Quantifying synoptic eddy feedback onto the low-frequency flow associated with anomalous temperature events in January over China

2014 ◽  
Vol 35 (8) ◽  
pp. 1976-1983 ◽  
Author(s):  
Gui-Rong Tan ◽  
Hong-Li Ren ◽  
Haishan Chen
Keyword(s):  
Low Frequency ◽  
Anomalous Temperature ◽  
Synoptic Eddy

Anomalous Temperature Regimes during the Cool Season: Long-Term Trends, Low-Frequency Mode Modulation, and Representation in CMIP5 Simulations

2013 ◽  
Vol 26 (22) ◽  
pp. 9061-9076 ◽  
Author(s):  
Rebecca M. Westby ◽  
Yun-Young Lee ◽  
Robert X. Black
Keyword(s):  
United States ◽  
Linear Regression Analysis ◽  
Low Frequency ◽  
The United States ◽  
Cmip5 Models ◽  
Southern United States ◽  
Anomalous Temperature ◽  
Temperature Regimes ◽  
Collective Influence

Abstract During boreal winter, anomalous temperature regimes (ATRs), including cold air outbreaks (CAOs) and warm waves (WWs), provide important societal influences upon the United States. The current study analyzes reanalysis and model data for the period from 1949 to 2011 to assess (i) long-term variability in ATRs, (ii) interannual modulation of ATRs by low-frequency modes, and (iii) the representation of ATR behavior in models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). No significant trends in either WWs or CAOs are identified for the continental United States. On interannual time scales, CAOs are modulated by the (i) North Atlantic Oscillation (NAO) over the U.S. Southeast and (ii) the Pacific–North American (PNA) pattern over the Northwest. WW frequency is modulated by (i) the NAO over the eastern United States and (ii) the combined influence of the PNA, Pacific decadal oscillation (PDO), and ENSO over the southern United States. In contrast to previous studies of seasonal-mean temperature, the influence of ENSO upon ATRs is found to be mainly limited to a modest modulation of WWs over the southern United States. Multiple linear regression analysis reveals that the regional collective influence of low-frequency modes accounts for as much as 50% of interannual ATR variability. Although similar behavior is observed in CMIP5 models, WW (CAO) frequency is typically overestimated (underestimated). All models considered are unable to replicate observed associations between ATRs and the PDO. Further, the collective influence of low-frequency modes upon ATRs is generally underestimated in CMIP5 models. The results indicate that predictions of future ATR behavior are limited by climate model ability to represent the evolving behavior of low-frequency modes of variability.

scholarly journals A Barotropic Envelope Rossby Soliton Model for Block–Eddy Interaction. Part III: Wavenumber Conservation Theorems for Isolated Blocks and Deformed Eddies

2005 ◽  
Vol 62 (11) ◽  
pp. 3839-3859 ◽  
Author(s):  
Dehai Luo
Keyword(s):  
Low Frequency ◽  
Phase Speed ◽  
Vortex Pair ◽  
Synoptic Scale ◽  
Low Frequency Oscillation ◽  
Soliton Theory ◽  
Eddy Activity ◽  
Synoptic Eddy ◽  
Synoptic Eddies ◽  
Interactive Relationship

Abstract In a series of previous papers, an envelope Rossby soliton theory was formulated to investigate the interaction between a preexisting planetary wave and synoptic-scale eddies leading to a typical blocking flow. In this paper, numerical and analytical studies are presented in order to examine the interactive relationship between an isolated vortex pair block and deformed synoptic-scale eddies during their interaction. The deformed blocked flow and eddies are found to satisfy the wavenumber conservation theorem. It is shown that the feedback by a blocked flow on the preexisting synoptic eddies gives rise to two types of eddies: one is the Z-type eddies with a meridional monopole structure that appears at the middle of the channel and the other is the M-type eddies with a meridional tripole structure that have long wavelength and large amplitude. Both the total wavenumber of the blocked flow and M-type eddies and the total wavenumber of the Z- and M-type eddies are conserved. The M- and Z-type eddies are compressed and elongated, respectively, as the blocked flow is elongated zonally during its onset phase, but the reverse is observed during the decay phase. The zonally elongated Z-type eddies are found to counteract the compressed M-type eddies in the blocking region, but strengthen the M-type eddies upstream, causing the split of eddies around the blocking region. In addition, it is also verified theoretically that the blocked flow and synoptic-eddy activity are symbiotically dependent upon one another. The deformed (Z and M type) eddies also display a low-frequency oscillation in amplitude, wavenumber, group velocity, and phase speed, consistent with the blocked flow by the eddy forcing. Thus, it appears that the low-frequency eddy forcing is responsible for the low-frequency variability of the blocked flow and synoptic-eddy activity.

