Daytime and nighttime turbulence on Mars monitored by InSight

<p>The InSight instrumentation for atmospheric science combines high frequency, high accuracy and continuity. This makes InSight a mission particularly suitable for studies of the variability in the Planetary Boundary Layer (PBL) of Mars -- all the more since this topic is of direct interest for quake detectability given that turbulence is the main contributor to atmosphere-induced seismic signal. For the strong daytime buoyancy-driven PBL convection, InSight significantly extends the statistics of dust-devil-like convective vortices and turbulent wind gustiness, both of which are of strong interest for aeolian science. For the moderate nighttime shear-induced PBL convection, InSight enables to explore phenomena and variability left unexplored by previous in-situ measurements on Mars. In both daytime and nighttime environments, how the gravity waves and infrasound signals discovered by InSight are being guided within the PBL is also a central topic to InSight's atmospheric investigations, with the tantalizing possibility to identify possible sources for those phenomena. InSight has been operating at the surface of Mars since 18 months, thus the seasonal evolution of the many phenomena occurring in the PBL will be an emphasis of this report. Comparisons with turbulence-resolving modeling such as Large-Eddy Simulations will be also discussed.</p>

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Airborne measurements and large-eddy simulations of small-scale gravity waves at the tropopause inversion layer over Scandinavia

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-10091-2020 ◽

2020 ◽

Vol 20 (16) ◽

pp. 10091-10109 ◽

Cited By ~ 1

Author(s):

Sonja Gisinger ◽

Johannes Wagner ◽

Benjamin Witschas

Keyword(s):

Gravity Waves ◽

Vertical Velocity ◽

Inversion Layer ◽

Large Eddy Simulations ◽

Interfacial Waves ◽

Airborne Measurements ◽

Large Eddy ◽

Wave Event ◽

Wind Lidar

Abstract. Coordinated airborne measurements were performed by two research aircraft – Deutsches Zentrum für Luft- und Raumfahrt (DLR) Falcon and High Altitude and Long Range Aircraft (HALO) – in Scandinavia during the GW-LCYCLE II (Investigation of the life cycle of gravity waves) campaign in 2016 to investigate gravity wave processes in the upper troposphere and lower stratosphere (UTLS) region. A mountain wave event was probed over southern Scandinavia on 28 January 2016. The collected dataset constitutes a valuable combination of in situ measurements and horizontal- and altitude-resolved Doppler wind lidar and water vapour measurements with the differential absorption lidar (DIAL). In situ data at different flight altitudes and downward-pointing wind lidar measurements show pronounced changes of the horizontal scales in the vertical velocity field and of the leg-averaged momentum fluxes (MFs) in the UTLS region. The vertical velocity field was dominated by small horizontal scales with a decrease from around 20 to < 10 km in the vicinity of the tropopause inversion layer (TIL). These small scales were also found in the water vapour data and backscatter data of the DIAL. The leg-averaged MF profile determined from the wind lidar data is characterized by a pronounced kink of positive fluxes in the TIL and negative fluxes below. The largest contributions to the MF are from waves with scales > 30 km. The combination of the observations and idealized large-eddy simulations revealed the occurrence of interfacial waves having scales < 10 km on the tropopause inversion during the mountain wave event. The contribution of the interfacial waves to the leg-averaged MF is basically zero due to the phase relationship of their horizontal and vertical velocity perturbations. Interfacial waves have already been observed on boundary-layer inversions but their concept has not been applied to tropopause inversions so far. Our idealized simulations reveal that the TIL affects the vertical trend of leg-averaged MF of mountain waves and that interfacial waves can occur also on tropopause inversions. Our analyses of the horizontal- and altitude-resolved airborne observations confirm that interfacial waves actually do occur in the TIL. As predicted by linear theory, the horizontal scale of those waves is determined by the wind and stability conditions above the inversion. They are found downstream of the main mountain peaks and their MF profile varies around zero and can clearly be distinguished from the MF profile of Kelvin–Helmholtz instability. Further, the idealized large-eddy simulations reveal that the presence of the TIL is crucial in producing this kind of trapped wave at tropopause altitude.

