Self‐Acceleration and Instability of Gravity Wave Packets: 3. Three‐Dimensional Packet Propagation, Secondary Gravity Waves, Momentum Transport, and Transient Mean Forcing in Tidal Winds

Fritts, David C.; Dong, Wenjun; Lund, Thomas S.; Wieland, Scott A.; Laughman, B.

doi:10.1029/2019jd030692

Cited by 28 publications

(56 citation statements)

References 48 publications

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“…CGCAM‐PMC modeling presented above shows that GW SA and breaking dynamics play the major roles in the formation of the large, primary voids and the smaller, secondary void(s) at their trailing edges, and that they are directly linked. Large‐scale accelerations of the central flow in the direction of GW propagation due to momentum deposition accompanying GW SA dynamics account for the asymmetric void shape, and the “dipole” response in the large‐scale circulation over a range of altitudes (see Figure 10 and Fritts, Dong et al., 2020). Importantly, this occurs below and above the altitudes at which GW SA and breaking occurs (compare Figures 7–9, 11, and 12 at 82 km).…”

Section: Discussionmentioning

confidence: 99%

Modeling Responses of Polar Mesospheric Clouds to Gravity Wave and Instability Dynamics and Induced Large‐Scale Motions

et al. 2021

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A gravity wave (GW) model that includes influences of temperature variations and large‐scale advection on polar mesospheric cloud (PMC) brightness having variable dependence on particle radius is developed. This Complex Geometry Compressible Atmosphere Model for PMCs (CGCAM‐PMC) is described and applied here for three‐dimensional (3‐D) GW packets undergoing self‐acceleration (SA) dynamics, breaking, momentum deposition, and secondary GW (SGW) generation below and at PMC altitudes. Results reveal that GW packets exhibiting strong SA and instability dynamics can induce significant PMC advection and large‐scale transport, and cause partial or total PMC sublimation. Responses modeled include PMC signatures of GW propagation and SA dynamics, “voids” having diameters of ∼500–1,200 km, and “fronts” with horizontal extents of ∼400–800 km. A number of these features closely resemble PMC imaging by the Cloud Imaging and Particle Size (CIPS) instrument aboard the Aeronomy of Ice in the Mesosphere (AIM) satellite. Specifically, initial CGCAM‐PMC results closely approximate various CIPS images of large voids surrounded by smaller void(s) for which dynamical explanations have not been offered to date. In these cases, the GW and instabilities dynamics of the initial GW packet are responsible for formation of the large void. The smaller void(s) at the trailing edge of a large void is (are) linked to the lower‐ or higher‐altitude SGW generation and primary mean‐flow forcing. We expect an important benefit of such modeling to be the ability to infer local forcing of the mesosphere and lower thermosphere (MLT) over significant depths when CGCAM‐PMC modeling is able to reasonably replicate PMC responses.

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Section: Discussionmentioning

confidence: 99%

Modeling Responses of Polar Mesospheric Clouds to Gravity Wave and Instability Dynamics and Induced Large‐Scale Motions

et al. 2021

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“…During winter the polar vortex is characterized by a strong longitudinal and latitudinal variation. The strength of the polar vortex appears to be rather different with longitude and month providing significant differences for the vertical propagation of gravity waves and their encounters with critical lines, fostering wave breaking and the emission of non-primary waves due to localised body forces (Vadas and Fritts, 2001;Becker and Vadas, 2018;Dong et al, 2020;Fritts et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Where they approach a critical level at which their phase speed, ch, along their direction of propagation equals the mean wind, Uh, in this plane, they undergo breaking and dissipation, resulting in local mean flow accelerations that act as sources of secondary GWs (SGWs). GW breaking dynamics lead to SGWs that occur on relatively small horizontal scales, 10-100 km; SGWs at larger scales, 100-300 km, arise due to the local, transient mean-flow accelerations accompanying GW momentum transport (Dong et al, 2020;Fritts et al, 2020). SGWs at larger scales also arise due to interactions among larger-scale GWs in global models unable to resolve GW breaking dynamics (Becker and Vadas, 2018;Vadas and Fritts, 2001;.…”

Section: Introductionmentioning

confidence: 99%

Seasonal evolution of winds, atmospheric tides and Reynolds stress components in the Southern hemisphere mesosphere/lower thermosphere in 2019