Synthesis and dielectric properties of tungsten-based complex perovskites

2003 ◽  
Vol 18 (11) ◽  
pp. 2600-2607 ◽  
Author(s):  
D.D. Khalyavin ◽  
Jiaping Han ◽  
A.M.R Senos ◽  
P.Q. Mantas
Keyword(s):  
Dielectric Properties ◽  
Temperature Variation ◽  
Single Phase ◽  
Low Frequency ◽  
Double Perovskites ◽  
Dielectric Measurements ◽  
Anomalous Temperature ◽  
Conventional Solid State Reaction ◽  
Thermally Activated ◽  
Second Phases

Ba2MeWO6 (Me=Mg, Ni, Zn) double perovskites were prepared by the conventional solid-state reaction in a wide temperature range. Single-phase ceramics were obtained only at low temperatures approximately 1200°C, whereas a small amount of second phases existed in the samples sintered at higher temperatures. All the compounds are characterized by the cubic perovskite structure (space group Fm3m) with a complete NaCl type ordering between B-site ions. Anomalous temperature variation of the dielectric loss tangent found in the Ba2NiWO6 perovskite is supposed to be connected with a dielectric relaxation due to electronic hopping within thermally activated Ni3+-6W(6-1/6)+/W5+-6Ni(2+1/6)+ clusters. Dielectric measurements showed that the other two perovskites—Ba2ZnWO6 and Ba2MgWO6—exhibit a positive value of the temperature coefficient of permittivity. Such temperature variation is assumed to be caused by a considerable influence of the second polar mode involving B-site ion vibrations on the low-frequency dielectric properties.

scholarly journals Dynamics of Synoptic Eddy and Low-Frequency Flow Interaction. Part II: A Theory for Low-Frequency Modes

2006 ◽  
Vol 63 (7) ◽  
pp. 1695-1708 ◽  
Author(s):  
F-F. Jin ◽  
L-L. Pan ◽  
M. Watanabe
Keyword(s):  
Storm Track ◽  
Low Frequency ◽  
Prototype Model ◽  
Mean Flow ◽  
Zonal Scale ◽  
Synoptic Eddy ◽  
The Pacific ◽  
Storm Track Activity ◽  
Recurrent Patterns ◽  
The Antarctic

Abstract Amidst stormy atmospheric circulation, there are prominent recurrent patterns of variability in the planetary circulation, such as the Antarctic Oscillation (AAO), Arctic Oscillation (AO) or North Atlantic Oscillation (NAO), and the Pacific–North America (PNA) pattern. The role of the synoptic eddy and low-frequency flow (SELF) feedback in the formation of these dominant low-frequency modes is investigated in this paper using the linear barotropic model with the SELF feedback proposed in Part I. It is found that the AO-like and AAO-like leading singular modes of the linear dynamical system emerge from the stormy background flow as the result of a positive SELF feedback. This SELF feedback also prefers a PNA-like singular vector as well among other modes under the climatological conditions of northern winters. A model with idealized conditions of basic mean flow and activity of synoptic eddy flow and a prototype model are also used to illustrate that there is a natural scale selection for the AAO- and AO-like modes through the positive SELF feedback. The zonal scale of the localized features in the Atlantic (southern Indian Ocean) for AO (AAO) is largely related to the zonal extent of the enhanced storm track activity in the region. The meridional dipole structures of AO- and AAO-like low-frequency modes are favored because of the scale-selective positive SELF feedback, which can be heuristically understood by the tilted-trough mechanism.

scholarly journals Anatomy of Synoptic Eddy–NAO Interaction through Eddy Structure Decomposition

2012 ◽  
Vol 69 (7) ◽  
pp. 2171-2191 ◽  
Author(s):  
Hong-Li Ren ◽  
Fei-Fei Jin ◽  
Li Gao
Keyword(s):  
Velocity Field ◽  
Flow Structure ◽  
Low Frequency ◽  
Vorticity Field ◽  
Eddy Structure ◽  
Synoptic Eddy ◽  
The North ◽  
Different Types ◽  
Structure Decomposition ◽  
Vorticity Flux

