The Role of Shearwise and Transverse Quasigeostrophic Vertical Motions in the Midlatitude Cyclone Life Cycle

2006 ◽  
Vol 134 (4) ◽  
pp. 1174-1193 ◽  
Author(s):  
Jonathan E. Martin
Keyword(s):  
Life Cycle ◽  
Vertical Motion ◽  
Development Stage ◽  
Life Cycles ◽  
Vertical Shear ◽  
Mature Stage ◽  
Motion Field ◽  
Initial Development ◽  
Frontal Zones ◽  
Oriented Parallel

Abstract The total quasigeostrophic (QG) vertical motion field is partitioned into transverse and shearwise couplets oriented parallel to, and along, the geostrophic vertical shear, respectively. The physical role played by each of these components of vertical motion in the midlatitude cyclone life cycle is then illustrated by examination of the life cycles of two recently observed cyclones. The analysis suggests that the origin and subsequent intensification of the lower-tropospheric cyclone responds predominantly to column stretching associated with the updraft portion of the shearwise QG vertical motion, which displays a single, dominant, middle-tropospheric couplet at all stages of the cyclone life cycle. The transverse QG omega, associated with the cyclones’ frontal zones, appears only after those frontal zones have been established. The absence of transverse ascent maxima and associated column stretching in the vicinity of the surface cyclone center suggests that the transverse ω plays little role in the initial development stage of the storms examined here. Near the end of the mature stage of the life cycle, however, in what appears to be a characteristic distribution, a transverse ascent maximum along the western edge of the warm frontal zone becomes superimposed with the shearwise ascent maximum that fuels continued cyclogenesis. It is suggested that use of the shearwise/transverse diagnostic approach may provide new and/or supporting insight regarding a number of synoptic processes including the development of upper-level jet/front systems and the nature of the physical distinction between type A and type B cyclogenesis events.

Prognostic criteria for Polar Lows

2021 ◽  
Author(s):  
Natalia Vazaeva ◽  
Otto Chkhetiani ◽  
Michael Kurgansky
Keyword(s):  
Numerical Simulation ◽  
Wind Velocity ◽  
Large Scale ◽  
Satellite Image ◽  
Development Stage ◽  
Mature Stage ◽  
Initial Development ◽  
Polar Lows ◽  
Prognostic Criteria ◽  
Main Challenge

<p>Polar lows (PLs) are important mesoscale (horizontal diameter up to 1000 km) maritime weather systems at high latitudes, forming pole ward from the polar front. We consider the possible prognostic criteria of PLs, in particular, the kinematic helicity as a quadratic characteristic related to the integral vortex formations and the kinematic vorticity number (KVN). To calculate such characteristics we use reanalysis data and the results of numerical simulation with the WRF-ARW model (Version 4.1.) for the PLs over the Nordic (Norwegian and Barents) seas. For comparison, experimental data are used.</p><p>Our estimate of helicity is based on the connection of an integral helicity (IH) in the Ekman layer with the geostrophic wind velocity, due to the good correlation between IH and half the sum of the wind velocity squared. We have chosen IH averaged over preselected area covering the locality of PLs genesis. This area was moving along with the centre of PL during the numerical simulation.</p><p>The genesis of PLs can be divided into three stages: (i) an initial development stage, in which a number of small vortices appear in a shear zone; (ii) a late development stage, characterized by the merger of vortices; (iii) a mature stage, in which only a single PL is present. Approximately one day before PL formation, a significant increase in helicity was observed. The average helicity bulk density of large-scale motions has values of 0.3 – 0.4 ms<sup>-2</sup>. The local changes in helicity are adjacent to the front side of the PLs. The IH criterion described facilitates the identification of the PLs genesis area. For a more detailed analysis of the PL genesis, it is recommended to apply KVN, which is the additional indicator of PL size and intensity. At the moment of maximum intensity of PLs KVN can reach values of 12 – 14 units. The advantage of using KVN is also in its clear change directly in the centre of the emerging PLs, which allows to precisely indicates the limits of the most intense part of PLs.</p><p>The main challenge is to make the operational forecast of PLs possible through the selection of the prognostic integral characteristics of PLs, sufficient for PLs identification and for analysis of their size and intensity in a convenient, usable and understandable way. The criteria associated with vorticity and helicity are reflected in the PLs genesis and development quite clearly. At this time, such a claim is only a hypothesis, which must be tested using a larger set of cases. Future work will need to extend these analyses to other active PL basins. Also, it would be interesting to compare the representation of PLs by using any other criteria. It is intended to use our combined criteria as a precursor to machine learning-based PLs identification procedure where satellite image analysis and capture of particular cloud patterns are currently applied in most of the cases. It would eliminate the time consuming first stage of collecting data sets.</p><p>This work was supported by the Russian Science Foundation (project No. 19-17-00248).</p>

