Upper tropospheric energetics of standing eddies In wave number domain during contrasting Monsoon activity over India

The upper tropospheric energetics of the standing eddies in wave number domain during contrasting monsoon' activity over India have been investigated. Two normal monsoon years (1970. 1971) and two drought monsoon years (1972, 1979) are considered for a comparative study, Energy equations of Saltzman (1957) are used to compute wave-wave Interaction and wave to zonal mean flow Interaction. Analysis of the results show that the standing eddies in the region of tropical easterlies (5°S-24 .2°N) have larger kinetic energy than those in the region of southern hemispheric, westerlies (24.2°S-5°S). Wave to zonal mean flow interaction of all waves (waves 1-15) Indicate that the standing eddies are a source of kinetic energy to zonal mean flow ID the region of easterlies and there sink of kinetic energy to zonal mean flow in the region of westerlies. In the region of easterlies planetary standing waves (waves 1-2) are the major kinetic energy source to other standing waves and wave-wave Interaction of all waves leads to positive Imbalance of kinetic energy during normal monsoon years (1970, 1971) and negative imbalance, of kinetic, energy during drought monsoon years (1972, 19~9). In the region of westerlies the imbalance of kinetic energy IS negative during normal monsoon years and positive during drought monsoon years.

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Ageostrophic instability in rotating, stratified interior vertical shear flows

Journal of Fluid Mechanics ◽

10.1017/jfm.2014.426 ◽

2014 ◽

Vol 755 ◽

pp. 397-428 ◽

Cited By ~ 5

Author(s):

Peng Wang ◽

James C. McWilliams ◽

Claire Ménesguen

Keyword(s):

Energy Source ◽

Kinetic Energy ◽

Potential Energy ◽

Gravity Waves ◽

Shear Flows ◽

Vertical Shear ◽

Mean Flow ◽

Efficient Energy Transfer ◽

The Mean ◽

Inertia Gravity Waves

AbstractThe linear instability of several rotating, stably stratified, interior vertical shear flows $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\overline{U}(z)$ is calculated in Boussinesq equations. Two types of baroclinic, ageostrophic instability, AI1 and AI2, are found in odd-symmetric $\overline{U}(z)$ for intermediate Rossby number ($\mathit{Ro}$). AI1 has zero frequency; it appears in a continuous transformation of the unstable mode properties between classic baroclinic instability (BCI) and centrifugal instability (CI). It begins to occur at intermediate $\mathit{Ro}$ values and horizontal wavenumbers ($k,l$) that are far from $l= 0$ or $k = 0$, where the growth rate of BCI or CI is the strongest. AI1 grows by drawing kinetic energy from the mean flow, and the perturbation converts kinetic energy to potential energy. The instability AI2 has inertia critical layers (ICL); hence it is associated with inertia-gravity waves. For an unstable AI2 mode, the coupling is either between an interior balanced shear wave and an inertia-gravity wave (BG), or between two inertia-gravity waves (GG). The main energy source for an unstable BG mode is the mean kinetic energy, while the main energy source for an unstable GG mode is the mean available potential energy. AI1 and BG type AI2 occur in the neighbourhood of $A-S= 0$ (a sign change in the difference between absolute vertical vorticity and horizontal strain rate in isentropic coordinates; see McWilliams et al., Phys. Fluids, vol. 10, 1998, pp. 3178–3184), while GG type AI2 arises beyond this condition. Both AI1 and AI2 are unbalanced instabilities; they serve as an initiation of a possible local route for the loss of balance in 3D interior flows, leading to an efficient energy transfer to small scales.

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Dynamic Balances in a Wavy Boundary Layer

Journal of Physical Oceanography ◽

10.1175/jpo-d-13-0209.1 ◽

2014 ◽

Vol 44 (12) ◽

pp. 3185-3194 ◽

Cited By ~ 15

Author(s):

Tihomir Hristov ◽

Jesus Ruiz-Plancarte

Keyword(s):

Kinetic Energy ◽

Wind Wave ◽

Empirical Studies ◽

Wave Interaction ◽

Mean Flow ◽

Atmospheric Flow ◽

Wave Effects ◽

Sea Surface Waves ◽

Horizontal Inhomogeneity ◽

Wave Induced

Abstract The authors analyze the influence of waves on the budgets of momentum flux and kinetic energy in the atmospheric flow over sea surface waves and use the findings to reinterpret the results from the earlier empirical studies on the subject. This analysis employs the framework of wave–mean flow interaction and experimental data collected recently over the open ocean. From a minimal set of plausible assumptions, limited to small-slope waves and uncorrelated turbulent and wave-induced motions in the wind, this study demonstrates that the budgets apply separately to the turbulent and the wave-induced flows. The explicit forms of the wave-supported fluxes of momentum and kinetic energy favor wave spectra ∝ ω−β, 4 ≤ β ≤ 5 for wind–wave equilibrium. These explicit forms also show that in common conditions at heights above one significant wave height from the unperturbed surface, the wave-supported fluxes are a small fraction of the total, of the order of 5%. The wave influence on the kinetic energy budget and on the shape of the wind profile is therefore also small at these heights and thus difficult to identify experimentally next to influences from nonstationarity or horizontal inhomogeneity. Consequently, the predictions of Monin–Obukhov phenomenology show little sensitivity to wave effects. This makes the phenomenology as valid over the ocean as it is over land, but a poor instrument for studying wind–wave interaction. Describing the wind–wave interaction through the dynamics and statistics of the wave-induced motion remains a viable and productive alternative.

