics Data System (ADS)

Yue, J.; Wang, W.

2013-12-01

Traveling planetary waves, such as the quasi-two-day wave (QTDW), are one essential element of the mesosphere and lower thermosphere dynamics. These planetary waves have been observed to cause strong ionospheric day-to-day variations. However, the mechanisms of this effect either by penetrating directly into the thermosphere or by perturbing the dynamo electrodynamics have not been determined. We employ the NCAR TIME-GCM to simulate the interaction between traveling planetary waves and mean wind or tides, and the impact of this interaction on the ionospheric E-region dynamo, F-region plasma density, thermospheric density and O/N2. In particular, as shown in Figure 1, the TEC decreases by 20-30% during a strong QTDW event in the lower thermosphere from the TIME-GCM output. We find a simultaneously 20-30% decrease of O/N2 in the F2 peak in Figure 2. Therefore, the changes of the thermosphere general circulation, neutral temperature and eddy diffusivity are investigated to account for the O/N2 decrease. Because the QTDW dissipates in the lower thermosphere and drive the mean wind westward, the general circulation patterns are altered and the upwelling is enhanced. On the other hand, the QTDW interacts strongly with tides in the mesosphere and lower thermosphere, consequently changing the wind dynamo in the E-region. The effects of these interactions on the changes of the thermosphere and ionosphere will be reported. Decrease of TEC by the QTDW forcing Change of O/N2 by the QTDW forcing

Investigation of Surface Waves in Deep and Shallow Water using Coherent Radars at Grazing Incidence

NASA Astrophysics Data System (ADS)

Buckley, M.; Horstmann, J.; Carrasco, R.; Seemann, J.; Stresser, M.

2016-02-01

Coherent microwave radars operating at X-band near grazing incidence are utilized to measure the backscatter intensity and Doppler velocity from the small-scale surface roughness of the ocean. The radar backscatter is dependent on the wind and strongly modulated by the surface waves and therefore enables to retrieve the surface wind as well as surface waves. The radar measured Doppler velocities are also modulated by contributions from the wind, current and waves and allow getting additional information on these parameters. In addition coherent marine radars allow to observe breaking waves, which lead to a increase in radar backscatter as well as a strong change of the Doppler speed.Within this presentation we will introduce and validate new methods to measure spectral wave properties such as wave directions, periods and significant wave height from coherent marine radars. The methods have been applied in deep and shallow water and validated to measurements of directional wave riders as well as an Acoustic Wave and Current Profiler. These comparisons show an overall excellent performance of coherent radars for the retrieval of spectral wave properties (e.g. Hs rms of 0.2 m). Furthermore, new methodologies will be presented that enable to observe and quantify wave breaking in deep water as well as in the littoral zone. The above mentioned methods have been applied to investigate the influence of Offshore Wind Farms (OWF) on the wave field with respect to the spectral properties as well as the amount of wave breaking. We will present the results obtained during a cruise in May 2015 within and around the OWF Dantysk in the German Bight of the North Sea, which consist of eighty 3.5 MW wind turbines. In addition we will present our initial results on the investigation of wave dissipation in the littoral zone at the coast of the island Sylt using marine radars, pressure gauges as well as directional wave riders.

The Source of Planetary Period Oscillations in Saturn's Magnetosphere

NASA Astrophysics Data System (ADS)

Khurana, Krishan K.; Mitchell, Jonathan L.; Mueller, Ingo C. F.

2017-04-01

In this presentation, we resolve a three-decades old mystery of how Saturn is able to modulate its kilometric wave radiation and many field and plasma parameters at the planetary rotation period even though its magnetic field is extremely axisymmetric. Such waves emanating from the auroral regions of planets lacking solid surfaces have been used as clocks to measure the lengths of their days, because asymmetric internal magnetic fields spin-modulate wave amplitudes. A review by Carbary and Mitchell (2013, Periodicities in Saturn's magnetosphere, Reviews of Geophysics, 51, 1-30) on the topic summarized findings from over 200 research articles, on what the phenomena is, how it is manifested in a host of magnetospheric and auroral parameters; examined several proposed models and pointed out their shortcomings. The topic has now been explored in several topical international workshops, but the problem has remained unsolved so far. By quantitatively modeling the amplitudes and phases of these oscillations in the magnetic field observed by the Cassini spacecraft, we have now uncovered the generation mechanism responsible for these oscillations. We show that the observed oscillations are the manifestations of two global convectional conveyor belts excited in Saturn's upper atmosphere by auroral heating below its northern and southern auroral belts. We demonstrate that a feedback process develops in Saturn system such that the magnetosphere expends energy to drive convection in Saturn's upper stratosphere but gains back an amplified share in the form of angular momentum that it uses to enforce corotation in the magnetosphere and power its aurorae and radio waves. In essence, we have uncovered a new mechanism (convection assisted loss of angular momentum in an atmosphere) by which gaseous planets lose their angular momentum to their magnetospheres and outflowing plasma at rates far above previous predictions. We next show how the m = 1 convection system in the upper atmosphere generates the observed plasma and magnetic field periodicities. This breakthrough in our understanding of an important planetary physics problem has immediate and extensive applications in fields as diverse as theoretical fluid dynamics, planetary angular momentum loss, maintenance of corotation in planetary magnetospheres, astrophysical magneto-braking and future telescopic observations of planets and exoplanets.

Laboratory Studies of Sea-Ice-Wave Interactions

NASA Astrophysics Data System (ADS)

Monty, J.; Meylan, M. H.; Babanin, A. V.; Toffoli, A.; Bennetts, L.

2016-12-01

A world-first facility for studying the Marginal Ice Zone has been constructed in the Michell Hydrodynamics Laboratory at the University of Melbourne. A 14m long wave tank (0.75m wide, 0.6m deep) resides in a freezer, where air temperature can be controlled down to -15C. This permits the freezing of the water surface. Large stainless steel ice-making trays (up to 4 m long) are also available to create ice of desired thickness and microstructure, which can be lowered onto the water surface. A computer controlled wave generator is capable of creating waves of any desired form. The temperature of the water in the tank can also be controlled between 2 and 30C. The tank frame is constructed of marine-treated wood and the entire tank is glass and acrylic, permitting the use of corrosive fluids, such as salt water. Here we present the first laboratory experiments of break-up of a controlled thickness, fresh water ice sheet impacted by regular and JONSWAP spectrum surface waves. The geometry of the resultant ice-floes is measured with high-resolution, time-resolved imaging, providing the crucial data of floe size distribution. Initial observations show that, in the case of high steepness waves, the primary mechanisms of ice break-up at the ice edge are overwash and rafting, both of which put weight on the ice interior to the ice-water interface. This additional weight (and impact in the case of rafting) breaks more ice, which allows overwash and rafting deeper into the ice sheet, breaking more ice and so on. For lower steepness waves, overwash and rafting are still present but far less significant. Finally, results of vertical ice movement using laser height gauges will be presented showing the attenuation of waves into an ice sheet and through a pack of ice floes. These results are compared with field data and theory available (e.g. Squire & Moore, Nature, 1980 and Kohout et al., Nature, 2014).

Laboratory modeling of edge wave generation over a plane beach by breaking waves

NASA Astrophysics Data System (ADS)

Abcha, Nizar; Ezersky, Alexander; Pelinovsky, Efim

2015-04-01

Edge waves play an important role in coastal hydrodynamics: in sediment transport, in formation of coastline structure and coastal bottom topography. Investigation of physical mechanisms leading to the edge waves generation allows us to determine their effect on the characteristics of spatially periodic patterns like crescent submarine bars and cusps observed in the coastal zone. In the present paper we investigate parametric excitation of edge wave with frequency two times less than the frequency of surface wave propagating perpendicular to the beach. Such mechanism of edge wave generation has been studied previously in a large number of papers using the assumption of non-breaking waves. This assumption was used in theoretical calculations and such conditions were created in laboratory experiments. In the natural conditions, the wave breaking is typical when edge waves are generated at sea beach. We study features of such processes in laboratory experiments. Experiments were performed in the wave flume of the Laboratory of Continental and Coast Morphodynamics (M2C), Caen. The flume is equipment with a wave maker controlled by computer. To model a plane beach, a PVC plate is placed at small angle to the horizontal bottom. Several resistive probes were used to measure characteristics of waves: one of them was used to measure free surface displacement near the wave maker and two probes were glued on the inclined plate. These probes allowed us to measure run-up due to parametrically excited edge waves. Run-up height is determined by processing a movie shot by high-speed camera. Sub-harmonic generation of standing edge waves is observed for definite control parameters: edge waves represent themselves a spatial mode with wavelength equal to double width of the flume; the frequency of edge wave is equal to half of surface wave frequency. Appearance of sub-harmonic mode instability is studied using probes and movie processing. The dependence of edge wave exponential growth rate index on the amplitude of surface wave is found. On the plane of parameters (amplitude - frequency) of surface wave we have found a region corresponding parametric instability leading to excitation of edge waves. It is shown that for small super criticalities, the amplitude of edge wave grows with amplitude of surface wave. For large amplitude of surface wave, wave breaking appears and parametric instability is suppressed. Such suppression of instability is caused by increasing of turbulent viscosity in near shore zone. It was shown that parametric excitation of edge wave can increase significantly (up to two times) the maximal run-up. Theoretical model is developed to explain suppression of instability due to turbulent viscosity. This theoretical model is based on nonlinear mode amplitude equation including terms responsible for parametric forcing, frequency detuning, nonlinear detuning, linear and nonlinear edge wave damping. Dependence of coefficients on turbulent viscosity is discussed.

Dynamics of Scroll Wave in a Three-Dimensional System with Changing Gradient.

PubMed

Yuan, Xiao-Ping; Chen, Jiang-Xing; Zhao, Ye-Hua; Liu, Gui-Quan; Ying, He-Ping

2016-01-01

The dynamics of a scroll wave in an excitable medium with gradient excitability is studied in detail. Three parameter regimes can be distinguished by the degree of gradient. For a small gradient, the system reaches a simple rotating synchronization. In this regime, the rigid rotating velocity of spiral waves is maximal in the layers with the highest filament twist. As the excitability gradient increases, the scroll wave evolutes into a meandering synchronous state. This transition is accompanied by a variation in twisting rate. Filament twisting may prevent the breakup of spiral waves in the bottom layers with a low excitability with which a spiral breaks in a 2D medium. When the gradient is large enough, the twisted filament breaks up, which results in a semi-turbulent state where the lower part is turbulent while the upper part contains a scroll wave with a low twisting filament.

Planetary and Gravity Waves in the Mesosphere and Lower Thermosphere

NASA Technical Reports Server (NTRS)

Vincent, R. A.

1985-01-01

Rocket and ground based studies of the mesosphere and lower thermosphere show that waves play an important role in the dynamics of their region. The waves manifest themselves in wind, temperature, density, pressure, ionization and airglow fluctuations in the 80-120 km height range. Rockets have enabled the density and temperature structure to be measured with excellent height resolution, while long term studies of wind motions using MST, partial reflection and meteor radars and, more recently, lidar investigations of temperature and density, have enabled the temporal behaviour of the waves to be better understood. A composite of power spectra is shown of wind motions measured near the mesopause at widely separated locations and illustrates how wave energy is distributed as a function of frequency. The spectra show three distinct parts; (1) a long period section corresponding to periods longer than 24 h; (2) a section between 12 and 24 h priod where the spectra are dominated by narrow; peaks associated with the semidiurnal and diurnal tides and (3) a section at periods less than 12 h where the spectral density decreases montonically (except for the 8 h tidal peak). The long period section is associated with transient planetary scale waves while the short period motions are caused by gravity waves.

Ensemble Sensitivity Analysis of a Severe Downslope Windstorm in Complex Terrain: Implications for Forecast Predictability Scales and Targeted Observing Networks

DTIC Science & Technology

2013-09-01

wave breaking (NWB) and eight wave breaking (WB) storms are shown...studies, and it follows that the wind storm characteristics are likely more three dimensional as well. For the purposes of this study, a severe DSWS is...regularly using the HWAS network at USAFA since its installation in 2004. A careful examination of these events reveals downslope storms that are

Verification and Validation of the Coastal Modeling System. Report 3: CMS-Flow: Hydrodynamics

DTIC Science & Technology

2011-12-01

Jansen (1978) Spectrum TMA Directional spreading distribution Cosine Power Directional spreading parameter γ 3.3 Bottom friction Off (default...Ramp duration 3 hr The wave breaking formula applied was Battjes and Jansen (1978) because it is the recommended wave breaking formula when using...Li, Z.H., K.D. Nguyen , J.C. Brun-Cottan and J.M. Martin. 1994. Numerical simulation of the turbidity maximum transport in the Gironde Estuary (France

Disks around stars and the growth of planetary systems.

PubMed

Greaves, Jane S

2005-01-07

Circumstellar disks play a vital evolutionary role, providing a way to move gas inward and onto a young star. The outward transfer of angular momentum allows the star to contract without breaking up, and the remnant disk of gas and particles is the reservoir for forming planets. High-resolution spectroscopy is uncovering planetary dynamics and motion within the remnant disk, and imaging at infrared to millimeter wavelengths resolves disk structure over billions of years of evolution. Most stars are born with a disk, and models of planet formation need to form such bodies from the disk material within the disk's 10-million-year life-span.

Equatorial waves in the stratosphere of Uranus

NASA Technical Reports Server (NTRS)

Hinson, David P.; Magalhaes, Julio A.

1991-01-01

Analyses of radio occultation data from Voyager 2 have led to the discovery and characterization of an equatorial wave in the Uranus stratosphere. The observed quasi-periodic vertical atmospheric density variations are in close agreement with theoretical predictions for a wave that propagates vertically through the observed background structure of the stratosphere. Quantitative comparisons between measurements obtained at immersion and at emersion yielded constraints on the meridional and zonal structure of the wave; the fact that the two sets of measurements are correlated suggests a wave of planetary scale. Two equatorial wave models are proposed for the wave.

Waves and instability in the atmosphere of Mars: NASA planetary atmospheres program

NASA Technical Reports Server (NTRS)

Barnes, Jeffrey R.

1990-01-01

A broad range of phenomena were addressed by the study including the following: (1) polar warming; (2) forced stationary waves; (3) gravity waves; (4) transient baroclinic eddies; and (5) radiative-dynamical instabilities. A variety of numerical models have been employed in these studies, as well as analytical approaches. Some of the most significant results from this work are very briefly summarized.

Numerical modeling of planetary-scale waves on Jupiter

NASA Astrophysics Data System (ADS)

Cosentino, Richard; Morales-Juberias, Raul; Simon, Amy

2014-11-01

The atmosphere of Jupiter has multiple alternating east-wind wind jets with different cloud morphologies some of which can be explained by the presence of atmospheric waves. One jet feature observed by Cassini and HST at 30N, called the Jovian Ribbon for its similarity to Saturn's Ribbon, displays chaotic cloud morphology caused by multiple wave components with dominating planetary scale wave-numbers ranging from 13 to 30. Both the cloud morphology and the dominant wave numbers observed change as a function of time and correlate to changes in the jet's speed. The average speed of the westward jet where this Jovian Ribbon is found is small compared to other notable jets that display wave behavior, namely the high velocity eastward jets at 7N (hot spots) and 7S (chevrons). We present the results of numerical simulations that show how attributes like jet speed, location, vertical shear and other background properties of the atmosphere (e.g. static stability) contribute to the development and evolution of wave structures in jets similar to those observed. Additionally, we explore the effects of local convective events and other atmospheric disturbances such as spots, on the morphology of these jets and waves. This work was supported by NASA PATM grant number NNX14AH47G. Computing resources for this research were provided by NMT and Yellowstone at CISL.

Spontaneous Wave Generation from Submesoscale Fronts and Filaments

NASA Astrophysics Data System (ADS)

Shakespeare, C. J.; Hogg, A.

2016-02-01

Submesoscale features such as eddies, fronts, jets and filaments can be significant sources of spontaneous wave generation at the ocean surface. Unlike near-inertial waves forced by winds, these spontaneous waves are typically of higher frequency and can propagate through the thermocline, whereupon they break and drive mixing in the ocean interior. Here we investigate the spontaneous generation, propagation and subsequent breaking of these waves using a combination of theory and submesoscale resolving numerical models. The mechanism of generation is nearly identical to that of lee waves where flow is deflected over a rigid obstacle on the sea floor. Here, very sharp fronts and filaments of order 100m width moving in the submesoscale surface flow generate "surface lee waves" by presenting an obstacle to the surrounding stratified fluid. Using our numerical model we quantify the net downward wave energy flux from the surface, and where it is dissipated in the water column. Our results suggest an alternative to the classical paradigm where the energy associated with mixing in the ocean interior is sourced from bottom-generated lee waves.

Shock wave apparatus for studying minerals at high pressure and impact phenomena on planetary surfaces

NASA Astrophysics Data System (ADS)

Ahrens, Thomas J.; Boslough, Mark B.; Ginn, Warren G.; Vassiliou, Mario S.; Lange, Manfred A.; Watt, J. Peter; Kondo, Ken-Ichi; Svendsen, Robert F.; Rigden, Sally M.; Stolper, Edward M.

1982-04-01

Shock wave and experimental impact phenomena research on geological and planetary materials is being carried out using two propellant (18 and 40 mm) guns (up to 2.5 km/sec) and a two-stage light gas gun (up to 7 km/sec). Equation of state measurements on samples initially at room temperture and at low and high temperatures are being conducted using the 40 mm propellant apparatus in conjunction with Helmholtz coils, and radiative detectors and, in the case of the light gas gun, with streak cameras. The 18 mm propellant gun is used for recovery experiments on minerals, impact on cryogenic targets, and radiative post-shock temperature measurements.

Impacts of the 2015 Heat Waves on Mortality in the Czech Republic-A Comparison with Previous Heat Waves.

PubMed

Urban, Aleš; Hanzlíková, Hana; Kyselý, Jan; Plavcová, Eva

2017-12-13

This study aimed to assess the impacts of heat waves during the summer of 2015 on mortality in the Czech Republic and to compare them with those of heat waves back to the previous record-breaking summer of 1994. We analyzed daily natural-cause mortality across the country's entire population. A mortality baseline was determined using generalized additive models adjusted for long-term trends, seasonal and weekly cycles, and identified heat waves. Mortality deviations from the baseline were calculated to quantify excess mortality during heat waves, defined as periods of at least three consecutive days with mean daily temperature higher than the 95th percentile of annual distribution. The summer of 2015 was record-breaking in the total duration of heat waves as well as their total heat load. Consequently, the impact of the major heat wave in 2015 on the increase in excess mortality relative to the baseline was greater than during the previous record-breaking heat wave in 1994 (265% vs. 240%). Excess mortality was comparable among the younger age group (0-64 years) and the elderly (65+ years) in the 1994 major heat wave while it was significantly larger among the elderly in 2015. The results suggest that the total heat load of a heat wave needs to be considered when assessing its impact on mortality, as the cumulative excess heat factor explains the magnitude of excess mortality during a heat wave better than other characteristics such as duration or average daily mean temperature during the heat wave. Comparison of the mortality impacts of the 2015 and 1994 major heat waves suggests that the recently reported decline in overall heat-related mortality in Central Europe has abated and simple extrapolation of the trend would lead to biased conclusions even for the near future. Further research is needed toward understanding the additional mitigation measures required to prevent heat-related mortality in the Czech Republic and elsewhere.

Impacts of the 2015 Heat Waves on Mortality in the Czech Republic—A Comparison with Previous Heat Waves

PubMed Central

Urban, Aleš; Hanzlíková, Hana; Kyselý, Jan; Plavcová, Eva

2017-01-01

This study aimed to assess the impacts of heat waves during the summer of 2015 on mortality in the Czech Republic and to compare them with those of heat waves back to the previous record-breaking summer of 1994. We analyzed daily natural-cause mortality across the country’s entire population. A mortality baseline was determined using generalized additive models adjusted for long-term trends, seasonal and weekly cycles, and identified heat waves. Mortality deviations from the baseline were calculated to quantify excess mortality during heat waves, defined as periods of at least three consecutive days with mean daily temperature higher than the 95th percentile of annual distribution. The summer of 2015 was record-breaking in the total duration of heat waves as well as their total heat load. Consequently, the impact of the major heat wave in 2015 on the increase in excess mortality relative to the baseline was greater than during the previous record-breaking heat wave in 1994 (265% vs. 240%). Excess mortality was comparable among the younger age group (0–64 years) and the elderly (65+ years) in the 1994 major heat wave while it was significantly larger among the elderly in 2015. The results suggest that the total heat load of a heat wave needs to be considered when assessing its impact on mortality, as the cumulative excess heat factor explains the magnitude of excess mortality during a heat wave better than other characteristics such as duration or average daily mean temperature during the heat wave. Comparison of the mortality impacts of the 2015 and 1994 major heat waves suggests that the recently reported decline in overall heat-related mortality in Central Europe has abated and simple extrapolation of the trend would lead to biased conclusions even for the near future. Further research is needed toward understanding the additional mitigation measures required to prevent heat-related mortality in the Czech Republic and elsewhere. PMID:29236040

Antarctic Polar Descent and Planetary Wave Activity Observed in ISAMS CO from April to July 1992

NASA Technical Reports Server (NTRS)

Allen, D. R.; Stanford, J. L.; Nakamura, N.; Lopez-Valverde, M. A.; Lopez-Puertas, M.; Taylor, F. W.; Remedios, J. J.

2000-01-01

Antarctic polar descent and planetary wave activity in the upper stratosphere and lower mesosphere are observed in ISAMS CO data from April to July 1992. CO-derived mean April-to-May upper stratosphere descent rates of 15 K/day (0.25 km/day) at 60 S and 20 K/day (0.33 km/day) at 80 S are compared with descent rates from diabatic trajectory analyses. At 60 S there is excellent agreement, while at 80 S the trajectory-derived descent is significantly larger in early April. Zonal wavenumber 1 enhancement of CO is observed on 9 and 28 May, coincident with enhanced wave 1 in UKMO geopotential height. The 9 May event extends from 40 to 70 km and shows westward phase tilt with height, while the 28 May event extends from 40 to 50 km and shows virtually no phase tilt with height.

Zones, spots, and planetary-scale waves beating in brown dwarf atmospheres.

PubMed

Apai, D; Karalidi, T; Marley, M S; Yang, H; Flateau, D; Metchev, S; Cowan, N B; Buenzli, E; Burgasser, A J; Radigan, J; Artigau, E; Lowrance, P

2017-08-18

Brown dwarfs are massive analogs of extrasolar giant planets and may host types of atmospheric circulation not seen in the solar system. We analyzed a long-term Spitzer Space Telescope infrared monitoring campaign of brown dwarfs to constrain cloud cover variations over a total of 192 rotations. The infrared brightness evolution is dominated by beat patterns caused by planetary-scale wave pairs and by a small number of bright spots. The beating waves have similar amplitudes but slightly different apparent periods because of differing velocities or directions. The power spectrum of intermediate-temperature brown dwarfs resembles that of Neptune, indicating the presence of zonal temperature and wind speed variations. Our findings explain three previously puzzling behaviors seen in brown dwarf brightness variations. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Inclusion of surface gravity wave effects in vertical mixing parameterizations with application to Chesapeake Bay, USA

NASA Astrophysics Data System (ADS)

Fisher, A. W.; Sanford, L. P.; Scully, M. E.; Suttles, S. E.

2016-02-01

Enhancement of wind-driven mixing by Langmuir turbulence (LT) may have important implications for exchanges of mass and momentum in estuarine and coastal waters, but the transient nature of LT and observational constraints make quantifying its impact on vertical exchange difficult. Recent studies have shown that wind events can be of first order importance to circulation and mixing in estuaries, prompting this investigation into the ability of second-moment turbulence closure schemes to model wind-wave enhanced mixing in an estuarine environment. An instrumented turbulence tower was deployed in middle reaches of Chesapeake Bay in 2013 and collected observations of coherent structures consistent with LT that occurred under regions of breaking waves. Wave and turbulence measurements collected from a vertical array of Acoustic Doppler Velocimeters (ADVs) provided direct estimates of TKE, dissipation, turbulent length scale, and the surface wave field. Direct measurements of air-sea momentum and sensible heat fluxes were collected by a co-located ultrasonic anemometer deployed 3m above the water surface. Analyses of the data indicate that the combined presence of breaking waves and LT significantly influences air-sea momentum transfer, enhancing vertical mixing and acting to align stress in the surface mixed layer in the direction of Lagrangian shear. Here these observations are compared to the predictions of commonly used second-moment turbulence closures schemes, modified to account for the influence of wave breaking and LT. LT parameterizations are evaluated under neutrally stratified conditions and buoyancy damping parameterizations are evaluated under stably stratified conditions. We compare predicted turbulent quantities to observations for a variety of wind, wave, and stratification conditions. The effects of fetch-limited wave growth, surface buoyancy flux, and tidal distortion on wave mixing parameterizations will also be discussed.

Modeling Water Waves with Smoothed Particle Hydrodynamics

DTIC Science & Technology

2013-09-30

SPH Model for Water Waves and Other Free Surface Flows ...Lagrangian nature of SPH allows the modeling of wave breaking, surf zones, ship waves, and wave-structure interaction, where the free surface becomes...proving to be a competent modeling scheme for free surface flows in three dimensions including the complex flows of the surf zone. As the GPU

Wave-Breaking Turbulence in the Ocean Surface Layer

DTIC Science & Technology

2016-06-01

bubbles may be important, both to the process of energy dissipation and to the quality of acoustic Doppler data, especially during rough conditions...energy beneath a breaking wave. For the roughest conditions in this dataset (20ms21 winds), bubbles and ‘‘spindrift’’ (spraying foam ) may become...to occur at the upper end of this dataset (U10 5 20ms 21). The pulse-coherent acoustic Doppler methods used on board the SWIFTs are not capable of

Transformation of Waves Across the Surf Zone.

DTIC Science & Technology

1981-03-01

Kuo is more realis- tic but still results in a sharp cut-off of the distribution at the breaking heights. 5. Goda Distribution Goda (1975) derived a...J.I., "Probabilities of Breaking Wave Characteris- tics ," Proc. 12th Coastal Engineering Conf., pp. 399- 412, 1970. Chakrabarty, S.K. and R.P. Cooley...Spring, MD 20910 21. Director 2 Instituto Oceanografico de la Armada Guayaquil, Ecuador 22. Director de Educacion de la Armada Comandancia General de

The case for 6-component ground motion observations in planetary seismology

NASA Astrophysics Data System (ADS)

Joshi, Rakshit; van Driel, Martin; Donner, Stefanie; Nunn, Ceri; Wassermann, Joachim; Igel, Heiner

2017-04-01

The imminent INSIGHT mission will place a single seismic station on Mars to learn more about the structure of the Martian interior. Due to cost and difficulty, only single stations are currently feasible for planetary missions. We show that future single station missions should also measure rotational ground motions, in addition to the classic 3 components of translational motion. The joint, collocated, 6 component (6C) observations offer access to additional information that can otherwise only be obtained through seismic array measurements or are associated with large uncertainties. An example is the access to local phase velocity information from measurements of amplitude ratios of translations and rotations. When surface waves are available, this implies (in principle) that 1D velocity models can be estimated from Love wave dispersion curves. In addition, rotational ground motion observations can distinguish between Love and Rayleigh waves as well as S and P type motions. Wave propagation directions can be estimated by maximizing (or minimizing) coherence between translational and rotational motions. In combination with velocity-depth estimates, locations of seismic sources can be determined from a single station with little or no prior knowledge of the velocity structure. We demonstrate these points with both theoretical and real data examples using the vertical component of motion from ring laser recordings at Wettzell and all components of motion from the ROMY ring near Munich. Finally, we present the current state of technology concerning portable rotation sensors and discuss the relevance to planetary seismology.

