Turbulence and stress owing to gravity wave and tidal breakdown
TL;DR: In this article, the effects of mean winds and gravity waves on the mean momentum budget were investigated and it was shown that the existence of critical levels in the mesosphere significantly limits the ability of gravity waves to generate turbulence.
Abstract: It has been suggested (Lindzen, 1967, 1968a, b; Lindzen and Blake, 1971; Hodges, 1969) that turbulence in the upper mesosphere arises from the unstable breakdown of tides and gravity waves. Crudely speaking, it was expected that sufficient turbulence would be generated to prevent the growth of wave amplitude with height (roughly as (basic pressure)−1/2). This work has been extended to allow for the generation of turbulence by smaller amplitude waves, the effects of mean winds on the waves, and the effects of the waves on the mean momentum budget. The effects of mean winds, while of relatively small importance for tides, are crucial for internal gravity waves originating in the troposphere. Winds in the troposphere and stratosphere sharply limit the phase speeds of waves capable of reaching the upper mesosphere. In addition, the existence of critical levels in the mesosphere significantly limits the ability of gravity waves to generate turbulence, while the breakdown of gravity waves contributes to the development of critical levels. The results of the present study suggest that at middle latitudes in winter, eddy coefficients may peak at relatively low altitudes (50 km) and at higher altitudes in summer and during sudden warmings (70–80 km), and decrease with height rather sharply above these levels. Rocket observations are used to estimate momentum deposition by gravity waves. Accelerations of about 100 m/s/day are suggested. Such accelerations are entirely capable of producing the warm winter and cold summer mesopauses.
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TL;DR: In this article, a review of gravity wave sources and characteristics, the evolution of the gravity wave spectrum with altitude and with variations of wind and stability, the character and implications of observed climatologies, and the wave interaction and instability processes that constrain wave amplitudes and spectral shape are discussed.
Abstract: [1] Atmospheric gravity waves have been a subject of intense research activity in recent years because of their myriad effects and their major contributions to atmospheric circulation, structure, and variability. Apart from occasionally strong lower-atmospheric effects, the major wave influences occur in the middle atmosphere, between ∼ 10 and 110 km altitudes because of decreasing density and increasing wave amplitudes with altitude. Theoretical, numerical, and observational studies have advanced our understanding of gravity waves on many fronts since the review by Fritts [1984a]; the present review will focus on these more recent contributions. Progress includes a better appreciation of gravity wave sources and characteristics, the evolution of the gravity wave spectrum with altitude and with variations of wind and stability, the character and implications of observed climatologies, and the wave interaction and instability processes that constrain wave amplitudes and spectral shape. Recent studies have also expanded dramatically our understanding of gravity wave influences on the large-scale circulation and the thermal and constituent structures of the middle atmosphere. These advances have led to a number of parameterizations of gravity wave effects which are enabling ever more realistic descriptions of gravity wave forcing in large-scale models. There remain, nevertheless, a number of areas in which further progress is needed in refining our understanding of and our ability to describe and predict gravity wave influences in the middle atmosphere. Our view of these unknowns and needs is also offered.
2,206 citations
Cites background or methods from "Turbulence and stress owing to grav..."
...[158] There are currently at least eight parameterization schemes proposed or in various stages of implementation in global models [Lindzen, 1981; Holton, 1982; Palmer et al., 1986; McFarlane, 1987; Fritts and Lu, 1993; Medvedev and Klaasen, 1995; Hines, 1997a, 1997b; Lott and Miller, 1997; Alexander and Dunkerton, 1999; Scinocca and McFarlane, 2000; Warner and McIntyre, 2001]....
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...We had recognized the role of gravity waves in transporting energy and momentum, in contributing turbulence and mixing, and in influencing the mean circulation and thermal structure of the middle atmosphere, based on limited theoretical, numerical, and observational studies [Lindzen, 1981; Holton, 1982, 1983; Vincent and Reid, 1983]....
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...[29] A momentum eddy diffusion coefficient associated with gravity wave dissipation may be approximated for a single wave [Lindzen, 1981; Holton, 1982] as DM ĉ X , Y N2 ....