Abstract A method of eddy structure decomposition is proposed to detect how low-frequency flow associated with the North Atlantic Oscillation (NAO) organizes systematically synoptic eddy (SE) activity to generate in-phase and upstream feedbacks. In this method, a statistical eddy streamfunction (SES) field, defined by the three-point covariance of synoptic-scale streamfunction, is introduced to characterize spatiotemporal SE flow structures. The SES field is decomposed into basic and anomalous parts to represent the climatological SE flow structure and its departure. These two parts are used to calculate the basic and anomalous eddy velocity, eddy vorticity, and thus eddy vorticity flux fields, in order to elucidate those two SE feedbacks onto the NAO. This method is validated by the fact that the observed anomalous eddy vorticity flux field can be reproduced well by two linear terms: the basic eddy velocity field multiplied by anomalous eddy vorticity field and the anomalous eddy velocity field multiplied by basic eddy vorticity field. With this method, it is found that, in the positive and negative phases, the NAO flow tends to induce two different types of anomalous SE flow structure, which are largely responsible for generating the net meridional and zonal eddy vorticity fluxes that, in return, feed back onto the NAO. The two processes that are related to these two different types dominate in the in-phase and upstream feedbacks, which are delineated conceptually into two kinematic mechanisms associated with zonal-slanting and meridional-shifting changes in the SE structure. The present observational evidence supports the theory of eddy-induced instability for low-frequency variability and also provides insights into the reason for the asymmetry between the SE feedbacks onto the two NAO phases.

scholarly journals Eddy-Induced Instability for Low-Frequency Variability

2010 ◽  
Vol 67 (6) ◽  
pp. 1947-1964 ◽  
Author(s):  
F-F. Jin
Keyword(s):  
Dynamic Instability ◽  
Low Frequency ◽  
Basic Flow ◽  
Mean Flow ◽  
Eddy Activity ◽  
Planetary Scale ◽  
Synoptic Eddy ◽  
Low Frequency Variability ◽  
Eddy Structures ◽  
Scale Perturbation

Abstract Synoptic eddy–mean flow interaction has been recognized as one of the key sources for extratropical low-frequency variability. In this paper, the underlying dynamics of this interaction are examined from the perspective of a synoptic eddy-induced dynamic instability. To delineate this instability, a barotropic model is used that is linearized with respect to a stochastic basic flow prescribed with both climatologic-mean flow and synoptic eddy statistics. This linear model captures the dynamics of feedback between synoptic eddy and low-frequency flow through a dynamic closure that relates the anomalous eddy vorticity forcing to low-frequency flow anomalies. After reducing this dynamic closure to its fundamental components, this stability is elucidated with analytical results under the most idealized consideration of basic flow. It is shown that through systematic alteration of the synoptic eddy structures in the basic flow, a low-frequency planetary-scale perturbation generates anomalous eddy vorticity forcing positively proportional to the vorticity of the perturbation. Such a perturbation amplifies itself; the energy source for its growth comes from the reservoir residing in the basic synoptic eddy activity. Thus, the growth rate of the synoptic eddy-induced dynamic instability depends primarily on the kinetic energy level of the basic synoptic eddy activity. Moreover, this instability is scale selective with preference for zonal symmetric and asymmetric planetary-scale modes, whose meridional and zonal scales are roughly in the range of those of the observed leading low-frequency patterns. Analysis of this synoptic eddy-induced instability provides insight into the origin of extratropical low-frequency variability.

Dynamics of Synoptic Eddy and Low-Frequency Flow Interaction. Part I: A Linear Closure

2006 ◽  
Vol 63 (7) ◽  
pp. 1677-1694 ◽  
Author(s):  
F-F. Jin ◽  
L-L. Pan ◽  
M. Watanabe
Keyword(s):  
Atmospheric Circulation ◽  
Low Frequency ◽  
Equation Model ◽  
The Self ◽  
Quasi Equilibrium ◽  
Mean Flow ◽  
Linear Dynamic ◽  
Synoptic Eddy ◽  
Linear Framework ◽  
Low Frequency Variability