Spontaneous symmetry breaking in quasi one dimension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Satpathi, Urbashi, E-mail: urbashi@bose.res.in; Deo, P. Singha

2015-06-24

Electronic charge and spin separation leading to charge density wave and spin density wave is well established in one dimension in the presence and absence of Coulomb interaction. We start from quasi one dimension and show the possibility of such a transition in quasi one dimension as well as in two dimensions by going to a regime where it can be shown for electrons that just interact via Fermi statistics. Such density waves arise due to internal symmetry breaking in a many fermion quantum system. We can extend this result to very wide rings with infinitely many electrons including Coulombmore » interaction.« less

PELS (Planetary Environmental Liquid Simulator): a new type of simulation facility to study extraterrestrial aqueous environments.

PubMed

Martin, Derek; Cockell, Charles S

2015-02-01

Investigations of other planetary bodies, including Mars and icy moons such as Enceladus and Europa, show that they may have hosted aqueous environments in the past and may do so even today. Therefore, a major challenge in astrobiology is to build facilities that will allow us to study the geochemistry and habitability of these extraterrestrial environments. Here, we describe a simulation facility (PELS: Planetary Environmental Liquid Simulator) with the capability for liquid input and output that allows for the study of such environments. The facility, containing six separate sample vessels, allows for statistical replication of samples. Control of pressure, gas composition, UV irradiation conditions, and temperature allows for the precise replication of aqueous conditions, including subzero brines under martian atmospheric conditions. A sample acquisition system allows for the collection of both liquid and solid samples from within the chamber without breaking the atmospheric conditions, enabling detailed studies of the geochemical evolution and habitability of past and present extraterrestrial environments. The facility we describe represents a new frontier in planetary simulation-continuous flow-through simulation of extraterrestrial aqueous environments.

Standing wave contributions to the linear interference effect in stratosphere-troposphere coupling

NASA Astrophysics Data System (ADS)

Watt-Meyer, Oliver; Kushner, Paul

2014-05-01

A body of literature by Hayashi and others [Hayashi 1973, 1977, 1979; Pratt, 1976] developed a decomposition of the wavenumber-frequency spectrum into standing and travelling waves. These techniques directly decompose the power spectrum—that is, the amplitudes squared—into standing and travelling parts. This, incorrectly, does not allow for a term representing the covariance between these waves. We propose a simple decomposition based on the 2D Fourier transform which allows one to directly compute the variance of the standing and travelling waves, as well as the covariance between them. Applying this decomposition to geopotential height anomalies in the Northern Hemisphere winter, we show the dominance of standing waves for planetary wavenumbers 1 through 3, especially in the stratosphere, and that wave-1 anomalies have a significant westward travelling component in the high-latitude (60N to 80N) troposphere. Variations in the relative zonal phasing between a wave anomaly and the background climatological wave pattern—the "linear interference" effect—are known to explain a large part of the planetary wave driving of the polar stratosphere in both hemispheres. While the linear interference effect is robust across observations, models of varying degrees of complexity, and in response to various types of perturbations, it is not well understood dynamically. We use the above-described decomposition into standing and travelling waves to investigate the drivers of linear interference. We find that the linear part of the wave activity flux is primarily driven by the standing waves, at all vertical levels. This can be understood by noting that the longitudinal positions of the antinodes of the standing waves are typically close to being aligned with the maximum and minimum of the background climatology. We discuss implications for predictability of wave activity flux, and hence polar vortex strength variability.

Ground Magnetic Manifestations of Atmosphere-Ionosphere Coupling by Planetary Waves

NASA Astrophysics Data System (ADS)

Elhawary, R.; Forbes, J. M.; Wu, Q.

2014-12-01

Understanding the relation between tides, planetary waves and geomagnetic solar quiet (Sq) variations is an important aspect of atmosphere-ionosphere coupling, and much remains to be learned. In this paper we quantify the contribution of the planetary waves (PW) at 6.5-, 10- and 16-day periods on the variability of ground magnetic perturbations. Solar quiet days with Kp index <3 are examined from six different stations at low and middle latitudes in two different longitudinal sectors [(IAGA code, geographic latitude, geomagnetic latitude, geographic longitude),(IRT 52.27°, 42.20°, 104.45°), (LZH,36.1°, 26.14°,103.84°),(PHU,21.03°,11.05°,105.95°),(FRD,38.30°, 48.14°,-52.73°),( SJG, 18.11°, 28.04°, -66.15°),( KOU, 5.21°, 14.61°, -77.37°)] during Sept 2008-Sept 2010.The ground-based geomagnetic perturbations are compared with co-located TIMED/TIDI measurements of PW wind amplitudes at the same periods near 110 km. The wind and magnetic field PW amplitudes are not highly correlated at each station, and reasons for that are discussed. The contributions of these PW to the total variability of the magnetic perturbations will be reported.

Global Lunar Geochemistry and Its Significant Parallel With Terrestrial One

NASA Astrophysics Data System (ADS)

Kochemasov, G.

Planetary geochemistry reflects planetary tectonic pattern. The most global tectonic feature is the ubiquitous dichotomy (Theorem 1, [1]) with one hemisphere of a di- minished radius (concave) opposed by the convex hemisphere with an increased ra- dius. The terrestrial case is well known: the pressed in Pacific hemisphere is opposed by the bulging out continental one. This tectonics finds its demonstration in global geochemistry: the concave part is filled with denser basalts, rich in Fe, Ti, and the convex part is built of more acidic less dense lithologies, on average of andesitic composition. Much smaller Moon (almost 100 times less massive) reveals the same tectonic-geochemical construction. The near concave side is occupied by Procellarum basin and large marea filled with dense basalts rich in Fe, Ti. The far convex side is built of less dense anarthosites. On both planetary bodies the convex hemispheres are complicated by large subsided sectors (Theorem 2, [1]) filled with, as required by Theorem 4 [1], denser basalts. At Earth it is the Indoceanic sector, on the Moon the South Pole-Aitken basin. Genetically they are similar and constitute regular parts of global tectono-geochemistry (here there is no place for random impact or plate tec- tonic origin of these deep global depressions, they are components of "wave1-wave2" produced structures). The Lunar Prospector global geochemical coverage [2] allows to make lunar - terrestrial parallels not only in dichotomic distribution of iron and ti- tanium but also in distribution of potassium and thorium marking a contact between two dichotomic hemispheres. At Earth the seismically active contact is famous by its andesitic volcanism. Andesites comparative to basalts are richer in K and Th. On the Moon this transitional zone between the dichotomic halves is enriched with Th and K as well [2]. The transition to highlands requires less dense than mare basalts lithologies and they appear as feldspar-rich KREEP basalts enriched with K and Th. The geochemical parallel between two planetary bodies is not occasional and is a con- sequence of the wave planetary tectonics. References: [1] Kochemasov G.G. (1999) Theorems of wave planetary tectonics //Geophys. Res. Abstr., v.1, #3, 700; [2]Chevrel 1 S.D., Pinet P.C., Daydou Y. et al (2001) Global scale multielement analysis of the lunar surface using iron, titanium and thorium abundances // 34th Vernadsky-Brown microsymposium. Topics in comparative planetology. Moscow, Vernadsky Inst., Oct. 8-9, 2001,Abstracts, (CD-ROM).

The Thermal Phase Curve Offset on Tidally and Nontidally Locked Exoplanets: A Shallow Water Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penn, James; Vallis, Geoffrey K, E-mail: jp492@exeter.ac.uk, E-mail: g.vallis@exeter.ac.uk

2017-06-20

Using a shallow water model with time-dependent forcing, we show that the peak of an exoplanet thermal phase curve is, in general, offset from the secondary eclipse when the planet is rotating. That is, the planetary hot spot is offset from the point of maximal heating (the substellar point) and may lead or lag the forcing; the extent and sign of the offset are functions of both the rotation rate and orbital period of the planet. We also find that the system reaches a steady state in the reference frame of the moving forcing. The model is an extension ofmore » the well-studied Matsuno–Gill model into a full spherical geometry and with a planetary-scale translating forcing representing the insolation received on an exoplanet from a host star. The speed of the gravity waves in the model is shown to be a key metric in evaluating the phase curve offset. If the velocity of the substellar point (relative to the planet’s surface) exceeds that of the gravity waves, then the hot spot will lag the substellar point, as might be expected by consideration of forced gravity wave dynamics. However, when the substellar point is moving slower than the internal wave speed of the system, the hottest point may lead the passage of the forcing. We provide an interpretation of this result by consideration of the Rossby and Kelvin wave dynamics, as well as, in the very slowly rotating case, a one-dimensional model that yields an analytic solution. Finally, we consider the inverse problem of constraining planetary rotation rate from an observed phase curve.« less

Quasi two day wave-related variability in the background dynamics and composition of the mesosphere/thermosphere and the ionosphere

PubMed Central

Chang, Loren C; Yue, Jia; Wang, Wenbin; Wu, Qian; Meier, R R

2014-01-01

Dissipating planetary waves in the mesosphere/lower thermosphere (MLT) region may cause changes in the background dynamics of that region, subsequently driving variability throughout the broader thermosphere/ionosphere system via mixing due to the induced circulation changes. We report the results of case studies examining the possibility of such coupling during the northern winter in the context of the quasi two day wave (QTDW)—a planetary wave that recurrently grows to large amplitudes from the summer MLT during the postsolstice period. Six distinct QTDW events between 2003 and 2011 are identified in the MLT using Sounding of the Atmosphere using Broadband Emission Radiometry temperature observations. Concurrent changes to the background zonal winds, zonal mean column O/N2 density ratio, and ionospheric total electron content (TEC) are examined using data sets from Thermosphere Ionosphere Mesosphere Energetics and Dynamics Doppler Interferometer, Global Ultraviolet Imager, and Global Ionospheric Maps, respectively. We find that in the 5–10 days following a QTDW event, the background zonal winds in the MLT show patterns of eastward and westward anomalies in the low and middle latitudes consistent with past modeling studies on QTDW-induced mean wind forcing, both below and at turbopause altitudes. This is accompanied by potentially related decreases in zonal mean thermospheric column O/N2, as well as to low-latitude TECs. The recurrent nature of the above changes during the six QTDW events examined point to an avenue for vertical coupling via background dynamics and chemistry of the thermosphere/ionosphere not previously observed. Key Points Dissipating planetary waves (PWs) in the MLT can drive background wind changes Mixing from dissipating PWs drive thermosphere/ionosphere composition changes First observations of QTDW-driven variability from this mechanism PMID:26312201

Quasi two day wave-related variability in the background dynamics and composition of the mesosphere/thermosphere and the ionosphere.

PubMed

Chang, Loren C; Yue, Jia; Wang, Wenbin; Wu, Qian; Meier, R R

2014-06-01

Dissipating planetary waves in the mesosphere/lower thermosphere (MLT) region may cause changes in the background dynamics of that region, subsequently driving variability throughout the broader thermosphere/ionosphere system via mixing due to the induced circulation changes. We report the results of case studies examining the possibility of such coupling during the northern winter in the context of the quasi two day wave (QTDW)-a planetary wave that recurrently grows to large amplitudes from the summer MLT during the postsolstice period. Six distinct QTDW events between 2003 and 2011 are identified in the MLT using Sounding of the Atmosphere using Broadband Emission Radiometry temperature observations. Concurrent changes to the background zonal winds, zonal mean column O/N 2 density ratio, and ionospheric total electron content (TEC) are examined using data sets from Thermosphere Ionosphere Mesosphere Energetics and Dynamics Doppler Interferometer, Global Ultraviolet Imager, and Global Ionospheric Maps, respectively. We find that in the 5-10 days following a QTDW event, the background zonal winds in the MLT show patterns of eastward and westward anomalies in the low and middle latitudes consistent with past modeling studies on QTDW-induced mean wind forcing, both below and at turbopause altitudes. This is accompanied by potentially related decreases in zonal mean thermospheric column O/N 2 , as well as to low-latitude TECs. The recurrent nature of the above changes during the six QTDW events examined point to an avenue for vertical coupling via background dynamics and chemistry of the thermosphere/ionosphere not previously observed. Dissipating planetary waves (PWs) in the MLT can drive background wind changesMixing from dissipating PWs drive thermosphere/ionosphere composition changesFirst observations of QTDW-driven variability from this mechanism.

Attenuation of stress waves in single and multi-layered structures. [mitigation of elastic and plastic stress waves during spacecraft landing

NASA Technical Reports Server (NTRS)

Yang, J. C. S.; Tsui, C. Y.

1972-01-01

Analytical and experimental studies were made of the attenuation of the stress waves during passage through single and multilayer structures. The investigation included studies on elastic and plastic stress wave propagation in the composites and those on shock mitigating material characteristics such as dynamic stress-strain relations and energy absorbing properties. The results of the studies are applied to methods for reducing the stresses imposed on a spacecraft during planetary or ocean landings.

Cyclic Steps and Antidunes : Relating Their Features to a Suspension Index

NASA Astrophysics Data System (ADS)

Yokokawa, M.; Kishima, Y.; Parker, G.

2010-12-01

Cyclic Steps and Antidunes : Relating Their Features to a Suspension Index Miwa Yokokawa (1), Yasushi Kishima (1), Gary Parker (2, 3) 1: Osaka Institute of Technology, Hirakata, Osaka, Japan 2: Dept. of Civil & Environmental Engineering, University of Illinois, Urbana, Illinois, U.S.A. 3: Dept. of Geology, University of Illinois, Urbana, Illinois, U.S.A. There are very few comparative studies of the differences in hydraulic conditions and morphologic features of bed- and water-surface-waves associated with cyclic steps and antidunes. In this study, the features of both the bed and the water surface, as well as hydraulic conditions are examined over the spectrum from antidune to cyclic steps. Experiments were performed using a flume at the Osaka Institute of Technology. The resultant features of the bedforms are as follows. In the case of antidunes, bed waves and water surface waves are in phase except when they collapse. Antidunes show several kinds of behavior; migrating downstream, standing, or migrating upstream. Upstream-migrating antidunes are divided into non-breaking, and breaking-types. Breaking antidunes appear alternatively with the plane bed state. Cyclic steps migrate upstream regularly associated with trains of hydraulic jumps, which divide each step. There is a significant change in water depth at the hydraulic jump, so that the phasing between the bed waves and water surface waves break at the each hydraulic jump. There is a kind of compromise between cyclic steps and antidunes, which we designate as “intermediate steps”. They move upstream and are associated with regular trains of hydraulic jumps. The jumps, however, occasionally collapse toward upstream. When this happens, bed waves move rapidly upstream; low-amplitude water surface waves and bed waves become in phase all over the bed shortly after the collapse. Then after some time, water surface waves become sufficiently prominent to yield regular hydraulic jumps. This cycle is then repeated.The hydraulic conditions for these bedfoms were examined using three non-dimensional parameters, i.e. the Froude Number, the Suspension Index, and the dimensionless particle size. The suspension index is a newly introduced parameter which is the ratio of the shear velocity divided by the settling velocity of the sediment (u*/Vs). Data from previous experimental studies are examined together with the present data in studying the characteristic regimes of bedform formation. In a diagram of Froude Number v.s. Suspension Index, antidunes, intermediate steps and cyclic steps can be divided along the axis of the Suspension Index. In the lowest range of the suspension index, downstream-migrating antidunes and upstream-migrating antidunes that do not break are found. The intermediate steps discussed above are located in the middle range. The highest range corresponds to cyclic steps and breaking antidunes. As described above, the Suspension Index can serve as a scale to quantify the spectrum between antidunes and cyclic steps. The use of the parameter also helps verify that suspension plays an important role in the formation and maintenance of cyclic steps.

Measurements of Two-Phase Suspended Sediment Transport in Breaking Waves Using Volumetric Three-Component Velocimetry

NASA Astrophysics Data System (ADS)

Ting, F. C. K.; LeClaire, P.

2016-02-01

Understanding the mechanisms of sediment pickup and distribution in breaking waves is important for modeling sediment transport in the surf zone. Previous studies were mostly concerned with bulk sediment transport under specific wave conditions. The distribution of suspended sediments in breaking waves had not been measured together with coherent flow structures. In this study, two-phase flow measurements were obtained under a train of plunging regular waves on a plane slope using the volumetric three-component velocimetry (V3V) technique. The measurements captured the motions of sediment particles simultaneously with the three-component, three-dimensional (3C3D) velocity fields of turbulent coherent structures (large eddies) induced by breaking waves. Sediment particles (solid glass spheres diameter 0.125 to 0.15 mm, specific gravity 2.5) were separated from fluid tracers (mean diameter 13 µm, specific gravity 1.3) based on a combination of particle spot size and brightness in the two-phase images. The interactions between the large eddies and glass spheres were investigated for plunger vortices generated at incipient breaking and for splash-up vortices generated at the second plunge point. The measured data show that large eddies impinging on the bottom was the primary mechanism which lift sediment particles into suspension and momentarily increased near-bed suspended sediment concentration. Although eddy impingement events were sporadic in space and time, the distributions of suspended sediments in the large eddies were not uniform. High suspended sediment concentration and vertical sediment flux were found in the wall-jet region where the impinging flow was deflected outward and upward. Sediment particles were also trapped and carried around by counter-rotating vortices (Figure 1). Suspended sediment concentration was significantly lower in the impingement region where the fluid velocity was downward, even though turbulent kinetic energy in the down flow was very high. These results suggest that vertical velocity or turbulent shear stress may be a better parameter for predicting sediment pick-up rate than turbulent kinetic energy. It was also found that splash-up vortices enhanced onshore transport relative to the condition when no vortex impinged on the bottom.

Effects of temperature and wave conditions on chemical dispersion efficacy of heavy fuel oil in an experimental flow-through wave tank.

PubMed

Li, Zhengkai; Lee, Kenneth; King, Thomas; Boufadel, Michel C; Venosa, Albert D

2010-09-01

The effectiveness of chemical dispersants (Corexit 9500 and SPC 1000) on heavy fuel oil (IFO180 as test oil) has been evaluated under different wave conditions in a flow-through wave tank. The dispersant effectiveness was determined by measuring oil concentrations and droplet size distributions. An analysis of covariance (ANCOVA) model indicated that wave type and temperature significantly (p<0.05) affected the dynamic dispersant effectiveness (DDE). At higher temperatures (16 degrees C), the test IFO180 was effectively dispersed under breaking waves with a DDE of 90% and 50% for Corexit 9500 and SPC 1000, respectively. The dispersion was ineffective under breaking waves at lower temperature (10 degrees C), and under regular wave conditions at all temperatures (10-17 degrees C), with DDE<15%. Effective chemical dispersion was associated with formation of smaller droplets (with volumetric mean diameters or VMD < or = 200 microm), whereas ineffective dispersion produced large oil droplets (with VMD > or = 400 microm). Copyright 2010 Elsevier Ltd. All rights reserved.

Arctic Sea Ice Export Through Fram Strait and Atmospheric Planetary Waves

NASA Technical Reports Server (NTRS)

Cavalieri, Donald J.; Koblinsky, Chester (Technical Monitor)

2001-01-01

A link is found between the variability of Arctic sea ice export through Ram Strait and the phase of the longest atmospheric planetary wave (zonal wave 1) in SLP for the period 1958-1997. Previous studies have identified a link between From Strait ice export and the North Atlantic Oscillation (NAO), but this link has been described as unstable because of a lack of consistency over time scales longer than the last two decades. Inconsistent and low correlations are also found between From Strait ice export and the Arctic Oscillation (AD) index. This paper shows that the phase of zonal wave 1 explains 60% - 70% of the simulated From Strait ice export variance over the Goodyear period 1958 - 1997. Unlike the NAB and AD links, these high variances are consistent for both the first and second halves of the Goodyear period. This consistency is attributed to the sensitivity of the wave I phase at high latitudes to the presence of secondary low pressure systems in the Barents Sea that serve to drive sea ice southward through From Strait. These results provide further evidence that the phase of zonal wave 1 in SLP at high latitudes drives regional as well as hemispheric low frequency Arctic Ocean and sea ice variability.

Wave-Current Conditions and Navigation Safety at an Inlet Entrance

DTIC Science & Technology

2015-06-26

effects of physical processes. Wave simulations with refraction, shoaling, and breaking provide estimates of wave-related parameters of interest to...summer and winter months and to better understand the cause- effect relationship between navigability conditions at Tillamook Inlet and characteristics of...the Coriolis force, wind stress, wave stress, bottom stress, vegetation flow drag, bottom friction, wave roller, and turbulent diffusion. Governing

Observation-Based Dissipation and Input Terms for Spectral Wave Models, with End-User Testing

DTIC Science & Technology

2014-09-30

scale influence of the Great barrier reef matrix on wave attenuation, Coral Reefs [published, refereed] Ghantous, M., and A.V. Babanin, 2014: One...Observation-Based Dissipation and Input Terms for Spectral Wave Models...functions, based on advanced understanding of physics of air-sea interactions, wave breaking and swell attenuation, in wave - forecast models. OBJECTIVES The

Waves: Internal Tides

NASA Technical Reports Server (NTRS)

Ray, Richard D.

1999-01-01

Oceanic internal tides are internal waves with tidal periodicities. They are ubiquitous throughout the ocean, although generally more pronounced near large bathymetric features such as mid-ocean ridges and continental slopes. The internal vertical displacements associated with these waves can be extraordinarily large. Near some shelf breaks where the surface tides are strong, internal displacements (e.g., of an isothermal surface) can exceed 200 meters. Displacements of 10 meters in the open ocean are not uncommon. The associated current velocities are usually comparable to or larger than the currents of the surface tide. On continental shelves internal tides can occasionally generate packets of internal solitons, which are detectable in remote sensing imagery. Other common nonlinear features are generation of higher harmonics (e.g., 6-hr waves) and wave breaking. Internal tides are known to be an important energy source for mixing of shelf waters. Recent research suggests that they may also be a significant energy source for deep-ocean mixing.

Celeris: A GPU-accelerated open source software with a Boussinesq-type wave solver for real-time interactive simulation and visualization

NASA Astrophysics Data System (ADS)

Tavakkol, Sasan; Lynett, Patrick

2017-08-01

In this paper, we introduce an interactive coastal wave simulation and visualization software, called Celeris. Celeris is an open source software which needs minimum preparation to run on a Windows machine. The software solves the extended Boussinesq equations using a hybrid finite volume-finite difference method and supports moving shoreline boundaries. The simulation and visualization are performed on the GPU using Direct3D libraries, which enables the software to run faster than real-time. Celeris provides a first-of-its-kind interactive modeling platform for coastal wave applications and it supports simultaneous visualization with both photorealistic and colormapped rendering capabilities. We validate our software through comparison with three standard benchmarks for non-breaking and breaking waves.

Integrated modeling of the dynamic meteorological and sea surface conditions during the passage of Typhoon Morakot

NASA Astrophysics Data System (ADS)

Lee, Han Soo; Yamashita, Takao; Hsu, John R.-C.; Ding, Fei

2013-01-01

In August 2009, Typhoon Morakot caused massive flooding and devastating mudslides in the southern Taiwan triggered by extremely heavy rainfall (2777 mm in 4 days) which occurred during its passage. It was one of the deadliest typhoons that have ever attacked Taiwan in recent years. In this study, numerical simulations are performed for the storm surge and ocean surface waves, together with dynamic meteorological fields such as wind, pressure and precipitation induced by Typhoon Morakot, using an atmosphere-waves-ocean integrated modelling system. The wave-induced dissipation stress from breaking waves, whitecapping and depth-induced wave breaking, is parameterized and included in the wave-current interaction process, in addition to its influence on the storm surge level in shallow water along the coast of Taiwan. The simulated wind and pressure field captures the characteristics of the observed meteorological field. The spatial distribution of the accumulated rainfall within 4 days, from 00:00 UTC 6 August to 00:00 UTC 10 August 2009, shows similar patterns as the observed values. The 4-day accumulated rainfall of 2777 mm at the A-Li Shan mountain weather station for the same period depicted a high correlation with the observed value of 2780 mm/4 days. The effects of wave-induced dissipation stress in the wave-current interaction resulted in increased surge heights on the relatively shallow western coast of Taiwan, where the bottom slope of the bathymetry ranges from mild to moderate. The results also show that wave-breaking has to be considered for accurate storm surge prediction along the east coast of Taiwan over the narrow bank of surf zone with a high horizontal resolution of the model domain.

Planetary atmospheres program

NASA Technical Reports Server (NTRS)

1982-01-01

Non-solar compositional models of the troposphere of Jupiter, halide cloud condensation and volatile element inventories on Venus, and shock-wave processing of interstellar cloud materials are discussed.

Ice Floe Breaking in Contemporary Third Generation Operational Wave Models

NASA Astrophysics Data System (ADS)

Sévigny, C.; Baudry, J.; Gauthier, J. C.; Dumont, D.

2016-02-01

The dynamical zone observed at the edge of the consolidated ice area where are found the wave-fractured floes (i.e. marginal ice zone or MIZ) has become an important topic in ocean modeling. As both operational and climate ocean models now seek to reproduce the complex atmosphere-ice-ocean system with realistic coupling processes, many theoretical and numerical studies have focused on understanding and modeling this zone. Few attempts have been made to embed wave-ice interactions specific to the MIZ within a two-dimensional model, giving the possibility to calculate both the attenuation of surface waves by sea ice and the concomitant breaking of the sea ice-cover into smaller floes. One of the first challenges consists in improving the parameterization of wave-ice dynamics in contemporary third generation operational wave models. A simple waves-in-ice model (WIM) similar to the one proposed by Williams et al. (2013a,b) was implemented in WAVEWATCH III. This WIM considers ice floes as floating elastic plates and predicts the dimensionless attenuation coefficient by the use of a lookup-table-based, wave scattering scheme. As in Dumont et al. (2011), the different frequencies are treated individually and floe breaking occurs for a particular frequency when the expected wave amplitude exceeds the allowed strain amplitude, which considers ice floes properties and wavelength in ice field. The model is here further refined and tested in idealized two-dimensional cases, giving preliminary results of the performance and sensitivity of the parameterization to initial wave and ice conditions. The effects of the wave-ice coupling over the incident wave spectrum are analyzed as well as the resulting floe size distribution. The model gives prognostic values of the lateral extent of the marginal ice zone with maximum ice floe diameter that progressively increases with distance from the ice edge.

Hard Break-Up of Two-Nucleons and QCD Dynamics of NN Interaction

NASA Astrophysics Data System (ADS)

Sargsian, Misak; Granados, Carlos

2009-05-01

We investigate hard photodisintegration of two nucleons from ^3He nucleus within the framework of hard rescattering model (HRM). In HRM a quark of one nucleon knocked-out by incoming photon rescatters with a quark of the other nucleon leading to the production of two nucleons with high relative momentum. HRM allows to express the amplitude of two-nucleon break-up reaction through the convolution of photon-quark scattering, NN hard scattering amplitude and nuclear spectral function which can be calculated using nonrelativistic ^3He wave function. HRM predicts several specific features for hard break-up reaction. First, the cross section will approximately scale as s-11. Also one predicts comparable or larger cross section for pp break up as compared to that of pn break-up, which is opposite to what is observed in low energy kinematics. Another result is the prediction of different spectator momentum dependencies of pp and pn break-up cross sections. This is due to the fact that same-helicity pp-component is strongly suppressed in the ground state wave function of ^3He. Due to this suppression HRM predicts significantly different asymmetries for the cross section of polarization transfer NN break-up reactions for circularly polarized photons. For the pp break-up this asymmetry is predicted to be zero while for the pn it is close to 23.

