Large-scale Flow Patterns Research Articles

2D numerical experiments on a plume-fed asthenosphere: Necessary preconditions and implications for geoid and dynamic topography

We explore the conditions necessary for mantle flow to include a plume-fed asthenosphere (PFA) as a key structure within its large-scale flow pattern. Using 2D finite element-based experiments, we examine temperature-dependent rheological effects of ridge accretion, plate cooling, and numerically well-resolved ∼10–30 km-thick asthenosphere dragdown by subducting slabs. We find that an average plume flux ∼1.2 times big as the average slab flux is needed to maintain a persistent PFA. These numerical experiments also demonstrate that, instead of generating dynamic topography on the sea floor, flow-induced dynamic relief due to sub-asthenospheric density anomalies will preferentially form at the buoyancy contrast associated with the base of a buoyant asthenosphere. This mode of dynamic internal relief may contribute significantly to near-surface density anomalies that are associated with Earth's low-order geoid, and local relief at the base of the asthenosphere near plumes, ridges, and trenches that can be imaged in seismic experiments.

New constraints to subduction zone arc and backarc mantle temperatures: a test of the corner flow model

The heat source for the hot volcanic arc of subduction zones and the uniformly warm backarc is not well understood, particularly where backarc extension is absent. In the widely studied corner flow model, the traction of the underthrusting plate drags down the overlying viscous mantle, and the induced shallower seaward flow brings in heat from the landward and deeper asthenosphere. However, earlier comparisons with observations, especially backarc heat flow, gave poor agreement. There are several new constraints to the temperatures and structures above the underthrusting plate and in the backarc, especially those in western North America, for comparison with model predictions. Seismic receiver functions map horizontal boundaries, including the lithosphere-asthenosphere boundary (LAB). Seismic shear wave tomography gives mantle velocity-depth that provides an approximate proxy for temperature. Attenuation of seismic wave speed indicates high temperature or partial melting. The presence of recent backarc volcanics and their geochemistry give the depth and temperature of the LAB. From these constraints in western North America, the LAB reflects ponding of partial melt, is consistently at a depth of 65±3 km and temperature of 1350±25°C, and overlies nearly constant temperature (adiabatic) asthenosphere across the backarc from Mexico to Alaska. These depth and temperature estimates are greatly different from corner flow model predictions. An alternative hypothesis more consistent with these constraints is vigorous small-scale convection in the backarc asthenosphere. Whether or how this convection coexists with the large-scale flow patterns inferred from the interpretation of seismic anisotropy analyses, and to what degree it prevails in the arc-forearc region, deserve further research.

How Does the Interaction of the Human Thermal Plume and Breathing Affect the Microenvironment and Macroenvironment of an Elevator Cabin?

The details of the interaction of human thermal plume and breathing activities are simulated in the current study of an unsteady turbulent flow field in an elevator cabin. Air velocity and temperature distributions of the circulation flow pattern (i.e., the macroenvironment), the breathing-scale microenvironment’s characteristics, and the thermal plume’s fate are analyzed. The current study is aimed at showing how respiratory activities such as breathing and human thermal plumes affect the flow field and respiratory contaminants dispersion pattern in a nonventilated enclosed environment (the elevator cabin). The results from three cases, i.e., breathing thermal manikins, nonbreathing thermal manikins, and isothermal breathing manikins, are contrasted to unveil better the effects of human thermal plume and breathing on the flow field, including the velocity distribution, dispersion pattern of the exhaled contaminant, the human body’s heat transfer coefficient, and the large-scale flow pattern. Results reveal that breathing inhalation increases the upward velocity of the thermal plume on the one hand, which directly affects the microenvironment and indirectly impacts the macroenvironment due to the more vigorous reflected thermal plume. On the other hand, the upward thermal plume reduces the penetration length of the exhaled jet. Breathing activities create ring vortices that connect the microenvironment and the macroenvironment. The circulation flow features a downward flow in the cabin’s center, affecting the vortex strength and contaminant dispersion pattern. Overall, the human thermal plume and human breathing make comparable contributions to the resulting elevator-cabin flow characteristics.