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Non-equilibrium scaling laws in axisymmetric turbulent wakes

Journal of Fluid Mechanics ◽

10.1017/jfm.2015.493 ◽

2015 ◽

Vol 781 ◽

pp. 166-195 ◽

Cited By ~ 53

Author(s):

T. Dairay ◽

M. Obligado ◽

J. C. Vassilicos

Keyword(s):

Kinetic Energy ◽

Turbulent Kinetic Energy ◽

Scaling Laws ◽

Reynolds Shear Stress ◽

Mean Flow ◽

Turbulent Dissipation ◽

Turbulent Wakes ◽

The Mean ◽

Energy Equations ◽

Non Equilibrium

We present a combined direct numerical simulation and hot-wire anemometry study of an axisymmetric turbulent wake. The data lead to a revised theory of axisymmetric turbulent wakes which relies on the mean streamwise momentum and turbulent kinetic energy equations, self-similarity of the mean flow, turbulent kinetic energy, Reynolds shear stress and turbulent dissipation profiles, non-equilibrium dissipation scalings and an assumption of constant anisotropy. This theory is supported by the present data up to a distance of 100 times the wake generator’s size, which is as far as these data extend.

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Modeling of Wall Pressure Fluctuations Based on Time Mean Flow Field

Journal of Fluids Engineering ◽

10.1115/1.1881698 ◽

2004 ◽

Vol 127 (2) ◽

pp. 233-240 ◽

Cited By ~ 31

Author(s):

Yu-Tai Lee ◽

William K. Blake ◽

Theodore M. Farabee

Keyword(s):

Kinetic Energy ◽

Turbulent Kinetic Energy ◽

Pressure Fluctuations ◽

Wall Pressure ◽

Wave Number ◽

Mean Flow ◽

Local Flow ◽

Outer Flow ◽

Wall Pressure Fluctuations ◽

Flow Activity

Time-mean flow fields and turbulent flow characteristics obtained from solving the Reynolds averaged Navier-Stokes equations with a k‐ε turbulence model are used to predict the frequency spectrum of wall pressure fluctuations. The vertical turbulent velocity is represented by the turbulent kinetic energy contained in the local flow. An anisotropic distribution of the turbulent kinetic energy is implemented based on an equilibrium turbulent shear flow, which assumes flow with a zero streamwise pressure gradient. The spectral correlation model for predicting the wall pressure fluctuation is obtained through a Green’s function formulation and modeling of the streamwise and spanwise wave number spectra. Predictions for equilibrium flow agree well with measurements and demonstrate that when outer-flow and inner-flow activity contribute significantly, an overlap region exists in which the pressure spectrum scales as the inverse of frequency. Predictions of the surface pressure spectrum for flow over a backward-facing step are used to validate the current approach for a nonequilibrium flow.

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Energetics of Eddy–Mean Flow Interactions in the Gulf Stream Region

Journal of Physical Oceanography ◽

10.1175/jpo-d-14-0200.1 ◽

2015 ◽

Vol 45 (4) ◽

pp. 1103-1120 ◽

Cited By ~ 37

Author(s):

Dujuan Kang ◽

Enrique N. Curchitser

Keyword(s):

Kinetic Energy ◽

Potential Energy ◽

Gulf Stream ◽

Mean Flow ◽

Available Potential Energy ◽

Flow Energy ◽

Flow Interaction ◽

The Mean ◽

Eddy Field ◽

Coast Region

AbstractA detailed energetics analysis of the Gulf Stream (GS) and associated eddies is performed using a high-resolution multidecadal regional ocean model simulation. The energy equations for the time-mean and time-varying flows are derived as a theoretical framework for the analysis. The eddy–mean flow energy components and their conversions show complex spatial distributions. In the along-coast region, the cross-stream and cross-bump variations are seen in the eddy–mean flow energy conversions, whereas in the off-coast region, a mixed positive–negative conversion pattern is observed. The local variations of the eddy–mean flow interaction are influenced by the varying bottom topography. When considering the domain-averaged energetics, the eddy–mean flow interaction shows significant along-stream variability. Upstream of Cape Hatteras, the energy is mainly transferred from the mean flow to the eddy field through barotropic and baroclinic instabilities. Upon separating from the coast, the GS becomes highly unstable and both energy conversions intensify. When the GS flows into the off-coast region, an inverse conversion from the eddy field to the mean flow dominates the power transfer. For the entire GS region, the mean current is intrinsically unstable and transfers 28.26 GW of kinetic energy and 26.80 GW of available potential energy to the eddy field. The mesoscale eddy kinetic energy is generated by mixed barotropic and baroclinic instabilities, contributing 28.26 and 9.15 GW, respectively. Beyond directly supplying the barotropic pathway, mean kinetic energy also provides 11.55 GW of power to mean available potential energy and subsequently facilitates the baroclinic instability pathway.