A Weakly Nonlinear Model for the Damping of Resonantly Forced Density Waves in Dense Planetary Rings

NASA Astrophysics Data System (ADS)

Lehmann, Marius; Schmidt, Jürgen; Salo, Heikki

2016-10-01

In this paper, we address the stability of resonantly forced density waves in dense planetary rings. Goldreich & Tremaine have already argued that density waves might be unstable, depending on the relationship between the ring’s viscosity and the surface mass density. In the recent paper Schmidt et al., we have pointed out that when—within a fluid description of the ring dynamics—the criterion for viscous overstability is satisfied, forced spiral density waves become unstable as well. In this case, linear theory fails to describe the damping, but nonlinearity of the underlying equations guarantees a finite amplitude and eventually a damping of the wave. We apply the multiple scale formalism to derive a weakly nonlinear damping relation from a hydrodynamical model. This relation describes the resonant excitation and nonlinear viscous damping of spiral density waves in a vertically integrated fluid disk with density dependent transport coefficients. The model consistently predicts density waves to be (linearly) unstable in a ring region where the conditions for viscous overstability are met. Sufficiently far away from the Lindblad resonance, the surface mass density perturbation is predicted to saturate to a constant value due to nonlinear viscous damping. The wave’s damping lengths of the model depend on certain input parameters, such as the distance to the threshold for viscous overstability in parameter space and the ground state surface mass density.

Studies of planetary upper atmospheres through occultations

NASA Technical Reports Server (NTRS)

Elliot, J. L.

1982-01-01

The structure, composition, dynamics and energy balance of planetary upper atmospheres through interpretation of steller occultation data from Uranus is discussed. The wave-optical problem of modelling strong scintillation for arbitrary turbulent atmospheres is studied, as well as influence of turbulence. It was concluded that quasi-global features of atmospheric structure are accurately determined by numerical inversion. Horizontally inhomogeneous structures are filtered out and have little effect on temperature profiles.

Implementation of the vortex force formalism in the coupled ocean-atmosphere-wave-sediment transport (COAWST) modeling system for inner shelf and surf zone applications

NASA Astrophysics Data System (ADS)

Kumar, Nirnimesh; Voulgaris, George; Warner, John C.; Olabarrieta, Maitane

The coupled ocean-atmosphere-wave-sediment transport modeling system (COAWST) enables simulations that integrate oceanic, atmospheric, wave and morphological processes in the coastal ocean. Within the modeling system, the three-dimensional ocean circulation module (ROMS) is coupled with the wave generation and propagation model (SWAN) to allow full integration of the effect of waves on circulation and vice versa. The existing wave-current coupling component utilizes a depth dependent radiation stress approach. In here we present a new approach that uses the vortex force formalism. The formulation adopted and the various parameterizations used in the model as well as their numerical implementation are presented in detail. The performance of the new system is examined through the presentation of four test cases. These include obliquely incident waves on a synthetic planar beach and a natural barred beach (DUCK' 94); normal incident waves on a nearshore barred morphology with rip channels; and wave-induced mean flows outside the surf zone at the Martha's Vineyard Coastal Observatory (MVCO). Model results from the planar beach case show good agreement with depth-averaged analytical solutions and with theoretical flow structures. Simulation results for the DUCK' 94 experiment agree closely with measured profiles of cross-shore and longshore velocity data from Garcez Faria et al. (1998, 2000). Diagnostic simulations showed that the nonlinear processes of wave roller generation and wave-induced mixing are important for the accurate simulation of surf zone flows. It is further recommended that a more realistic approach for determining the contribution of wave rollers and breaking induced turbulent mixing can be formulated using non-dimensional parameters which are functions of local wave parameters and the beach slope. Dominant terms in the cross-shore momentum balance are found to be the quasi-static pressure gradient and breaking acceleration. In the alongshore direction, bottom stress, breaking acceleration, horizontal advection and horizontal vortex forces dominate the momentum balance. The simulation results for the bar/rip channel morphology case clearly show the ability of the modeling system to reproduce horizontal and vertical circulation patterns similar to those found in laboratory studies and to numerical simulations using the radiation stress representation. The vortex force term is found to be more important at locations where strong flow vorticity interacts with the wave-induced Stokes flow field. Outside the surf zone, the three-dimensional model simulations of wave-induced flows for non-breaking waves closely agree with flow observations from MVCO, with the vertical structure of the simulated flow varying as a function of the vertical viscosity as demonstrated by Lentz et al. (2008).

Quantification of nearshore morphology based on video imaging

USGS Publications Warehouse

Alexander, P.S.; Holman, R.A.

2004-01-01

The Argus network is a series of video cameras with aerial views of beaches around the world. Intensity contrasts in time exposure images reveal areas of preferential breaking, which are closely tied to underlying bed morphology. This relationship was further investigated, including the effect of tidal elevation and wave height on the presence of wave breaking and its cross-shore position over sand bars. Computerized methods of objectively extracting shoreline and sand bar locations were developed, allowing the vast quantity of data generated by Argus to be more effectively examined. Once features were identified in the images, daily alongshore mean values were taken to create time series of shoreline and sand bar location, which were analyzed for annual cycles and cross-correlated with wave data to investigate environmental forcing and response. These data extraction techniques were applied to images from four of the Argus camera sites. A relationship between wave height and shoreline location was found in which increased wave heights resulted in more landward shoreline positions; given the short lag times over which this correlation was significant, and that the strong annual signal in wave height was not replicated in the shoreline time series, it is likely that this relationship is a result of set-up during periods of large waves. Wave height was also found to have an effect on sand bar location, whereby an increase in wave height resulted in offshore bar migration. This correlation was significant over much longer time lags than the relationship between wave height and shoreline location, and a strong annual signal was found in the location of almost all observed bars, indicating that the sand bars are migrating with changes in wave height. In the case of the site with multiple sand bars, the offshore bars responded more significantly to changes in wave height, whereas the innermost bar seemed to be shielded from incident wave energy by breaking over the other bars. A relationship was also found between a site's mean wave height and inner sand bar location; sites with the highest wave heights tended to have sand bars farther from shore than those with relatively low wave heights. ?? 2004 Elsevier B.V. All rights reserved.

The local properties of ocean surface waves by the phase-time method

NASA Technical Reports Server (NTRS)

Huang, Norden E.; Long, Steven R.; Tung, Chi-Chao; Donelan, Mark A.; Yuan, Yeli; Lai, Ronald J.

1992-01-01

A new approach using phase information to view and study the properties of frequency modulation, wave group structures, and wave breaking is presented. The method is applied to ocean wave time series data and a new type of wave group (containing the large 'rogue' waves) is identified. The method also has the capability of broad applications in the analysis of time series data in general.

High Power K Sub a -band Transmitter for Planetary Radar and Spacecraft Uplink

NASA Technical Reports Server (NTRS)

Bhanji, A. M.; Hoppe, D. J.; Hartop, R. W.; Stone, E. W.; Imbriale, W. A.; Stone, D.; Caplan, M.

1984-01-01

A proposed conceptual design of a 400 kW continuous wave (CW)K sub a band transmitter and associated microwave components to be used for planetary radar and serve as a prototype for future spacecraft uplinks is discussed. System requirements for such a transmitter are presented. Performance of the proposed high-power millimeter wave tube, the gyroklystron is discussed. Parameters of the proposed power amplifier, beam supply, and monitor and control devices are also presented. Microwave transmission line components consisting of signal monitoring devices, signal filtering devices, and an overmoded corrugated feed are discussed. Finally, an assessment of the state of the art technology to meet the system requirements is given and possible areas of difficulty are summarized.

A Mechanism for Land-Atmosphere Feedback Involving Planetary Wave Structures

NASA Technical Reports Server (NTRS)

Koster, Randal D.; Chang, Yehui; Schubert, Siegfried D.

2014-01-01

While the ability of land surface conditions to influence the atmosphere has been demonstrated in various modeling and observational studies, the precise mechanisms by which land-atmosphere feedback occurs are still largely unknown particularly the mechanisms that allow land moisture state in one region to affect atmospheric conditions in another. Such remote impacts are examined here in the context of atmospheric general circulation model (AGCM) simulations, leading to the identification of one potential mechanism: the phase-locking and amplification of a planetary wave through the imposition of a spatial pattern of soil moisture at the land surface. This mechanism, shown here to be relevant in the AGCM, apparently also operates in nature, as suggested by supporting evidence found in reanalysis data.

The covariance of temperature and ozone due to planetary-wave forcing

NASA Technical Reports Server (NTRS)

Fraser, G. J.

1976-01-01

The cross-spectra of temperature and ozone mass mixing ratio at 42 km and 28 km has been determined for spring (1971) and summer (1971-2) over Christchurch, New Zealand (44 S, 172 E). The sources of data are the SCR and BUV experiments on Nimbus 4. The observed covariances are compared with a model in which the temperature and ozone perturbations are forced by an upward propagating planetary wave. The agreement between the observations and the model is reasonable. It is suggested that this cross-spectral method permits an estimate of the meridional gradient of ozone mass mixing ratio from measurements of the vertical profile of ozone mass mixing ratio at one location, supported by temperature profiles from at least two locations.

The role of coral reef rugosity in dissipating wave energy and coastal protection

NASA Astrophysics Data System (ADS)

Harris, Daniel; Rovere, Alessio; Parravicini, Valeriano; Casella, Elisa

2016-04-01

Coral reefs are the most effective natural barrier in dissipating wave energy through breaking and bed friction. The attenuation of wave energy by coral reef flats is essential in the protection and stability of coral reef aligned coasts and reef islands. However, the effectiveness of wave energy dissipation by coral reefs may be diminished under future climate change scenarios with a potential reduction of coral reef rugosity due to increased stress environmental stress on corals. The physical roughness or rugosity of coral reefs is directly related to ecological diversity, reef health, and hydrodynamic roughness. However, the relationship between physical roughness and hydrodynamic roughness is not well understood despite the crucial role of bed friction in dissipating wave energy in coral reef aligned coasts. We examine the relationship between wave energy dissipation across a fringing reef in relation to the cross-reef ecological zonation and the benthic hydrodynamic roughness. Waves were measured by pressure transducers in a cross-reef transect on the reefs flats and post processed on a wave by wave basis to determine wave statistics such as significant wave height and wave period. Results from direct wave measurement were then used to calibrate a 1D wave dissipation model that incorporates dissipation functions due to bed friction and wave breaking. This model was used to assess the bed roughness required to produce the observed wave height dissipation during propagation from deep water and across the coral reef flats. Changes in wave dissipation was also examined under future scenarios of sea level rise and reduced bed roughness. Three dimensional models of the benthic reef structure were produced through structure-from-motion photogrammetry surveys. Reef rugosity was then determined from these surveys and related to the roughness results from the calibrated model. The results indicate that applying varying roughness coefficients as the benthic ecological assemblage changes produces the most accurate assessment of wave energy dissipation across the reef flat. However, the modelled results of bed roughness (e.g. 0.01 for the fore-reef slope) were different to the directly measured rugosity values (0.05 for the fore-reef slope) from three dimension structure-from-motion surveys. In spite of this, the modelled and directly measured values of roughness are similar considering the difficulties outlined in previous research when relating the coral reef structural complexity to a single value of hydrodynamic roughness. Bed roughness was shown to be a secondary factor behind wave breaking in dissipating wave energy. However, without bed friction waves could be an order of magnitude higher in the back-reef environment. Bed friction is also increasingly important in wave dissipation at higher sea levels as wave energy dissipation due to wave breaking is reduced at greater depths. This shows that maintaining a structurally diverse and healthy reef is crucial under future sea level rise scenarios in order to maintain the protection of coastal environments. These results also indicate that significant geomorphic change in coastal environments will occur due to reduced wave dissipation at higher sea levels unless reefs are capable of keeping up with forecasted sea level rise.

The dynamical link between deep Atlantic extratropical cyclones and intense Mediterranean cyclones

NASA Astrophysics Data System (ADS)

Raveh-Rubin, Shira; Flaounas, Emmanouil

2017-04-01

Breaking of atmospheric Rossby waves has been previously shown to lead to intense Mediterranean cyclones, one of the most prominent environmental risks in the region. Wave breaking may be enhanced by warm conveyor belts (WCBs) associated with extratropical cyclones developing over the Atlantic Ocean. More precisely, WCBs supply the upper troposphere with air masses of low potential vorticity that, in turn, amplify ridges and thus favor Rossby wave breaking. This study identifies and validates the relevance of the mechanism that connects Atlantic cyclones and intense mature Mediterranean cyclones through ridge amplification by WCBs. Using ECMWF ERA-Interim reanalyses and a feature-based approach, we analyze the 200 most intense Mediterranean cyclones for the years 1989-2008 and show that their majority (181 cases) is indeed associated with this mechanism upstream. Results show that multiple Atlantic cyclones are associated with each case of intense Mediterranean cyclone downstream. Moreover, the associated Atlantic cyclones are particularly deep compared to climatology.

Experimental and theoretical study of Rayleigh-Lamb waves in a plate containing a surface-breaking crack

NASA Technical Reports Server (NTRS)

Paffenholz, Joseph; Fox, Jon W.; Gu, Xiaobai; Jewett, Greg S.; Datta, Subhendu K.

1990-01-01

Scattering of Rayleigh-Lamb waves by a normal surface-breaking crack in a plate has been studied both theoretically and experimentally. The two-dimensionality of the far field, generated by a ball impact source, is exploited to characterize the source function using a direct integration technique. The scattering of waves generated by this impact source by the crack is subsequently solved by employing a Green's function integral expression for the scattered field coupled with a finite element representation of the near field. It is shown that theoretical results of plate response, both in frequency and time, are similar to those obtained experimentally. Additionally, implication for practical applications are discussed.

Charge and current orders in the spin-fermion model with overlapping hot spots

NASA Astrophysics Data System (ADS)

Volkov, Pavel A.; Efetov, Konstantin B.

2018-04-01

Experiments carried over the last years on the underdoped cuprates have revealed a variety of symmetry-breaking phenomena in the pseudogap state. Charge-density waves, breaking of C4 rotational symmetry as well as time-reversal symmetry breaking have all been observed in several cuprate families. In this regard, theoretical models where multiple nonsuperconducting orders emerge are of particular interest. We consider the recently introduced [Volkov and Efetov, Phys. Rev. B 93, 085131 (2016), 10.1103/PhysRevB.93.085131] spin-fermion model with overlapping `hot spots' on the Fermi surface. Focusing on the particle-hole instabilities we obtain a rich phase diagram with the chemical potential relative to the dispersion at (0 ,π );(π ,0 ) and the Fermi surface curvature in the antinodal regions being the control parameters. We find evidence for d-wave Pomeranchuk instability, d-form factor charge density waves, as well as commensurate and incommensurate staggered bond current phases similar to the d-density wave state. The current orders are found to be promoted by the curvature. Considering the appropriate parameter range for the hole-doped cuprates, we discuss the relation of our results to the pseudogap state and incommensurate magnetic phases of the cuprates.

Deep Space Network Radiometric Remote Sensing Program

NASA Technical Reports Server (NTRS)

Walter, Steven J.

1994-01-01

Planetary spacecraft are viewed through a troposphere that absorbs and delays radio signals propagating through it. Tropospheric water, in the form of vapor, cloud liquid, and precipitation, emits radio noise which limits satellite telemetry communication link performance. Even at X-band, rain storms have severely affected several satellite experiments including a planetary encounter. The problem will worsen with DSN implementation of Ka-band because communication link budgets will be dominated by tropospheric conditions. Troposphere-induced propagation delays currently limit VLBI accuracy and are significant sources of error for Doppler tracking. Additionally, the success of radio science programs such as satellite gravity wave experiments and atmospheric occultation experiments depends on minimizing the effect of water vapor-induced propagation delays. In order to overcome limitations imposed by the troposphere, the Deep Space Network has supported a program of radiometric remote sensing. Currently, water vapor radiometers (WVRs) and microwave temperature profilers (MTPs) support many aspects of the Deep Space Network operations and research and development programs. Their capability to sense atmospheric water, microwave sky brightness, and atmospheric temperature is critical to development of Ka-band telemetry systems, communication link models, VLBI, satellite gravity wave experiments, and radio science missions. During 1993, WVRs provided data for propagation model development, supported planetary missions, and demonstrated advanced tracking capability. Collection of atmospheric statistics is necessary to model and predict performance of Ka-band telemetry links, antenna arrays, and radio science experiments. Since the spectrum of weather variations has power at very long time scales, atmospheric measurements have been requested for periods ranging from one year to a decade at each DSN site. The resulting database would provide reliable statistics on daily, monthly, and seasonal variations. Only long-term monitoring will prevent biases from being introduced by an exceptionally wet or dry year. Support for planetary missions included tropospheric calibration for the recent Mars Observer gravity wave experiments and Ka-band link experiment (KaBLE). Additionally, several proposed radio science experiments such as profiling planetary atmospheres using satellite occultations and Ka-band gravitational wave searches require advanced radiometer technology development. Finally, there has been a consistent advanced technology program to advance satellite navigational and tracking capabilities. This year that included an experiment with radiometer based tropospheric calibration for a series of VLBI catalog measurements.

Near-inertial waves and deep ocean mixing

NASA Astrophysics Data System (ADS)

Shrira, V. I.; Townsend, W. A.

2013-07-01

For the existing pattern of global oceanic circulation to exist, there should be sufficiently strong turbulent mixing in the abyssal ocean, the mechanisms of which are not well understood as yet. The review discusses a plausible mechanism of deep ocean mixing caused by near-inertial waves in the abyssal ocean. It is well known how winds in the atmosphere generate near-inertial waves in the upper ocean, which then propagate downwards losing their energy in the process; only a fraction of the energy at the surface reaches the abyssal ocean. An open question is whether and, if yes, how these weakened inertial motions could cause mixing in the deep. We review the progress in the mathematical description of a mechanism that results in an intense breaking of near-inertial waves near the bottom of the ocean and thus enhances the mixing. We give an overview of the present state of understanding of the problem covering both the published and the unpublished results; we also outline the key open questions. For typical ocean stratification, the account of the horizontal component of the Earth's rotation leads to the existence of near-bottom wide waveguides for near-inertial waves. Due to the β-effect these waveguides are narrowing in the poleward direction. Near-inertial waves propagating poleward get trapped in the waveguides; we describe how in the process these waves are focusing more and more in the vertical direction, while simultaneously their group velocity tends to zero and wave-induced vertical shear significantly increases. This causes the development of shear instability, which is interpreted as wave breaking. Remarkably, this mechanism of local intensification of turbulent mixing in the abyssal ocean can be adequately described within the framework of linear theory. The qualitative picture is similar to wind wave breaking on a beach: the abyssal ocean always acts as a surf zone for near-inertial waves.

Temporal Clustering of Regional-Scale Extreme Precipitation Events in Southern Switzerland

NASA Astrophysics Data System (ADS)

Barton, Yannick; Giannakaki, Paraskevi; Von Waldow, Harald; Chevalier, Clément; Pfhal, Stephan; Martius, Olivia

2017-04-01

Temporal clustering of extreme precipitation events on subseasonal time scales is a form of compound extremes and is of crucial importance for the formation of large-scale flood events. Here, the temporal clustering of regional-scale extreme precipitation events in southern Switzerland is studied. These precipitation events are relevant for the flooding of lakes in southern Switzerland and northern Italy. This research determines whether temporal clustering is present and then identifies the dynamics that are responsible for the clustering. An observation-based gridded precipitation dataset of Swiss daily rainfall sums and ECMWF reanalysis datasets are used. To analyze the clustering in the precipitation time series a modified version of Ripley's K function is used. It determines the average number of extreme events in a time period, to characterize temporal clustering on subseasonal time scales and to determine the statistical significance of the clustering. Significant clustering of regional-scale precipitation extremes is found on subseasonal time scales during the fall season. Four high-impact clustering episodes are then selected and the dynamics responsible for the clustering are examined. During the four clustering episodes, all heavy precipitation events were associated with an upperlevel breaking Rossby wave over western Europe and in most cases strong diabatic processes upstream over the Atlantic played a role in the amplification of these breaking waves. Atmospheric blocking downstream over eastern Europe supported this wave breaking during two of the clustering episodes. During one of the clustering periods, several extratropical transitions of tropical cyclones in the Atlantic contributed to the formation of high-amplitude ridges over the Atlantic basin and downstream wave breaking. During another event, blocking over Alaska assisted the phase locking of the Rossby waves downstream over the Atlantic.

Nonlinear modeling of wave-topography interactions, shear instabilities and shear induced wave breaking using vortex method

NASA Astrophysics Data System (ADS)

Guha, Anirban

2017-11-01

Theoretical studies on linear shear instabilities as well as different kinds of wave interactions often use simple velocity and/or density profiles (e.g. constant, piecewise) for obtaining good qualitative and quantitative predictions of the initial disturbances. Moreover, such simple profiles provide a minimal model to obtain a mechanistic understanding of shear instabilities. Here we have extended this minimal paradigm into nonlinear domain using vortex method. Making use of unsteady Bernoulli's equation in presence of linear shear, and extending Birkhoff-Rott equation to multiple interfaces, we have numerically simulated the interaction between multiple fully nonlinear waves. This methodology is quite general, and has allowed us to simulate diverse problems that can be essentially reduced to the minimal system with interacting waves, e.g. spilling and plunging breakers, stratified shear instabilities (Holmboe, Taylor-Caulfield, stratified Rayleigh), jet flows, and even wave-topography interaction problem like Bragg resonance. We found that the minimal models capture key nonlinear features (e.g. wave breaking features like cusp formation and roll-ups) which are observed in experiments and/or extensive simulations with smooth, realistic profiles.

Surf physics

NASA Astrophysics Data System (ADS)

Edge, Ronald

2001-05-01

Just what is happening when a surfer taps into the energy of a breaking wave and rides to shore? It's sport, it's art, it's skill, stamina, and drama. It is also physics — hydrodynamics, wave propagation, kinematics, and dynamics.

Modeling quiescent phase transport of air bubbles induced by breaking waves

NASA Astrophysics Data System (ADS)

Shi, Fengyan; Kirby, James T.; Ma, Gangfeng

Simultaneous modeling of both the acoustic phase and quiescent phase of breaking wave-induced air bubbles involves a large range of length scales from microns to meters and time scales from milliseconds to seconds, and thus is computational unaffordable in a surfzone-scale computational domain. In this study, we use an air bubble entrainment formula in a two-fluid model to predict air bubble evolution in the quiescent phase in a breaking wave event. The breaking wave-induced air bubble entrainment is formulated by connecting the shear production at the air-water interface and the bubble number intensity with a certain bubble size spectra observed in laboratory experiments. A two-fluid model is developed based on the partial differential equations of the gas-liquid mixture phase and the continuum bubble phase, which has multiple size bubble groups representing a polydisperse bubble population. An enhanced 2-DV VOF (Volume of Fluid) model with a k - ɛ turbulence closure is used to model the mixture phase. The bubble phase is governed by the advection-diffusion equations of the gas molar concentration and bubble intensity for groups of bubbles with different sizes. The model is used to simulate air bubble plumes measured in laboratory experiments. Numerical results indicate that, with an appropriate parameter in the air entrainment formula, the model is able to predict the main features of bubbly flows as evidenced by reasonable agreement with measured void fraction. Bubbles larger than an intermediate radius of O(1 mm) make a major contribution to void fraction in the near-crest region. Smaller bubbles tend to penetrate deeper and stay longer in the water column, resulting in significant contribution to the cross-sectional area of the bubble cloud. An underprediction of void fraction is found at the beginning of wave breaking when large air pockets take place. The core region of high void fraction predicted by the model is dislocated due to use of the shear production in the algorithm for initial bubble entrainment. The study demonstrates a potential use of an entrainment formula in simulations of air bubble population in a surfzone-scale domain. It also reveals some difficulties in use of the two-fluid model for predicting large air pockets induced by wave breaking, and suggests that it may be necessary to use a gas-liquid two-phase model as the basic model framework for the mixture phase and to develop an algorithm to allow for transfer of discrete air pockets to the continuum bubble phase. A more theoretically justifiable air entrainment formulation should be developed.

Stellar Metamorphosis:

NASA Technical Reports Server (NTRS)

2002-01-01

[TOP LEFT AND RIGHT] The Hubble Space Telescope's Wide Field and Planetary Camera 2 has captured images of the birth of two planetary nebulae as they emerge from wrappings of gas and dust, like butterflies breaking out of their cocoons. These images highlight a fleeting phase in the stellar burnout process, occurring just before dying stars are transformed into planetary nebulae. The left-hand image is the Cotton Candy nebula, IRAS 17150-3224; the right-hand image, the Silkworm nebula, IRAS 17441-2411. Called proto-planetary nebulae, these dying stars have been caught in a transition phase between a red giant and a planetary nebula. This phase is only about 1,000 years long, very short in comparison to the 1 billion-year lifetime of a star. These images provide the earliest snapshots of the transition process. Studying images of proto-planetary nebulae is important to understanding the process of star death. A star begins to die when it has exhausted its thermonuclear fuel - hydrogen and helium. The star then becomes bright and cool (red giant phase) and swells to several tens of times its normal size. It begins puffing thin shells of gas off into space. These shells become the star's cocoon. In the Hubble images, the shells are the concentric rings seen around each nebula. But the images also reveal the nebulae breaking out from those shells. The butterfly-like wings of gas and dust are a common shape of planetary nebulae. Such butterfly shapes are created by the 'interacting winds' process, in which a more recent 'fast wind' - material propelled by radiation from the hot central star - punches a hole in the cocoon, allowing the nebula to emerge. (This 'interacting wind' theory was first proposed by Dr. Sun Kwok to explain the origin of planetary nebulae, and has been subsequently proven successful in explaining their shapes.) The nebulae are being illuminated by light from the invisible central star, which is then reflected toward us. We are viewing the nebulae edge-on, where the direct starlight is blocked by the dusty cocoon. Otherwise, the starlight would overwhelm the nebular light, making it very difficult to see the butterfly-shaped nebula. In a few hundred years, intense ultraviolet radiation from the central star will energize the surrounding gas, causing it to glow brightly, and a planetary nebula is born. These observations were made with the Wide Field and Planetary Camera 2 using three filters: yellow-green, blue, and near-infrared. The images were taken in 1997 by Sun Kwok and in 1996 by Matt Bobrowsky. Credits: Sun Kwok and Kate Su (University of Calgary), Bruce Hrivnak (Valparaiso University), and NASA ----------------- The Hubble Space Telescope Sees Remarkable Structure in the Heart of a Planetary Nebula [BOTTOM LEFT AND RIGHT] This Wide Field and Planetary Camera 2 image of NGC 6818 shows two distinct layers of gas (with dust): a spherical outer region and a brighter, vase-shaped interior 'bubble.' Astronomers believe that a fast wind - material propelled by radiation from the hot central star - is creating the inner elongated shape. The central star of the planetary nebula appears as a tiny blue dot. The material in the wind is traveling so fast that it smashes through older, slower-moving stellar debris, causing a 'blowout' at both ends of the bubble (lower right and upper left). This nebula looks like a twin of NGC 3918, another planetary nebula that has been observed by the Hubble telescope. The structure of NGC 3918 is remarkably similar to that of NGC 6818. It has an outer spherical envelope and an inner, brighter, elongated bubble. A fast-moving wind also appears to have created an orifice at one end (bottom right-hand corner) of the inner bubble. There are even faint wisps of material that were probably blown out of this hole. In the opposite direction (top left-hand corner), there is a protrusion that seems on the verge of breaking through to form a hole. By finding and studying such similar objects, astronomers hope to learn crucial details about the evolutionary history of planetary nebulae. The Hubble telescope observation was taken March 10, 1997. This picture is a composite of images taken with three filters that are representative of the true colors of the object. Two of these are, respectively, in the light of a red and a blue spectral line of hydrogen - the major constituent of the nebula. The third image is in the light of a luminous green line due to doubly ionized oxygen. NGC 6818 is about 6,000 light-years away in the constellation Sagittarius. The nebula has a diameter of about 0.5 light-years. Credits: Robert Rubin (NASA Ames Research Center), Reginald Dufour and Matt Browning (Rice University), Patrick Harrington (University of Maryland), and NASA

Langmuir circulation inhibits near-surface water turbulence

NASA Astrophysics Data System (ADS)

Schultz, Colin

2012-07-01

In the surface ocean, breaking waves are a major source of air bubbles and turbulent kinetic energy. During the presence of a consistent surface wind, these wave-generated bubbles, along with other surface material like seaweed or foam, can be drawn into long rows along the surface. Driving this organization is Langmuir circulation, a phenomenon in which the wind and waves cause surface waters to rotate helically, moving like a wire wrapped around a pole in the windward direction. These spiral currents oscillate between clockwise and counterclockwise rotations, such that in some places the surface waters are pushed together and in others they are pulled apart. Researchers have previously found that at sites of convergence the bubbles produced by breaking waves are pushed to depths of 15 meters or more, with important implications for air-sea gas mixing and other processes.

