scholarly journals Dynamics of Extreme Stratospheric Negative Heat Flux Events in an Idealized Model

2018 ◽  
Vol 75 (10) ◽  
pp. 3521-3540 ◽  
Author(s):  
Etienne Dunn-Sigouin ◽  
Tiffany Shaw
Keyword(s):  
Heat Flux ◽  
Wave Propagation ◽  
Recent Work ◽  
Wave Interaction ◽  
Higher Order ◽  
Negative Events ◽  
Flow Mechanism ◽  
Mean Flow ◽  
Idealized Model

Recent work has shown that extreme stratospheric wave-1 negative heat flux events couple with the troposphere via an anomalous wave-1 signal. Here, a dry dynamical core model is used to investigate the dynamical mechanisms underlying the events. Ensemble spectral nudging experiments are used to isolate the role of specific dynamical components: 1) the wave-1 precursor, 2) the stratospheric zonal-mean flow, and 3) the higher-order wavenumbers. The negative events are partially reproduced when nudging the wave-1 precursor and the zonal-mean flow whereas they are not reproduced when nudging either separately. Nudging the wave-1 precursor and the higher-order wavenumbers reproduces the events, including the evolution of the stratospheric zonal-mean flow. Mechanism denial experiments, whereby one component is fixed to the climatology and others are nudged to the event evolution, suggest higher-order wavenumbers play a role by modifying the zonal-mean flow and through stratospheric wave–wave interaction. Nudging all tropospheric wave precursors (wave-1 and higher-order wavenumbers) confirms they are the source of the stratospheric waves. Nudging all stratospheric waves reproduces the tropospheric wave-1 signal. Taken together, the experiments suggest the events are consistent with downward wave propagation from the stratosphere to the troposphere and highlight the key role of higher-order wavenumbers.

scholarly journals Dynamics of Anomalous Stratospheric Eddy Heat Flux Events in an Idealized Model

2020 ◽  
Vol 77 (6) ◽  
pp. 2187-2202 ◽  
Author(s):  
Etienne Dunn-Sigouin ◽  
Tiffany Shaw
Keyword(s):  
Heat Flux ◽  
Large Fraction ◽  
Wave Interaction ◽  
Higher Order ◽  
Stratospheric Warming ◽  
Mean Flow ◽  
Sudden Stratospheric Warming ◽  
Eddy Heat Flux ◽  
Stratospheric Dynamics

Abstract Extreme stratospheric eddy and sudden stratospheric warming (SSW) events both involve anomalous stratospheric eddy heat flux. The cause of the anomaly has been hypothesized to be due to tropospheric or stratospheric dynamics. Here, ensemble spectral nudging experiments in a dry dynamical-core model are used to quantify the role of the troposphere versus the stratosphere. The experiments focus on the wavenumber-1 heat flux since it dominates the anomalous stratospheric eddy heat flux during both events. Nudging the stratospheric zonal-mean flow does not account for the anomalous stratospheric wave-1 heat flux. Nudging either tropospheric wave-1 or higher-order wavenumbers (k ≥ 2) accounts for a large fraction of the anomalous stratospheric wave-1 heat flux. Mechanism denial experiments, whereby tropospheric eddies (wave 1 or k ≥ 2) are nudged and the zonal-mean flow is fixed to climatology, suggest the climatological stratospheric zonal-mean flow is sufficient to account for the anomalous stratospheric wave-1 heat flux and wave–wave interaction plays a role in generating the anomalous tropospheric wave-1 source. Taken together, the experiments suggest the troposphere dominates the anomalous stratospheric eddy heat flux during extreme stratospheric eddy and SSW events while the stratospheric zonal-mean flow plays secondary role.

Eddy Modulation of Air–Sea Interaction and Convection

2008 ◽  
Vol 38 (1) ◽  
pp. 65-83 ◽  
Author(s):  
Ivana Cerovečki ◽  
John Marshall
Keyword(s):  
Heat Flux ◽  
Heat Budget ◽  
Formation Rate ◽  
Mean Flow ◽  
Mode Water ◽  
Ocean Eddies ◽  
Eddy Heat Flux ◽  
Water Formation ◽  
Transformed Eulerian Mean

Abstract Eddy modulation of the air–sea interaction and convection that occurs in the process of mode water formation is analyzed in simulations of a baroclinically unstable wind- and buoyancy-driven jet. The watermass transformation analysis of Walin is used to estimate the formation rate of mode water and to characterize the role of eddies in that process. It is found that diabatic eddy heat flux divergences in the mixed layer are comparable in magnitude, but of opposite sign, to the surface air–sea heat flux and largely cancel the direct effect of buoyancy loss to the atmosphere. The calculations suggest that mode water formation estimates based on climatological air–sea heat flux data and outcrops, which do not fully resolve ocean eddies, may neglect a large opposing term in the heat budget and are thus likely to significantly overestimate true formation rates. In Walin’s watermass transformation framework, this manifests itself as a sensitivity of formation rate estimates to the averaging period over which the outcrops and air–sea fluxes are subjected. The key processes are described in terms of a transformed Eulerian-mean formalism in which eddy-induced mean flow tends to cancel the Eulerian-mean flow, resulting in weaker residual mean flow, subduction, and mode water formation rates.

