Observations of Misovortices within a Long-Lake-Axis-Parallel Lake-Effect Snowband during the OWLeS Project

Recent lake-effect snow field projects in the eastern Great Lakes region have revealed the presence of misovortices with diameters between 40 and 4000 m along cyclonic horizontal shear zones within long-lake-axis-parallel bands. One particular band in which an abundance of misovortices developed occurred on 7 January 2014. The leading hypothesis for lake-effect misovortexgenesis is the release of horizontal shearing instability (HSI). An analysis of three-dimensional dual-Doppler wind syntheses reveals that two criteria for HSI are satisfied along the horizontal shear zone, strongly suggesting that HSI was the likely cause of the misovortices in this case. Furthermore, the general lack of anticyclonic–cyclonic vortex couplets throughout the event reveal that tilting of horizontal vorticity into the vertical is of less importance compared to the release of HSI and subsequent strengthening via vortex stretching. A WRF simulation depicts misovortices along the horizontal shear zone within the simulated band. The simulated vortices display remarkable similarities to the observed vortices in terms of intensity, depth, spacing, and size. The simulated vortices persist over the eastern end of the lake; however, once the vortices move inland, they quickly dissipate. HSI criteria are also calculated from the WRF simulation and are satisfied along the shear zone. Competing hypotheses of misovortexgenesis are presented, with results indicating that the release of HSI is the likely mechanism of vortex formation.

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Circulations, Bounded Weak Echo Regions, and Horizontal Vortices Observed within Long-Lake-Axis-Parallel–Lake-Effect Storms by the Doppler on Wheels*

Monthly Weather Review ◽

10.1175/mwr-d-12-00226.1 ◽

2013 ◽

Vol 141 (8) ◽

pp. 2821-2840 ◽

Cited By ~ 27

Author(s):

Scott M. Steiger ◽

Robert Schrom ◽

Alfred Stamm ◽

Daniel Ruth ◽

Keith Jaszka ◽

...

Keyword(s):

Great Lakes ◽

Velocity Structure ◽

Lake Ontario ◽

Shear Instability ◽

Doppler Velocity ◽

Horizontal Shear ◽

Structure And Dynamics ◽

Lake Effect ◽

Axis Parallel ◽

Western Great Lakes

Abstract The eastern Great Lakes (Erie and Ontario) are often affected by intense lake-effect snowfalls. Lake-effect storms that form parallel to the major axes of these lakes can strongly impact communities by depositing more than 100 cm of snowfall in less than 24 h. Long-lake-axis-parallel (LLAP) storms are significantly different in structure and dynamics compared to the much more studied wind-parallel roll storms that typically form over the western Great Lakes. A Doppler on Wheels (DOW) mobile radar sampled several of these storms at fine spatial and temporal resolutions (and close to the surface) during the winter of 2010–11 over and downwind of Lake Ontario to document and improve understanding of how these storms develop. Over 1100 observations of vortices were catalogued within the 16 December 2010 and 4–5 January 2011 events. The majority of these vortices were less than 1 km in diameter with a statistical modal difference in Doppler velocity (delta-V) value across the vortex of 11 m s−1. Vortices developed along boundaries, which formed within the bands, suggesting horizontal shear instability was the main cause. Other features noted in the DOW observations included bounded weak echo regions, anvils, and horizontal vortices, typically on the south side of west–east-oriented LLAP bands. The reflectivity and velocity structure of LLAP bands were found to be much more complex than previously thought, which may impact localized precipitation amounts and errors in forecast location/intensity.