Comparison between Developing and Nondeveloping Disturbances for Tropical Cyclogenesis in Different Large-Scale Flow Patterns over the Western North Pacific

Abstract This study classifies 407 developing disturbances (DEV) and 2309 nondeveloping disturbances (NONDEV) over the western North Pacific into five large-scale circulation patterns, namely the pre-existing cyclone (PC), easterly wave (EW), zonal wind convergence (CON), zonal wind shear line (SL), and mixed zonal wind convergence and shear line (CON-SL) patterns. The SL pattern has the highest TC yield percentage, followed by the CON-SL, while the EW is the least favorable pattern. The composite analysis shows that upper-level divergence, midlevel relative humidity, and surface heat flux (SHF) growth are crucial to the disturbance development in all the five patterns. Besides, large lower-level barotropic kinetic energy conversion and a well-developed primary circulation are good indicators for disturbance development in the PC, EW, and CON rather than in the SL and CON-SL patterns. Furthermore, for the PC, EW and CON patterns, the DEV features strong and rapidly growing SHF and mesoscale convective systems (MCS) closer to the disturbance center, which allows deep-layer warming and moistening, and drives a deep secondary circulation. Interestingly, due to an environment with high lower-level vorticity, the SL and CON-SL patterns typically foster a relatively mature primary circulation with strong SHF and MCS concentrated close to the center, especially for the NONDEV at the pre-genesis stage. However, a drier mid-to-upper-level environment for the NONDEV inhibits deep convection, which may explain its shallow secondary circulation and therefore poor potential to develop further.

High-Fidelity Simulations of Shield Assembly Mixed-Convection Flows with Applications Toward Reduced-Resolution Modeling

Flow circulation and heat removal through shield and reflector assemblies can have major impacts on safety in long transients for sodium fast reactors (SFRs). These transients are typically categorized by reduced flow rates and large-scale organized flow patterns, including potential intra-assembly circulation. Such low-flow cases can provide challenges for experiments because of complications in measuring the flow rates and temperatures with high accuracy in different areas. This consequently also raises the uncertainty of many modeling approaches for these phenomena. In an effort to address some of these issues, high-fidelity large eddy simulations are performed using the highly parallel solver NekRS. A 19-pin configuration of a tight-lattice wire-wrapped hexagonal bundle (pitch-to-diameter ratio = 1.07), representing a prototypical internal configuration of a shield assembly, was investigated. The sodium flow was set at a bundle Reynolds number of 2000, with simulations being performed for modified Richardson numbers of 0.0 (i.e., no buoyancy), 0.01, and 0.04, where mixed-convection effects are anticipated. The flow and temperature fields for these cases are discussed in detail. The high-fidelity data should prove useful as reference data for expanding and improving on various reduced-resolution approaches. A basic framework for combining subchannel and computational fluid dynamics methodologies in SFRs is also presented, with preliminary results from simulations of light water reactor bundles and a discussion of changes that need to be made for potential application to SFRs.

The performance of different unsteady Reynolds-averaged Navier-Stokes models mined by Fuzzy C-means algorithm with Fourier coefficient-based distance on the constructed vortex structures around a single building

ABSTRACT The Fuzzy C-means (FCM) method with Fourier coefficient-based distance was firstly used to construct the vortex features and analyze the large-scale unsteady flow pattern around the building by the transient ensemble velocity magnitude and Q criterion value. The performance of the unsteady Reynolds-averaged Navier-Stokes (URANS) turbulence models, including Standardmodel, Realizable, Renormalization Group (RNG) theoryand Shear-Stress Transport (SST) models on the flow structures around a high-rise building, was examined and compared by data analysis. The transient data was analyzed to identify the root of the different flow structures. The vortex structure was used to distinguish the different turbulence simulation performance directly. The result indicated that the RNGmodel shown the best simulation results on the mean velocity and total turbulent kinetic energy fields. The RNG model could simulate the modest scales of vortices which approximates the experiment data around the building, while the SSTmodel could simulate the abundant scales of vortices which led larger turbulence viscosity coefficient. In addition, the nature pressure difference ventilation partition method was proposed and verified in simulating the nature pressure difference around a single building.