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...We also had explored only the most rudimentary schemes for describing gravity wave effects in large-scale models [Lindzen, 1981; Holton, 1982; Matsuno, 1982; Dunkerton, 1982a] and had no appreciation for the rich range of Copyright 2003 by the American Geophysical Union....
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...We also had explored only the most rudimentary schemes for describing gravity wave effects in large-scale models [Lindzen, 1981; Holton, 1982; Matsuno, 1982; Dunkerton, 1982a] and had no appreciation for the rich range of...
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TL;DR: In this paper, a set of two general circulation models of the Martian atmosphere derived from the models originally developed in the early 1990s are described. But the models share the same physical parameterizations but use two complementary numerical methods to solve the atmospheric dynamic equations.
Abstract: We describe a set of two “new generation” general circulation models of the Martian atmosphere derived from the models we originally developed in the early 1990s. The two new models share the same physical parameterizations but use two complementary numerical methods to solve the atmospheric dynamic equations. The vertical resolution near the surface has been refined, and the vertical domain has been extended to above 80 km. These changes are accompanied by the inclusion of state-of-the-art parameterizations to better simulate the dynamical and physical processes near the surface (boundary layer scheme, subgrid-scale topography parameterization, etc.) and at high altitude (gravity wave drag). In addition, radiative transfer calculations and the representation of polar processes have been significantly improved. We present some examples of zonal-mean fields from simulations using the model at several seasons. One relatively novel aspect, previously introduced by Wilson [1997], is that around northern winter solstice the strong pole to pole diabatic forcing creates a quasi-global, angular-momentum conserving Hadley cell which has no terrestrial equivalent. Within such a cell the Coriolis forces accelerate the winter meridional flow toward the pole and induce a strong warming of the middle polar atmosphere down to 25 km. This winter polar warming had been observed but not properly modeled until recently. In fact, thermal inversions are generally predicted above one, and often both, poles around 60–70 km. However, the Mars middle atmosphere above 40 km is found to be very model-sensitive and thus difficult to simulate accurately in the absence of observations.
1,194 citations
TL;DR: The latest version of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3) is described in this article, where the changes in both physical and dynamical formulation from CCM2 to CCM3 are presented.
Abstract: The latest version of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3) is described. The changes in both physical and dynamical formulation from CCM2 to CCM3 are presented. The major differences in CCM3 compared to CCM2 include changes to the parameterization of cloud properties, clear sky longwave radiation, deep convection, boundary layer processes, and land surface processes. A brief description of each of these parameterization changes is provided. These modifications to model physics have led to dramatic improvements in the simulated climate of the CCM. In particular, the top of atmosphere cloud radiative forcing is now in good agreement with observations, the Northern Hemisphere winter dynamical simulation has significantly improved, biases in surface land temperatures and precipitation have been substantially reduced, and the implied ocean heat transport is in very good agreement with recent observational estimates. The improvement in implied ocean heat transport is among the more important attributes of the CCM3 since it is used as the atmospheric component of the NCAR Climate System Model. Future improvements to the CCM3 are also discussed.
1,106 citations
Cites background from "Turbulence and stress owing to grav..."
...The lower bound in (62) comes from the analytic solution of Lindzen (1981) and is applied to ensure that the stress divergence is of reasonable magnitude and correct sign, given the large shears that can be encountered in many of the profiles and the relatively coarse vertical resolution at which these equations are normally solved....
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...The lower bound in (62) comes from the analytic solution of Lindzen (1981) and is applied to ensure that the stress divergence is of reasonable magnitude and correct sign, given the large shears that can be encountered in many of the profiles and the relatively coarse vertical resolution at which…...
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28 Sep 1998TL;DR: In this paper, the authors propose numerical solutions to partial differential equations and finite-differencing the equations of atmospheric dynamics, including boundary-layer and surface processes, and Radiative energy transfer.