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Simple shear is not so simple! Kinematics and shear senses in Newtonian viscous simple shear zones

Geological Magazine ◽

10.1017/s0016756811001075 ◽

2012 ◽

Vol 149 (5) ◽

pp. 819-826 ◽

Cited By ~ 56

Author(s):

SOUMYAJIT MUKHERJEE

Keyword(s):

Pressure Gradient ◽

Shear Zone ◽

Simple Shear ◽

Shear Zones ◽

Horizontal Shear ◽

Flow Parameters ◽

Uniform Shear ◽

Shear Sense ◽

Simple Shear Deformation ◽

Gravity Component

AbstractThis work develops an analytical model of shear senses within an inclined ductile simple shear zone with parallel rigid boundaries and incompressible Newtonian viscous rheology. Taking account of gravity that tends to drive the material downdip and a possible pressure gradient that drives it upward along the shear zone, it is shown that (i) contradictory shear senses develop within two sub-zones even as a result of a single simple shear deformation; (ii) the highest velocity and least shear strain develop along the contact between the two sub-zones of reverse shear; (iii) for a uniform shear sense of the boundaries, a zone of reverse shear may develop within the top of the shear zone if the pressure gradient dominates the gravity component; otherwise it forms near the bottom boundary; (iv-a) a ‘pivot’ defined by the intersection between the velocity profile and the initial marker position distinguishes two sub-zones of opposite movement directions (not shear sense); (iv-b) a pivot inside any non-horizontal shear zone indicates a part of the zone that extrudes while the other subducts simultaneously; (v) the same shear sense develops: (v-a) when under a uniform shear of the boundaries, the shear zone remains horizontal and the pressure gradient vanishes; or alternatively (v-b) if the shear zone is inclined but the gravity component counterbalances the pressure gradient. Zones with shear sense reversal need to be reinterpreted since a pro-sheared sub-zone can retro-shear if the flow parameters change their magnitudes even though the same shear sense along the boundaries is maintained.

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THREE-DIMENSIONAL STRUCTURE OF DEFORMED MIGMATITES AND GRANITES IN THE NORUMBEGA SHEAR ZONE SYSTEM, SOUTHERN MAINE

10.1130/abs/2017ne-291058 ◽

2017 ◽

Author(s):

Steven M. Caldwell ◽

◽

Victor M. Morales ◽

Gary S. Solar ◽

Paul B. Tomascak

Keyword(s):

Shear Zone ◽

Three Dimensional ◽

Dimensional Structure ◽

Three Dimensional Structure

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Lake-to-Lake Cloud Bands: Frequencies and Locations

Monthly Weather Review ◽

10.1175/2007mwr1960.1 ◽

2007 ◽

Vol 135 (12) ◽

pp. 4202-4213 ◽

Cited By ~ 24

Author(s):

Yarice Rodriguez ◽

David A. R. Kristovich ◽

Mark R. Hjelmfelt

Keyword(s):

High Resolution ◽

Great Lakes ◽

Satellite Imagery ◽

Lake Superior ◽

Great Lakes Region ◽

Lake Effect ◽

Time Period ◽

High Resolution Satellite Imagery

Abstract Premodification of the atmosphere by upwind lakes is known to influence lake-effect snowstorm intensity and locations over downwind lakes. This study highlights perhaps the most visible manifestation of the link between convection over two or more of the Great Lakes lake-to-lake (L2L) cloud bands. Emphasis is placed on L2L cloud bands observed in high-resolution satellite imagery on 2 December 2003. These L2L cloud bands developed over Lake Superior and were modified as they passed over Lakes Michigan and Erie and intervening land areas. This event is put into a longer-term context through documentation of the frequency with which lake-effect and, particularly, L2L cloud bands occurred over a 5-yr time period over different areas of the Great Lakes region.

