Gravity Wave Dynamics in a Mesospheric Inversion Layer: 1. Reflection, Trapping, and Instability Dynamics

Fritts, David C.; Laughman, B.; Wang, Ling; Lund, Thomas S.; Collins, R. L.

doi:10.1002/2017jd027440

Cited by 35 publications

(41 citation statements)

References 141 publications

(208 reference statements)

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“…The potential for GWs arising from these various sources to propagate into the MLT and above depends on their amplitudes, scales, and phase speeds, and the intervening wind and temperature fields. GWs having small phase speeds and vertical wavelengths may encounter adverse wind shears and critical levels leading to breaking and dissipation at lower altitudes (Fritts et al, ). GWs attaining large amplitudes can undergo breaking at lower and higher altitudes, whether or not a critical level is present (Doyle et al, ; Horinouchi et al, ; Lilly, ; Lilly & Kennedy, ).…”

Section: Introductionmentioning

confidence: 99%

Self‐Acceleration and Instability of Gravity Wave Packets: 2. Two‐Dimensional Packet Propagation, Instability Dynamics, and Transient Flow Responses

et al. 2020

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Results of two-dimensional and narrow three-dimensional (2-D and 2.5-D) simulations of a gravity wave (GW) packet localized in altitude and along its propagation direction employing a new, versatile compressible model are described. The simulations explore self-acceleration and instability dynamics in an idealized atmosphere at rest under mean solar conditions in a domain extending to an altitude of 260 km and 1,800 km horizontally without artificial dissipation. High resolution in the central 2.5-D domain enables the description of 3-D instability dynamics accounting for breaking, dissipation, and momentum deposition within the GW packet. 2-D results describe responses to localized self-acceleration effects, including generation of secondary GWs (SGWs) at larger scales able to propagate to much higher altitudes. 2.5-D results exhibit instability forms consistent with previous 3-D simulations of instability dynamics and cause SGW generation and propagation at smaller spatial scales to weaken significantly compared to the 2-D results. SGW responses at larger scales are driven primarily by GW/mean flow interactions arising at early stages of the self-acceleration dynamics prior to strong GW instabilities and dissipation. As a result, they exhibit similar responses in both the 2-D and 2.5-D simulations and readily propagate to high altitudes at large distances from the initial GW packet. A companion paper examines these dynamics for an initial GW packet localized in three dimensions and evolving in a representative 3-D tidal wind field.

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Section: Introductionmentioning

confidence: 99%

Self‐Acceleration and Instability of Gravity Wave Packets: 2. Two‐Dimensional Packet Propagation, Instability Dynamics, and Transient Flow Responses

et al. 2020

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“…Additionally, GWs having significant amplitudes and momentum fluxes can exhibit strong interactions with the local mean flow. These manifest as “self‐acceleration” events that have been modeled under idealized and more realistic conditions (Dosser & Sutherland, ; Fritts et al, ; Fritts, Laughman, et al, ; Fritts, Wang, et al, ; Sutherland, , ) and that have recently been identified in the MLT OH airglow layer and by the Polar Mesospheric Cloud Turbulence (PMC Turbo) experiment, to be reported separately.…”

Section: Introductionmentioning

confidence: 99%

PMC Turbo: Studying Gravity Wave and Instability Dynamics in the Summer Mesosphere Using Polar Mesospheric Cloud Imaging and Profiling From a Stratospheric Balloon

et al. 2019

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The Polar Mesospheric Cloud Turbulence (PMC Turbo) experiment was designed to observe and quantify the dynamics of small‐scale gravity waves (GWs) and instabilities leading to turbulence in the upper mesosphere during polar summer using instruments aboard a stratospheric balloon. The PMC Turbo scientific payload comprised seven high‐resolution cameras and a Rayleigh lidar. Overlapping wide and narrow camera field of views from the balloon altitude of ~38 km enabled resolution of features extending from ~20 m to ~100 km at the PMC layer altitude of ~82 km. The Rayleigh lidar provided profiles of temperature below the PMC altitudes and of the PMCs throughout the flight. PMCs were imaged during an ~5.9‐day flight from Esrange, Sweden, to Northern Canada in July 2018. These data reveal sensitivity of the PMCs and the dynamics driving their structure and variability to tropospheric weather and larger‐scale GWs and tides at the PMC altitudes. Initial results reveal strong modulation of PMC presence and brightness by larger‐scale waves, significant variability in the occurrence of GWs and instability dynamics on time scales of hours, and a diversity of small‐scale dynamics leading to instabilities and turbulence at smaller scales. At multiple times, the overall field of view was dominated by extensive and nearly continuous GWs and instabilities at horizontal scales from ~2 to 100 km, suggesting sustained turbulence generation and persistence. At other times, GWs were less pronounced and instabilities were localized and/or weaker, but not absent. An overview of the PMC Turbo experiment motivations, scientific goals, and initial results is presented here.