Spatial-Temporal Patterns of Shallow Groundwater Levels in the Yellow River Delta, China

Analysis of the various hydrologic features responsible for the spatial and temporal variability in large scale subsurface systems is a critical component of water resources engineering and management. Traditionally, modeling large-scale groundwater flow patterns includes simulations with underlying parameter estimations and associated overarching assumptions. More recently, subsurface hydrologists are using empirical orthogonal function analysis to separate and quantify the primary hydrologic components contributing to observed regional and local-scale groundwater hydrodynamics. In this case study, modern spatiotemporal geostatistics plus primary hydrologic component analysis were conducted on spatially and temporally distributed groundwater levels measured in the Yellow River Delta. The results demonstrate the significant interplay between surface water hydrodynamics, overall groundwater quality, and groundwater utilization at the local scale, plus the significant impact of regional-scale aquifer recharge on groundwater level seasonal variation, largely driven by precipitation events. With increased accessibility to remote sensing data, additional research using these or similar statistical approaches to interpolate, compress, and decompose those features driving subsurface fluid-flow variability will prove to be highly beneficial to water resource engineers and managers.

Structure dominated two-dimensional turbulence: formation, dynamics and interactions of dipole vortices

Two dimensional turbulence in geophysical fluids and plasma physics tends to be spotty, intermittent and rich in large scale structures such as coherent vortices or zonal flows, due to various mechanisms of self organization. Nonlinear solutions that rely on the vanishing of nonlinearity, especially the dipole vortex solution, stand out as key aspects of this structure dominated turbulence state. Using numerical simulations, it is demonstrated that an initial condition with a small number of high intensity turbulent patches, evolves towards a state dominated by coherent structures, and in particular dipole vortices, as each patch is organized into a finite number of dipole vortices that are ejected from this initially active region. In order to study the details of this process, an initial condition of two Gaussian peaks of the stream function is considered, and it was shown to result in a Chaplygin–Lamb dipole if the peaks have the same amplitude, or a Flierl–Stern–Whitehead dipole that rotates in the direction implied by the excess of vorticity if they do not. Analytical estimates for the velocity, the radius and the radius of curvature of the resulting dipole vortex is given in terms of the peaks and widths of the initial conditions. These are then verified by a detailed comparison of the analytical form of the vorticity of the dipole vortex and its numerical realization. It is argued that since these coherent structures are spared from the strong shear forces normally exerted by the nonlinearities, and can coexist with other localized solutions, or large scale flow patterns, they provide the backbone of the structure dominated or ‘sporadic’ turbulent state in two dimensions, on top of which other structures, waves and instabilities can develop. In order to elucidate these, a number of collision scenarios are considered. It is also shown that a simple two point vortex approximation to a dipole vortex seems to be appropriate for describing their evolution far from each-other, or for computing head on collisions between two or more dipole vortices, but not in the case of close or grazing collisions or their interaction with a nontrivial large scale flow.