Stober¹,

Janches²,

Matthias³

et al. 2020

Preprint

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Abstract. In this study we explore the seasonal variability of the mean winds, diurnal, semidiurnal tidal amplitude and phases as well as the Reynolds stress components during 2019, utilizing meteor radars at six southern hemisphere locations ranging from from mid- to polar latitudes. These include Tierra del Fuego, King Edward Point on South Georgia island, King Sejong Station, Rothera, Davis and McMurdo stations. The year 2019 was exceptional in the southern hemisphere, due to the occurrence of a rare minor stratospheric warming in September. Our results show a substantial longitudinal and latitudinal seasonal variability of mean winds and tides pointing towards a wobbling and asymmetric polar vortex. Furthermore, the derived momentum fluxes and wind variances, utilizing a recently developed algorithm, reveal a characteristic seasonal pattern at each location included in this study. The longitudinal and latitudinal variability of vertical flux of zonal and meridional momentum is discussed in the context of polar vortex asymmetry, spatial and temporal variability, and the longitude and latitude dependence of the vertical propagation conditions of gravity waves. The horizontal momentum fluxes exhibit a rather consistent seasonal structure between the stations while the wind variances indicate a clear seasonal behaviour and altitude dependence showing the largest values at higher altitudes during the hemispheric winter and two variance minima during the equinoxes. Also the hemispheric summer mesopause and the zonal wind reversal can be identified in the wind variances.

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“…To the best of our knowledge to date, numerical simulation of the multistep vertical coupling mechanism requires the explicit description of GWs from the surface up to high altitudes in the thermosphere. While idealized models with regional geometry resolve small‐scale GWs and acoustic waves up to the thermosphere (e.g., Fritts et al., 2020; Heale et al., 2018, 2020), a high‐resolution GCM (which includes radiative transfer, moisture cycle, orography and boundary layer processes, as well as synoptic to planetary‐scale waves and realistic tidal variations) is needed to address the role of secondary and tertiary GWs in a global context. The primary purpose of this study is to present such a GCM and to provide some validation and first applications.…”

Section: Introductionmentioning

confidence: 99%

Explicit Global Simulation of Gravity Waves in the Thermosphere

2020

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We present a new version of the high-resolution Kühlungsborn Mechanistic general Circulation Model (KMCM) extended to z ∼ 450 km. This model is called HIAMCM (HI Altitude Mechanistic general Circulation Model) and explicitly simulates gravity waves (GWs) down to horizontal wavelengths of λ h ∼ 165 km. We find predominant tertiary GWs in the winter thermosphere at middle/high latitudes. These GWs typically have horizontal wavelengths λ h ∼ 300-1,100 km, ground-based periods ∼ 25-90 min, and intrinsic horizontal phase speeds c Ih ∼ 250-350 m s −1. Above z ∼ 200 km, the predominant GW horizontal propagation directions are roughly against the background winds from the diurnal tide; the GWs propagate mainly poleward at midnight, eastward at 6 local time (LT), equatorward at noon, and westward at 18 LT. Wintertime GWs at z ∼ 300 km having 165 km ≤ λ h ≤ 330 km create a large hot spot over the Southern Andes/Antarctic Peninsula that agrees well with quiet time satellite measurements. Due to cancelation effects, the time-averaged zonal mean Eliassen-Palm flux divergence from the resolved GWs in the thermosphere is negligible compared to that of the tides and compared to the zonal component of the time-averaged zonal mean ion drag. We also find that the thermospheric GWs dissipate mainly from macroturbulent diffusion and, above z ∼ 200 km, from molecular diffusion, whereas the tides dissipate mainly from ion drag. The averaged dissipative heating in the thermosphere due to tides is much stronger than that due to GWs.

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Self‐Acceleration and Instability of Gravity Wave Packets: 3. Three‐Dimensional Packet Propagation, Secondary Gravity Waves, Momentum Transport, and Transient Mean Forcing in Tidal Winds

Cited by 28 publications

References 48 publications

Modeling Responses of Polar Mesospheric Clouds to Gravity Wave and Instability Dynamics and Induced Large‐Scale Motions

Modeling Responses of Polar Mesospheric Clouds to Gravity Wave and Instability Dynamics and Induced Large‐Scale Motions

Seasonal evolution of winds, atmospheric tides and Reynolds stress components in the Southern hemisphere mesosphere/lower thermosphere in 2019

Explicit Global Simulation of Gravity Waves in the Thermosphere

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