Abstract: Preface Acknowledgements 1. Introduction 2. Atmospheric structure, composition and thermodynamics 3. The continuity and thermodynamic energy equations 4. The momentum equation in Cartesian and spherical coordinates 5. Vertical-coordinate conversions 6. Numerical solutions to partial differential equations 7. Finite-differencing the equations of atmospheric dynamics 8. Boundary-layer and surface processes 9. Radiative energy transfer 10. Gas-phase species, chemical reactions and reaction rates 11. Urban, free-tropospheric and stratospheric chemistry 12. Methods of solving chemical ordinary differential equations 13. Particle components, size distributions and size structures 14. Aerosol emission and nucleation 15. Coagulation 16. Condensation, evaporation, deposition and sublimation 17. Chemical equilibrium and dissolution processes 18. Cloud thermodynamics and dynamics 19. Irreversible aqueous chemistry 20. Sedimentation, dry deposition and air-sea exchange 21. Model design, application and testing Appendix A. Conversions and constants Appendix B. Tables References Index.
863 citations
TL;DR: In this paper, the influence of breaking gravity waves on the dynamics and chemical composition of the 60- to 110-km region has been investigated with a two-dimensional dynamical/chemical model that includes a parameterization of gravity wave drag and diffusion.
Abstract: The influence of breaking gravity waves on the dynamics and chemical composition of the 60- to 110-km region has been investigated with a two-dimensional dynamical/chemical model that includes a parameterization of gravity wave drag and diffusion. The momentum deposited by breaking waves at mesospheric altitudes reverses the zonal winds, drives a strong mean meridional circulation, and produces a very cold summer and warm winter mesopause, in general agreement with observations. The seasonal variations of the computed eddy diffusion coefficient are consistent with the behavior of mesospheric turbulence inferred from MST radar echoes. In particular, it is found that eddy diffusion is strong in summer and winter but much weaker at the equinoxes and that this seasonal behavior has important consequences for the distribution of chemical species. Comparison between computed atomic oxygen and ozone, and the abundances of these constituents inferred from the 557.7-nm and 1.27-μm airglow emissions, reveals excellent agreement. The consistency between model results and these diverse types of observations lends strong support to the hypothesis that gravity waves play a very important role in determining the zonally averaged structure of the mesosphere and lower thermosphere.
805 citations
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TL;DR: In this paper, the proper interpretation of irregular motions in the upper atmosphere has been investigated by a variety of techniques, but their proper interpretation has yet to be established. But their proper meaning has not yet been established.
Abstract: Irregularities and irregular motions in the upper atmosphere have been detected and studied by a variety of techniques during recent years, but their proper interpretation has yet to be established...
1,886 citations
TL;DR: In this article, a new generalization of the Eliassen-Palm relations is proposed to study the zonal mean-flow tendency ∂ū/∂t due to waves in a stratified, rotating atmosphere with particular attention to equatorially trapped modes.
Abstract: Using a new generalization of the Eliassen-Palm relations, we discuss the zonal-mean-flow tendency ∂ū/∂t due to waves in a stratified, rotating atmosphere, with particular attention to equatorially trapped modes. Wave transience, forcing and dissipation are taken into account in a very general way. The theory makes it possible to discuss the latitudinal (y) and vertical (z) dependence of ∂ū/∂t qualitatively and calculate it directly from an approximate knowledge of the wave structure. For equatorial modes it reveals that the y profile of ∂ū/∂t is strongly dependent on the nature of the forcing or dissipation mechanism. A by-product of the theory is a far-reaching generalization of the theorems of Charney-Drazin, Dickinson and Holton on the forcing of ∂ū/∂t by conservative linear waves. Implications for the quasi-biennial oscillation in the equatorial stratosphere are discussed. Graphs of y profiles of ∂ū/∂t are given for the equatorial waves considered in the recent analysis of observational data...
986 citations
01 Jan 1974
TL;DR: In this article, the proper interpretation of irregular motions in the upper atmosphere has been investigated by a variety of techniques, but their proper interpretation has yet to be established. But their proper meaning has not yet been established.
Abstract: Irregularities and irregular motions in the upper atmosphere have been detected and studied by a variety of techniques during recent years, but their proper interpretation has yet to be established...
692 citations
01 Jan 1975
TL;DR: In this paper, the authors propose a method to solve the problem of how to find the shortest path between two points of interest in a set of images. Index Reference Record created on 2004-09-07, modified on 2016-08-08
Abstract: Note: Bibliogr. : p. 423-440. Index Reference Record created on 2004-09-07, modified on 2016-08-08
604 citations