Wave Interactions and Fluid Flows

NASA Astrophysics Data System (ADS)

Craik, Alex D. D.

1988-07-01

This up-to-date and comprehensive account of theory and experiment on wave-interaction phenomena covers fluids both at rest and in their shear flows. It includes, on the one hand, water waves, internal waves, and their evolution, interaction, and associated wave-driven means flow and, on the other hand, phenomena on nonlinear hydrodynamic stability, especially those leading to the onset of turbulence. This study provide a particularly valuable bridge between these two similar, yet different, classes of phenomena. It will be of value to oceanographers, meteorologists, and those working in fluid mechanics, atmospheric and planetary physics, plasma physics, aeronautics, and geophysical and astrophysical fluid dynamics.

Fourier Analysis and the Rhythm of Conversation.

ERIC Educational Resources Information Center

Dabbs, James M., Jr.

Fourier analysis, a common technique in engineering, breaks down a complex wave form into its simple sine wave components. Communication researchers have recently suggested that this technique may provide an index of the rhythm of conversation, since vocalizing and pausing produce a complex wave form pattern of alternation between two speakers. To…

DARLA: Data Assimilation and Remote Sensing for Littoral Applications

DTIC Science & Technology

2017-03-01

in the surf zone. The foam produced in an actively breaking crest, or wave roller, has a distinct signature in IR imagery. A retrieval algorithm is...the surface. The velocity profiles are obtained from a pulse-coherent acoustic Doppler sonar on a wave-following platform, termed a Surface Wave

Gravity Waves in the Martian Atmosphere detected by the Radio Science Experiment MaRS on Mars Express

NASA Astrophysics Data System (ADS)

Tellmann, S.; Pätzold, M.; Häusler, B.; Tyler, G. L.; Hinson, D. P.

2013-09-01

Gravity waves are an ubiquitous feature in all stably stratified planetary atmospheres. They are known to play a significant role in the energy and momentum budget of the Earth, and they are assumed to be of importance for the redistribution of energy and momentum throughout the Martian atmosphere.

The circulation pattern and day-night heat transport in the atmosphere of a synchronously rotating aquaplanet: Dependence on planetary rotation rate

NASA Astrophysics Data System (ADS)

Noda, S.; Ishiwatari, M.; Nakajima, K.; Takahashi, Y. O.; Takehiro, S.; Onishi, M.; Hashimoto, G. L.; Kuramoto, K.; Hayashi, Y.-Y.

2017-01-01

In order to investigate a possible variety of atmospheric states realized on a synchronously rotating aquaplanet, an experiment studying the impact of planetary rotation rate is performed using an atmospheric general circulation model (GCM) with simplified hydrological and radiative processes. The entire planetary surface is covered with a swamp ocean. The value of planetary rotation rate is varied from zero to the Earth's, while other parameters such as planetary radius, mean molecular weight and total mass of atmospheric dry components, and solar constant are set to the present Earth's values. The integration results show that the atmosphere reaches statistically equilibrium states for all runs; none of the calculated cases exemplifies the runaway greenhouse state. The circulation patterns obtained are classified into four types: Type-I characterized by the dominance of a day-night thermally direct circulation, Type-II characterized by a zonal wave number one resonant Rossby wave over a meridionally broad westerly jet on the equator, Type-III characterized by a long time scale north-south asymmetric variation, and Type-IV characterized by a pair of mid-latitude westerly jets. With the increase of planetary rotation rate, the circulation evolves from Type-I to Type-II and then to Type-III gradually and smoothly, whereas the change from Type-III to Type-IV is abrupt and discontinuous. Over a finite range of planetary rotation rate, both Types-III and -IV emerge as statistically steady states, constituting multiple equilibria. In spite of the substantial changes in circulation, the net energy transport from the day side to the night side remains almost insensitive to planetary rotation rate, although the partition into dry static energy and latent heat energy transports changes. The reason for this notable insensitivity is that the outgoing longwave radiation over the broad area of the day side is constrained by the radiation limit of a moist atmosphere, so that the transport to the night side, which is determined as the difference between the incoming solar radiation and the radiation limit, cannot change greatly.

A modeling study of the thermosphere-ionosphere interactions during the boreal winter and spring 2015-2016: Tidal and planetary-scale waves effect on the ionospheric structure.

NASA Astrophysics Data System (ADS)

Sassi, F.; McDonald, S. E.; McCormack, J. P.; Tate, J.; Liu, H.; Kuhl, D.

2017-12-01

The 2015-2016 boreal winter and spring is a dynamically very interesting time in the lower atmosphere: a minor high latitude stratospheric warming occurred in February 2016; an interrupted descent of the QBO was found in the tropical stratosphere; and a large warm ENSO took place in the tropical Pacific Ocean. The stratospheric warming, the QBO and ENSO are known to affect in different ways the meteorology of the upper atmosphere in different ways: low latitude solar tides and high latitude planetary-scale waves have potentially important implications on the structure of the ionosphere. In this study, we use global atmospheric analyses from a high-altitude version of the High-Altitude Navy Global Environmental Model (HA-NAVGEM) to constrain the meteorology of numerical simulations of the Specified Dynamics Whole Atmosphere Community Climate Model, extended version (SD-WACCM-X). We describe the large-scale behavior of tropical tides and mid-latitude planetary waves that emerge in the lower thermosphere. The effect on the ionosphere is captured by numerical simulations of the Navy Highly Integrated Thermosphere Ionosphere Demonstration System (Navy-HITIDES) that uses the meteorology generated by SD-WACCM-X to drive ionospheric simulations during this time period. We will analyze the impact of various dynamical fields on the zonal behavior of the ionosphere by selectively filtering the relevant dynamical modes.

Realization of localized Bohr-like wave packets.

PubMed

Mestayer, J J; Wyker, B; Lancaster, J C; Dunning, F B; Reinhold, C O; Yoshida, S; Burgdörfer, J

2008-06-20

We demonstrate a protocol to create localized wave packets in very-high-n Rydberg states which travel in nearly circular orbits around the nucleus. Although these wave packets slowly dephase and eventually lose their localization, their motion can be monitored over several orbital periods. These wave packets represent the closest analog yet achieved to the original Bohr model of the hydrogen atom, i.e., an electron in a circular classical orbit around the nucleus. The possible extension of the approach to create "planetary atoms" in highly correlated stable multiply excited states is discussed.

SPIRAL PATTERNS IN PLANETESIMAL CIRCUMBINARY DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demidova, Tatiana V.; Shevchenko, Ivan I., E-mail: iis@gao.spb.ru

Planet formation scenarios and the observed planetary dynamics in binaries pose a number of theoretical challenges, especially concerning circumbinary planetary systems. We explore the dynamical stirring of a planetesimal circumbinary disk in the epoch when the gas component disappears. For this purpose, following theoretical approaches by Heppenheimer and Moriwaki and Nakagawa, we develop a secular theory of the dynamics of planetesimals in circumbinary disks. If a binary is eccentric and its components have unequal masses, a spiral density wave is generated, engulfing the disk on a secular timescale, which may exceed 10{sup 7} yr, depending on the problem parameters. The spiralmore » pattern is transient; thus, its observed presence may betray a system’s young age. We explore the pattern both analytically and in numerical experiments. The derived analytical spiral is a modified lituus; it matches the numerical density wave in the gas-free case perfectly. Using the smoothed particle hydrodynamics scheme, we explore the effect of residual gas on the wave propagation.« less

Nonlinear dynamics of global atmospheric and Earth system processes

NASA Technical Reports Server (NTRS)

Saltzman, Barry

1993-01-01

During the past eight years, we have been engaged in a NASA-supported program of research aimed at establishing the connection between satellite signatures of the earth's environmental state and the nonlinear dynamics of the global weather and climate system. Thirty-five publications and four theses have resulted from this work, which included contributions in five main areas of study: (1) cloud and latent heat processes in finite-amplitude baroclinic waves; (2) application of satellite radiation data in global weather analysis; (3) studies of planetary waves and low-frequency weather variability; (4) GCM studies of the atmospheric response to variable boundary conditions measurable from satellites; and (5) dynamics of long-term earth system changes. Significant accomplishments from the three main lines of investigation pursued during the past year are presented and include the following: (1) planetary atmospheric waves and low frequency variability; (2) GCM studies of the atmospheric response to changed boundary conditions; and (3) dynamics of long-term changes in the global earth system.

Coherent Structures and Evolution of Vorticity in Short-Crested Breaking Surface Waves

NASA Astrophysics Data System (ADS)

Kirby, James; Derakhti, Morteza

2017-11-01

We employ a multi-phase LES/VOF code to study turbulence and coherent structures generated during breaking of short-crested surface water waves. We examine the evolution of coherent vortex structures evolving at the scale of the width of the breaking event, and their long-time interaction with smaller vortex loops formed by the local instability of the breaking crest. Long-time results are often characterized by the detachment of the larger scale vortex loop from the surface and formation of a closed vortex ring. The evolution of circulation for the vortical flow field is examined. The initial concentration of forcing close to the free surface leads to spatial distributions of both span-wise and vertical vorticity distributions which are concentrated close to the surface. This result, which persists into shallow water, is at odds with the basic simplicity of the Peregrine mechanism, suggesting that even shallow flows such as the surf zone should be regarded as being forced (in dissipative situations) by a wave-induced surface stress rather than a uniform-over-depth body force. The localized forcing leads to the development of a complex pattern of stream-wise vorticity, comparable in strength to the vertical and span-wise components, and also persist into shallow water. NSF OCE-1435147.

Aggression and Rule-breaking: Heritability and stability of antisocial behavior problems in childhood and adolescence

PubMed Central

Niv, Sharon; Tuvblad, Catherine; Raine, Adrian; Baker, Laura A.

2013-01-01

Purpose This twin study examined the structure of genetic and environmental influences on aggression and rule-breaking in order to examine change and stability across the span of childhood to mid-adolescence. Methods Behavioral assessments were conducted at two time points: age 9–10 years and 14–15 years. Using behavioral genetics biometric modeling, the longitudinal structure of influences was investigated. Results Aggression and rule-breaking were found to be influenced by a latent common factor of antisocial behavior (ASB) within each wave of data collection. The childhood-age common factor of ASB was influenced by 41% genetics, 40% shared environment and 19% nonshared environment. In adolescence, 41% of influences on the common factor were novel and entirely genetic, while the remainder of influences were stable across time. Additionally, both aggression and rule-breaking within each wave were found to have unique influences not common across subscales or across waves, highlighting specificity of influences on different problem behaviors at both ages. Conclusions This research sheds light on the commonality of influences on etiology of different forms of antisocial behavior, and suggests future directions for research into intervention for antisocial behavior problems in youth, such as investigation of adolescence-specific environmental influences on the development of antisocial behavior problems. PMID:24347737

An Instability in Narrow Planetary Rings

NASA Astrophysics Data System (ADS)

Weiss, J. W.; Stewart, G. R.

2003-08-01

We will present our work investigating the behavior of narrow planetary rings with low dispersion velocities. Such narrow a ring will be initially unstable to self-gravitational collapse. After the collapse, the ring is collisionally very dense. At this stage, it is subject to a new instability. Waves appear on the inner and outer edges of the ring within half of an orbital period. The ring then breaks apart radially, taking approximately a quarter of an orbital period of do so. As clumps of ring particles expand radially away from the dense ring, Kepler shear causes these clumps to stretch out azimuthally, and eventually collapse into a new set of dense rings. Small-scale repetitions of the original instability in these new rings eventually leads to a stabilized broad ring with higher dispersion velocities than the initial ring. Preliminary results indicate that this instability may be operating on small scales in broad rings in the wake-like features seen by Salo and others. Some intriguing properties have been observed during this instability. The most significant is a coherence in the epicyclic phases of the particles. Both self-gravity and collisions in the ring operated to create and enforce this coherence. The coherence might also be responsible for the instability to radial expansion. We also observe that guiding centers of the particles do not migrate to the center of the ring during the collapse phase of the ring. In fact, guiding centers move radially away from the core of the ring during this phase, consistent with global conservation of angular momentum. We will show the results of our simulations to date, including movies of the evolution of various parameters. (Audiences members wanting popcorn are advised to bring their own.) This work is supported by a NASA Graduate Student Research Program grant and by the Cassini mission.

Zonostrophic turbulence

NASA Astrophysics Data System (ADS)

Galperin, Boris; Sukoriansky, Semion; Dikovskaya, Nadejda

2008-12-01

Geostrophic turbulence is a flow regime attained by turbulent, rotating, stably stratified fluids in near-geostrophic balance. When a small-scale forcing is present, flows in this regime may develop an inverse energy cascade. Geostrophic turbulence has been used in geophysical fluid dynamics as a relatively simple model of the large-scale planetary and terrestrial circulations. When the meridional variation of the Coriolis parameter (or a β-effect) is taken into account, the horizontal flow symmetry breaks down giving rise to the emergence of jet flows. In a certain parameter range, a new flow regime comes to life. Its main characteristics include strongly anisotropic kinetic energy spectrum and slowly evolving systems of alternating zonal jets. This regime is a subset of geostrophic turbulence and has been coined zonostrophic turbulence; it can develop both on a β-plane and on the surface of a rotating sphere. This regime was first discovered in computer simulations but later revealed in the laboratory experiments, in the deep terrestrial oceans, and on solar giant planets where it is believed to be the primary physical mechanism responsible for the generation and maintenance of the stable systems of alternating zonal jets. The hallmarks of zonostrophic turbulence are the anisotropic inverse energy cascade and complicated interaction between turbulence and Rossby-Haurwitz waves. Addressing the goals of the conference 'Turbulent Mixing and Beyond' that took place in August 2007 in Trieste, Italy, this paper exposes the regime of zonostrophic turbulence to a wide scientific community, provides a survey of this regime, elaborates its main characteristics, offers novel approaches to describe and understand this phenomenon, and discusses its applicability as a model of the large-scale planetary and terrestrial circulations.

Projections of extreme water level events for atolls in the western Tropical Pacific

NASA Astrophysics Data System (ADS)

Merrifield, M. A.; Becker, J. M.; Ford, M.; Yao, Y.

2014-12-01

Conditions that lead to extreme water levels and coastal flooding are examined for atolls in the Republic of the Marshall Islands based on a recent field study of wave transformations over fringing reefs, tide gauge observations, and wave model hindcasts. Wave-driven water level extremes pose the largest threat to atoll shorelines, with coastal levels scaling as approximately one-third of the incident breaking wave height. The wave-driven coastal water level is partitioned into a mean setup, low frequency oscillations associated with cross-reef quasi-standing modes, and wind waves that reach the shore after undergoing high dissipation due to breaking and bottom friction. All three components depend on the water level over the reef; however, the sum of the components is independent of water level due to cancelling effects. Wave hindcasts suggest that wave-driven water level extremes capable of coastal flooding are infrequent events that require a peak wave event to coincide with mid- to high-tide conditions. Interannual and decadal variations in sea level do not change the frequency of these events appreciably. Future sea-level rise scenarios significantly increase the flooding threat associated with wave events, with a nearly exponential increase in flooding days per year as sea level exceeds 0.3 to 1.0 m above current levels.

A Locally Generated High-Mode Nonlinear Internal Wave Detected on the Shelf of the Northern South China Sea From Marine Seismic Observations

NASA Astrophysics Data System (ADS)

Tang, Qunshu; Xu, Min; Zheng, Chan; Xu, Xing; Xu, Jiang

2018-02-01

In this work, a secondary nonlinear internal wave (NIW) on the continental shelf of the northern South China Sea is investigated using high-resolution seismic imaging and joint inversion of water structure properties combined with in situ hydrographic observations. It is an extraordinary wave combination with two mode-2 NIWs and one elevated NIW occurring within a short distance of 2 km. The most energetic part of the NIW could be regarded as a mode-2 NIW in the upper layer between 40 and 120 m depth. The vertical particle velocity of ˜41 cm/s may exceed the critical value of wave breaking and thus collapse the strong stratification followed by a series of processes including internal wave breaking, overturning, Kelvin-Helmholtz instability, stratification splitting, and eventual restratification. Among these processes, the shear-induced Kelvin-Helmholtz instability is directly imaged using the seismic method for the first time. The stratification splitting and restratification show that the unstable stage lasts only for a few hours and spans several kilometers. It is a new observation that the elevated NIW could be generated in a deepwater region (as deep as ˜370 m). Different from the periodical NIWs originating from the Luzon Strait, this secondary NIW is most likely generated locally, at the continental shelf break during ebb tide.

Controllable robust laser driven ion acceleration from near-critical density relativistic self-transparent plasma

NASA Astrophysics Data System (ADS)

Liu, Bin; Meyer-Ter-Vehn, Juergen; Ruhl, Hartmut

2017-10-01

We introduce an alternative approach for laser driven self-injected high quality ion acceleration. We call it ion wave breaking acceleration. It operates in relativistic self-transparent plasma for ultra-intense ultra-short laser pulses. Laser propagating in a transparent plasma excites an electron wave as well as an ion wave. When the ion wave breaks, a fraction of ions is self-injected into the positive part of the laser driven wake. This leads to a superior ion pulse with peaked energy spectra; in particular in realistic three-dimensional geometry, the injection occurs localized close to the laser axis producing highly directed bunches. A theory is developed to investigate the ion wave breaking dynamics. Three dimensional Particle-in-Cell simulations with pure-gaussian laser pulses and pre-expanded near-critical density plasma targets have been done to verify the theoretical results. It is shown that hundreds of MeV, easily controllable and manipulable, micron-scale size, highly collimated and quasi-mono-energetic ion beams can be produced by using ultra-intense ultra-short laser pulses with total laser energies less than 10 Joules. Such ion beams may find important applications in tumour therapy. B. Liu acknowledges support from the Alexander von Humboldt Foundation. B. Liu and H. Ruhl acknowledge supports from the Gauss Centre for Supercomputing (GCS), and the Cluster-of-Excellence Munich Centre for Advanced Photonics (MAP).

Charge independence, charge symmetry breaking in the S-wave nucleon-nucleon interaction, and renormalization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alvaro Calle Cordon,Manuel Pavon Valderrama,Enrique Ruiz Arriola

2012-02-01

We study the interplay between charge symmetry breaking and renormalization in the NN system for S-waves. We find a set of universality relations which disentangle explicitly the known long distance dynamics from low energy parameters and extend them to the Coulomb case. We analyze within such an approach the One-Boson-Exchange potential and the theoretical conditions which allow to relate the proton-neutron, proton-proton and neutron-neutron scattering observables without the introduction of extra new parameters and providing good phenomenological success.

Framing topographic Rossby waves in the Southern Adriatic Sea

NASA Astrophysics Data System (ADS)

Bonaldo, Davide; Orlic, Mirko; Bergamasco, Andrea; Benetazzo, Alvise; Carniel, Sandro

2017-04-01

Topographic Rossby Waves (TRWs) are oscillatory phenomena associated with modulations induced by seabed morphology in the potential vorticity field. These features could be confined to a single layer or could involve the whole water column, and they are controlled by a combination of the bathymetric gradient and the uniform rotation in the same way as planetary Rossby waves are controlled by the meridional modulation of the Coriolis parameter. In terms of deep-sea circulation, TRWs provide a fundamental contribution by radiating large amounts of energy along and off a continental shelf. Under favorable conditions TRWs can be triggered by a number of factors, such as intense vorticity injections from the wind or the bathymetric perturbations - e.g., a promontory or a canyon crossing the path of a current. In this work we combine observational data and numerical model fields for detecting the presence of TRWs along the Southern Adriatic Margin (SAM, Eastern Mediterranean Sea) and investigating their dynamics during an episode of dense water downflow in spring 2012. Starting from the observation of high-intensity velocity pulses with a period of approximately 2 days, we carry out a sequence of operations on the results of a high-resolution, ocean currents-waves coupled numerical modelling experiment aiming to reproduce dense water formation and migration in the Adriatic Sea in winter-spring 2012. First, we apply a wavelet analysis to modelled velocity time series at several locations off the Italian coast and along the SAM in order to identify the spatial and temporal extent of the pulsing episodes. Then, the properties of the oscillations are assessed via rotary analysis; the propagation of the band-filtered signal along the continental margin is characterized by extracting wave length and propagation velocity, therefore allowing the comparison against theoretical dispersion relations associated with the bathymetry of the SAM. Our results show that the observed modulation was indeed related to a perturbation system propagating south-eastward along the Italian coast and amplified as a train of TRWs along the shelf break and on the continental slope, thus providing, to the best of our knowledge, the first evidence of the existence of such waves on the SAM. This work paves the way to further investigations of these waves and their implications on dense water dynamics and related impacts on the benthic environments.

Collaborative analysis of Planetary Waves in the Mesospheric Neutral Winds with SuperDARN and TIMED Observations

NASA Astrophysics Data System (ADS)

Ruohoniemi, J. M.

2004-12-01

The SuperDARN HF radars are best known for observing the ExB drift of ionospheric plasma in the high-latitude F region. At mesospheric altitudes the trails of ionization produced by meteors provide another kind of target for radar backscatter, and the motions imparted to these trails by winds in the neutral atmosphere can be measured. In the northern hemisphere the coverage of mesospheric winds currently extends over a 180 deg longitude sector but is confined by propagation conditions to latitudes near 55 deg geographic. We have analyzed several extended periods of simultaneous observations of the neutral wind involving SuperDARN and the TIMED suite of instruments. Often, the winds show clear evidence of large-scale wave events. The quasi 2-day planetary waves are prominent and their occurrence is seen to depend on season. By comparing the wave characteristics between the satellite and ground observations we obtain a complete breakdown of the wave activity in terms of wave periods and zonal wavenumbers. In addition, the semidiurnal tide is a ubiquitous feature of the mid-latitude mesosphere. A single radar station cannot resolve the sun-synchronous component from other contributions at the semidiurnal frequency. We show that with a chain of radars along a latitude band, the true sun-synchronous, or migrating, component can be inferred. Joint analysis can be performed chiefly with data from the SABRE and TIDI instruments.

Effective holographic theory of charge density waves

NASA Astrophysics Data System (ADS)

Amoretti, Andrea; Areán, Daniel; Goutéraux, Blaise; Musso, Daniele

2018-04-01

We use gauge/gravity duality to write down an effective low energy holographic theory of charge density waves. We consider a simple gravity model which breaks translations spontaneously in the dual field theory in a homogeneous manner, capturing the low energy dynamics of phonons coupled to conserved currents. We first focus on the leading two-derivative action, which leads to excited states with nonzero strain. We show that including subleading quartic derivative terms leads to dynamical instabilities of AdS2 translation invariant states and to stable phases breaking translations spontaneously. We compute analytically the real part of the electric conductivity. The model allows to construct Lifshitz-like hyperscaling violating quantum critical ground states breaking translations spontaneously. At these critical points, the real part of the dc conductivity can be metallic or insulating.

Midwinter Disturbances in the Middle Atmosphere

NASA Technical Reports Server (NTRS)

Labitzke, K.

1984-01-01

The Middle Atmosphere is coupled to the troposphere during winter because planetary scale waves can propagate upwards if the prevailing winds are from the west. It is during this time of the year that the well-known midwinter disturbances are observed which ultimately affect the whole of the Middle Atmosphere. The mechanism of these disturbances is not completely understood. The large-scale circulation features up to the upper mesosphere are investigated to demonstrate the synoptic-scale behavior of the midwinter disturbances. Ground-based and satellite observations are combined. The interannual variability of the disturbances is discussed briefly. It is shown that the QBO (Quasi Biennial Oscillation) of the equatorial stratosphere appears to modulate the planetary waves during the northern winters, in the troposphere as well as in the Middle Atmosphere.

Mercury's magnetosphere after MESSENGER's first flyby.

PubMed

Slavin, James A; Acuña, Mario H; Anderson, Brian J; Baker, Daniel N; Benna, Mehdi; Gloeckler, George; Gold, Robert E; Ho, George C; Killen, Rosemary M; Korth, Haje; Krimigis, Stamatios M; McNutt, Ralph L; Nittler, Larry R; Raines, Jim M; Schriver, David; Solomon, Sean C; Starr, Richard D; Trávnícek, Pavel; Zurbuchen, Thomas H

2008-07-04

Observations by MESSENGER show that Mercury's magnetosphere is immersed in a comet-like cloud of planetary ions. The most abundant, Na+, is broadly distributed but exhibits flux maxima in the magnetosheath, where the local plasma flow speed is high, and near the spacecraft's closest approach, where atmospheric density should peak. The magnetic field showed reconnection signatures in the form of flux transfer events, azimuthal rotations consistent with Kelvin-Helmholtz waves along the magnetopause, and extensive ultralow-frequency wave activity. Two outbound current sheet boundaries were observed, across which the magnetic field decreased in a manner suggestive of a double magnetopause. The separation of these current layers, comparable to the gyro-radius of a Na+ pickup ion entering the magnetosphere after being accelerated in the magnetosheath, may indicate a planetary ion boundary layer.

Greenhouse effect in planetary atmospheres caused by molecular symmetry breaking in intermolecular interactions

NASA Astrophysics Data System (ADS)

Vigasin, A. A.; Mokhov, I. I.

2017-03-01

It is believed that the greenhouse effect is related to the parameters of absorption spectra of polyatomic molecules, usually trace gases, in planetary atmospheres. The main components of all known atmospheres of celestial bodies are symmetrical molecules that do not possess the dipole-allowed purely rotational (and in the case of diatomic molecules, vibrational-rotational) absorption spectrum. Upon increased pressure, a weak absorption appears, induced by intermolecular interaction, which can lead to a greenhouse effect. The contribution of the induced absorption in radiative forcing of a dense atmosphere may amount to a few or even tens of W/m2. In conditions typical for the atmospheres of terrestrial planets (including paleoatmospheres), the collision-induced absorption and associated greenhouse effect may lead to an increase in surface temperature above the freezing point of water. There is a correlation between the temperature of an atmosphere and the intermolecular bonding energy of gases that dominate in planetary atmospheres of the Solar System.

Lightweight Low Force Rotary Percussive Coring Tool for Planetary Applications

NASA Technical Reports Server (NTRS)

Hironaka, Ross; Stanley, Scott

2010-01-01

A prototype low-force rotary-percussive rock coring tool for use in acquiring samples for geological surveys in future planetary missions was developed. The coring tool could eventually enable a lightweight robotic system to operate from a relatively small (less than 200 kg) mobile or fixed platform to acquire and cache Mars or other planetary rock samples for eventual return to Earth for analysis. To gain insight needed to design an integrated coring tool, the coring ability of commercially available coring bits was evaluated for effectiveness of varying key parameters: weight-on-bit, rotation speed, percussive rate and force. Trade studies were performed for different methods of breaking a core at its base and for retaining the core in a sleeve to facilitate sample transfer. This led to a custom coring tool design which incorporated coring, core breakage, core retention, and core extraction functions. The coring tool was tested on several types of rock and demonstrated the overall feasibility of this approach for robotic rock sample acquisition.