Financial flexibility, managerial efficiency and firm life cycle on firm performance

2019 ◽  
Vol 16 (2) ◽  
pp. 168-180
Author(s):  
Heng-Yu Chang ◽  
Chun-Ai Ma
Keyword(s):  
Life Cycle ◽  
Firm Performance ◽  
Stock Market ◽  
Life Cycles ◽  
Mature Stage ◽  
Chinese Stock Market ◽  
Financial Flexibility ◽  
Content Type ◽  
Listed Firms ◽  
Managerial Efficiency

Purpose As the capital market in China is still developing, several constraints on a Chinese-listed firm’s financing strategy have a direct impact on its financial flexibility. The purpose of this paper is to reconstruct traditional financial flexibility index (FFI) derived from the western context, provide empirical evidence within eastern context by modified FFI and examine how the managerial efficiency of Chinese-listed firms is demonstrated with modified FFI to escort corporate life cycle hypothesis. Design/methodology/approach By tailored FFI to fit the contemporary operations of Chinese-listed firms, this study investigates how managerial efficiency varies across different life stages to demonstrate the moderating power in the firm performance of financially flexible firm. Findings It is found that financially flexible firms in the Chinese stock market generally experience good firm performance, yet the managerial efficiency could gradually be diminishing at their mature stage even firms’ financial flexibility remains consistent with the agency theory. This paper sheds light on the necessity to reexamine the components in financial flexibility based on the eastern context, and provides avenue to further understand the managerial behavior of Chinese listed firms when considering firm life cycles. Research limitations/implications Although it is difficult for this current study to offer the precise weights on each factor in calculating financial flexibility, the judgment matrix method is adopted to at least provide reliable estimates in accordance with Chinese business contexts with less than 10 percent errors in contrast to the actual weights. Practical implications This modified FFI is particularly suitable for Chinese-listed firms under certain unique financial reporting regulations by adjusting a number of weights and factors. This study may help practitioners understand the managerial conduct of publicly listed firms in China. Originality/value The paper constructs a modified FFI with Chinese stock market characteristics embedded, and provides insightful evidence to explain the new pecking order theory by considering the life cycle stage of Chinese-listed companies.

Genesis and Development Mechanisms of a Polar Mesocyclone over the Japan Sea

2014 ◽  
Vol 142 (6) ◽  
pp. 2248-2270 ◽  
Author(s):  
Shun-ichi I. Watanabe ◽  
Hiroshi Niino
Keyword(s):  
Numerical Simulation ◽  
Life Cycle ◽  
Shear Zone ◽  
Latent Heat ◽  
Japan Sea ◽  
Development Stage ◽  
Heat Fluxes ◽  
Mature Stage ◽  
Late Development ◽  
The Japan Sea

Abstract A polar mesocyclone (PMC) observed over the Japan Sea on 30 December 2010 was studied using a nonhydrostatic mesoscale numerical model with a horizontal resolution of 2 km. The numerical simulation successfully reproduced the observed life cycle of the PMC. The results of the numerical simulation suggest that the life cycle of the PMC may be divided into three stages: an early development stage, in which a number of small vortices appear in a shear zone; a late development stage, which is characterized by the merger of vortices and the formation of a few larger vortices; and a mature stage, in which only a single PMC is present. During the early development stage, vortices are generated in the shear zones of strong updrafts in discrete cumulus convection cells. In contrast, during the late development stage, the vortices develop as a result of barotropic instability in the shear zone. A cloud-free eye and spiral cloud bands accompany the mature stage of a simulated PMC. A warm core structure also forms at the center of the PMC on account of adiabatic warming associated with downdrafts. The structures in the PMC during the mature stage resemble those of a tropical cyclone. Sensitivity experiments, in which sensible and latent heat fluxes from the sea surface and condensational heating were switched on/off, demonstrate that condensational heating is critical to the development of the PMC at all stages, and that sensible and latent heat fluxes play secondary roles.