Cenozoic upper mantle flow history of the Atlantic realm based on Couette/Poiseuille models: Towards paleo-mantle-flowgraphy

Mantle convection is a fundamental process in the Earth’s system, yet its history remains poorly known. Sophisticated inverse geodynamic Earth models are available to retrodict past mantle states, but their high computational cost and complex parameterizations limit their ability to isolate key effects and interpret simulated paleo-mantle-flow patterns. This calls for an approach to conceptualize paleo-mantle-flow at a simple analytical level. The existence of weak asthenosphere allows one to formulate a Couette/Poiseuille model of upper mantle flow, where flow is linked to movements of overlying tectonic plates, and to lateral pressure gradients induced by rising plumes and sinking slabs. Here we present results from such models for the Atlantic realm in the Cenozoic, and link them to seismically inferred anisotropy along with mantle flow retrodictions from inverse geodynamic modeling. Our analytical paleo-mantle-flow indicates that (1) material sourced by plumes is carried towards slab locations, as expected, (2) it is broadly consistent with the orientation of seismic azimuthal anisotropy, and (3) it agrees with the large-scale flow patterns and amplitudes from mantle flow retrodictions. Our results suggest using a hierarchy of models together with growing geological constraints on past plate motions and dynamic topography to gain a better understanding of paleo-mantle-flow.

Impact of wall displacements on the large-scale flow coherence in ascending aorta

In the context of aortic hemodynamics, uncertainties affecting blood flow simulations hamper their translational potential as supportive technology in clinics. Computational fluid dynamics (CFD) simulations under rigid-walls assumption are largely adopted, even though the aorta contributes markedly to the systemic compliance and is characterized by a complex motion. To account for personalized wall displacements in aortic hemodynamics simulations, the moving-boundary method (MBM) has been recently proposed as a computationally convenient strategy, although its implementation requires dynamic imaging acquisitions not always available in clinics.In this study we aim to clarify the real need for introducing aortic wall displacements in CFD simulations to accurately capture the large-scale flow structures in the healthy human ascending aorta (AAo). To do that, the impact of wall displacements is analyzed using subject-specific models where two CFD simulations are performed imposing (1) rigid walls, and (2) personalized wall displacements adopting a MBM, integrating dynamic CT imaging and a mesh morphing technique based on radial basis functions. The impact of wall displacements on AAo hemodynamics is analyzed in terms of large-scale flow patterns of physiological significance, namely axial blood flow coherence (quantified applying the Complex Networks theory), secondary flows, helical flow and wall shear stress (WSS).From the comparison with rigid-wall simulations, it emerges that wall displacements have a minor impact on the AAo large-scale axial flow, but they can affect secondary flows and WSS directional changes. Overall, helical flow topology is moderately affected by aortic wall displacements, whereas helicity intensity remains almost unchanged. We conclude that CFD simulations with rigid-wall assumption can be a valid approach to study large-scale aortic flows of physiological significance.

Emergence of Spatial Scales and Macroscopic Tissue Dynamics in Active Epithelial Monolayers

Migrating cells in tissues are often known to exhibit collective swirling movements. In this paper, we develop an active vertex model with polarity dynamics based on contact inhibition of locomotion (CIL). We show that under this dynamics, the cells form steady-state vortices in velocity, polarity, and cell stress with length scales that depend on polarity alignment rate (ζ), self-motility (v0), and cell-cell bond tension (λ). When the ratio λ/v0 becomes larger, the tissue reaches a near jamming state because of the inability of the cells to exchange their neighbors, and the length scale associated with tissue kinematics increases. A deeper examination of this jammed state provides insights into the mechanism of sustained swirl formation under CIL rule that is governed by the feedback between cell polarities and deformations. To gain additional understanding of how active forcing governed by CIL dynamics leads to large-scale tissue dynamics, we systematically coarse-grain cell stress, polarity, and motility and show that the tissue remains polar even on larger length scales. Overall, we explore the origin of swirling patterns during collective cell migration and obtain a connection between cell-level dynamics and large-scale cellular flow patterns observed in epithelial monolayers.