Collective bubble oscillations as a component of surf infrasound.

PubMed

Park, Joseph; Garcés, Milton; Fee, David; Pawlak, Geno

2008-05-01

Plunging surf is a known generator of infrasound, though the mechanisms have not been clearly identified. A model based on collective bubble oscillations created by demise of the initially entrained air pocket is examined. Computed spectra are compared to infrasound data from the island of Kauai during periods of medium, large, and extreme surf. Model results suggest that bubble oscillations generated by plunging waves are plausible generators of infrasound, and that dynamic bubble plume evolution on a temporal scale comparable to the breaking wave period may contribute to the broad spectral lobe of dominant infrasonic energy observed in measured data. Application of an inverse model has potential to characterize breaking wave size distributions, energy, and temporal changes in seafloor morphology based on remotely sensed infrasound.

Asymmetric nonlinear system is not sufficient for a nonreciprocal wave diode

NASA Astrophysics Data System (ADS)

Wu, Gaomin; Long, Yang; Ren, Jie

2018-05-01

We demonstrate symmetric wave propagations in asymmetric nonlinear systems. By solving the nonlinear Schördinger equation, we first analytically prove the existence of symmetric transmission in asymmetric systems with a single nonlinear delta-function interface. We then point out that a finite width of the nonlinear interface region is necessary to produce nonreciprocity in asymmetric systems. However, a geometrical resonant condition for breaking nonreciprocal propagation is then identified theoretically and verified numerically. With such a resonant condition, the nonlinear interface region of finite width behaves like a single nonlinear delta-barrier so that wave propagations in the forward and backward directions are identical under arbitrary incident wave intensity. As such, reciprocity reemerges periodically in the asymmetric nonlinear system when changing the width of interface region. Finally, similar resonant conditions of discrete nonlinear Schördinger equation are discussed. Therefore, we have identified instances of reciprocity that breaking spatial symmetry in nonlinear interface systems is not sufficient to produce nonreciprocal wave propagation.

Planetary Waves and Mesoscale Disturbances in the Middle and Upper Atmosphere

DTIC Science & Technology

1998-05-14

processing of ionogram records made us to begin designing a computer - controlled system to collect, store, display and scale the ionograms in digital...circuit board " L - 154". L - 154 passed signals from the re- ceiver and the system of the control to computer in order to collect in for motion...the main purpose of the PSMOS project is the establishment of a ground-based mesopause observing system for the investigation of planetary scale

Laboratory and theoretical models of planetary-scale instabilities and waves

NASA Technical Reports Server (NTRS)

Hart, John E.; Toomre, Juri

1991-01-01

Meteorologists and planetary astronomers interested in large-scale planetary and solar circulations recognize the importance of rotation and stratification in determining the character of these flows. The two outstanding problems of interest are: (1) the origins and nature of chaos in baroclinically unstable flows; and (2) the physical mechanisms responsible for high speed zonal winds and banding on the giant planets. The methods used to study these problems, and the insights gained, are useful in more general atmospheric and climate dynamic settings. Because the planetary curvature or beta-effect is crucial in the large scale nonlinear dynamics, the motions of rotating convecting liquids in spherical shells were studied using electrohydrodynamic polarization forces to generate radial gravity and centrally directed buoyancy forces in the laboratory. The Geophysical Fluid Flow Cell (GFFC) experiments performed on Spacelab 3 in 1985 were analyzed. The interpretation and extension of these results have led to the construction of efficient numerical models of rotating convection with an aim to understand the possible generation of zonal banding on Jupiter and the fate of banana cells in rapidly rotating convection as the heating is made strongly supercritical. Efforts to pose baroclinic wave experiments for future space missions using a modified version of the 1985 instrument have led us to develop theoretical and numerical models of baroclinic instability. Some surprising properties of both these models were discovered.

Planetary Rings

NASA Astrophysics Data System (ADS)

Gordon, M. K.; Araki, S.; Black, G. J.; Bosh, A. S.; Brahic, A.; Brooks, S. M.; Charnoz, S.; Colwell, J. E.; Cuzzi, J. N.; Dones, L.; Durisen, R. H.; Esposito, L. W.; Ferrari, C.; Festou, M.; French, R. G.; Giuliatti-Winter, S. M.; Graps, A. L.; Hamilton, D. P.; Horanyi, M.; Karjalainen, R. M.; Krivov, A. V.; Krueger, H.; Larson, S. M.; Levison, H. F.; Lewis, M. C.; Lissauer, J. J.; Murray, C. D.; Namouni, F.; Nicholson, P. D.; Olkin, C. B.; Poulet, F.; Rappaport, N. J.; Salo, H. J.; Schmidt, J.; Showalter, M. R.; Spahn, F.; Spilker, L. J.; Srama, R.; Stewart, G. R.; Yanamandra-Fisher, P.

2002-08-01

The past two decades have witnessed dramatic changes in our view and understanding of planetary rings. We now know that each of the giant planets in the Solar System possesses a complex and unique ring system. Recent studies have identified complex gravitational interactions between the rings and their retinues of attendant satellites. Among the four known ring systems, we see elegant examples of Lindblad and corotation resonances (first invoked in the context of galactic disks), electromagnetic resonances, spiral density waves and bending waves, narrow ringlets which exhibit internal modes due to collective instabilities, sharp-edged gaps maintained via tidal torques from embedded moonlets, and tenuous dust belts created by meteoroid impact onto, or collisions between, parent bodies. Yet, as far as we have come, our understanding is far from complete. The fundamental questions confronting ring scientists at the beginning of the twenty-first century are those regarding the origin, age and evolution of the various ring systems, in the broadest context. Understanding the origin and age requires us to know the current ring properties, and to understand the dominant evolutionary processes and how they influence ring properties. Here we discuss a prioritized list of the key questions, the answers to which would provide the greatest improvement in our understanding of planetary rings. We then outline the initiatives, missions, and other supporting activities needed to address those questions, and recommend priorities for the coming decade in planetary ring science.

Comparative study of ion cyclotron waves at Mars, Venus and Earth

NASA Astrophysics Data System (ADS)

Wei, H. Y.; Russell, C. T.; Zhang, T. L.; Blanco-Cano, X.

2011-08-01

Ion cyclotron waves are generated in the solar wind when it picks up freshly ionized planetary exospheric ions. These waves grow from the free energy of the highly anisotropic distribution of fresh pickup ions, and are observed in the spacecraft frame with left-handed polarization and a wave frequency near the ion's gyrofrequency. At Mars and Venus and in the Earth's polar cusp, the solar wind directly interacts with the planetary exospheres. Ion cyclotron waves with many similar properties are observed in these diverse plasma environments. The ion cyclotron waves at Mars indicate its hydrogen exosphere to be extensive and asymmetric in the direction of the interplanetary electric field. The production of fast neutrals plays an important role in forming an extended exosphere in the shape and size observed. At Venus, the region of exospheric proton cyclotron wave production may be restricted to the magnetosheath. The waves observed in the solar wind at Venus appear to be largely produced by the solar-wind-Venus interaction, with some waves at higher frequencies formed near the Sun and carried outward by the solar wind to Venus. These waves have some similarity to the expected properties of exospherically produced proton pickup waves but are characterized by magnetic connection to the bow shock or by a lack of correlation with local solar wind properties respectively. Any confusion of solar derived waves with exospherically derived ion pickup waves is not an issue at Mars because the solar-produced waves are generally at much higher frequencies than the local pickup waves and the solar waves should be mostly absorbed when convected to Mars distance as the proton cyclotron frequency in the plasma frame approaches the frequency of the solar-produced waves. In the Earth's polar cusp, the wave properties of ion cyclotron waves are quite variable. Spatial gradients in the magnetic field may cause this variation as the background field changes between the regions in which the fast neutrals are produced and where they are re-ionized and picked up. While these waves were discovered early in the magnetospheric exploration, their generation was not understood until after we had observed similar waves in the exospheres of Mars and Venus.

EFFECTS OF CHEMICAL DISPERSANTS AND MINERAL FINES ON CRUDE OIL DISPERSION IN A WAVE TANK UNDER BREAKING WAVES

EPA Science Inventory

The interaction of chemical dispersants and suspended sediments with crude oil influences the fate and transport of oil spills in coastal waters. A wave tank study was conducted to investigate the effects of chemical dispersants and mineral fines on the dispersion of oil and the ...

Manipulating one-way space wave and its refraction by time-reversal and parity symmetry breaking

PubMed Central

Poo, Yin; He, Cheng; Xiao, Chao; Lu, Ming-Hui; Wu, Rui-Xin; Chen, Yan-Feng

2016-01-01

One-way transmission and negative refraction are the exotic wave properties founded in photonic crystals which attract a great attention due to their promising applications in photonic devices. How to integrate such two phenomena in one material or device is interesting and valuable. In this work, we theoretically and experimentally demonstrate that one-way electromagnetic space wave can be realized by means of two-dimensional magnetic photonic crystals. Simultaneously breaking the time-reversal and parity symmetries of the magnetic photonic crystals designed, we observe oblique incident space wave propagating one-way in the magnetic photonic crystals with positive or negative refraction occurring at interfaces, which can be manipulated upon the incident angle and operating frequency. Our work may offer a potential platform to realize some exotic photoelectronic and microwave devices such as one-way imaging and one-way cloaking. PMID:27387438

Translational Symmetry-Breaking for Spiral Waves

NASA Astrophysics Data System (ADS)

LeBlanc, V. G.; Wulff, C.

2000-10-01

Spiral waves are observed in numerous physical situations, ranging from Belousov-Zhabotinsky (BZ) chemical reactions, to cardiac tissue, to slime-mold aggregates. Mathematical models with Euclidean symmetry have recently been developed to describe the dynamic behavior (for example, meandering) of spiral waves in excitable media. However, no physical experiment is ever infinite in spatial extent, so the Euclidean symmetry is only approximate. Experiments on spiral waves show that inhomogeneities can anchor spirals and that boundary effects (for example, boundary drifting) become very important when the size of the spiral core is comparable to the size of the reacting medium. Spiral anchoring and boundary drifting cannot be explained by the Euclidean model alone. In this paper, we investigate the effects on spiral wave dynamics of breaking the translation symmetry while keeping the rotation symmetry. This is accomplished by introducing a small perturbation in the five-dimensional center bundle equations (describing Hopf bifurcation from one-armed spiral waves) which is SO(2)-equivariant but not equivariant under translations. We then study the effects of this perturbation on rigid spiral rotation, on quasi-periodic meandering and on drifting.

On the response to ocean surface currents in synthetic aperture radar imagery

NASA Technical Reports Server (NTRS)

Phillips, O. M.

1984-01-01

The balance of wave action spectral density for a fixed wave-number is expressed in terms of a new dimensionless function, the degree of saturation, b, and is applied to an analysis of the variations of this quantity (and local spectral level) at wave-numbers large compared to that of the spectral peak, that are produced by variations in the ocean surface currents in the presence of wind input and wave breaking. Particular care is taken to provide physically based representations of wind input and loss by wave breaking and a relatively convenient equation is derived that specifies the distribution of the degree of saturation in a current field, relative to its ambient (undisturbed) background in the absence of currents. The magnitude of the variations in b depends on two parameters, U(o)/c, where U/(o) is the velocity scale of the current and c the phase speed of the surface waves at the (fixed) wave-number considered or sampled by SAR, and S = (L/lambda) (u*/c)(2), where L is the length scale of the current distribution, lambda the wavelength of the surface waves the length scale of the current distribution, lambda the wavelength of the surface waves and u* the friction velocity of the wind.

Strong and highly variable push of ocean waves on Southern Ocean sea ice.

PubMed

Stopa, Justin E; Sutherland, Peter; Ardhuin, Fabrice

2018-06-05

Sea ice in the Southern Ocean has expanded over most of the past 20 y, but the decline in sea ice since 2016 has taken experts by surprise. This recent evolution highlights the poor performance of numerical models for predicting extent and thickness, which is due to our poor understanding of ice dynamics. Ocean waves are known to play an important role in ice break-up and formation. In addition, as ocean waves decay, they cause a stress that pushes the ice in the direction of wave propagation. This wave stress could not previously be quantified due to insufficient observations at large scales. Sentinel-1 synthetic aperture radars (SARs) provide high-resolution imagery from which wave height is measured year round encompassing Antarctica since 2014. Our estimates give an average wave stress that is comparable to the average wind stress acting over 50 km of sea ice. We further reveal highly variable half-decay distances ranging from 400 m to 700 km, and wave stresses from 0.01 to 1 Pa. We expect that this variability is related to ice properties and possibly different floe sizes and ice thicknesses. A strong feedback of waves on sea ice, via break-up and rafting, may be the cause of highly variable sea-ice properties.

Mesospheric Non-Migrating Tides Generated With Planetary Waves: II Influence of Gravity Waves

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Mengel, J. G.; Talaat, E. L.; Porter, H. S.; Chan, K. L.

2003-01-01

We demonstrated that, in our model, non-linear interactions between planetary waves (PW) and migrating tides could generate in the upper mesosphere non-migrating tides with amplitudes comparable to those observed. The Numerical Spectral Model (NSM) we employ incorporates Hines Doppler Spread Parameterization for small-scale gravity waves (GW), which affect in numerous ways the dynamics of the mesosphere. The latitudinal (seasonal) reversals in the temperature and zonal circulation, which are largely caused by GWs (Lindzen, 198l), filter the PWs and contribute to the instabilities that generate the PWs. The PWs in turn are amplified by the momentum deposition of upward propagating GWs, as are the migrating tides. The GWs thus affect significantly the migrating tides and PWs, the building blocks of non-migrating tides. In the present paper, we demonstrate that GW filtering also contributes to the non-linear coupling between PWs and tides. Two computer experiments are presented to make this point. In one, we simply turn off the GW source to show the effect. In the second case, we demonstrate the effect by selectively suppressing the momentum source for the m = 0 non-migrating tides.

Model-Data Assimilation of Internal Waves during ASIAEX-2001

NASA Technical Reports Server (NTRS)

Liu, Antony; Zhao, Yun-He; Tang, T. Y.; Ramp, Steven R.

2003-01-01

In recent Asian Seas International Acoustics Experiment (ASIAEX), extensive moorings have been deployed around the continental shelf break area in the northeast of South China Sea in May 2001. Simultaneous RADARSAT SAR images have been collected during the field test to integrate with the in-situ measurements from moorings, ship-board sensors, and CTD casts. Besides it provides synoptic information, satellite imagery is very useful for tracking the internal waves, and locating surface fronts and mesoscale features. During ASIAEX in May 2001, many large internal waves were observed at the test area and were the major oceanic features for acoustic volume interaction. Based on the internal wave distribution maps compiled from satellite data, the wave crest can be as long as 200 km with amplitude of 100 m. Environmental parameters have been calculated based on extensive CTD casts data near the ASIAEX area. Nonlinear internal wave models have been applied to integrate and assimilate both SAR and mooring data. Using SAR data in deep water as an initial condition, numerical simulations produce the wave evolution on the continental shelf and compared reasonably well with the mooring measurements at the downstream station. The shoaling, turning, and dissipation of large internal waves on the shelf break, elevation solitons, and wave-wave interaction have been studied and are very important issues for acoustic propagation. The internal wave effects on acoustic modal coupling has been implicated and discussed.

Constraints on the spin evolution of young planetary-mass companions

NASA Astrophysics Data System (ADS)

Bryan, Marta L.; Benneke, Björn; Knutson, Heather A.; Batygin, Konstantin; Bowler, Brendan P.

2018-02-01

Surveys of young star-forming regions have discovered a growing population of planetary-mass (<13 MJup) companions around young stars1. There is an ongoing debate as to whether these companions formed like planets (that is, from the circumstellar disk)2, or if they represent the low-mass tail of the star-formation process3. In this study, we utilize high-resolution spectroscopy to measure rotation rates of three young (2-300 Myr) planetary-mass companions and combine these measurements with published rotation rates for two additional companions4,5 to provide a picture of the spin distribution of these objects. We compare this distribution to complementary rotation-rate measurements for six brown dwarfs with masses <20 MJup, and show that these distributions are indistinguishable. This suggests that either these two populations formed via the same mechanism, or that processes regulating rotation rates are independent of formation mechanism. We find that rotation rates for both populations are well below their break-up velocities and do not evolve significantly during the first few hundred million years after the end of accretion. This suggests that rotation rates are set during the late stages of accretion, possibly by interactions with a circumplanetary disk. This result has important implications for our understanding of the processes regulating the angular momentum evolution of young planetary-mass objects, and of the physics of gas accretion and disk coupling in the planetary-mass regime.

Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Sheng; Ji, Jianghui; Mordasini, Christoph

2014-11-01

We apply hydrodynamic evaporation models to different synthetic planet populations that were obtained from a planet formation code based on the core-accretion paradigm. We investigated the evolution of the planet populations using several evaporation models, which are distinguished by the driving force of the escape flow (X-ray or EUV), the heating efficiency in energy-limited evaporation regimes, or both. Although the mass distribution of the planet populations is barely affected by evaporation, the radius distribution clearly shows a break at approximately 2 R {sub ⊕}. We find that evaporation can lead to a bimodal distribution of planetary sizes and to anmore » 'evaporation valley' running diagonally downward in the orbital distance—planetary radius plane, separating bare cores from low-mass planets that have kept some primordial H/He. Furthermore, this bimodal distribution is related to the initial characteristics of the planetary populations because low-mass planetary cores can only accrete small primordial H/He envelopes and their envelope masses are proportional to their core masses. We also find that the population-wide effect of evaporation is not sensitive to the heating efficiency of energy-limited description. However, in two extreme cases, namely without evaporation or with a 100% heating efficiency in an evaporation model, the final size distributions show significant differences; these two scenarios can be ruled out from the size distribution of Kepler candidates.« less

Kelvin waves in the tropical stratosphere observed in OMPS-LP ozone measurements

NASA Astrophysics Data System (ADS)

Randel, W. J.; Park, M.

2017-12-01

We investigate equatorial waves in the tropical stratosphere using OMPS limb profiler (LP) ozone measurements spanning 2012-2017. The OMPS-LP data show clear evidence of eastward propagating planetary-scale Kelvin waves with periods near 15-20 days, and these feature are strongly modulated by the background winds linked to the quasi-biennial oscillation (QBO). We study coherence between OMPS-LP ozone and GPS radio occultation temperature measurements, and use these analyses to evaluate data quality and variability in the tropical stratosphere.

Approximate Solutions for Ideal Dam-Break Sediment-Laden Flows on Uniform Slopes

NASA Astrophysics Data System (ADS)

Ni, Yufang; Cao, Zhixian; Borthwick, Alistair; Liu, Qingquan

2018-04-01

Shallow water hydro-sediment-morphodynamic (SHSM) models have been applied increasingly widely in hydraulic engineering and geomorphological studies over the past few decades. Analytical and approximate solutions are usually sought to verify such models and therefore confirm their credibility. Dam-break flows are often evoked because such flows normally feature shock waves and contact discontinuities that warrant refined numerical schemes to solve. While analytical and approximate solutions to clear-water dam-break flows have been available for some time, such solutions are rare for sediment transport in dam-break flows. Here we aim to derive approximate solutions for ideal dam-break sediment-laden flows resulting from the sudden release of a finite volume of frictionless, incompressible water-sediment mixture on a uniform slope. The approximate solutions are presented for three typical sediment transport scenarios, i.e., pure advection, pure sedimentation, and concurrent entrainment and deposition. Although the cases considered in this paper are not real, the approximate solutions derived facilitate suitable benchmark tests for evaluating SHSM models, especially presently when shock waves can be numerically resolved accurately with a suite of finite volume methods, while the accuracy of the numerical solutions of contact discontinuities in sediment transport remains generally poorer.

The Role of Gravity Waves in Generating Equatorial Oscillations in Modulating Atmospheric Tides

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Mengel, J. G.; Chan, K. L.; Porter, H. S.; Reddy, C. A.

1999-01-01

We discuss a Numerical Spectral Mode (NSM) that extends from the ground up into the thermosphere and incorporates Hines' Doppler spread parameterization (DSP) for small scale gravity waves (GW). This model is applied to describe the seasonal variations in the mean zonal circulation, the semi-annual and quasi-biennial oscillations (SAO and QBO), as well as the tides and planetary waves in the middle atmosphere. Initial results showed that this model can reproduce the salient features observed, including the QBO extending into the upper mesosphere inferred from UARS measurements. The model has now been extended to simulate also: (a) the zonal circulation of the lower stratosphere and upper troposphere, and (b) the upwelling at equatorial latitudes associated with the Brewer Dobsen circulation that affects the dynamics significantly as pointed out by Dunkerton. Upward vertical winds increase the period of the QBO observed from the ground. To compensate for that, one needs to increase in the model the eddy diffusivity and the GW momentum flux, bringing the latter closer to values recommended in the DSP. This development is conducive to extending the QBO and SAO to higher latitudes through global scale momentum redistribution. Multi-year interannual oscillations are generated through wave filtering by the solar driven annual oscillation in the zonal circulation. In a 3D version of the model, wave momentum is absorbed and dissipated by tides and planetary waves. A somewhat larger GW source (well within the DSP range) is then required to generate realistic QBO and SAO amplitudes. Since GW momentum is deposited in the altitude regime of increasing winds, the amplitude of the diurnal tide is amplified and its vertical wavelength is reduced at altitudes between 70 and 120 km. Wave filtering by the mean zonal circulation causes the GW flux to peak during equinox, and this produces a large semi-annual variation in the tide that has been observed on UARS. Without the diurnal tide, the semidiurnal tide would also be modulated in this way. But the diurnal tide filters out the GW preferentially during equinox, so that the semidiurnal tide tends to peak during solstice. Under the influence of GW, the tides are modulated significantly by planetary waves that are generated preferentially during solstice in part due to baroclinic instability.

Scale Interactions in the Tropics from a Simple Multi-Cloud Model

NASA Astrophysics Data System (ADS)

Niu, X.; Biello, J. A.

2017-12-01

Our lack of a complete understanding of the interaction between the moisture convection and equatorial waves remains an impediment in the numerical simulation of large-scale organization, such as the Madden-Julian Oscillation (MJO). The aim of this project is to understand interactions across spatial scales in the tropics from a simplified framework for scale interactions while a using a simplified framework to describe the basic features of moist convection. Using multiple asymptotic scales, Biello and Majda[1] derived a multi-scale model of moist tropical dynamics (IMMD[1]), which separates three regimes: the planetary scale climatology, the synoptic scale waves, and the planetary scale anomalies regime. The scales and strength of the observed MJO would categorize it in the regime of planetary scale anomalies - which themselves are forced from non-linear upscale fluxes from the synoptic scales waves. In order to close this model and determine whether it provides a self-consistent theory of the MJO. A model for diabatic heating due to moist convection must be implemented along with the IMMD. The multi-cloud parameterization is a model proposed by Khouider and Majda[2] to describe the three basic cloud types (congestus, deep and stratiform) that are most responsible for tropical diabatic heating. We implement a simplified version of the multi-cloud model that is based on results derived from large eddy simulations of convection [3]. We present this simplified multi-cloud model and show results of numerical experiments beginning with a variety of convective forcing states. Preliminary results on upscale fluxes, from synoptic scales to planetary scale anomalies, will be presented. [1] Biello J A, Majda A J. Intraseasonal multi-scale moist dynamics of the tropical atmosphere[J]. Communications in Mathematical Sciences, 2010, 8(2): 519-540. [2] Khouider B, Majda A J. A simple multicloud parameterization for convectively coupled tropical waves. Part I: Linear analysis[J]. Journal of the atmospheric sciences, 2006, 63(4): 1308-1323. [3] Dorrestijn J, Crommelin D T, Biello J A, et al. A data-driven multi-cloud model for stochastic parametrization of deep convection[J]. Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences, 2013, 371(1991): 20120374.

Helicity, geostrophic balance and mixing in rotating stratified turbulence: a multi-scale problem

NASA Astrophysics Data System (ADS)

Pouquet, A.; Marino, R.; Mininni, P.; Rorai, C.; Rosenberg, D. L.

2012-12-01

Helicity, geostrophic balance and mixing in rotating stratified turbulence: a multi-scale problem A. Pouquet, R. Marino, P. D. Mininni, C. Rorai & D. Rosenberg, NCAR Interactions between winds and waves have important roles in planetary and oceanic boundary layers, affecting momentum, heat and CO2 transport. Within the Abyssal Southern Ocean at Mid latitude, this may result in a mixed layer which is too shallow in climate models thereby affecting the overall evolution because of poor handling of wave breaking as in Kelvin-Helmoltz instabilities: gravity waves couple nonlinearly on slow time scales and undergo steepening through resonant interactions, or due to the presence of shear. In the oceans, sub-mesoscale frontogenesis and significant departure from quasi-geostrophy can be seen as turbulence intensifies. The ensuing anomalous vertical dispersion may not be simply modeled by a random walk, due to intermittent structures, wave propagation and to their interactions. Conversely, the energy and seeds required for such intermittent events to occur, say in the stable planetary boundary layer, may come from the wave field that is perturbed, or from winds and the effect of topography. Under the assumption of stationarity, weak nonlinearities, dissipation and forcing, one obtains large-scale geostrophic balance linking pressure gradient, gravity and Coriolis force. The role of helicity (velocity-vorticity correlations) has not received as much attention, outside the realm of astrophysics when considering the growth of large-scale magnetic fields. However, it is measured routinely in the atmosphere in order to gauge the likelihood of supercell convective storms to strengthen, and it may be a factor to consider in the formation of hurricanes. In this context, we examine the transition from a wave-dominated regime to an isotropic small-scale turbulent one in rotating flows with helical forcing. Using a direct numerical simulation (DNS) on a 3072^3 grid with Rossby and Reynolds numbers of 0.07 and 27000, one can resolve both the Zeman scale at which the inertial and eddy turn-over times equalize, and the dissipation scale. We show that fully helical vertical columns dominate at intermediate scales, presumably self-similar and shrouded by a sea of small-scale vortex filaments as in Kolmogorov turbulence. Helicity has a profound effect on the structures of the flow, and a previously developed model that includes a helical component in its eddy viscosity and eddy noise shows a measurable improvement. Indeed, if dimensionless parameters for inertial and gravity waves are reachable numerically, the Reynolds number is too low in DNS for geophysics unless one uses parametrizations of small scale interactions. For spin-down stably-stratified flows, energy and helicity undergo a substantially slower decay than in the unstratified case, and a type of large-scale cyclostrophic balance is invoked to explain this behavior. The decay rate is similar to that occurring in the unstratified rotating case, as modeled by taking into account the quasi-conservation of helicity. We finally mention helicity production when rotation and stratification are both combined. In conclusion, much remains to be done, e.g. examining transport properties of rotating stratified turbulence, such as the effect of helicity on mixing in geophysical flows that can be studied with high-performance computing allowing multi-scale interactions and intermittency to develop.