scholarly journals A Local Energetics Analysis of the Life Cycle Differences between Consecutive, Explosively Deepening, Continental Cyclones

2005 ◽  
Vol 133 (1) ◽  
pp. 295-316 ◽  
Author(s):  
Steven G. Decker ◽  
Jonathan E. Martin
Keyword(s):  
Life Cycle ◽  
Wave Packet ◽  
Sea Level ◽  
Life Cycles ◽  
Maximum Intensity ◽  
Mature Stage ◽  
Extratropical Cyclones ◽  
Baroclinic Wave ◽  
Sea Level Pressure ◽  
Level Pressure

Abstract Local energetics diagnostics of the life cycles of consecutive, explosively deepening, extratropical cyclones that migrated across central North America in April 2001 are presented. Both storms developed rapidly and followed nearly identical tracks through the region. Despite similar mature-stage intensities, the two storms underwent vastly different evolutions during cyclolysis; the first decayed as rapidly as it had developed, and the second decayed very slowly. Examination of the volume-integrated eddy kinetic energy (EKE) budget for each storm reveals that the sea level pressure minimum associated with the first cyclone developed well after its associated EKE center had reached its maximum intensity. In contrast, the second cyclone’s sea level pressure minimum developed much more in concert with the development of its associated EKE center. As a consequence, the first cyclone began losing EKE through downstream energy fluxes even as it was developing at the surface, whereas the second cyclone did not disperse EKE downstream until later in its life cycle. Consideration of the EKE budget results in terms of baroclinic wave packets demonstrates that the first cyclone developed and decayed on the upstream edge of a wave packet, whereas the second cyclone developed in the midst of a wave packet, only decaying once it had reached the upstream edge. Thus, it is suggested that postmature phase decay is dynamically linked to a cyclone’s position in a given wave packet.

scholarly journals Lower-Tropospheric Height Tendencies Associated with the Shearwise and Transverse Components of Quasigeostrophic Vertical Motion

2007 ◽  
Vol 135 (7) ◽  
pp. 2803-2809 ◽  
Author(s):  
Jonathan E. Martin
Keyword(s):  
Life Cycle ◽  
Sea Level ◽  
Vertical Motion ◽  
Direct Calculation ◽  
Vorticity Equation ◽  
Mature Stage ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Surface Cyclone ◽  
Vorticity Production

Abstract The recent suggestion that lower-tropospheric cyclogenesis is predominantly a result of column stretching associated with the updraft portion of the shearwise quasigeostrophic (QG) vertical motion is quantified through direct calculation of 900-hPa height tendencies via the QG vorticity equation. Comparison of the separate lower-tropospheric height tendencies associated with the shearwise and transverse portions of QG omega in a robust cyclogenesis event demonstrates that the shearwise updraft drives the largest part (>80%) of the cyclogenetic height falls at least through the end of the mature stage of the life cycle. The lower-tropospheric height falls and vorticity production near the sea level pressure minimum of the occluded surface cyclone are driven nearly equally by shearwise and transverse updrafts.

scholarly journals The dynamics of spiral banding in a symmetric vortex with vertical shear

1964 ◽  
Author(s):  
◽  
Michael Stephen Sher
Keyword(s):  
Tropical Cyclones ◽  
Gravity Waves ◽  
Inversion Layer ◽  
Vertical Wind Shear ◽  
Vertical Motion ◽  
Ekman Layer ◽  
Vertical Shear ◽  
Necessary Condition ◽  
Motion Field ◽  
Dynamical Mechanism