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Three-dimensional model and late stage warping of the Plattengneis Shear Zone in the Eastern Alps

Tectonophysics ◽

10.1016/j.tecto.2005.10.003 ◽

2006 ◽

Vol 412 (1-2) ◽

pp. 87-103 ◽

Cited By ~ 18

Author(s):

Martin Putz ◽

Kurt Stüwe ◽

Mark Jessell ◽

Philippe Calcagno

Keyword(s):

Shear Zone ◽

Late Stage ◽

Three Dimensional ◽

Eastern Alps ◽

Dimensional Model ◽

Three Dimensional Model

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The Dabie Extensional Tectonic System: Structural Framework

Journal of Geological Research ◽

10.1155/2012/369513 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Quanlin Hou ◽

Hongyuan Zhang ◽

Qing Liu ◽

Jun Li ◽

Yudong Wu

Keyword(s):

Shear Zone ◽

Shear Zones ◽

Ultrahigh Pressure ◽

Metamorphic Complex ◽

The South ◽

Magma Intrusion ◽

The North ◽

Extensional Tectonic ◽

Mechanism Transition ◽

Tectonic System

A previous study of the Dabie area has been supposed that a strong extensional event happened between the Yangtze and North China blocks. The entire extensional system is divided into the Northern Dabie metamorphic complex belt and the south extensional tectonic System according to geological and geochemical characteristics in our study. The Xiaotian-Mozitan shear zone in the north boundary of the north system is a thrust detachment, showing upper block sliding to the NNE, with a displacement of more than 56 km. However, in the south system, the shearing direction along the Shuihou-Wuhe and Taihu-Mamiao shear zones is tending towards SSE, whereas that along the Susong-Qingshuihe shear zone tending towards SW, with a displacement of about 12 km. Flinn index results of both the north and south extensional systems indicate that there is a shear mechanism transition from pure to simple, implying that the extensional event in the south tectonic system could be related to a magma intrusion in the Northern Dabie metamorphic complex belt. Two 40Ar-39Ar ages of mylonite rocks in the above mentioned shear zones yielded, separately, ~190 Ma and ~124 Ma, referring to a cooling age of ultrahigh-pressure rocks and an extensional era later.

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Effect of kinematics of orogenic wedge on kinematic evolutionary paths and deformation profiles of major shear zones: An example from the eastern Himalaya

10.5194/egusphere-egu21-3824 ◽

2021 ◽

Author(s):

Pritam Ghosh ◽

Kathakali Bhattacharyya

Keyword(s):

Shear Zone ◽

Strain Softening ◽

Leading Edge ◽

Shear Zones ◽

Deformation History ◽

Progressive Deformation ◽

Trailing Edge ◽

Orogenic Wedge ◽

Transport Direction ◽

Evolutionary Paths

We examine how the deformation profile and kinematic evolutionary paths of two major shear zones with prolonged deformation history and large translations differ with varying structural positions along its transport direction in an orogenic wedge. We conduct this analysis on multiple exposures of the internal thrusts from the Sikkim Himalayan fold thrust belt, the Pelling-Munsiari thrust (PT), the roof thrust of the Lesser Himalayan duplex (LHD), and the overlying Main Central thrust (MCT). These two thrusts are regionally folded due to growth of the LHD and are exposed at different structural positions. The hinterlandmost exposures of the MCT and PT zones lie in the trailing parts of the duplex, while the foreland-most exposures of the same studied shear zones lie in the leading part of the duplex, and thus have recorded a greater connectivity with the duplex. The thicknesses of the shear zones progressively decrease toward the leading edge indicating variation in deformation conditions. Thickness-displacement plot reveals strain-softening from all the five studied MCT and the PT mylonite zones. However, the strain-softening mechanisms varied along its transport direction with the hinterland exposures recording dominantly dislocation-creep, while dissolution-creep and reaction-softening are dominant in the forelandmost exposures. Based on overburden estimation, the loss of overburden on the MCT and the PT zones is more in the leading edge (~26km and ~15km, respectively) than in the trailing edge (~10km and ~17km, respectively), during progressive deformation. Based on recalibrated recrystallized quartz grain thermometer (Law, 2014), the estimated deformation temperatures in the trailing edge are higher (~450-650&#176;C) than in the leading edge (350-550&#176;C) of the shear zones. This variation in the deformation conditions is also reflected in the shallow-crustal deformation structures with higher fracture intensity and lower spacing in the leading edge exposures of the shear zones as compared to the trailing edge exposures.The proportion of mylonitic domains and micaceous minerals within the exposed shear zones increase and grain-size of the constituent minerals decreases progressively along the transport direction. This is also consistent with progressive increase in mean Rs-values toward leading edge exposures of the same shear zones. Additionally, the &#945;-value (stretch ratio) gradually increases toward the foreland-most exposures along with increasing angular shear strain. Vorticity estimates from multiple incremental strain markers indicate that the MCT and PT zones generally record a decelerating strain path. Therefore, the results from this study are counterintuitive to the general observation of a direct relationship between higher Rs-value and higher pure-shear component. We explain this observation in the context of the larger kinematics of the orogen, where the leading edge exposures have passed through the duplex structure, recording the greatest connectivity and most complete deformation history, resulting in the weakest shear zone that is also reflected in the deformation profiles and strain attributes. This study demonstrates that the same shear zone records varying deformation profile, strain and kinematic evolutionary paths due to varying deformation conditions and varying connectivity to the underlying footwall structures during progressive deformation of an orogenic wedge.