Damping of Resonantly Forced Density Waves in Dense Planetary Rings

NASA Astrophysics Data System (ADS)

Lehmann, Marius; Schmidt, Jürgen; Salo, Heikki

2016-10-01

We address the stability of resonantly forced density waves in dense planetary rings.Already by Goldreich and Tremaine (1978) it has been argued that density waves might be unstable, depending on the relationship between the ring's viscosity and the surface mass density. In the recent paper (Schmidt et al. 2016) we have pointed out that when - within a fluid description of the ring dynamics - the criterion for viscous overstability is satisfied, forced spiral density waves become unstable as well. In this case, linear theory fails to describe the damping.We apply the multiple scale formalism to derive a weakly nonlinear damping relation from a hydrodynamical model.This relation describes the resonant excitation and nonlinear viscous damping of spiral density waves in a vertically integrated fluid disk with density dependent transport coefficients. The model consistently predicts linear instability of density waves in a ring region where the conditions for viscous overstability are met. In this case, sufficiently far away from the Lindblad resonance, the surface mass density perturbation is predicted to saturate to a constant value due to nonlinear viscous damping. In general the model wave damping lengths depend on a set of input parameters, such as the distance to the threshold for viscous overstability and the ground state surface mass density.Our new model compares reasonably well with the streamline model for nonlinear density waves of Borderies et al. 1986.Deviations become substantial in the highly nonlinear regime, corresponding to strong satellite forcing.Nevertheless, we generally observe good or at least qualitative agreement between the wave amplitude profiles of both models. The streamline approach is superior at matching the total wave profile of waves observed in Saturn's rings, while our new damping relation is a comparably handy tool to gain insight in the evolution of the wave amplitude with distance from resonance, and the different regimes of wave formation and the dependence on the parameters of the model.

Long-lived planetary vortices and their evolution: Conservative intermediate geostrophic model.

PubMed

Sutyrin, Georgi G.

1994-06-01

Large, long-lived vortices, surviving during many turnaround times and far longer than the dispersive linear Rossby wave packets, are abundant in planetary atmospheres and oceans. Nonlinear effects which prevent dispersive decay of intense cyclones and anticyclones and provide their self-propelling propagation are revised here using shallow water equations and their balanced approximations. The main physical mechanism allowing vortical structures to be long-lived in planetary fluid is the quick fluid rotation inside their cores which prevents growth in the amplitude of asymmetric circulation arising due to the beta-effect. Intense vortices of both signs survive essentially longer than the linear Rossby wave packet if their azimuthal velocity is much larger than the Rossby wave speed. However, in the long-time evolution, cyclonic and anticyclonic vortices behave essentially differently that is illustrated by the conservative intermediate geostrophic model. Asymmetric circulation governing vortex propagation is described by the azimuthal mode m=1 for the initial value problem as well as for steadily propagating solutions. Cyclonic vortices move west-poleward decaying gradually due to Rossby wave radiation while anticyclonic ones adjust to non-radiating solitary vortices. Slow weakening of an intense cyclone with decreasing of its size and shrinking of the core is described assuming zero azimuthal velocity outside the core while drifting poleward. The poleward tendency of the cyclone motion relative to the stirring flow corresponds to characteristic trajectories of tropical cyclones in the Earth's atmosphere. The asymmetry in dispersion-nonlinear properties of cyclones and anticyclones is thought to be one of the essential reasons for the observed predominance of anticyclones among long-lived vortices in the atmospheres of the giant planets and also among intrathermoclinic eddies in the ocean.

Upstream waves and particles /Tutorial Lecture/. [from shocks in interplanetary space

NASA Technical Reports Server (NTRS)

Russell, C. T.; Hoppe, M. M.

1983-01-01

The plasma waves, MHD waves, energetic electrons and ions associated with the proximity of the region upstream from terrestrial, planetary and interplanetary shocks are discussed in view of observations and current theories concerning their origin. These waves cannot be separated from the study of shock structure. Since the shocks are supersonic, they continually overtake any ULF waves created in the plasma in front of the shock. The upstream particles and waves are also of intrinsic interest because they provide a plasma laboratory for the study of wave-particle interactions in a plasma which, at least at the earth, is accessible to sophisticated probing. Insight may be gained into interstellar medium cosmic ray acceleration through the study of these phenomena.

Formation and Internal Structure of Terrestrial Planets, and Atmospheric Escape

NASA Astrophysics Data System (ADS)

Jin, S.

2014-11-01

As of 2014 April 21, over 1490 confirmed exoplanets and 3705 Kepler candidates have been detected. This implies that exoplanets may be ubiquitous in the universe. In this paper, we focus on the formation, evolution, and internal structure of terrestrial planets, and the atmospheric escape of close-in planets. In chapter 2, we investigate the dynamical evolution of planetary system after the protoplanetary disk has dissipated. We find that in the final assembly stage, the occurrence of terrestrial planets is quite common and in 40% of our simulations finally at least one planet is formed in the habitable zone. We also find that if there is a highly-inclined giant planet in the system, a great many bodies will be either driven out of the system, or collide with the giant planet or the central star. This will lead to the difficulty in planetary accretion. Moreover, our results show that planetary migration can lead to the formation of close-in planets. Besides migration, close-in terrestrial planets can also be formed by a collision-merger mechanism, which means that planetary embryos can kick terrestrial planets directly into orbits that are extremely close to their parent stars. In chapter 3, we construct numerically an internal structure model for terrestrial planets, and provide three kinds of possible internal structures of Europa (Jupiter's moon) based on this model. Then, we calculate the radii of low-mass exoplanets for various mass combinations of core and mantle, and find that some of them are inconsistent with the observed radius of rocky planets. This phenomenon can be explained only if there exists a large amount of water in the core, or they own gaseous envelopes. In chapter 4, we improve our planetary evolution codes using the semi-gray model of Guillot (2010), which includes the incident flux from the host star as a heating source in planetary atmosphere. The updated codes can solve the structure of the top radiative zone of intensely irradiated planets, and thus can simulate the atmospheric escape of close-in planets driven by strong stellar X-ray or EUV emissions. We find that low-mass planets are sensitive to the atmospheric escape, and they could lose all their initial H/He envelopes during the evolution. On the other hand, gas giant can only lose a small fraction of their initial envelopes. We then carry out a parameter study of atmospheric escape at the planetary core mass, envelope mass fraction, and semi-major axis space. We find that the most intense phase of evaporation occurs within the early 100 Myr. Afterwards, atmospheric escape only has a small impact on the planetary evolution. In chapter 5, we apply our new planetary evolution model to different synthetic planet populations that are directly produced by the core-accretion paradigm (Mordasini et al. 2012a,b). We show that although the mass distribution of the planet populations is hardly affected by evaporation, the radius distribution clearly shows a break around 2 R_{⊕}. This break leads to a bimodal distribution in planet sizes (Owen & Wu 2013). Furthermore, the bimodal distribution is related to the initial characteristics of the planetary populations. We find that in two extreme cases, namely without any evaporation or with a 100% heating efficiency in the evaporation model, the final radius distributions show significant differences compared to the radius distribution of Kepler candidates. In chapter 6, we introduce a radiative transfer model that can calculate the radiation spectrum of close-in exoplanets.

Kinematics and dynamics of green water on a fixed platform in a large wave basin in focusing wave and random wave conditions

NASA Astrophysics Data System (ADS)

Chuang, Wei-Liang; Chang, Kuang-An; Mercier, Richard

2018-06-01

Green water kinematics and dynamics due to wave impingements on a simplified geometry, fixed platform were experimentally investigated in a large, deep-water wave basin. Both plane focusing waves and random waves were employed in the generation of green water. The focusing wave condition was designed to create two consecutive plunging breaking waves with one impinging on the frontal vertical wall of the fixed platform, referred as wall impingement, and the other directly impinging on the deck surface, referred as deck impingement. The random wave condition was generated using the JONSWAP spectrum with a significant wave height approximately equal to the freeboard. A total of 179 green water events were collected in the random wave condition. By examining the green water events in random waves, three different flow types are categorized: collapse of overtopping wave, fall of bulk water, and breaking wave crest. The aerated flow velocity was measured using bubble image velocimetry, while the void fraction was measured using fiber optic reflectometry. For the plane focusing wave condition, measurements of impact pressure were synchronized with the flow velocity and void fraction measurements. The relationship between the peak pressures and the pressure rise times is examined. For the high-intensity impact in the deck impingement events, the peak pressures are observed to be proportional to the aeration levels. The maximum horizontal velocities in the green water events in random waves are well represented by the lognormal distribution. Ritter's solution is shown to quantitatively describe the green water velocity distributions under both the focusing wave condition and the random wave condition. A prediction equation for green water velocity distribution under random waves is proposed.

The Three-Dimensionality of Spiral Shocks: Did Chondrules Catch a Breaking Wave?

NASA Astrophysics Data System (ADS)

Boley, A. C.; Durisen, R. H.; Pickett, M. K.

2005-12-01

Spiral shocks in vertically stratified disks lead to hydraulic/shock-jumps (hs-jumps) that stimulate large scale (tenths of an AU or more) radial and vertical motions, breaking surface waves, high-altitude shocks, and vortical flows. These effects are demonstrated by three-dimensional hydrodynamics simulations in Solar Nebula models. Trajectories of fluid elements, along with their thermal histories, suggest that hs-jumps mix the nebular gas and provide diverse pre-shock conditions, some of which are conducive to chondrule formation. In addition, hs-jumps may provide an energy source for driving nebular turbulence to size-sort chondrules.

Electrogram fractionation in murine HL-1 atrial monolayer model.

PubMed

Umapathy, Karthikeyan; Masse, Stephane; Kolodziejska, Karolina; Veenhuyzen, George D; Chauhan, Vijay S; Husain, Mansoor; Farid, Talha; Downar, Eugene; Sevaptsidis, Elias; Nanthakumar, Kumaraswamy

2008-07-01

Complex fractionated atrial electrograms have been suggested as important targets for catheter ablation of atrial fibrillation. The etiology and the mechanism of these signals have not been completely elucidated because of limitations of interpretation of these signals in relation to simultaneously acquired signals in the neighboring atrial tissue. This study sought to study the origin of electrogram fractionation under the conditions of rotor formation and wave fragmentation, using atrial monolayer preparations. We performed optical mapping of 45 atrial monolayer preparations using a complementary metal oxide semiconductor (CMOS) Brainvision Ultima camera system (SciMedia-Brainvision, Tokyo, Japan). We observed stable rotors in 32 of the 45 recordings. The derived bipolar electrograms did not show complex fractionation at the core of the rotor in any of the 32 recordings. We were also able to show that 2 bipolar electrodes placed adjacent to the core of a stable rotor in a zone where there is no wave break will record electrical activity for the majority of the rotor's cycle length. In 13 of the 45 recordings, wave break or wave collision events were present. Of these, 8 of 13 recordings showed complex fractionation. In 19 of the 27, simulation of meandering rotors also showed complex fractionation. Complex fractionated electrograms can be recorded at sites of migrating rotors and wave break. No fractionation occurs at the core of a stable rotor. Electrograms that span the rotor cycle length and alternate between 2 bipoles that straddle the core can identify site of a stable rotor.

Mechanisms of myocardial capture and temporal excitable gap during spiral wave reentry in a bidomain model.

PubMed

Ashihara, Takashi; Namba, Tsunetoyo; Ikeda, Takanori; Ito, Makoto; Nakazawa, Kazuo; Trayanova, Natalia

2004-02-24

Recent studies have demonstrated that regional capture during cardiac fibrillation is associated with an elevated capture threshold. It is typically assumed that the temporal excitable gap (capture window) during fibrillation reflects the size of the spatial excitable gap (excitable tissue between fibrillation waves). Because capture threshold is high, virtual electrode polarization is expected to be involved in the process. However, little is known about the underlying mechanisms of myocardial capture during fibrillation. To clarify these issues, we conducted altogether 3168 simulations of single spiral wave capture in a bidomain sheet. Unipolar stimuli of strengths 4, 8, 16, and 24 mA and 2-ms duration were delivered at 99 locations in the sheet. We found that cathode-break rather than cathode-make excitation was the dominant mechanism of myocardial capture. When the stimulation site was located diagonally with respect to the core (upper left or lower right if the spiral wave rotates counterclockwise), the cathode-break excitation easily invaded the spatial excitable gap and resulted in a successful capture as a result of the formation of virtual anodes in the direction of the myocardial fibers. Thus, the spatial distribution of the temporal excitable gap did not reflect the spatial excitable gap. The areas exhibiting wide temporal excitable gaps were areas in which the cathode-break excitation wave fronts easily invaded the spatial excitable gap via the virtual anodes. This study provides mechanistic insight into myocardial capture.

Rossby Wave Propagation into the Northern Hemisphere Stratosphere: The Role of Zonal Phase Speed

NASA Astrophysics Data System (ADS)

Domeisen, Daniela I. V.; Martius, Olivia; Jiménez-Esteve, Bernat

2018-02-01

Sudden stratospheric warming (SSW) events are to a dominant part induced by upward propagating planetary waves. While theory predicts that the zonal phase speed of a tropospheric wave forcing affects wave propagation into the stratosphere, its relevance for SSW events has so far not been considered. This study shows in a linear wave diagnostic and in reanalysis data that phase speeds tend eastward as waves propagate upward, indicating that the stratosphere preselects eastward phase speeds for propagation, especially for zonal wave number 2. This also affects SSW events: Split SSW events tend to be preceded by anomalously eastward zonal phase speeds. Zonal phase speed may indeed explain part of the increased wave flux observed during the preconditioning of SSW events, as, for example, for the record 2009 SSW event.

Modeling Water Waves with Smoothed Particle Hydrodynamics

DTIC Science & Technology

2011-09-30

Lagrangian nature of SPH allows the modeling of wave breaking, surf zones, ship waves, and wave-structure interaction, where the free surface becomes...particle detection--To study free surface flows and analyze their complex deformations, we need to know which particles are located on the free surface ...Hydrodynamics is proving to be a competent modeling scheme for free surface flows in two and three dimensions. As the GPU hardware improves, it is

Controlling Wavebreaking in a Viscous Fluid Conduit

NASA Astrophysics Data System (ADS)

Anderson, Dalton; Maiden, Michelle; Hoefer, Mark

2015-11-01

This poster will present a new technique in the experimental investigation of dispersive hydrodynamics. In shallow water flows, internal ocean waves, superfluids, and optical media, wave breaking can be resolved by a dispersive shock wave (DSW). In this work, an experimental method to control the location of DSW formation (gradient catastrophe) is explained. The central idea is to convert an initial value problem (Riemann problem) into an equivalent boundary value problem. The system to which this technique is applied is a fluid conduit resulting from high viscosity contrast between a buoyant interior and heavier exterior fluid. The conduit cross-sectional area is modeled by a nonlinear, conservative, dispersive, third order partial differential equation. Using this model, the aim is to predict the breaking location of a DSW by controlling one boundary condition. An analytical expression for this boundary condition is derived by solving the dispersionless equation backward in time from the desired step via the method of characteristics. This is used in experiment to generate an injection rate profile for a high precision piston pump. This translates to the desired conduit shape. Varying the jump height and desired breaking location indicates good control of DSW formation. This result can be improved by deriving a conduit profile by numerical simulation of the full model equation. Controlling the breaking location of a DSW allows for the investigation of dynamics independent of the boundary. Support provided by NSF CAREER DMS-1255422 , NSF EXTREEMS.

Laboratory for Extraterrestrial Physics

NASA Technical Reports Server (NTRS)

Vondrak, Richard R. (Technical Monitor)

2001-01-01

The NASA Goddard Space Flight Center (GSFC) Laboratory for Extraterrestrial Physics (LEP) performs experimental and theoretical research on the heliosphere, the interstellar medium, and the magnetospheres and upper atmospheres of the planets, including Earth. LEP space scientists investigate the structure and dynamics of the magnetospheres of the planets including Earth. Their research programs encompass the magnetic fields intrinsic to many planetary bodies as well as their charged-particle environments and plasma-wave emissions. The LEP also conducts research into the nature of planetary ionospheres and their coupling to both the upper atmospheres and their magnetospheres. Finally, the LEP carries out a broad-based research program in heliospheric physics covering the origins of the solar wind, its propagation outward through the solar system all the way to its termination where it encounters the local interstellar medium. Special emphasis is placed on the study of solar coronal mass ejections (CME's), shock waves, and the structure and properties of the fast and slow solar wind. LEP planetary scientists study the chemistry and physics of planetary stratospheres and tropospheres and of solar system bodies including meteorites, asteroids, comets, and planets. The LEP conducts a focused program in astronomy, particularly in the infrared and in short as well as very long radio wavelengths. We also perform an extensive program of laboratory research, including spectroscopy and physical chemistry related to astronomical objects. The Laboratory proposes, develops, fabricates, and integrates experiments on Earth-orbiting, planetary, and heliospheric spacecraft to measure the characteristics of planetary atmospheres and magnetic fields, and electromagnetic fields and plasmas in space. We design and develop spectrometric instrumentation for continuum and spectral line observations in the x-ray, gamma-ray, infrared, and radio regimes; these are flown on spacecraft to study the interplanetary medium, asteroids, comets, and planets. Suborbital sounding rockets and groundbased observing platforms form an integral part of these research activities. This report covers the period from approximately October 1999 through September 2000.

Influence of large-scale zonal flows on the evolution of stellar and planetary magnetic fields

NASA Astrophysics Data System (ADS)

Petitdemange, Ludovic; Schrinner, Martin; Dormy, Emmanuel; ENS Collaboration

2011-10-01

Zonal flows and magnetic field are present in various objects as accretion discs, stars and planets. Observations show a huge variety of stellar and planetary magnetic fields. Of particular interest is the understanding of cyclic field variations, as known from the sun. They are often explained by an important Ω-effect, i.e., by the stretching of field lines because of strong differential rotation. We computed the dynamo coefficients for an oscillatory dynamo model with the help of the test-field method. We argue that this model is of α2 Ω -type and here the Ω-effect alone is not responsible for its cyclic time variation. More general conditions which lead to dynamo waves in global direct numerical simulations are presented. Zonal flows driven by convection in planetary interiors may lead to secondary instabilities. We showed that a simple, modified version of the MagnetoRotational Instability, i.e., the MS-MRI can develop in planteray interiors. The weak shear yields an instability by its constructive interaction with the much larger rotation rate of planets. We present results from 3D simulations and show that 3D MS-MRI modes can generate wave pattern at the surface of the spherical numerical domain. Zonal flows and magnetic field are present in various objects as accretion discs, stars and planets. Observations show a huge variety of stellar and planetary magnetic fields. Of particular interest is the understanding of cyclic field variations, as known from the sun. They are often explained by an important Ω-effect, i.e., by the stretching of field lines because of strong differential rotation. We computed the dynamo coefficients for an oscillatory dynamo model with the help of the test-field method. We argue that this model is of α2 Ω -type and here the Ω-effect alone is not responsible for its cyclic time variation. More general conditions which lead to dynamo waves in global direct numerical simulations are presented. Zonal flows driven by convection in planetary interiors may lead to secondary instabilities. We showed that a simple, modified version of the MagnetoRotational Instability, i.e., the MS-MRI can develop in planteray interiors. The weak shear yields an instability by its constructive interaction with the much larger rotation rate of planets. We present results from 3D simulations and show that 3D MS-MRI modes can generate wave pattern at the surface of the spherical numerical domain. The first author thanks DFG and PlanetMag project for financial support.

Selection of Multiarmed Spiral Waves in a Regular Network of Neurons

PubMed Central

Hu, Bolin; Ma, Jun; Tang, Jun

2013-01-01

Formation and selection of multiarmed spiral wave due to spontaneous symmetry breaking are investigated in a regular network of Hodgkin-Huxley neuron by changing the excitability and imposing spatial forcing currents on the neurons in the network. The arm number of the multiarmed spiral wave is dependent on the distribution of spatial forcing currents and excitability diversity in the network, and the selection criterion for supporting multiarmed spiral waves is discussed. A broken spiral segment is measured by a short polygonal line connected by three adjacent points (controlled nodes), and a double-spiral wave can be developed from the spiral segment. Multiarmed spiral wave is formed when a group of double-spiral waves rotate in the same direction in the network. In the numerical studies, a group of controlled nodes are selected and spatial forcing currents are imposed on these nodes, and our results show that l-arm stable spiral wave (l = 2, 3, 4,...8) can be induced to occupy the network completely. It is also confirmed that low excitability is critical to induce multiarmed spiral waves while high excitability is important to propagate the multiarmed spiral wave outside so that distinct multiarmed spiral wave can occupy the network completely. Our results confirm that symmetry breaking of target wave in the media accounts for emergence of multiarmed spiral wave, which can be developed from a group of spiral waves with single arm under appropriate condition, thus the potential formation mechanism of multiarmed spiral wave in the media is explained. PMID:23935966

33 CFR 162.80 - Mississippi River below mouth of Ohio River, including South and Southwest passes.

Code of Federal Regulations, 2012 CFR

2012-07-01

... withstand currents, winds, wave action, suction from passing vessels or any other forces which might cause... sufficient fastenings to prevent the vessels from breaking loose by wind, current, wave action, suction from...

33 CFR 162.80 - Mississippi River below mouth of Ohio River, including South and Southwest passes.

Code of Federal Regulations, 2010 CFR

2010-07-01

... withstand currents, winds, wave action, suction from passing vessels or any other forces which might cause... sufficient fastenings to prevent the vessels from breaking loose by wind, current, wave action, suction from...

33 CFR 162.80 - Mississippi River below mouth of Ohio River, including South and Southwest passes.

Code of Federal Regulations, 2013 CFR

2013-07-01

... withstand currents, winds, wave action, suction from passing vessels or any other forces which might cause... sufficient fastenings to prevent the vessels from breaking loose by wind, current, wave action, suction from...

33 CFR 162.80 - Mississippi River below mouth of Ohio River, including South and Southwest passes.

Code of Federal Regulations, 2014 CFR

2014-07-01

... withstand currents, winds, wave action, suction from passing vessels or any other forces which might cause... sufficient fastenings to prevent the vessels from breaking loose by wind, current, wave action, suction from...

33 CFR 162.80 - Mississippi River below mouth of Ohio River, including South and Southwest passes.

Code of Federal Regulations, 2011 CFR

2011-07-01

... withstand currents, winds, wave action, suction from passing vessels or any other forces which might cause... sufficient fastenings to prevent the vessels from breaking loose by wind, current, wave action, suction from...

Application of satellite data in observational and theoretical studies of the evolving structure of baroclinic waves

NASA Technical Reports Server (NTRS)

Saltzman, Barry

1987-01-01

A variety of observational and theoretical studies were performed which were designed to clarify the relationship between satellite measurements of cloud and radiation and the evolution of transient and stationary circulation in middle latitudes. Satellite outgoing longwave radiation data are used to: (1) estimate the generation of available potential energy due to infrared radiation, and (2) show the extent to which these data can provide the signature of high and low frequency weather phenomena including blocking. In a significant series of studies the nonlinear, energetical, and predictability properties of these blocking situations, and the ralationship of blocking to the planetary, scale longwave structure are described. These studies form the background for continuing efforts to describe and theoretically account for these low frequency planetary wave phenomena in terms of their bimodal properties.

Toward an Improved Representation of Middle Atmospheric Dynamics Thanks to the ARISE Project

NASA Astrophysics Data System (ADS)

Blanc, E.; Ceranna, L.; Hauchecorne, A.; Charlton-Perez, A.; Marchetti, E.; Evers, L. G.; Kvaerna, T.; Lastovicka, J.; Eliasson, L.; Crosby, N. B.; Blanc-Benon, P.; Le Pichon, A.; Brachet, N.; Pilger, C.; Keckhut, P.; Assink, J. D.; Smets, P. S. M.; Lee, C. F.; Kero, J.; Sindelarova, T.; Kämpfer, N.; Rüfenacht, R.; Farges, T.; Millet, C.; Näsholm, S. P.; Gibbons, S. J.; Espy, P. J.; Hibbins, R. E.; Heinrich, P.; Ripepe, M.; Khaykin, S.; Mze, N.; Chum, J.

2018-03-01

This paper reviews recent progress toward understanding the dynamics of the middle atmosphere in the framework of the Atmospheric Dynamics Research InfraStructure in Europe (ARISE) initiative. The middle atmosphere, integrating the stratosphere and mesosphere, is a crucial region which influences tropospheric weather and climate. Enhancing the understanding of middle atmosphere dynamics requires improved measurement of the propagation and breaking of planetary and gravity waves originating in the lowest levels of the atmosphere. Inter-comparison studies have shown large discrepancies between observations and models, especially during unresolved disturbances such as sudden stratospheric warmings for which model accuracy is poorer due to a lack of observational constraints. Correctly predicting the variability of the middle atmosphere can lead to improvements in tropospheric weather forecasts on timescales of weeks to season. The ARISE project integrates different station networks providing observations from ground to the lower thermosphere, including the infrasound system developed for the Comprehensive Nuclear-Test-Ban Treaty verification, the Lidar Network for the Detection of Atmospheric Composition Change, complementary meteor radars, wind radiometers, ionospheric sounders and satellites. This paper presents several examples which show how multi-instrument observations can provide a better description of the vertical dynamics structure of the middle atmosphere, especially during large disturbances such as gravity waves activity and stratospheric warming events. The paper then demonstrates the interest of ARISE data in data assimilation for weather forecasting and re-analyzes the determination of dynamics evolution with climate change and the monitoring of atmospheric extreme events which have an atmospheric signature, such as thunderstorms or volcanic eruptions.

An Atlantic streamer in stratospheric ozone observations and SD-WACCM simulation data

NASA Astrophysics Data System (ADS)

Hocke, Klemens; Schranz, Franziska; Maillard Barras, Eliane; Moreira, Lorena; Kämpfer, Niklaus

2017-03-01

Observation and simulation of individual ozone streamers are important for the description and understanding of non-linear transport processes in the middle atmosphere. A sudden increase in mid-stratospheric ozone occurred above central Europe on 4 December 2015. The GROund-based Millimeter-wave Ozone Spectrometer (GROMOS) and the Stratospheric Ozone MOnitoring RAdiometer (SOMORA) in Switzerland measured an ozone enhancement of about 30 % at 34 km altitude (8.3 hPa) from 1 to 4 December. A similar ozone increase is simulated by the Specified Dynamics Whole Atmosphere Community Climate (SD-WACCM) model. Further, the global ozone fields at 34 km altitude (8.3 hPa) from SD-WACCM and the satellite experiment Aura/MLS show a remarkable agreement for the location and timing of an ozone streamer (large-scale tongue-like structure) extending from the subtropics in northern America over the Atlantic to central Europe. This agreement indicates that SD-WACCM can inform us about the wind inside the Atlantic ozone streamer. SD-WACCM shows an eastward wind of about 100 m s-1 inside the Atlantic streamer in the mid-stratosphere. SD-WACCM shows that the Atlantic streamer flows along the edge of the polar vortex. The Atlantic streamer turns southward at an erosion region of the polar vortex located above the Caspian Sea. The spatial distribution of stratospheric water vapour indicates a filament outgoing from this erosion region. The Atlantic streamer, the polar vortex erosion region and the water vapour filament belong to the process of planetary wave breaking in the so-called surf zone of the northern midlatitude winter stratosphere.

The Role of Gravity Waves in Modulating Atmospheric Tides

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Mengel, J. G; Chan, K. L.; Porter, H. S.