Local estimation of quasi-geostrophic flows in Earth’s core

SUMMARYThe inference of fluid motion below the core–mantle boundary from geomagnetic observations presents a highly non-unique inverse problem. We propose a new method that provides a unique local estimate of the velocity field, assuming quasi-geostrophic flow in the core interior (which implies equatorial mirror symmetry) and negligible magnetic diffusion. These assumptions remove the theoretical underdetermination, enabling us to invert for the flow at each point of a spherical grid representing the core surface. The unreliable reconstruction of small-scale flows, which arises because only large-scale observations are available, is mitigated by smoothing the locally estimated velocity field using a Gaussian process regression. Application of this method to synthetic data provided by a state-of-the-art geodynamo simulation suggests that using this approach, the large-scale flow pattern of the core surface flow can be well reconstructed, while the flow amplitude tends to be underestimated. We compare these results with a core flow inversion using a Bayesian framework that incorporates statistics from numerical geodynamo models as prior information. We find that whether the latter method provides a more accurate recovery of the reference flow than the local estimation depends heavily on how realistic/relevant the chosen prior information is. Application to real geomagnetic data shows that both methods are able to reproduce the main features found in previous core flow studies.

Virtual laboratory experiments on the interaction of a vortex with small-scale topography

This study presents numerical analogs of laboratory experiments designed to explore the interaction of broad geophysical flows with irregular small-scale bathymetry. The previously reported “sandpaper” theory offered a succinct description of the cumulative effect of small-scale topographic features on large-scale flow patterns. However, initial investigations have been conducted using numerical models with simplified quasi-geostrophic equations that may inadequately represent the dynamics realized in the world’s oceans. This investigation advances previous efforts by using a fully nonlinear Navier–Stokes model configured for rotating tank experiments to (i) validate the theory and (ii) offer guidance for future physical experiments that will confirm theoretical ideas.

Regional Extreme Precipitation Events in Wintertime Japan Facilitated by East-Asian Large-Scale Flow Patterns

Regional Extreme Precipitation Events in Wintertime Japan Facilitated by East-Asian Large-Scale Flow Patterns

An Open Surface Drifter for River Flow Field Characterization.

The continuous observation of flows is required to assess a river's ecological status, to allocate irrigation withdrawals, to provide sustainable hydropower production and to plan actions as well as develop adaptive management plans. Drifters have the potential of facilitating the monitoring and modeling of river behavior at a fraction of traditional monitoring costs. They are floating objects equipped with sensors able to passively follow the movements of water. During their travel, they collect and transmit information about their movement and their surrounding environment. In this paper, we present and assess a low-cost (<150 EUR) customizable drifter developed with off-the-shelf components. The open drifter is capable of handling the majority of use cases defined in the specialized literature and in addition it offers a general river flow characterization toolkit. One of the main goals of this work is to establish an open hardware and software basis to increase the use of drifters in river studies. Results show that the proposed drifter provides reliable surface velocity estimates when compared to a commercial flow meter, offering a lower cost per data point and in contrast to traditional point measurements it can be used to identify and classify large-scale surface flow patterns. The diverse sensor payload of the open drifter presented in this work makes it a new and unique tool for autonomous river characterization.

North Pacific and North Atlantic Jet Covariability and Its Relationship to Cool Season Temperature and Precipitation Extremes