Spiral rain bands in tropical cyclones were revealed by Wexler (1947) through analysis of radar observations, and many investigators have directed their attention to them. The bands may now be easily observed through the use of radar (figure 1) and Tiros photographs. However, the mechanism responsible for this frequently observed phenomena is not as yet fully understood. As a possible mechanism for the formation of the spiral bands, Haurwitz (1947), Wexler (1947) and Kuettner (1959) have suggested elongation of convection cells in the tangential direction by vertical wind shear. Further studies are needed to establish this hypothesis, since there is as yet no clear evidence for the existence of Bernard cells in tropical cyclones. Tepper (1958) proposed a hypothesis of internal gravity waves. However, a necessary condition for the existence of gravity waves is an inversion layer which has not been observed in tropical cyclones, except in the eye. Thus, although the entire depth of the fluid may be subject to banded disturbances, the origin and energy source for these disturbances is restricted to those layers with marked vertical shear of the undisturbed flow, principally the Ekman layer. In the case of the atmosphere, moist air in the Ekman layer may be lifted by the periodic vertical motion field to its lifting condensation level becoming visible upon condensation in the form of spiral clouds and rain bands. The release of latent heat in the regions of maximum lifting should serve to increase the vertical motion in these bands and accentuate the upward propagation of the disturbances into the otherwise undisturbed layers above. Arons' observations and Stern's theoretical findings strongly suggest that the vertical shear in the Ekman layer is the dynamical mechanism for instability in the vertical motion field, which may manifest itself in the form of periodic motion in the radial direction. One might even suggest that without the presence of shear the banded structure might not arise. It was these findings and considerations that led the present author to re-examine Yamamoto's work and attempt to retain the vertical shear terms rather than consider only the case of zero shear as did Yamamoto.--Introduction.

scholarly journals The Generation of Turbulence below Midlevel Cloud Bases: The Effect of Cooling due to Sublimation of Snow

2013 ◽  
Vol 52 (4) ◽  
pp. 819-833 ◽  
Author(s):  
Atsushi Kudo
Keyword(s):  
Numerical Simulations ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Vertical Motion ◽  
Vertical Shear ◽  
Cloud Base ◽  
Base Temperature ◽  
Sequence Of Events ◽  
Frontal Zones ◽  
The Stability

AbstractIn the author’s experience as a forecaster, commercial aircraft sometimes report turbulence beneath midlevel clouds that extend above upper frontal zones. Turbulence caused by Kelvin–Helmholtz instability occurs in upper frontal zones with strong vertical shear of horizontal winds. However, the turbulence seems to occur not only in the cloud bases (where upper frontal zones are) but also below the cloud bases where the vertical shear is not strong. Because those clouds are usually accompanied by precipitation that does not reach the ground, cooling by evaporation or sublimation seems to contribute to the generation of turbulence. In this paper, the mechanisms generating turbulence below midlevel cloud bases are examined by using observations and high-resolution three-dimensional numerical simulations with idealized initial conditions. The numerical simulations showed that the following sequence of events led to turbulence. Falling snow sublimated below cloud bases and cooled the air, which created absolute instability. This generated Rayleigh–Bénard convection cells. The vertical motion caused turbulence. The horizontal scale of the convection was about 800–1000 m, and the variations of vertical wind velocity were up to about 7 m s−1. The cloud base was accompanied by a virga-like distribution of snow. Sensitivity experiments showed the appropriate conditions to cause the turbulence: 1) the cloud-base temperature was between about 0° and −15°C, 2) the relative humidity in subcloud layers was sufficiently low, and 3) the stability in subcloud layers was weak. The results of the numerical simulations agreed well with the observations.

scholarly journals The Static Stability of the Tropopause Region in Adiabatic Baroclinic Life Cycle Experiments

2011 ◽  
Vol 68 (6) ◽  
pp. 1178-1193 ◽  
Author(s):  
Andre R. Erler ◽  
Volkmar Wirth
Keyword(s):  
Life Cycle ◽  
Wave Breaking ◽  
Inversion Layer ◽  
Static Stability ◽  
Relative Vorticity ◽  
Theoretical Explanation ◽  
Life Cycles ◽  
Skewed Distribution ◽  
Mature Stage ◽  
Global Mean