1999-01-01

We discuss results for the diurnal and semidiurnal tides obtained from our 3-D, time dependent numerical spectral model (NMS), extending from the ground up into the thermosphere, which incorporates Hines' Doppler spread parameterization of small scale gravity waves (GW). In the DSP, GW momentum (and energy) are conserved as the waves modulate the background flow and are filtered by the flow.As a consequence, the GW interaction tightly couples the dynamic components of the middle atmosphere with strong non-linear interactions between mean zonal circulation, tides and planetary waves to produce complicated patterns of variability much like those observed. The major conclusions are: (1) Since GW momentum is deposited in the altitude regime of increasing winds, the amplitude of the diurnal tide is amplified and its vertical wavelength is reduced at altitudes between 80 and 120 km. Wave filtering by the mean zonal circulation (with peak velocities during solstice) causes the GW flux to peak during equinox, and this produces a large semi-annual variation in the tide that has been observed on UARS. (2) Without the diurnal tide, the semidiurnal tide would also be modulated in this way. But the diurnal tide filters out the GW preferentially during equinox, so that the semidiurnal tide, at higher altitudes, tends to peak during solstice. (3) Under the influence of GW, the tides are modulated also significantly by planetary waves, with periods between 2 and 30 days, which are generated preferentially during solstice in part due to baroclinic instability.

Signature of 3-4 day planetary waves in the equatorial ionospheric F layer height and medium frequency radar winds over Tirunelveli (8.7oN)

NASA Astrophysics Data System (ADS)

Sundararaman, Sathishkumar

Signature of 3-4 day planetary waves in the equatorial ionospheric F layer height and medium frequency radar winds over Tirunelveli (8.7oN) S. Sathishkumar1, R. Dhanya1, K. Emperumal1, D. Tiwari2, S. Gurubaran1 and A. Bhattacharyya2 1. Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli, India 2. Indian Institute of Geomagnetism, Navi Mumbai, India Email: sathishmaths@gmail.com Abstract The equatorial atmosphere-ionosphere system has been studied theoretically and observationally in the past. In the equatorial atmosphere, oscillations with periods of 3-4 days are often observed in the medium frequency (MF) radar over Tirunelveli (8.7oN, 77.8oE, 1.34oN geomag. lat.). Earlier observations show the clear evidence that these waves can propagate from the stratosphere to ionosphere. A digital ionosonde has been providing useful information on several ionospheric parameters from the same site. Simultaneous observations of mesospheric winds using medium frequency radar and F-layer height (h'F) from ionosonde reveal that the 3-4 day wave was evident in both the component during the 01 June 2007 and 31 July 2007. The 3-4 day wave could have an important role in the day to day variability of the equatorial ionosphere evening uplift. Results from an extensive analysis that is being carried out in the direction of 3-4 day wave present in the ionosphere will be presented.

Mesoscale dynamics in the Lofoten Basin - a sub-Arctic "hot spot" of oceanic variability

NASA Astrophysics Data System (ADS)

Volkov, D. L.; Belonenko, T. V.; Foux, V. R.

2012-12-01

A sub-Arctic "hot spot" of intense mesoscale variability is observed in the Lofoten Basin (LB) - a topographic depression with a maximum depth of about 3250 m, located in the Norwegian Sea. The standard deviation of sea surface height (SSH), measured with satellite altimetry, reaches nearly 15 cm in the center of the basin (Figure 1a). Using a space-time lagged correlation analysis of altimetry data, we discover a cyclonic propagation of the mesoscale SSH anomalies around the center of the LB with time-averaged phase speeds of 2-4 km/day, strongly linked to bottom topography (Figure 1c). The fact that surface drifter trajectories do not exhibit cyclonic circulation in the LB (Figure 1b) suggests that, at least in the upper ocean, satellite altimetry observes only the propagation of form without the corresponding transfer of mass. Linearly propagating wavelike disturbances that do not trap fluid inside are related to planetary or Rossby waves. Variations in topography may lead to the concentration of wave energy in certain regions or wave trapping. The dispersion analysis suggests that the observed wavelike cyclonic propagation of SSH anomalies in the LB is the manifestation of baroclinic topographic Rossby waves, that we term "the basin waves" in order to distinguish them from the other types of topographic waves, such as shelf or trench waves. We identify two modes of basin waves in the LB: a di-pole mode and a quadri-pole mode. The wavelength of each mode is about 500 km. The frequency of these modes is not constant and the phase speed varies from about 2 to 8 km/day. We show that the cyclonically rotating basin waves are responsible for the observed amplification of SSH variability in the LB. Because the baroclinic basin waves in the LB are probably associated with large vertical displacements of the thermocline and due to possible wave breaking events, they can play an important role in the mixing of the inflowing Atlantic Water with ambient water masses.(a) Standard deviation of SSH (cm) in the Nordic seas. Bottom topography is shown by 1000, 2000, and 3000 m isobaths. Abbreviations: GB - Greenland Basin, LB - Lofoten Basin, NB - Norwegian Basin, NwAC - Norwegian Atlantic Current, VP - Vøring Plateau. The study region is bounded by the blue rectangle. (b) Trajectories of 100 surface drifters (blue curves) that were present in the study region from September 1996 to August 2010 and their geostrophic velocity vectors (red arrows) averaged over 1°×0.25° (longitude × latitude) bins. (c) MDT_CNES_CLS09 mean dynamic topography (color, cm) and the velocities of eddy propagation (arrows). Two ellipsoidal contours, along which the dispersion relation was analyzed, are shown.

Laboratory and theoretical models of planetary-scale instabilities and waves

NASA Technical Reports Server (NTRS)

Hart, John E.; Toomre, Juri

1990-01-01

Meteorologists and planetary astronomers interested in large-scale planetary and solar circulations recognize the importance of rotation and stratification in determining the character of these flows. In the past it has been impossible to accurately model the effects of sphericity on these motions in the laboratory because of the invariant relationship between the uni-directional terrestrial gravity and the rotation axis of an experiment. Researchers studied motions of rotating convecting liquids in spherical shells using electrohydrodynamic polarization forces to generate radial gravity, and hence centrally directed buoyancy forces, in the laboratory. The Geophysical Fluid Flow Cell (GFFC) experiments performed on Spacelab 3 in 1985 were analyzed. Recent efforts at interpretation led to numerical models of rotating convection with an aim to understand the possible generation of zonal banding on Jupiter and the fate of banana cells in rapidly rotating convection as the heating is made strongly supercritical. In addition, efforts to pose baroclinic wave experiments for future space missions using a modified version of the 1985 instrument led to theoretical and numerical models of baroclinic instability. Rather surprising properties were discovered, which may be useful in generating rational (rather than artificially truncated) models for nonlinear baroclinic instability and baroclinic chaos.

Hydrodynamic response of a fringing coral reef to a rise in mean sea level

NASA Astrophysics Data System (ADS)

Taebi, Soheila; Pattiaratchi, Charitha

2014-07-01

Ningaloo Reef, located along the northwest coast of Australia, is one of the longest fringing coral reefs in the world extending ~300 km. Similar to other fringing reefs, it consists of a barrier reef ~1-6 km offshore with occasional gaps, backed by a shallow lagoon. Wave breaking on the reef generates radiation stress gradients that produces wave setup across the reef and lagoon and mean currents across the reef. A section of Ningaloo Reef at Sandy Bay was chosen as the focus of an intense 6-week field experiment and numerical simulation using the wave model SWAN coupled to the three-dimensional circulation model ROMS. The physics of nearshore processes such as wave breaking, wave setup and mean flow across the reef was investigated in detail by examining the various momentum balances established in the system. The magnitude of the terms and the distance of their peaks from reef edge in the momentum balance were sensitive to the changes in mean sea level, e.g. the wave forces decreased as the mean water depth increased (and hence, wave breaking dissipation was reduced). This led to an increase in the wave power at the shoreline, a slight shift of the surf zone to the lee side of the reef and changes in the intensity of the circulation. The predicted hydrodynamic fields were input into a Lagrangian particle tracking model to estimate the transport time scale of the reef-lagoon system. Flushing time of the lagoon with the open ocean was computed using two definitions in renewal of semi-enclosed water basins and revealed the sensitivity of such a transport time scale to methods. An increase in the lagoon exchange rate at smaller mean sea-level rise and the decrease at higher mean sea-level rise was predicted through flushing time computed using both methods.

Observations of whitecaps during HiWinGS, their dependence on wave field, and relation to gas transfer velocities

NASA Astrophysics Data System (ADS)

Brumer, S. E.; Zappa, C. J.; Fairall, C. W.; Blomquist, B.; Brooks, I. M.; Tamura, H.; Yang, M.; Huebert, B. J.

2016-02-01

The High Wind Gas exchange Study (HiWinGS) presents the unique opportunity to gain new insights on the poorly understood aspects of air-sea interaction under high winds. The HiWinGS cruise took place in the North Atlantic during October and November 2013. Wind speeds exceeded 15 m s-1 25% of the time, including 48 hrs with U10 > 20 m s-1. Continuous measurements of turbulent fluxes of heat, momentum, and gas were taken from the bow of the R/V Knorr. Visible imagery was acquired from the port and starboard side of the flying bridge during daylight hours at 20Hz and directional wave spectra were obtained when on station from a wave rider buoy. Additional wave field statistics were computed from a laser altimeter as well as from a Wavewatch III hindcast. Taking advantage of the range of physical forcing and wave conditions sampled during HiWinGS, we investigate how the fractional whitecap coverage (W) and gas transfer velocity (K) vary with sea state. We distinguish between windseas and swell based on a separation algorithm applied to directional wave spectra, allowing contrasting pure windseas to swell dominated periods. For mixed seas, system alignment is considered when interpreting results. The four gases sampled during HiWinGS ranged from being mostly waterside controlled to almost entirely airside controlled. While bubble-mediated transfer appears to be small for moderately soluble gases like DMS, the importance of wave breaking turbulence transport has yet to be determined for all gases regardless of their solubility. This will be addressed by correlating measured K to estimates of active whitecap fraction (WA) and turbulent kinetic energy dissipation rate (ɛ). WA and ɛ are estimated from moments of the breaking crest length distribution derived from the imagery, focusing on young seas, when it is likely that large-scale breaking waves (i.e., whitecapping) will dominate the ɛ.

Gravity waves, Tides and Planetary wave characteristics revealed by network of MLT radars over Indian region

NASA Astrophysics Data System (ADS)

Venkat Ratnam, Madineni; Karanam, Kishore Kumar; Sunkara, Eswaraiah; Vijaya Bhaskara Rao, S.; Subrahmanyam, K. V.; Ramanjaneyulu, L.

2016-07-01

Mesosphere and Lower Thermosphere (MLT) mean winds, gravity waves, tidal and planetary wave characteristics are investigated using two years (2013-2015) of advanced meteor radar installed at Tirupathi (13.63oN, 79.4oE), India. The observations reveal the presence of high frequency gravity waves (30-120 minutes), atmospheric tides (diurnal, semi-diurnal and terr-diurnal) along with long period oscillations in both zonal and meridional winds. Background mean zonal winds show clear semi-annual oscillation in the mesosphere, whereas meridional winds are characterized by annual oscillation as expected. Diurnal tide amplitudes are significantly larger (60-80 m/s) than semi-diurnal (10-20 m/s) and terr-diurnal (5-8 m/s) tides and larger in meridional than zonal winds. The measured meridional components are in good agreement with Global Scale Wave Model (GSWM-09) predictions than zonal up to ~90 km in all the seasons, except fall equinox. Diurnal tidal phase matches well than the amplitudes between observations and model predictions. However, no similarity is being found in the semi-diurnal tides between observations and model. The measurements are further compared with nearby Thumba meteor radar (8.5oN, 77oE) observations. Some differences do exist between the measurements from Tirupati and Thumba meteor radar and model outputs at greater heights and the possible reasons are discussed. SVU meteor radar observations clearly showed the dominance of well-known ultra-fast kelvin waves (3.5 days), 5-8 day, 16 day, 27 day, and 30-40 day oscillations. Due to higher meteor count extending up to 110 km, we could investigate the variability of these PWs and oscillations covering wider range (70-110 km) for the first time. Significant change above 100 km is noticed in all the above mentioned PW activity and oscillations. We also used ERA-Interim reanalysis data sets available at 0.125x0.125 degree grids for investigating the characteristics of these PW right from surface to 1 hPa. The presence of these waves and oscillations right from upper troposphere to lower thermosphere simultaneously is noticed. Though these waves are expected to have higher wave number (higher horizontal wave lengths) few important differences are noticed between Tirupati and Thumba, that are separated by only 500 km. The implication of these waves and oscillations on the background atmosphere and vice versa are discussed. Thus, installation of SVU meteor radar made good complementary observations that can be effectively used to investigate vertical and lateral coupling. Role of these tides in modulating the mesopause altitude is further investigated using the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on-board Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite. It is found that mesopause altitude is always close to 100 km and is strongly affected by gravity waves, tides and planetary waves.

The Formation and Fate of Internal Waves in the South China Sea

DTIC Science & Technology

2015-11-05

FOf’miiiiiiM and Fate at Internal Waves In the South •C:hln;~t Sea --- --------· . _.,.. --- -------Author(s) Name{s) (Firsi,MI,La$t), Code, Atfi(iation...Tswen-Yung (David) Tang7 Internal gravity waves , the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in...for man-made structures in the ocean4. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their

Model of Wave Driven Flow Oscillation for Solar Cycle

NASA Technical Reports Server (NTRS)

Mayr, Hans G.; Wolff, Charles L.; Einaudi, Franco (Technical Monitor)

2001-01-01

At low latitudes in the Earth's atmosphere, the observed zonal flow velocities are dominated by the semi-annual and quasi-biennial oscillations with periods of 6 months and 20 to 32 months respectively. These terrestrial oscillations, the SAO and QBO respectively, are driven by wave-mean flow interactions due to upward propagating planetary-scale waves (periods of days) and small-scale gravity waves (periods of hours). We are proposing (see also Mayr et al., GRL, 2001) that such a mechanism may drive long period oscillations (reversing flows) in stellar and planetary interiors, and we apply it to the Sun. The reversing flows would occur below the convective envelope where waves can propagate. We apply a simplified, one dimensional, analytical flow model that incorporates a gravity wave parameterization due to Hines (1997). Based on this analysis, our estimates show that relatively small wave amplitudes less than 10 m/s can produce zonal flow amplitudes of 20 m/s, which should be sufficient to generate the observed variations in the magnetic field. To produce the 22-year period of oscillation, a low buoyancy frequency must be chosen, and this places the proposed flow in a region that is close to (and below) the base of the convective envelope. Enhanced turbulence associated with this low stability should help to generate the dynamo currents. With larger stability at deeper levels in the solar interior, the model can readily produce also oscillations with much longer periods. To provide an understanding of the fluid dynamics involved, we present numerical results from a 2D model for the terrestrial atmosphere that exemplify the non-linear nature of the wave interaction for which a mechanical analog is the escapement mechanism of the clock.

The Spiral Wave Instability Induced by a Giant Planet. I. Particle Stirring in the Inner Regions of Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Bae, Jaehan; Nelson, Richard P.; Hartmann, Lee

2016-12-01

We have recently shown that spiral density waves propagating in accretion disks can undergo a parametric instability by resonantly coupling with and transferring energy into pairs of inertial waves (or inertial-gravity waves when buoyancy is important). In this paper, we perform inviscid three-dimensional global hydrodynamic simulations to examine the growth and consequence of this instability operating on the spiral waves driven by a Jupiter-mass planet in a protoplanetary disk. We find that the spiral waves are destabilized via the spiral wave instability (SWI), generating hydrodynamic turbulence and sustained radially alternating vertical flows that appear to be associated with long wavelength inertial modes. In the interval 0.3 {R}{{p}}≤slant R≤slant 0.7{R}{{p}}, where R p denotes the semimajor axis of the planetary orbit (assumed to be 5 au), the estimated vertical diffusion rate associated with the turbulence is characterized by {α }{diff}∼ (0.2{--}1.2)× {10}-2. For the disk model considered here, the diffusion rate is such that particles with sizes up to several centimeters are vertically mixed within the first pressure scale height. This suggests that the instability of spiral waves launched by a giant planet can significantly disperse solid particles and trace chemical species from the midplane. In planet formation models where the continuous local production of chondrules/pebbles occurs over Myr timescales to provide a feedstock for pebble accretion onto these bodies, this stirring of solid particles may add a time constraint: planetary embryos and large asteroids have to form before a gas giant forms in the outer disk, otherwise the SWI will significantly decrease the chondrule/pebble accretion efficiency.

A Comparison Between Internal Waves Observed in the Southern Ocean and Lee Wave Generation Theory

NASA Astrophysics Data System (ADS)

Nikurashin, M.; Benthuysen, J.; Naveira Garabato, A.; Polzin, K. L.

2016-02-01

Direct observations in the Southern Ocean report enhanced internal wave activity and turbulence in a few kilometers above rough bottom topography. The enhancement is co-located with the deep-reaching fronts of the Antarctic Circumpolar Current, suggesting that the internal waves and turbulence are sustained by near-bottom flows interacting with rough topography. Recent numerical simulations confirm that oceanic flows impinging on rough small-scale topography are very effective generators of internal gravity waves and predict vigorous wave radiation, breaking, and turbulence within a kilometer above bottom. However, a linear lee wave generation theory applied to the observed bottom topography and mean flow characteristics has been shown to overestimate the observed rates of the turbulent energy dissipation. In this study, we compare the linear lee wave theory with the internal wave kinetic energy estimated from finestructure data collected as part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). We show that the observed internal wave kinetic energy levels are generally in agreement with the theory. Consistent with the lee wave theory, the observed internal wave kinetic energy scales quadratically with the mean flow speed, stratification, and topographic roughness. The correlation coefficient between the observed internal wave kinetic energy and mean flow and topography parameters reaches 0.6-0.8 for the 100-800 m vertical wavelengths, consistent with the dominant lee wave wavelengths, and drops to 0.2-0.5 for wavelengths outside this range. A better agreement between the lee wave theory and the observed internal wave kinetic energy than the observed turbulent energy dissipation suggests remote breaking of internal waves.

Radio scintillations observed during atmospheric occultations of Voyager: Internal gravity waves at Titan and magnetic field orientations at Jupiter and Saturn. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Hinson, D. P.

1983-01-01

The refractive index of planetary atmospheres at microwave frequencies is discussed. Physical models proposed for the refractive irregularities in the ionosphere and neutral atmosphere serve to characterize the atmospheric scattering structures, and are used subsequently to compute theoretical scintillation spectra for comparison with the Voyager occultation measurements. A technique for systematically analyzing and interpreting the signal fluctuations observed during planetary occultations is presented and applied to process the dual-wavelength data from the Voyager radio occultations by Jupiter, Saturn, and Titan. Results concerning the plasma irregularities in the upper ionospheres of Jupiter and Saturn are reported. The measured orientation of the irregularities is used to infer the magnetic field direction at several locations in the ionospheres of these two planets; the occultation measurements conflict with the predictions of Jovian magnetic field models, but generally confirm current models of Saturn's field. Wave parameters, including the vertical fluxes of energy and momentum, are estimated, and the source of the internal gravity waves discovered in Titan's upper atmosphere is considered.

Global atmospheric circulation statistics: Four year averages

NASA Technical Reports Server (NTRS)

Wu, M. F.; Geller, M. A.; Nash, E. R.; Gelman, M. E.

1987-01-01

Four year averages of the monthly mean global structure of the general circulation of the atmosphere are presented in the form of latitude-altitude, time-altitude, and time-latitude cross sections. The numerical values are given in tables. Basic parameters utilized include daily global maps of temperature and geopotential height for 18 pressure levels between 1000 and 0.4 mb for the period December 1, 1978 through November 30, 1982 supplied by NOAA/NMC. Geopotential heights and geostrophic winds are constructed using hydrostatic and geostrophic formulae. Meridional and vertical velocities are calculated using thermodynamic and continuity equations. Fields presented in this report are zonally averaged temperature, zonal, meridional, and vertical winds, and amplitude of the planetary waves in geopotential height with zonal wave numbers 1-3. The northward fluxes of sensible heat and eastward momentum by the standing and transient eddies along with their wavenumber decomposition and Eliassen-Palm flux propagation vectors and divergences by the standing and transient eddies along with their wavenumber decomposition are also given. Large interhemispheric differences and year-to-year variations are found to originate in the changes in the planetary wave activity.

How robust is the Holton-Tan relationship?

NASA Astrophysics Data System (ADS)

Braesicke, Peter; Kerzenmacher, Tobias

2017-04-01

The Holton-Tan relationship explains a possible link between tropical and extratropical variability (foremost in the northern hemisphere). The idea can be rationalised using simple linear wave theory. The quasi-biennial oscillation in the tropical lower stratosphere can be regarded as a kind of switch that influences the propagation of planetary waves. In a westerly phase of the QBO planetary waves in the stratosphere can propagate more equatorward and the polar vortex remains strong and undisturbed. In an easterly phase of the QBO the propagation is more poleward and the polar vortex is weaker and more disturbed. However, the robustness of this relationship depends on the precise definition of the QBO phase and the criteria used to define the polar vortex strength. Here, we will revisit the basic Holton-Tan relationship and will explore how other factors (including the state of the El Nino-Southern Oscillation) modify the relationship. Using reanalysis data and idealised model experiments a possible range for robust manifestations of the Holton-Tan relationship is determined, thus providing an improved framework for a better understanding of teleconnections between tropical and polar latitudes.

Numerical study of dam-break induced tsunami-like bore with a hump of different slopes

NASA Astrophysics Data System (ADS)

Cheng, Du; Zhao, Xi-zeng; Zhang, Da-ke; Chen, Yong

2017-12-01

Numerical simulation of dam-break wave, as an imitation of tsunami hydraulic bore, with a hump of different slopes is performed in this paper using an in-house code, named a Constrained Interpolation Profile (CIP)-based model. The model is built on a Cartesian grid system with the Navier Stokes equations using a CIP method for the flow solver, and employs an immersed boundary method (IBM) for the treatment of solid body boundary. A more accurate interface capturing scheme, the Tangent of hyperbola for interface capturing/Slope weighting (THINC/SW) scheme, is adopted as the interface capturing method. Then, the CIP-based model is applied to simulate the dam break flow problem in a bumpy channel. Considerable attention is paid to the spilling type reflected bore, the following spilling type wave breaking, free surface profiles and water level variations over time. Computations are compared with available experimental data and other numerical results quantitatively and qualitatively. Further investigation is conducted to analyze the influence of variable slopes on the flow features of the tsunami-like bore.

Weakly and strongly coupled Belousov-Zhabotinsky patterns.

PubMed

Weiss, Stephan; Deegan, Robert D

2017-02-01

We investigate experimentally and numerically the synchronization of two-dimensional spiral wave patterns in the Belousov-Zhabotinsky reaction due to point-to-point coupling of two separate domains. Different synchronization modalities appear depending on the coupling strength and the initial patterns in each domain. The behavior as a function of the coupling strength falls into two qualitatively different regimes. The weakly coupled regime is characterized by inter-domain interactions that distorted but do not break wave fronts. Under weak coupling, spiral cores are pushed around by wave fronts in the other domain, resulting in an effective interaction between cores in opposite domains. In the case where each domain initially contains a single spiral, the cores form a bound pair and orbit each other at quantized distances. When the starting patterns consist of multiple randomly positioned spiral cores, the number of cores decreases with time until all that remains are a few cores that are synchronized with a partner in the other domain. The strongly coupled regime is characterized by interdomain interactions that break wave fronts. As a result, the wave patterns in both domains become identical.

Weakly and strongly coupled Belousov-Zhabotinsky patterns

NASA Astrophysics Data System (ADS)

Weiss, Stephan; Deegan, Robert D.

2017-02-01

We investigate experimentally and numerically the synchronization of two-dimensional spiral wave patterns in the Belousov-Zhabotinsky reaction due to point-to-point coupling of two separate domains. Different synchronization modalities appear depending on the coupling strength and the initial patterns in each domain. The behavior as a function of the coupling strength falls into two qualitatively different regimes. The weakly coupled regime is characterized by inter-domain interactions that distorted but do not break wave fronts. Under weak coupling, spiral cores are pushed around by wave fronts in the other domain, resulting in an effective interaction between cores in opposite domains. In the case where each domain initially contains a single spiral, the cores form a bound pair and orbit each other at quantized distances. When the starting patterns consist of multiple randomly positioned spiral cores, the number of cores decreases with time until all that remains are a few cores that are synchronized with a partner in the other domain. The strongly coupled regime is characterized by interdomain interactions that break wave fronts. As a result, the wave patterns in both domains become identical.

Gravitational waves from dark first order phase transitions and dark photons

NASA Astrophysics Data System (ADS)

Addazi, Andrea; Marcianò, Antonino

2018-01-01

Cold Dark Matter particles may interact with ordinary particles through a dark photon, which acquires a mass thanks to a spontaneous symmetry breaking mechanism. We discuss a dark photon model in which the scalar singlet associated to the spontaneous symmetry breaking has an effective potential that induces a first order phase transition in the early Universe. Such a scenario provides a rich phenomenology for electron-positron colliders and gravitational waves interferometers, and may be tested in several different channels. The hidden first order phase transition implies the emission of gravitational waves signals, which may constrain the dark photon’s space of parameters. Compared limits from electron-positron colliders, astrophysics, cosmology and future gravitational waves interferometers such as eLISA, U-DECIGO and BBO are discussed. This highly motivates a cross-checking strategy of data arising from experiments dedicated to gravitational waves, meson factories, the International Linear Collider (ILC), the Circular Electron Positron Collider (CEPC) and other underground direct detection experiments of cold dark matter candidates. Supported by the Shanghai Municipality (KBH1512299) and Fudan University (JJH1512105)

Observations of the 5-day wave in the mesosphere and lower thermosphere

NASA Technical Reports Server (NTRS)

Wu, D. L.; Hays, P. B.; Skinner, W. R.

1994-01-01

The 5-day planetary wave has been detected in the winds measured by the High Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) in the mesosphere and lower thermosphere (50-110 km). The appearances of the 5-day wave are transient, with a lifetime of 10-20 days in the two-year data set. The structures of selected 5-day wave events are in generally good agreement with the (1,1) Rossby normal mode for both zonal and meridional components. A climatology of the 5-day wave is presented for an altitude of 95 km and latitudes mainly between 40 deg S and 40 deg N.

Hand-Held Calculator Algorithms for Coastal Engineering.

DTIC Science & Technology

1982-01-01

and water depth at the structure toe, ds. The development of the equation is derived on the solution sheet included with program 104R. Algorithm uses...Limited Design Breaking Wave Height at Structure (AOS logic)... .... ....... ......... .54 6. 105R Wave Transmission - Fuchs’ Equation (RPN logic...58 105A Wave Transmission - Fuchs’ Equation (AOS logic). . . . 61 APPENDIX BLANK PROGRAM FORMS ........ ....................... ... 67 4

Oceanography and Mine Warfare

DTIC Science & Technology

2000-03-13

of breaking waves , the position and strength of surface currents, and the propagation of the tide into very shallow waters. In the surf zone...6) sediment properties determine shock wave propagation , a method for mine neutralization in the surf zone. 48 OCEANOGRAPHY AND MINE WARFARE...mines will be buried in the sediments, sedimentary explosive shock wave propagation is critical for determining operational performance. Presently, we

Localization of ultra-low frequency waves in multi-ion plasmas of the planetary magnetosphere

DOE PAGES

Kim, Eun -Hwa; Johnson, Jay R.; Lee, Dong -Hun

2015-01-01

By adopting a 2D time-dependent wave code, we investigate how mode-converted waves at the Ion-Ion Hybrid (IIH) resonance and compressional waves propagate in 2D density structures with a wide range of field-aligned wavenumbers to background magnetic fields. The simulation results show that the mode-converted waves have continuous bands across the field line consistent with previous numerical studies. These waves also have harmonic structures in frequency domain and are localized in the field-aligned heavy ion density well. Lastly, our results thus emphasize the importance of a field-aligned heavy ion density structure for ultra-low frequency wave propagation, and suggest that IIH wavesmore » can be localized in different locations along the field line.« less

Observation of wave celerity evolution in the nearshore using digital video imagery

NASA Astrophysics Data System (ADS)

Yoo, J.; Fritz, H. M.; Haas, K. A.; Work, P. A.; Barnes, C. F.; Cho, Y.