Abstract Cool season (September–May) extreme temperature and precipitation events are frequently tied to surface cyclones and anticyclones, which are modulated on the synoptic scale by the state and evolution of the upper-tropospheric jet stream. This study adopts a jet-centered approach to classify the prevailing large-scale flow pattern into jet regimes based on the leading modes of variability of the North Pacific jet (NPJ) and the North Atlantic jet (NAJ), respectively. The characteristics of these joint NPJ–NAJ regimes are subsequently examined using composite analysis to identify large-scale flow environments conducive to the occurrence of anomalous temperatures and precipitation across North America. The analysis reveals that composite large-scale flow environments associated with each joint NPJ–NAJ regime can be approximated as a linear combination of the separate large-scale environments that characterize each NPJ regime and NAJ regime independently. Furthermore, knowledge of the joint NPJ–NAJ regime provides more precision regarding the relative likelihood and spatial coverage of anomalous temperatures and precipitation than would be obtained from consideration of the NPJ or NAJ regime in isolation. The frequencies of each joint NPJ–NAJ regime can also be modulated by the occurrence of sudden stratospheric warmings, with increased frequencies of an equatorward-shifted NAJ and a retracted NPJ during the 30-day period following a warming event. The results from the present study demonstrate that knowledge of the joint NPJ–NAJ regime exhibits the potential to inform forecasts of anomalous temperatures and precipitation at medium-range and subseasonal time scales. Significance Statement The development of cool season temperature and precipitation extremes are modulated by the state and evolution of the upper-tropospheric jet stream. Therefore, this study adopts a jet-centered approach to quantify the extent to which temperature and precipitation extremes over North America are related to the coevolution of the North Pacific and North Atlantic segments of the jet stream. The analysis demonstrates that the relative likelihood and spatial coverage of temperature and precipitation extremes varies significantly across North America based on the combined state of the North Pacific and North Atlantic jets. The jet-centered approach utilized in this study exhibits the potential to inform operational medium-range (6–10 day) and subseasonal forecasts of temperature and precipitation across North America.

Decadal variation in the frequency of tropical cyclones originating in the South China Sea and migrating from the western North Pacific

A decadal variation in the frequency of tropical cyclones (TCs) that reached their lifetime maximum intensity (LMI) in the South China Sea (SCS; 5°N-25°N, 107°E-121°E) from 1978 to 2020 was identified. TCs that generated and reached LMI in the SCS were named “local TCs,” while those that generated in the western North Pacific (WNP) and reached LMI in the SCS were named “migratory TCs.” A seesaw phenomenon in the frequencies of these two types of TCs was found before and after 1997. From 1978 to 1996, TC frequency was generally lower in local TCs but higher in migratory TCs. The opposite was true from 1997 to 2020. The main factors responsible for this “seesaw” phenomenon include changes in the genesis positions of TCs and the interdecadal variation of large-scale environmental flow patterns. From 1997 to 2020, during which the large-scale steering flow was favorable for local TCs, the monsoon trough over the WNP withdrew westward along with the warm pool and the subtropical high strengthened westward. Meanwhile, the sea surface temperature (SST) gradient between the equator and mid-latitudes decreased and the north wind weakened near 120°E. Easterly winds were strengthened in the equatorial region, which led to an abnormal anticyclone and the divergence of water vapor in the WNP. In contrast, the SST of the SCS, an internal sea, increased significantly. Under local atmosphere-ocean interaction, abnormal cyclonic circulation appeared in the SCS, which led to intensified convergence and intensified wet convection. Changes in the environmental fields in the WNP and SCS are the main reasons for the seesaw phenomenon observed in these two types of TCs.

Off-centre gravity induces large-scale flow patterns in spherical Rayleigh–Bénard convection

We perform direct numerical simulations to study the effect of the gravity centre offset in spherical Rayleigh–Bénard convection. When the gravity centre is shifted towards the south, we find that the shift of the gravity centre has a pronounced influence on the flow structures. At low Rayleigh number $Ra$ , a steady-state large-scale meridional circulation induced by the baroclinic imbalance, created by the misalignment of the gravity potentials and isotherms, is formed. At high $Ra$ , an energetic jet is created on the northern side of the inner sphere that is directed towards the outer sphere. The large-scale circulation induces a strong co-latitudinal dependence in the local heat flux. Nevertheless, the global heat flux is not affected by the changes in the large-scale flow organization induced by the gravity centre offset.

CT-Based Simulation of Left Ventricular Hemodynamics: A Pilot Study in Mitral Regurgitation and Left Ventricle Aneurysm Patients.