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Energetics of the lower tropospheric eddies in wave number domain during northern summer monsoon

MAUSAM ◽

10.54302/mausam.v51i2.1767 ◽

2021 ◽

Vol 51 (2) ◽

pp. 119-126

Author(s):

S. M. BAWISKAR ◽

M. D. CHIPADE ◽

S. S. SINGH

Keyword(s):

Kinetic Energy ◽

Summer Monsoon ◽

Standing Waves ◽

Wave Number ◽

Tropical Region ◽

Data Set ◽

Tropical Regions ◽

Northern Summer ◽

Energy Processes ◽

The Waves

Lower tropospheric energetics and energy processes of zonal waves for three consecutive northern summer monsoon seasons of 1994, 1995 and 1996 are presented. Fourier technique is used. The features of the tropical and extra-tropical regions are very well reflected by the data set used for this study. The results do not show marked year to year variations in the pattern of energy processes. The character of energy processes differs significantly from one latitudinal region to other. Wave to zonal mean flow interactions and wave to wave interactions are almost opposite in character over R1 (10° S -10° N) and R2 (10° N -30° N). L (n) interaction indicates that R1 acts as source of kinetic energy to the waves over R2. Particularly, standing waves I and 2 over RI are the major source of kinetic energy to the waves over R2. Extra-tropical region R3 (30° N -50° N) is dominated by transient waves while tropical regions R1 and R2 are dominated by standing waves. Medium and short waves have significant contributions over extra-tropical region whereas tropical regions are dominated by long waves. The pattern of energy processes over R3 is somewhat similar to the energy processes over R1. This is because both the regions have anti-cyclonic lateral shear.

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Wave-mean flow interaction, forced triads, and recharge-discharge Processes as noncanonical Hamiltonian Systems

10.5194/egusphere-egu2020-13284 ◽

2020 ◽

Author(s):

Richard Blender ◽

Joscha Fregin

Keyword(s):

Phase Space ◽

Three Dimensional ◽

Interaction Model ◽

Nonlinear Oscillators ◽

Atmospheric Dynamics ◽

Wave Number ◽

Mean Flow ◽

Forced Wave ◽

Flow Interaction ◽

Dimensional Phase Space

<p>We consider recharge-discharge processes in a forced wave-mean flow interaction model and in a forced Rossby wave triad. Such processes are common in atmospheric dynamics and are typically modelled by nonlinear oscillators, for example for mid-latitude storms by Ambaum and Novak (2013) and for convective cycles by Yano and Plant (2012). A similar behaviour can be seen in the simulation of a forced wave number triad by Lynch (2009). Here we construct noncanonical Hamiltonian and Nambu representations in three-dimensional phase space for available and prescribed conservation laws during the recharge and discharge regimes. Divergence in phase space is modelled by a pre-factor. The approach allows the design of conservative and forced dynamical systems.</p>

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Investigation of dominant traveling 10-day wave components using long-term MERRA-2 database

Earth Planets and Space ◽

10.1186/s40623-021-01410-7 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Chunming Huang ◽

Wei Li ◽

Shaodong Zhang ◽

Gang Chen ◽

Kaiming Huang ◽

...

Keyword(s):

Flow Instability ◽

Transmission Condition ◽

Wave Number ◽

Mean Flow ◽

Excited Wave ◽

Propagating Waves ◽

Zonal Wave Number ◽

The Mean

AbstractThe eastward- and westward-traveling 10-day waves with zonal wavenumbers up to 6 from surface to the middle mesosphere during the recent 12 years from 2007 to 2018 are deduced from MERRA-2 data. On the basis of climatology study, the westward-propagating wave with zonal wave number 1 (W1) and eastward-propagating waves with zonal wave numbers 1 (E1) and 2 (E2) are identified as the dominant traveling ones. They are all active at mid- and high-latitudes above the troposphere and display notable month-to-month variations. The W1 and E2 waves are strong in the NH from December to March and in the SH from June to October, respectively, while the E1 wave is active in the SH from August to October and also in the NH from December to February. Further case study on E1 and E2 waves shows that their latitude–altitude structures are dependent on the transmission condition of the background atmosphere. The presence of these two waves in the stratosphere and mesosphere might have originated from the downward-propagating wave excited in the mesosphere by the mean flow instability, the upward-propagating wave from the troposphere, and/or in situ excited wave in the stratosphere. The two eastward waves can exert strong zonal forcing on the mean flow in the stratosphere and mesosphere in specific periods. Compared with E2 wave, the dramatic forcing from the E1 waves is located in the poleward regions.

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