Abstract The tropopause inversion layer (TIL) is a region of enhanced static stability just above the WMO-defined thermal tropopause. It is a ubiquitous feature in midlatitudes and is well characterized by observations. However, it is still lacking a satisfactory theoretical explanation. This study utilizes adiabatic baroclinic life cycle experiments to investigate dynamical mechanisms that lead to TIL formation. As the baroclinic wave grows, a strong TIL forms above anticyclonic anomalies, while no TIL is found above cyclonic anomalies; this is consistent with previous results. However, during the early growth phase there is no TIL in the global or zonal average: positive and negative anomalies cancel out exactly. The zonal and global mean TIL only emerges during the mature stage of the life cycle, after the onset of wave breaking. The TIL predominantly occurs equatorward of the jet and the vertical structure bears resemblance to the TIL in midlatitudes; there is no equivalent to the subpolar TIL. Life cycles without significant wave breaking develop neither a global nor a zonal mean TIL. No global mean TIL is found in any life cycle if the dynamical tropopause definition is used. In addition, a new mechanism of dynamical TIL formation is presented, suggesting that the TIL in the global and zonal mean is linked to a strongly skewed distribution of relative vorticity after wave breaking.

scholarly journals On the Initial Development of Asymmetric Vertical Motion and Horizontal Relative Flow in a Mature Tropical Cyclone Embedded in Environmental Vertical Shear

2013 ◽  
Vol 70 (11) ◽  
pp. 3471-3491 ◽  
Author(s):  
Yamei Xu ◽  
Yuqing Wang
Keyword(s):  
Tropical Cyclone ◽  
Dominant Role ◽  
Vertical Motion ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Asymmetric Flow ◽  
Initial Development ◽  
Budget Analysis ◽  
Tangential Wind ◽  
Relative Flow

Abstract In this paper, the authors focus on the initial development of asymmetric vertical motion and horizontal relative flow in a mature tropical cyclone (TC) embedded in an environmental vertical shear. The fully compressible, nonhydrostatic TC model was used to perform a series of numerical experiments with a mature TC with different intensities embedded in shear with different magnitudes and different vertical profiles. Results show that the development of both the wavenumber-1 asymmetric vertical motion and horizontal relative flow for a TC embedded in vertical shear is quite sensitive to both the magnitude and the vertical profile of wind shear, as well as the intensity of the TC itself. Diagnostic analysis based on the quasi-balanced potential vorticity inversion indicates that the balanced dynamics can only explain a small portion of the asymmetric vertical motion and relative flow. The unbalanced processes contribute predominantly to the development of the asymmetric flow in the simulations. It is shown that the eyewall of a mature TC plays a role somewhat like a material cylinder embedded in an environmental flow with vertical shear. The interaction between the environmental shear and the eyewall produces vertical gradient of convergence/divergence of horizontal wind around the lateral edge of the eyewall. This forces much stronger asymmetric vertical motion than the balanced processes do and drives significant horizontal relative divergent flow over the storm core, which opposes vertical shear and reduces the vertical tilt of the storm axis. In addition, the budget analysis for the axisymmetric tangential wind demonstrates that the asymmetric flow plays a dominant role in weakening the storm top down.

MERGERS AND ACQUISITIONS AND THEIR CORRELATION WITH THE LIFE CYCLES OF MEMBER COMPANIES ON THE EXAMPLE OF THE RUSSIAN MARKET 2017–2019

2020 ◽  
Vol 1 (10) ◽  
pp. 26-35
Author(s):  
E. A. SHUBINA ◽  
◽  
Yu. A. KOMAROVSKY ◽  
A. V. MERKUSHEV ◽  
◽  
...  
Keyword(s):  
Life Cycle ◽  
Mergers And Acquisitions ◽  
Life Cycles ◽  
Russian Market

The article is devoted to the study of the largest mergers and acquisitions (M&A, “Mergers & Acquisitions”) in Russia for 2017–2019. (the acquired block of shares is not less than 99%). The concept of life cycles of organizations and theoretical aspects of mergers and acquisitions are described. The stages of the life cycle of the merged and reorganized companies, the goals of mergers and acquisitions, depending on the stages of the life cycle are analyzed.

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