BackgroundCardiac CT (CCT) is well suited for a detailed analysis of heart structures due to its high spatial resolution, but in contrast to MRI and echocardiography, CCT does not allow an assessment of intracardiac flow. Computational fluid dynamics (CFD) can complement this shortcoming. It enables the computation of hemodynamics at a high spatio-temporal resolution based on medical images. The aim of this proposed study is to establish a CCT-based CFD methodology for the analysis of left ventricle (LV) hemodynamics and to assess the usability of the computational framework for clinical practice.Materials and MethodsThe methodology is demonstrated by means of four cases selected from a cohort of 125 multiphase CCT examinations of heart failure patients. These cases represent subcohorts of patients with and without LV aneurysm and with severe and no mitral regurgitation (MR). All selected LVs are dilated and characterized by a reduced ejection fraction (EF). End-diastolic and end-systolic image data was used to reconstruct LV geometries with 2D valves as well as the ventricular movement. The intraventricular hemodynamics were computed with a prescribed-motion CFD approach and evaluated in terms of large-scale flow patterns, energetic behavior, and intraventricular washout.ResultsIn the MR patients, a disrupted E-wave jet, a fragmentary diastolic vortex formation and an increased specific energy dissipation in systole are observed. In all cases, regions with an impaired washout are visible. The results furthermore indicate that considering several cycles might provide a more detailed view of the washout process. The pre-processing times and computational expenses are in reach of clinical feasibility.ConclusionThe proposed CCT-based CFD method allows to compute patient-specific intraventricular hemodynamics and thus complements the informative value of CCT. The method can be applied to any CCT data of common quality and represents a fair balance between model accuracy and overall expenses. With further model enhancements, the computational framework has the potential to be embedded in clinical routine workflows, to support clinical decision making and treatment planning.

Multiscale Aspects of the 26–27 April 2011 Tornado Outbreak. Part II: Environmental Modifications and Upscale Feedbacks Arising from Latent Processes

Abstract One of the most prolific tornado outbreaks ever documented occurred on 26–27 April 2011 and comprised three successive episodes of tornadic convection that culminated with the development of numerous long-track, violent tornadoes over the southeastern United States during the afternoon of 27 April. This notorious afternoon supercell outbreak was preceded by two quasi-linear convective systems (hereinafter QLCS1 and QLCS2), the first of which was an anomalously severe nocturnal system that rapidly grew upscale during the previous evening. Here in Part II, we use a series of RUC 1-h forecasts and output from convection-permitting WRF-ARW simulations configured both with and without latent heat release to investigate how environmental modifications and upscale feedbacks produced by the two QLCSs contributed to the evolution and exceptional severity of this multiepisode outbreak. QLCS1 was primarily responsible for amplifying the large-scale flow pattern, inducing two upper-level jet streaks, and promoting secondary surface cyclogenesis downstream from the primary baroclinic system. Upper-level divergence markedly increased after QLCS1 developed, which yielded strong isallobaric forcing that rapidly strengthened the low-level jet (LLJ) and vertical wind shear over the warm sector and contributed to the system’s upscale growth and notable severity. Moreover, QLCS2 modified the mesoscale environment prior to the supercell outbreak by promoting the downstream formation of a pronounced upper-level jet streak, altering the midlevel jet structure, and furthering the development of a highly ageostrophic LLJ over the Southeast. Collectively, the flow modifications produced by both QLCSs contributed to the notably favorable shear profiles present during the afternoon supercell outbreak. Significance Statement The tornado outbreak that impacted the United States on 26–27 April 2011 was part of an extended outbreak that produced 343 tornadoes and numerous fatalities. This paper is Part II of a study that describes the meteorological factors supporting such a prolific event. Herein we investigate the convectively forced environmental modifications that occurred during a 36-h period encompassing three successive convective episodes. The first two episodes collectively altered the upper-level flow pattern and markedly enhanced low-level winds throughout the warm sector. These modifications served as upscale feedbacks that contributed to the first episode’s exceptional severity and to the remarkable vertical shear profiles that supported numerous long-track and violent tornadoes during the final episode on the afternoon of 27 April.