scholarly journals On the Control of the Residual Circulation and Stratospheric Temperatures in the Arctic by Planetary Wave Coupling

2013 ◽  
Vol 71 (1) ◽  
pp. 195-206 ◽  
Author(s):  
Tiffany A. Shaw ◽  
Judith Perlwitz
Keyword(s):  
Heat Flux ◽  
The Arctic ◽  
Dynamical Regime ◽  
Negative Events ◽  
Residual Circulation ◽  
Dynamical Processes ◽  
Diabatic Processes ◽  
New Interpretation ◽  
The Impact

Abstract It is well established that interannual variability of eddy (meridional) heat flux near the tropopause controls the variability of Arctic lower-stratospheric temperatures during spring via a modification of the strength of the residual circulation. While most studies focus on the role of anomalous heat flux values, here the impact of total (climatology plus anomaly) negative heat flux events on the Arctic stratosphere is investigated. Utilizing the Interim ECMWF Re-Analysis (ERA-Interim) dataset, it is found that total negative heat flux events coincide with a transient reversal of the residual circulation and cooling of the Arctic lower stratosphere. The negative events weaken the seasonally averaged adiabatic warming. The analysis provides a new interpretation of the winters of 1997 and 2011, which are known to have the lowest March Arctic lower-stratospheric temperatures in the satellite era. While most winters involve positive and negative heat flux extremes, the winters of 1997 and 2011 are unique in that they only involved extreme negative events. This behavior contributed to the weakest adiabatic downwelling in the satellite era and suggests a dynamical contribution to the extremely low temperatures during those winters that could not be accounted for by diabatic processes alone. While it is well established that dynamical processes contribute to the occurrence of stratospheric sudden warming events via extreme positive heat flux events, the results show that dynamical processes also contribute to cold winters with subsequent impact on Arctic ozone loss. The results highlight the importance of interpreting stratospheric temperatures in the Arctic in the context of the dynamical regime with which they are associated.

Evidence of higher-order effects in thermally driven rapid granular flows

2008 ◽  
Vol 598 ◽  
pp. 429-450 ◽  
Author(s):  
C. M. HRENYA ◽  
J. E. GALVIN ◽  
R. D. WILDMAN
Keyword(s):  
Heat Flux ◽  
Dissipation Rate ◽  
Md Simulations ◽  
Higher Order ◽  
Navier Stokes ◽  
Order Effects ◽  
Mean Flow ◽  
Order Of Magnitude ◽  
Percentage Basis ◽  
Higher Order Effects

Molecular dynamic (MD) simulations are used to probe the ability of Navier–Stokes-order theories to predict each of the constitutive quantities – heat flux, stress tensor and dissipation rate – associated with granular materials. The system under investigation is bounded by two opposite walls of set granular temperature and is characterized by zero mean flow. The comparisons between MD and theory provide evidence of higher-order effects in each of the constitutive quantities. Furthermore, the size of these effects is roughly one order of magnitude greater, on a percentage basis, for heat flux than it is for stress or dissipation rate. For the case of heat flux, these effects are attributed to super-Burnett-order contributions (third order in gradients) or greater, since Burnett-order contributions to the heat flux do not exist. Finally, for the system considered, these higher-order contributions to the heat flux outweigh the first-order contribution arising from a gradient in concentration (i.e. the Dufour effect)

scholarly journals The Role of Boundary Layer Processes in Limiting PV Homogenization

2009 ◽  
Vol 66 (6) ◽  
pp. 1612-1632 ◽  
Author(s):  
Yang Zhang ◽  
Peter H. Stone ◽  
Amy Solomon
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Temperature Gradient ◽  
Surface Friction ◽  
Mean Flow ◽  
Eddy Heat Flux ◽  
Boundary Layer Processes ◽  
The Mean ◽  
Pv Gradient

Abstract A β-plane multilevel quasigeostrophic channel model with interactive static stability and a simplified parameterization of atmospheric boundary layer physics is used to study the role of different boundary layer processes in eddy equilibration and their relative effect in maintaining the strong boundary layer potential vorticity (PV) gradient. The model results show that vertical thermal diffusion, along with the surface heat exchange, is primarily responsible for limiting PV homogenization by baroclinic eddies in the boundary layer. Under fixed SST boundary conditions, these two processes act as the source of the mean flow baroclinicity in the lower levels and result in stronger eddy heat fluxes. Reducing surface friction alone does not result in efficient elimination of the boundary layer PV gradient, but the equilibrium state temperature gradient is still largely influenced by surface friction and its response to changes in surface friction is not monotonic. In the regime of strong surface friction, with reduced poleward eddy heat flux, a strong temperature gradient is still retained. When the surface friction is sufficiently weak along with the stronger zonal wind, the critical level at the center of the jet drops below the surface. As a result, in the lower levels, the eddy heat flux forcing on the mean flow moves away from the center of the jet and the equilibrium state varies only slightly with the strength of the vertical momentum diffusion in the boundary layer.