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Large-Eddy Simulations of realistic atmospheric turbulence with the DLR-TAU-code initialized by in situ airborne measurements

Computers & Fluids ◽

10.1016/j.compfluid.2012.06.013 ◽

2012 ◽

Vol 66 ◽

pp. 121-129 ◽

Cited By ~ 6

Author(s):

Torsten Auerswald ◽

Jens Bange ◽

Tobias Knopp ◽

Keith Weinman ◽

Rolf Radespiel

Keyword(s):

Atmospheric Turbulence ◽

Large Eddy Simulations ◽

Airborne Measurements ◽

Large Eddy

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Disruption of the bottom log layer in large-eddy simulations of full-depth Langmuir circulation

Journal of Fluid Mechanics ◽

10.1017/jfm.2012.84 ◽

2012 ◽

Vol 699 ◽

pp. 79-93 ◽

Cited By ~ 18

Author(s):

A. E. Tejada-Martínez ◽

C. E. Grosch ◽

N. Sinha ◽

C. Akan ◽

G. Martinat

Keyword(s):

Gravity Waves ◽

Large Eddy Simulations ◽

Stokes Drift ◽

Navier Stokes ◽

Wake Region ◽

Langmuir Circulation ◽

Mean Velocity ◽

Wave Forcing ◽

Large Eddy ◽

Shear Current

AbstractWe report on disruption of the log layer in the resolved bottom boundary layer in large-eddy simulations (LES) of full-depth Langmuir circulation (LC) in a wind-driven shear current in neutrally-stratified shallow water. LC consists of parallel counter-rotating vortices that are aligned roughly in the direction of the wind and are generated by the interaction of the wind-driven shear with the Stokes drift velocity induced by surface gravity waves. The disruption is analysed in terms of mean velocity, budgets of turbulent kinetic energy (TKE) and budgets of TKE components. For example, in terms of mean velocity, the mixing due to LC induces a large wake region eroding the classical log-law profile within the range $90\lt { x}_{3}^{+ } \lt 200$. The dependence of this disruption on wind and wave forcing conditions is investigated. Results indicate that the amount of disruption is primarily determined by the wavelength of the surface waves generating LC. These results have important implications for turbulence parameterizations for Reynolds-averaged Navier–Stokes simulations of the coastal ocean.

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Vortex Encounter Rates with Fixed Barometer Stations: Comparison with Visual Dust Devil Counts and Large-Eddy Simulations

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-14-0138.1 ◽

2014 ◽

Vol 71 (12) ◽

pp. 4461-4472 ◽

Cited By ~ 30

Author(s):

Ralph D. Lorenz

Keyword(s):

Pressure Drop ◽

Field Studies ◽

Large Eddy Simulations ◽

Encounter Rate ◽

Dust Devil ◽

Dust Devils ◽

Translation Speed ◽

Pressure Drops ◽

Large Eddy ◽

Dust Lifting

Abstract A phenomenological model is developed wherein vortices are introduced at random into a virtual arena with specified distributions of diameter, core pressure drop, longevity, and translation speed, and the pressure history at a fixed station is generated using an analytic model of vortex structure. Only a subset of the vortices present are detected as temporary pressure drops, and the observed peak pressure-drop distribution has a shallower slope than the vortex-core pressure drops. Field studies indicate a detection rate of about two vortex events per day under favorable conditions for a threshold of 0.2 mb (1 mb = 1 hPa): this encounter rate and the observed falloff of events with increasing pressure drop can be reproduced in the model with approximately 300 vortices per square kilometer per day—rather more than the highest visual dust devil counts of approximately 100 devils per square kilometer per day. This difference can be reconciled if dust lifting typically only occurs in the field above a threshold core pressure drop of about 0.3 mb, consistent with observed laboratory pressure thresholds. The vortex population modeled to reproduce field results is concordant with recent high-resolution large-eddy simulations, which produce some thousands of 0.04–0.1-mb vortices per square kilometer per day, suggesting that these accurately reproduce the character of the strongly heated desert boundary layer. The amplitude and duration statistics of observed pressure drops suggest large dust devils may preferentially be associated with low winds.

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