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A 3D Unsteady Flow Analysis in a Doubly Constricted Tube

10.1115/imece2000-2106 ◽

2000 ◽

Author(s):

B. V. Rathish Kumar ◽

T. Yamaguchi ◽

H. Liu ◽

R. Himeno

Keyword(s):

Pressure Drop ◽

Unsteady Flow ◽

Stokes Equations ◽

Vortex Formation ◽

Flow Analysis ◽

Three Dimensional ◽

Navier Stokes ◽

Navier Stokes Equations ◽

In Series ◽

3D Unsteady Flow

Abstract Unsteady flow dynamics in a doubly constricted vessel is analyzed by using a time accurate Finite Volume solution of three dimensional incompressible Navier-Stokes equations. Computational experiments are carried out for various values of Reynolds number in order to assess the criticality of multiple mild constrictions in series and also to bring out the subtle 3D features like vortex formation. Studies reveal that pressure drop across a series of mild constrictions can get physiologically critical. Further this pressure drop is found to be sensitive to the spacing between the constrictions and also to the oscillatory nature of the inflow profile.

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Vortex formation on surging aerofoils with application to reverse flow modelling

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.800 ◽

2018 ◽

Vol 859 ◽

pp. 59-88 ◽

Cited By ~ 8

Author(s):

Philip B. Kirk ◽

Anya R. Jones

Keyword(s):

Surface Pressure ◽

Reverse Flow ◽

Vortex Formation ◽

Three Dimensional ◽

Tangential Velocity ◽

Leading Edge ◽

Field Measurements ◽

Reduced Frequency ◽

Advance Ratio ◽

Convection Speed

The leading-edge vortex (LEV) is a powerful unsteady flow structure that can result in significant unsteady loads on lifting blades and wings. Using force, surface pressure and flow field measurements, this work represents an experimental campaign to characterize LEV behaviour in sinusoidally surging flows with widely varying amplitudes and frequencies. Additional tests were conducted in reverse flow surge, with kinematics similar to the tangential velocity profile seen by a blade element in recent high-advance-ratio rotor experiments. General results demonstrate the variability of LEV convection properties with reduced frequency, which greatly affected the average lift-to-drag ratio in a cycle. Analysis of surface pressure measurements suggests that LEV convection speed is a function only of the local instantaneous flow velocity. In the rotor-comparison tests, LEVs formed in reverse flow surge were found to convect more quickly than the corresponding reverse flow LEVs that form on a high-advance-ratio rotor, demonstrating that rotary motion has a stabilizing effect on LEVs. The reverse flow surging LEVs were also found to be of comparable strength to those observed on the high-advance-ratio rotor, leading to the conclusion that a surging-wing simplification might provide a suitable basis for low-order models of much more complex three-dimensional flows.

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