MANUSCRIPT EVIDENCE FOR ALPHABET-SWITCHING IN THE WORKS OF CICERO: COMMON NOUNS AND ADJECTIVES

2018 ◽  
Vol 68 (2) ◽  
pp. 498-516
Author(s):  
Neil O'Sullivan
Keyword(s):  
Recent Work ◽  
Code Switching ◽  
Consistent Pattern ◽  
Current Interest ◽  
Reliable Transmission ◽  
Accurate Record ◽  
The Way

Of the hundreds of Greek common nouns and adjectives preserved in our MSS of Cicero, about three dozen are found written in the Latin alphabet as well as in the Greek. So we find, alongside συμπάθεια, also sympathia, and ἱστορικός as well as historicus. This sort of variation has been termed alphabet-switching; it has received little attention in connection with Cicero, even though it is relevant to subjects of current interest such as his bilingualism and the role of code-switching and loanwords in his works. Rather than addressing these issues directly, this discussion sets out information about the way in which the words are written in our surviving MSS of Cicero and takes further some recent work on the presentation of Greek words in Latin texts. It argues that, for the most part, coherent patterns and explanations can be found in the alphabetic choices exhibited by them, or at least by the earliest of them when there is conflict in the paradosis, and that this coherence is evidence for a generally reliable transmission of Cicero's original choices. While a lack of coherence might indicate unreliable transmission, or even an indifference on Cicero's part, a consistent pattern can only really be explained as an accurate record of coherent alphabet choice made by Cicero when writing Greek words.

Musical shape and feeling

2017 ◽  
Author(s):  
Daniel Leech-Wilkinson
Keyword(s):  
Everyday Life ◽  
Recent Work ◽  
Sensory Perception ◽  
Dynamic Processes ◽  
Sensorimotor System ◽  
Musical Sound ◽  
Sensory Mode ◽  
Daniel Stern

The concept of shape is widely used by musicians in talking and thinking about performance, yet the mechanisms that afford links between music and shape are little understood. Work on the psychodynamics of everyday life by Daniel Stern and on embodiment by Mark Johnson suggests relationships between the multiple dynamics of musical sound and the dynamics of feeling and motion. Recent work on multisensory and precognitive sensory perception and on the role of bimodal neurons in the sensorimotor system helps to explain how shape, as a percept representing changing quantity in any sensory mode, may be invoked by dynamic processes at many stages of perception and cognition. These processes enable ‘shape’ to do flexible and useful work for musicians needing to describe the quality of musical phenomena that are fundamental to everyday musical practice and yet too complex to calculate during performance.

On the Role of Marangoni Effects on the Critical Heat Flux for Pool Boiling of Binary Mixtures

1996 ◽  
Vol 118 (1) ◽  
pp. 103-109 ◽  
Author(s):  
W. R. McGillis ◽  
V. P. Carey
Keyword(s):  
Surface Tension ◽  
Heat Flux ◽  
Binary Mixtures ◽  
Critical Heat Flux ◽  
Full Range ◽  
Pool Boiling ◽  
Marangoni Effect ◽  
Restoring Force ◽  
Marangoni Effects

The Marangoni effect on the critical heat flux (CHF) condition in pool boiling of binary mixtures has been identified and its effect has been quantitatively estimated with a modified model derived from hydrodynamics. The physical process of CHF in binary mixtures, and models used to describe it, are examined in the light of recent experimental evidence, accurate mixture properties, and phase equilibrium revealing a correlation to surface tension gradients and volatility. A correlation is developed from a heuristic model including the additional liquid restoring force caused by surface tension gradients. The CHF condition was determined experimentally for saturated methanol/water, 2-propanol/water, and ethylene glycol/water mixtures, over the full range of concentrations, and compared to the model. The evidence in this study demonstrates that in a mixture with large differences in surface tension, there is an additional hydrodynamic restoring force affecting the CHF condition.

How Artefacts Do Leadership: A Ventriloquial Analysis

2021 ◽  
pp. 089331892199807
Author(s):  
Jonathan Clifton ◽  
Fernando Fachin ◽  
François Cooren
Keyword(s):  
Organizational Communication ◽  
Recent Work ◽  
Distributed Leadership ◽  
Network Theory ◽  
Actor Network Theory ◽  
Fine Grained ◽  
Naturally Occurring ◽  
Human Actors

To date there has been little work that uses fine-grained interactional analyses of the in situ doing of leadership to make visible the role of non-human as well as human actants in this process. Using transcripts of naturally-occurring interaction as data, this study seeks to show how leadership is co-achieved by artefacts as an in-situ accomplishment. To do this we situate this study within recent work on distributed leadership and argue that it is not only distributed across human actors, but also across networks that include both human and non-human actors. Taking a discursive approach to leadership, we draw on Actor Network Theory and adopt a ventriloquial approach to sociomateriality as inspired by the Montreal School of organizational communication. Findings indicate that artefacts “do” leadership when a hybrid presence is made relevant to the interaction and when this presence provides authoritative grounds for influencing others to achieve the group’s goals.

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