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“…Assuming a representative ϵ ≈0.5 m 2 s −3 as in recent GW breaking simulations (see, e.g., Fritts, Laughman, et al, ; Fritts, Wang, et al, ; Fritts et al, , ), the expected inner scale of turbulence for density fluctuations at 80 km can be approximated as

l_{0} = 7.4 η = 7.4 {((), ν^{3} false/ ϵ)}^{\frac{1}{4}} \approx 20 normalm

…”

Section: Finite Volume Model and Simulation Parametersmentioning

confidence: 93%

“…The Reynolds number ( Re ) is calculated from the GW length scale as

R e = \frac{λ_{z}^{2}}{T_{B} ν},

where ν = μ / ρ is the kinematic viscosity. We apply a turbulent kinematic viscosity of ν =3 ν 0 based on estimates of an elevated effective viscosity due to preexisting turbulence (Baumgarten & Fritts, ; Fritts, Baumgarten, et al, ; Fritts, Wan, et al, ; Hecht et al, , ) in the manner of Fritts, Laughman, et al (), where ν 0 is the true kinematic viscosity ∼1.5×10 −5 m 2 s −1 at ground level and ν ∼2.8 m 2 s −1 is the kinematic viscosity specified in the model at 80 km. For GW with λ z =10 km, this results in Re ≈10 5 where FSs arise accompanying flow instabilities.…”

Section: Finite Volume Model and Simulation Parametersmentioning

confidence: 99%

“…Though lidar and polar mesospheric cloud observations primarily identify sheet and layer structures defined by stratification, the high‐resolution studies carried out by Fritts et al (), Fritts and Wang (), Fritts et al (), and Fritts et al () considered only GW propagation through shear FS in a constant stratification environment. In a recent two‐part study, Fritts, Laughman, et al () and Fritts, Wang, et al () simulated GW propagation into a mesospheric inversion layer (MIL), imposing a 100% amplitude stability ( N 2 ) enhancement and deficit below and above 80 km, yielding a 10‐km MIL with an adiabatic layer on top. They identified important baroclinic influences on the vorticity evolution accompanying the initial instabilities, and they provided an extensive analysis of the turbulent energy dissipation and associated dynamics and fluxes.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Simulations of High‐Frequency Gravity Wave Propagation Through Fine Structures in the Mesosphere

et al. 2019

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An anelastic numerical model is used to study the influences of fine structure (FS) in the wind and stability profiles on gravity wave (GW) propagation in the Mesosphere and Lower Thermosphere (MLT). Large amplitude GWs interacting with FS, that is, thin regions of enhanced wind and stability, evolve very differently depending on the precise vorticity source and sink terms for small‐scale motions induced by the FS gradients. The resulting small‐scale dynamics are deterministic, promoting local instabilities, dissipation, and momentum deposition at locations and orientations determined by the initial FS. The resulting momentum depositions yield significant changes to the background wind structure, having scales and amplitudes comparable to the effects of large‐scale features in the ambient atmosphere. The deterministic nature of the large‐scale impacts further suggests that they can be estimated without fully resolving the underlying instability dynamics. Given the significant amplitudes and ubiquitous occurrence of FS throughout the atmosphere, the influences of these important and diverse flow evolutions merit inclusion in broader modeling efforts.

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Gravity Wave Dynamics in a Mesospheric Inversion Layer: 1. Reflection, Trapping, and Instability Dynamics

Cited by 35 publications

References 141 publications

Self‐Acceleration and Instability of Gravity Wave Packets: 2. Two‐Dimensional Packet Propagation, Instability Dynamics, and Transient Flow Responses

Self‐Acceleration and Instability of Gravity Wave Packets: 2. Two‐Dimensional Packet Propagation, Instability Dynamics, and Transient Flow Responses

PMC Turbo: Studying Gravity Wave and Instability Dynamics in the Summer Mesosphere Using Polar Mesospheric Cloud Imaging and Profiling From a Stratospheric Balloon

Numerical Simulations of High‐Frequency Gravity Wave Propagation Through Fine Structures in the Mesosphere

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