Abstract The interaction between synoptic eddy and low-frequency flow (SELF) has been recognized for decades to play an important role in the dynamics of the low-frequency variability of the atmospheric circulation. In this three-part study a linear framework with a stochastic basic flow capturing both the climatological mean flow and climatological measures of the synoptic eddy flow is proposed. Based on this linear framework, a set of linear dynamic equations is derived for the ensemble-mean eddy forcing that is generated by anomalous time-mean flows. By assuming that such dynamically determined eddy-forcing anomalies approximately represent the time-mean anomalies of the synoptic eddy forcing and by using a quasi-equilibrium approximation, an analytical nonlocal dynamical closure is obtained for the two-way SELF feedback. This linear closure, directly relating time-mean anomalies of the synoptic eddy forcing to the anomalous time–mean flow, becomes an internal part of a new linear dynamic system for anomalous time–mean flow that is referred to as the low-frequency variability of the atmospheric circulation in this paper. In Part I, the basic approach for the SELF closure is illustrated using a barotropic model. The SELF closure is tested through the comparison of the observed eddy-forcing patterns associated with the leading low-frequency modes with those derived using the SELF feedback closure. Examples are also given to illustrate an important role played by the SELF feedback in regulating the atmospheric responses to remote forcing. Further applications of the closure for understanding the dynamics of low-frequency modes as well as the extension of the closure to a multilevel primitive equation model will be given in Parts II and III, respectively.

scholarly journals Closures for Ensemble-Mean Linear Dynamics with Stochastic Basic Flows

2007 ◽  
Vol 64 (2) ◽  
pp. 497-514 ◽  
Author(s):  
F-F. Jin ◽  
L. Lin
Keyword(s):  
Low Frequency ◽  
Second Order ◽  
Basic Flow ◽  
External Forcing ◽  
Linear Dynamics ◽  
Ensemble Simulations ◽  
Synoptic Eddy ◽  
Low Frequency Variability ◽  
Ensemble Mean ◽  
Forced Responses

Abstract This paper demonstrates the validity of a second-order closure for the ensemble-mean dynamics using the approach of direct numerical ensemble simulations of a linear barotropic model with stochastic basic flows. For various configurations of the stochastic basic flow and external forcing, the deterministic solutions under the second-order closure capture, with remarkable accuracy, the ensemble means and the associated eddy covariance fields of forced responses simulated by a 500-member numerical ensemble. Thus, the second-order closure is found to be adequate for describing the ensemble-mean linear dynamics with stochastic basic flows. Moreover, simple analytical solutions based on the second-order closure also demonstrate that the stochastic component of a superrotational basic flow not only damps the ensemble-mean Rossby waves, but also enhances their eastward propagation. Various examples of ensemble-mean solutions all show the important role played by the stochastic synoptic eddy component of the basic flow in determining the ensemble-mean responses to external forcing. This study supports the notion that linear frameworks of ensemble-mean dynamics under second-order closure are useful tools for describing and understanding the dynamics of the synoptic eddy and the low-frequency flow (SELF) feedback and extratropical atmospheric low-frequency variability.

Dynamics of Synoptic Eddy and Low-Frequency Flow Interaction. Part III: Baroclinic Model Results

2006 ◽  
Vol 63 (7) ◽  
pp. 1709-1725 ◽  
Author(s):  
L-L. Pan ◽  
F-F. Jin ◽  
M. Watanabe
Keyword(s):  
Low Frequency ◽  
Equation System ◽  
The Self ◽  
The Arctic ◽  
Mean Flow ◽  
Synoptic Eddy ◽  
Model Study ◽  
Baroclinic Model ◽  
The Arctic Oscillation ◽  
Extratropical Circulation

Abstract In this three-part study, a linear closure has been developed for the synoptic eddy and low-frequency flow (SELF) interaction and demonstrated that internal dynamics plays an important role in generating the leading low-frequency modes in the extratropical circulation anomalies during cold seasons. In Part III, a new linearized primitive equation system is first derived for time-mean flow anomalies. The dynamical operator of the system includes a traditional part depending on the observed climatological mean state and an additional part from the SELF feedback closure utilizing the observed climatological properties of synoptic eddy activity. The latter part relates nonlocally all the anomalous eddy-forcing terms in equations of momentum, temperature, and surface pressure to the time-mean flow anomalies. Using the observational data, the closure was validated with reasonable success, and it was found that terms of the SELF feedback in the momentum and pressure equations tend to reinforce the low-frequency modes, whereas those in the thermodynamic equation tends to damp the temperature anomalies to make the leading modes equivalent barotropic. Through singular vector analysis of the linear dynamical operator, it is highlighted that the leading modes of the system resemble the observed patterns of the Arctic Oscillation, Antarctic Oscillation, and Pacific–North American pattern, in which the SELF feedback plays an essential role, consistent with the finding of the barotropic model study in Part II.

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