2008-12-01

Celerity of incident waves in the nearshore is observed from oblique video imagery collected at Myrtle Beach, S.C.. The video camera covers the field view of length scales O(100) m. Celerity of waves propagating in shallow water including the surf zone is estimated by applying advanced image processing and analysis methods to the individual video images sampled at 3 Hz. Original image sequences are processed through video image frame differencing, directional low-pass image filtering to reduce the noise arising from foam in the surf zone. The breaking wave celerity is computed along a cross-shore transect from the wave crest tracks extracted by a Radon transform-based line detection method. The observed celerity from the nearshore video imagery is larger than the linear wave celerity computed from the measured water depths over the entire surf zone. Compared to the nonlinear shallow water wave equation (NSWE)-based celerity computed using the measured depths and wave heights, in general, the video-based celerity shows good agreements over the surf zone except the regions across the incipient wave breaking locations. In the regions across the breaker points, the observed wave celerity is even larger than the NSWE-based celerity due to the transition of wave crest shapes. The observed celerity using the video imagery can be used to monitor the nearshore geometry through depth inversion based on the nonlinear wave celerity theories. For this purpose, the exceeding celerity across the breaker points needs to be corrected accordingly compared to a nonlinear wave celerity theory applied.

Numerical and Analytical Investigation of the Energy and Momentum Exchange Between the Shocked Solar Wind and Topside Ionosphere for Non-Magnetic Planets and Moons

NASA Astrophysics Data System (ADS)

Dobe, Z.; Shapiro, V. D.; Quest, K.; Szego, K.; Huba, J.

1998-11-01

Previously[1], we proposed a model of the planetary ions pick-up by the shocked solar wind flow developing in the mantle-turbulent boundary region surrounding the ionospheres of non-magnetic planets-Mars and Venus. In the present paper we are modifying this model taking into account the flow of the planetary elections immediately pick-up by E x B forces of the shocked solar wind. It is shown that flow of the cold planetary electrons drives a strong hydrodynamical instability of the electrostatic whistlers efficiently coupling planetary ions with the flow of the solar wind. The linear stage of the instability is investigated both analytically and numerically, and results are found to be in a good agreement. Nonlunear stage of the instability is investigated with the modified numerical hybrid code[2], and demonstrates both effects of acceleration and heating of the planetary ions by the solar wind. Field aligned electron acceleration is also investigated in a test particle approximation using wave power spectrum obtained in a self-consistent numerical simulation.

Variability of the Magnetic Field Power Spectrum in the Solar Wind at Electron Scales

NASA Astrophysics Data System (ADS)

Roberts, Owen Wyn; Alexandrova, O.; Kajdič, P.; Turc, L.; Perrone, D.; Escoubet, C. P.; Walsh, A.

2017-12-01

At electron scales, the power spectrum of solar-wind magnetic fluctuations can be highly variable and the dissipation mechanisms of the magnetic energy into the various particle species is under debate. In this paper, we investigate data from the Cluster mission’s STAFF Search Coil magnetometer when the level of turbulence is sufficiently high that the morphology of the power spectrum at electron scales can be investigated. The Cluster spacecraft sample a disturbed interval of plasma where two streams of solar wind interact. Meanwhile, several discontinuities (coherent structures) are seen in the large-scale magnetic field, while at small scales several intermittent bursts of wave activity (whistler waves) are present. Several different morphologies of the power spectrum can be identified: (1) two power laws separated by a break, (2) an exponential cutoff near the Taylor shifted electron scales, and (3) strong spectral knees at the Taylor shifted electron scales. These different morphologies are investigated by using wavelet coherence, showing that, in this interval, a clear break and strong spectral knees are features that are associated with sporadic quasi parallel propagating whistler waves, even for short times. On the other hand, when no signatures of whistler waves at ∼ 0.1{--}0.2{f}{ce} are present, a clear break is difficult to find and the spectrum is often more characteristic of a power law with an exponential cutoff.

Dehydration of planetary ices at high pressure; the role of analogue materials (Invited)

NASA Astrophysics Data System (ADS)

Fortes, A. D.

2013-12-01

Many planet-forming compounds become unstable with respect to their components under conditions of high pressure. In the Earth, for example, Mg2SiO4 breaks down to MgSiO3 + MgO at ~ 25 GPa, a pressure corresponding to the 670 km seismic discontinuity, with significance for the dynamics of convective flow in the mantle. A similar phenomenon occurs with many hydrate compounds thought to be major ';rock forming minerals' inside outer Solar System bodies, undoubtedly with important consequences for the structure and dynamics of icy worlds. It is well known that clathrates tend to form denser polymorphs with an incrementally greater concentration of the guest molecule, exsolving high-pressure phases of water ice in the process, or else (in the case of CO2), break down to entirely to their component molecular solids. My own recent work using high-pressure neutron powder diffraction has explored not only the behaviour of methane clathrates but also the exsolution of water from ammonia dihydrate and monohydrate, both of which break down eventually to ammonia hemihydrate + ice. In some cases, understanding the sequence of changes in both crystal structure and composition at high pressure is challenging, particularly when the starting materials have a complex crystal structure. Some years ago, I identified a high-pressure phase boundary where MgSO4.11H2O (meridianiite) appeared to break down to another hydrate and high-pressure ice VI. However, the powder diffraction pattern of the hydrate formed under these conditions resembled nothing encountered previously in my high-pressure studies of the next lowest hydrate, MgSO4.7H2O (epsomite). This led me to search for hydration states between 7 and 11 which might have escaped detection over several centuries of study of simple divalent metal sulfates. A wide-ranging systematic study of M2+X6+O4.nH2O compounds at low temperatures uncovered two new hydrates, an 8-hydrate and a 9-hydrate, the former occurring only in NiSO4 solutions, and the latter being found in Ni-, Zn-, Cu-, and Fe-doped MgSO4 solutions. Indeed, I determined that small quantities of pure MgSO4.9H2O can co-crystallise at ambient pressure with meridianiite. However, these all appear to be metastable states, and further work was necessary to try and discover stable forms of these hydrates for further study. In experiments carried out earlier this year, evidence has emerged not only that MgMoO4 can form a (possibly) stable 8-hydrate but also that MgSeO4 can form a 9-hydrate that exists in equilibrium with liquid near the eutectic. These apparently esoteric compounds (from a planetary perspective) may yet hold the key to understanding the high-pressure behaviour of true planetary materials. Just as the search for analogue materials over many decades has substantially advanced our knowledge of Earth materials, similar analogue studies are poised to unlock the mysteries of these planetary ices.

Normal mode Rossby waves observed in the upper stratosphere

NASA Technical Reports Server (NTRS)

Hirooka, T.; Hirota, I.

1985-01-01

In recent years, observational evidence has been obtained for westward traveling planetary waves in the middle atmosphere with the aid of global data from satellites. There is no doubt that the fair portion of the observed traveling waves can be understood as the manifestation of the normal mode Rossby waves which are theoretically derived from the tidal theory. Some observational aspects of the structure and behavior of the normal model Rossby waves in the upper stratosphere are reported. The data used are the global stratospheric geopotential thickness and height analyses which are derived mainly from the Stratospheric Sounding Units (SSUs) on board TIROS-N and NOAA satellites. A clear example of the influence of the normal mode Rossby wave on the mean flow is reported. The mechanism considered is interference between the normal mode Rossby wave and the quasi-stationary wave.

Ocean Surface Wave Optical Roughness - Innovative Measurement and Modeling

DTIC Science & Technology

2008-01-01

and microscale breaker crest length spectral density (e.g. Jessup and Phadnis , 2005) have been reported. 1 Report Documentation Page Form...297. Jessup, A.T. and Phadnis , K.R. 2005 Measurement of the geometric and kinematic properties of microsacle breaking waves from infrared imagery

Ocean Surface Wave Optical Roughness - Innovative Measurement and Modeling

DTIC Science & Technology

2008-01-01

and microscale breaker crest length spectral density (e.g. Jessup and Phadnis , 2005) have been reported. 1 Report Documentation Page Form...297. Jessup , A.T. and Phadnis , K.R. 2005 Measurement of the geometric and kinematic properties of microsacle breaking waves from infrared imagery

Inverse mirror plasma experimental device (IMPED) - a magnetized linear plasma device for wave studies

NASA Astrophysics Data System (ADS)

Bose, Sayak; Chattopadhyay, P. K.; Ghosh, J.; Sengupta, S.; Saxena, Y. C.; Pal, R.

2015-04-01

In a quasineutral plasma, electrons undergo collective oscillations, known as plasma oscillations, when perturbed locally. The oscillations propagate due to finite temperature effects. However, the wave can lose the phase coherence between constituting oscillators in an inhomogeneous plasma (phase mixing) because of the dependence of plasma oscillation frequency on plasma density. The longitudinal electric field associated with the wave may be used to accelerate electrons to high energies by exciting large amplitude wave. However when the maximum amplitude of the wave is reached that plasma can sustain, the wave breaks. The phenomena of wave breaking and phase mixing have applications in plasma heating and particle acceleration. For detailed experimental investigation of these phenomena a new device, inverse mirror plasma experimental device (IMPED), has been designed and fabricated. The detailed considerations taken before designing the device, so that different aspects of these phenomena can be studied in a controlled manner, are described. Specifications of different components of the IMPED machine and their flexibility aspects in upgrading, if necessary, are discussed. Initial results meeting the prerequisite condition of the plasma for such study, such as a quiescent, collisionless and uniform plasma, are presented. The machine produces δnnoise/n <= 1%, Luniform ~ 120 cm at argon filling pressure of ~10-4 mbar and axial magnetic field of B = 1090 G.

On the role of sea-state in bubble-mediated air-sea gas flux during a winter storm

NASA Astrophysics Data System (ADS)

Liang, Jun-Hong; Emerson, Steven R.; D'Asaro, Eric A.; McNeil, Craig L.; Harcourt, Ramsey R.; Sullivan, Peter P.; Yang, Bo; Cronin, Meghan F.

2017-04-01

Oceanic bubbles play an important role in the air-sea exchange of weakly soluble gases at moderate to high wind speeds. A Lagrangian bubble model embedded in a large eddy simulation model is developed to study bubbles and their influence on dissolved gases in the upper ocean. The transient evolution of mixed-layer dissolved oxygen and nitrogen gases at Ocean Station Papa (50°N, 145°W) during a winter storm is reproduced with the model. Among different physical processes, gas bubbles are the most important in elevating dissolved gas concentrations during the storm, while atmospheric pressure governs the variability of gas saturation anomaly (the relative departure of dissolved gas concentration from the saturation concentration). For the same wind speed, bubble-mediated gas fluxes are larger during rising wind with smaller wave age than during falling wind with larger wave age. Wave conditions are the primary cause for the bubble gas flux difference: when wind strengthens, waves are less-developed with respect to wind, resulting in more frequent large breaking waves. Bubble generation in large breaking waves is favorable for a large bubble-mediated gas flux. The wave-age dependence is not included in any existing bubble-mediated gas flux parameterizations.

Internal wave deposits in Jurassic Kermanshah pelagic carbonates and radiolarites (Kermanshah area, West Iran)

NASA Astrophysics Data System (ADS)

Abdi, Asad; Gharaie, Mohamad Hosein Mahmudy; Bádenas, Beatriz

2014-12-01

We report eventites generated by turbulence events triggered by breaking internal waves in Jurassic pelagic muds deposited in a graben area located between the Arabian and Bisotoun carbonate platforms, at the Kermanshah basin (West Iran). The 43 m-thick studied Pliensbachian-Aalenian succession at Kermanshah includes sponge spicule-radiolarian limestones and cherts with cm- to dm-thick intercalations of pyroclastic beds and coarse-grained deposits formed by neritic-derived grains and reworked pelagic material. Breaking of internal waves in localized areas reworked the available sediment on sea floor, including the erosion of cohesive pelagic muds and the resuspension of neritic-derived grains, which were resedimented from the Bisotoun platform most probably by storms or turbidity currents. The generated internal wave deposits include: flat- and round pebble limestone conglomerates, formed by deposition of pelagic clasts and neritic-derived grains near the breaker zone; laminated packstone-grainstones deposited by high-energy, upslope (swash) and downslope (backswash) flows; cm-thick packstone-grainstones with asymmetrical starved ripples and hummocy crossstratification, generated downdip by waning of backwash flows and internal wave oscillatory flows. These internal wave deposits predominate in the Pliensbachian-early Toarcian, and were related to internal waves developed along a thermocline linked to climate warming and excited by submarine volcanic eruptions, storms or tectonic shaking.

Fate of internal waves on a shallow shelf

NASA Astrophysics Data System (ADS)

Davis, Kristen; Arthur, Robert; Reid, Emma; Decarlo, Thomas; Cohen, Anne

2017-11-01

Internal waves strongly influence the physical and chemical environment of coastal ecosystems worldwide. We report novel observations from a distributed temperature sensing (DTS) system that tracked the transformation of internal waves from the shelf break to the surf zone over a shelf-slope region of a coral atoll in the South China Sea. The spatially-continuous view of the near-bottom temperature field provided by the DTS offers a perspective of physical processes previously available only in laboratory settings or numerical models. These processes include internal wave reflection off a natural slope, shoreward transport of dense fluid within trapped cores, internal ``tide pools'' (dense water left behind after the retreat of an internal wave), and internal run-down (near-bottom, offshore-directed jets of water preceding a breaking internal wave). Analysis shows that the fate of internal waves on this shelf - whether they are transmitted into shallow waters or reflected back offshore - is mediated by local water column density and shear structure, with important implications for nearshore distributions of energy, heat, and nutrients. We acknowledge the US Army Research Laboratory DoD Supercomputing Resource Center for computer time on Excalibur, which was used for the numerical simulations in this work. Funding for field work supported by Academia Sinica and for K.D. and E.R. from NSF.

Numerical Simulation of a Seaway with Breaking

NASA Astrophysics Data System (ADS)

Dommermuth, Douglas; O'Shea, Thomas; Brucker, Kyle; Wyatt, Donald

2012-11-01

The focus of this presentation is to describe the recent efforts to simulate a fully non-linear seaway with breaking by using a high-order spectral (HOS) solution of the free-surface boundary value problem to drive a three-dimensional Volume of Fluid (VOF) solution. Historically, the two main types of simulations to simulate free-surface flows are the boundary integral equations method (BIEM) and high-order spectral (HOS) methods. BIEM calculations fail at the point at which the surface impacts upon itself, if not sooner, and HOS methods can only simulate a single valued free-surface. Both also employ a single-phase approximation in which the effects of the air on the water are neglected. Due to these limitations they are unable to simulate breaking waves and air entrainment. The Volume of Fluid (VOF) method on the other hand is suitable for modeling breaking waves and air entrainment. However it is computationally intractable to generate a realistic non-linear sea-state. Here, we use the HOS solution to quickly drive, or nudge, the VOF solution into a non-linear state. The computational strategies, mathematical formulation, and numerical implementation will be discussed. The results of the VOF simulation of a seaway with breaking will also be presented, and compared to the single phase, single valued HOS results.

Importance of d-wave contributions in the charge symmetry breaking reaction dd →4Heπ0

NASA Astrophysics Data System (ADS)

Adlarson, P.; Augustyniak, W.; Bardan, W.; Bashkanov, M.; Bergmann, F. S.; Berłowski, M.; Bondar, A.; Büscher, M.; Calén, H.; Ciepał, I.; Clement, H.; Czerwiński, E.; Demmich, K.; Engels, R.; Erven, A.; Erven, W.; Eyrich, W.; Fedorets, P.; Föhl, K.; Fransson, K.; Goldenbaum, F.; Goswami, A.; Grigoryev, K.; Gullström, C.-O.; Hanhart, C.; Heijkenskjöld, L.; Hejny, V.; Hüsken, N.; Jarczyk, L.; Johansson, T.; Kamys, B.; Kemmerling, G.; Khatri, G.; Khoukaz, A.; Khreptak, O.; Kirillov, D. A.; Kistryn, S.; Kleines, H.; Kłos, B.; Krzemień, W.; Kulessa, P.; Kupść, A.; Kuzmin, A.; Lalwani, K.; Lersch, D.; Lorentz, B.; Magiera, A.; Maier, R.; Marciniewski, P.; Mariański, B.; Morsch, H.-P.; Moskal, P.; Ohm, H.; Parol, W.; Perez del Rio, E.; Piskunov, N. M.; Prasuhn, D.; Pszczel, D.; Pysz, K.; Pyszniak, A.; Ritman, J.; Roy, A.; Rudy, Z.; Rundel, O.; Sawant, S.; Schadmand, S.; Schätti-Ozerianska, I.; Sefzick, T.; Serdyuk, V.; Shwartz, B.; Sitterberg, K.; Skorodko, T.; Skurzok, M.; Smyrski, J.; Sopov, V.; Stassen, R.; Stepaniak, J.; Stephan, E.; Sterzenbach, G.; Stockhorst, H.; Ströher, H.; Szczurek, A.; Trzciński, A.; Wolke, M.; Wrońska, A.; Wüstner, P.; Yamamoto, A.; Zabierowski, J.; Zieliński, M. J.; Złomańczuk, J.; Żuprański, P.; Żurek, M.; WASA-at-COSY Collaboration

2018-06-01

This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction dd →4Heπ0 using the WASA-at-COSY detector setup at an excess energy of Q = 60MeV. The determined differential cross section can be parametrized as d σ /d Ω = a + bcos2 ⁡θ*, where θ* is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are a = (1.55 ± 0.46(stat) + 0.32 - 0.8 (syst)) pb /sr and b = (13.1 ± 2.1 (stat)-2.7+1.0 (syst)) pb /sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the Δ isobar to the dd →4Heπ0 reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions.

Plasma and radio waves from Neptune: Source mechamisms and propagation

NASA Technical Reports Server (NTRS)

Menietti, J. Douglas

1994-01-01

The purpose of this project was to conduct a comprehensive investigation of the radio wave emission observed by the planetary radio astronomy (PRA) instrument on board Voyager 2 as it flew by Neptune. The study has included data analysis, theoretical and numerical calculations, and ray tracing to determine the possible source mechanisms and locations of the radiation, including the narrowband bursty and smooth components of the Neptune radio emission.

Changes of the Ionosphere Caused By the Interaction Between the Quasi-Two-Day Wave and Tides

NASA Astrophysics Data System (ADS)

Yue, J.; Wang, W.; Chang, L. C.

2014-12-01

Traveling planetary waves, such as the quasi-two-day wave (QTDW), are one essential element of the mesosphere and lower thermosphere dynamics. These planetary waves have been observed to cause strong ionospheric day-to-day variations. We have understood that the QTDW can impact the thermosphere and ionosphere either by directly penetrating into the lower thermosphere and modulating E-region dynamo in a period of about 2-days, or by enhancing mixing and decreasing thermosphere O/N2 and in ionospheric electron density. In this work, we introduce the third mechanism of how the QTDW impacts the ionosphere, the QTDW-tidal interactions occurring in the mesosphere and lower thermosphere (MLT). We employ the NCAR TIME-GCM to simulate the interaction between the QTDW and tides, and the impact of this interaction on the ionospheric E-region dynamo, equatorial fountain effect, and F-region plasma density. We find that the tidal amplitudes and phases are dramatically altered during strong QTDW events during post-solstice. In particular, the amplitudes of the migrating tides can decrease as much as 20-30%. The changed tides result in different dynamo electric field, vertical ion drift, and thus different diurnal and semidiurnal cycles in F-region electron density.

Emergent Topological order from Spin-Orbit Density wave

NASA Astrophysics Data System (ADS)

Gupta, Gaurav; Das, Tanmoy

We study the emergence of a Z2 -type topological order because of Landau type symmetry breaking order parameter. When two Rashba type SOC bands of different chirality become nested by a magic wavevector [(0, ∖pi) or (∖pi,0)], it introduces the inversion of chirality between different lattice sites. Such a density wave state is known as spin-orbit density wave. The resulting quantum order is associated with the topological order which is classified by a Z2 invariant. So, this system can simultaneously be classified by both a symmetry breaking order parameter and the associated Z2 topological invariant. This order parameter can be realized or engineered in two- or quasi-two-dimensional fermionic lattices, quantum wires, with tunable RSOC and correlation strength. The work is facilitated by the computer cluster facility at Department of Physics, Indian Institute of Science.

Thermal Analysis of Brazing Seal and Sterilizing Technique to Break Contamination Chain for Mars Sample Return

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi; Badescu, Mircea; Bar-Cohen, Yoseph

2015-01-01

The potential to return Martian samples to Earth for extensive analysis is in great interest of the planetary science community. It is important to make sure the mission would securely contain any microbes that may possibly exist on Mars so that they would not be able to cause any adverse effects on Earth's environment. A brazing sealing and sterilizing technique has been proposed to break the Mars-to-Earth contamination chain. Thermal analysis of the brazing process was conducted for several conceptual designs that apply the technique. Control of the increase of the temperature of the Martian samples is a challenge. The temperature profiles of the Martian samples being sealed in the container were predicted by finite element thermal models. The results show that the sealing and sterilization process can be controlled such that the samples' temperature is maintained below the potentially required level, and that the brazing technique is a feasible approach to break the contamination chain.

Investigation of the relationship between hurricane waves and extreme runup

NASA Astrophysics Data System (ADS)

Thompson, D. M.; Stockdon, H. F.

2006-12-01

In addition to storm surge, the elevation of wave-induced runup plays a significant role in forcing geomorphic change during extreme storms. Empirical formulations for extreme runup, defined as the 2% exceedence level, are dependent on some measure of significant offshore wave height. Accurate prediction of extreme runup, particularly during hurricanes when wave heights are large, depends on selecting the most appropriate measure of wave height that provides energy to the nearshore system. Using measurements from deep-water wave buoys results in an overprediction of runup elevation. Under storm forcing these large waves dissipate across the shelf through friction, whitecapping and depth-limited breaking before reaching the beach and forcing swash processes. The use of a local, shallow water wave height has been shown to provide a more accurate estimate of extreme runup elevation (Stockdon, et. al. 2006); however, a specific definition of this local wave height has yet to be defined. Using observations of nearshore waves from the U.S. Army Corps of Engineers' Field Research Facility (FRF) in Duck, NC during Hurricane Isabel, the most relevant measure of wave height for use in empirical runup parameterizations was examined. Spatial and temporal variability of the hurricane wave field, which made landfall on September 18, 2003, were modeled using SWAN. Comparisons with wave data from FRF gages and deep-water buoys operated by NOAA's National Data Buoy Center were used for model calibration. Various measures of local wave height (breaking, dissipation-based, etc.) were extracted from the model domain and used as input to the runup parameterizations. Video based observations of runup collected at the FRF during the storm were used to ground truth modeled values. Assessment of the most appropriate measure of wave height can be extended over a large area through comparisons to observations of storm- induced geomorphic change.

A study of the mechanism of internal gravity wave generation by quasigeostrophic meteorological motions

NASA Technical Reports Server (NTRS)

Medvedev, A. S.

1987-01-01

Numerous experiments on the detection of atmospheric waves in the frequency range from acoustic to planetary at meteor heights have revealed that important wave sources are meteorological processes in the troposphere (cyclones, atmospheric fronts, jet streams, etc.). A dynamical theory based on the others work include describing the adaptation of meteorological fields to the geostropic equilibrium state. According to this theory, wave motions appear as a result of constant competition between the maladjustment of the wind and pressure fields due to nonlinear effects and the tendency of the atmosphere to establish a quasi-geostrophic equilibrium of these fields. These meteorological fields are discussed.

A study of the mechanism of internal gravity wave generation by quasigeostrophic meteorological motions

NASA Astrophysics Data System (ADS)

Medvedev, A. S.

1987-08-01

Numerous experiments on the detection of atmospheric waves in the frequency range from acoustic to planetary at meteor heights have revealed that important wave sources are meteorological processes in the troposphere (cyclones, atmospheric fronts, jet streams, etc.). A dynamical theory based on the others work include describing the adaptation of meteorological fields to the geostropic equilibrium state. According to this theory, wave motions appear as a result of constant competition between the maladjustment of the wind and pressure fields due to nonlinear effects and the tendency of the atmosphere to establish a quasi-geostrophic equilibrium of these fields. These meteorological fields are discussed.

Density of the Human Body in Gravity Contrasting Tectonic Blocks of Earth

NASA Astrophysics Data System (ADS)

Kochemasov, G. G.

Short duration cosmic experiments with humans in reduced gravity might be compared with results of practically time unlimited (many thousand of years!) existence of man in conditions of planetary tectonic blocks with rather small gravity gradient. These blocks with differing planetary radii are formed in the terrestrial globe (as well as in other celestial bodies) as a result of its movement in an elliptical orbit inevitably causing inertia-gravity warping waves. Depending on the wavelengths, Earth is tectonically dichotomic (wave1, 2π R-structure), sectoral (wave2, π R-structure) and granular (wave4, π R/2-structure) [1]. Alternations of uplifts (+) and subsidences (-) in rotating Earth requires an equilibration of angular momenta of different levels blocks by differing densities of composing them objects. ``Objects'' are geological as well as biological ones. Oceans (-) are filled with dense basaltic rocks, continents (+) are built by less dense granites (andesites, on average). Homo sapiens, widely spread over Earth, equally accommodates himself to conditions of tectonic blocks with differing radii (densities). The most pronounced (amplitudinal) tectonic dichotomy is an opposition of the subsided (-) western pacific hemisphere to the uplifted (+) eastern continental hemisphere. Recently populated (12 to 3 thousand years ago) America and Pacific made migrating mongoloids denser (higher the Rohrer's index* of Indians and Polynesians) than inhabitants of native Asia. Asia itself is a sector of the planetary sectoral π R-structure of the eastern hemisphere with the center at the Pamirs-Hindukush. Around this center converge 2 uplifted sectors (Africa-Mediterranean ++, Asian +) separated by 2 subsided ones (Eurasian -, Indoceanic - -). The 4 great races developed on these sectors have their own ``body density'' characteristics. The uplifted Africa bears ``light'' negroids, subsided Eurasia ``heavy'' europeoids. In the former USSR population of the Asian sector (+) has less mineralized bones and less Fe/Mn in hairs (thus less dense hairs) than population of the Eurasian sector (-) [2]. The differentiation of the great races can be traced to the gene level: frequencies of their Rh-system genetic markers are clearly different. the ratio of man's weight to his height in the cube power (can be used also the simple ratio of man's weight to his height, that means the ``linear density'' of man). References : [1] Kochemasov G. G. Theorems of wave planetary tectonics // Geophys. Res. Abstr., V. 1, # 3, 1999,700; [2] Alexeeva T. I. Geographical environment and human biology // Moscow, Mysl, 1977, 302 pp. (in Russian).

Electron beam interaction with space plasmas.

NASA Astrophysics Data System (ADS)

Krafft, C.; Bolokitin, A. S.

1999-12-01

Active space experiments involving the controlled injection of electron beams and the formation of artificially generated currents can provide in many cases a calibration of natural phenomena connected with the dynamic interaction of charged particles with fields. They have a long history beginning from the launches of small rockets with electron guns in order to map magnetic fields lines in the Earth's magnetosphere or to excite artificial auroras. Moreover, natural beams of charged particles exist in many space and astrophysical plasmas and were identified in situ by several satellites; a few examples are beams connected with solar bursts, planetary foreshocks or suprathermal fluxes traveling in planetary magnetospheres. Many experimental and theoretical works have been performed in order to interpret or plan space experiments involving beam injection as well as to understand the physics of wave-particle interaction, as wave radiation, beam dynamics and background plasma modification.