scholarly journals The Role of Stationary Eddies in Shaping Midlatitude Storm Tracks

2013 ◽  
Vol 70 (8) ◽  
pp. 2596-2613 ◽  
Author(s):  
Yohai Kaspi ◽  
Tapio Schneider
Keyword(s):  
Energy Transport ◽  
Storm Track ◽  
Static Stability ◽  
Surface Heating ◽  
Storm Tracks ◽  
Mean Flow ◽  
Wavelength Scale ◽  
The Mean ◽  
And Control

Abstract Transient and stationary eddies shape the extratropical climate through their transport of heat, moisture, and momentum. In the zonal mean, the transports by transient eddies dominate over those by stationary eddies, but this is not necessarily the case locally. In particular, in storm-track entrance and exit regions during winter, stationary eddies and their interactions with the mean flow dominate the atmospheric energy transport. Here it is shown that stationary eddies can shape storm tracks and control where they terminate by modifying local baroclinicity. Simulations with an idealized aquaplanet GCM show that zonally localized surface heating alone (e.g., ocean heat flux convergence) gives rise to storm tracks, which have a well-defined length scale that is similar to that of Earth's storm tracks. The storm tracks terminate downstream of the surface heating even in the absence of continents, at a distance controlled by the stationary Rossby wavelength scale. Stationary eddies play a dual role: within about half a Rossby wavelength downstream of the heating region, stationary eddy energy fluxes increase the baroclinicity and therefore contribute to energizing the storm track; farther downstream, enhanced poleward and upward energy transport by stationary eddies reduces the baroclinicity by reducing the meridional temperature gradients and enhancing the static stability. Transports both of sensible and latent heat (water vapor) play important roles in determining where storm tracks terminate.

scholarly journals Ocean and Atmosphere Storm Tracks: The Role of Eddy Vorticity Forcing

2007 ◽  
Vol 37 (9) ◽  
pp. 2267-2289 ◽  
Author(s):  
Richard G. Williams ◽  
Chris Wilson ◽  
Chris W. Hughes
Keyword(s):  
Storm Track ◽  
Heat Fluxes ◽  
Storm Tracks ◽  
Mean Flow ◽  
Ocean Eddies ◽  
Boundary Currents ◽  
The Mean ◽  
Circumpolar Current ◽  
The Antarctic

Abstract Signatures of eddy variability and vorticity forcing are diagnosed in the atmosphere and ocean from weather center reanalysis and altimetric data broadly covering the same period, 1992–2002. In the atmosphere, there are localized regions of eddy variability referred to as storm tracks. At the entrance of the storm track the eddies grow, providing a downgradient heat flux and accelerating the mean flow eastward. At the exit and downstream of the storm track, the eddies decay and instead provide a westward acceleration. In the ocean, there are similar regions of enhanced eddy variability along the extension of midlatitude boundary currents and the Antarctic Circumpolar Current. Within these regions of high eddy kinetic energy, there are more localized signals of high Eady growth rate and downgradient eddy heat fluxes. As in the atmosphere, there are localized regions in the Southern Ocean where ocean eddies provide statistically significant vorticity forcing, which acts to accelerate the mean flow eastward, provide torques to shift the jet, or decelerate the mean flow. These regions of significant eddy vorticity forcing are often associated with gaps in the topography, suggesting that the ocean jets are being locally steered by topography. The eddy forcing may also act to assist in the separation of boundary currents, although the diagnostics of this study suggest that this contribution is relatively small when compared with the advection of planetary vorticity by the time-mean flow.

Drivers of biases in the extratropical storm tracks in CMIP6

2020 ◽  
Author(s):  
Matthew Priestley ◽  
Duncan Ackerley ◽  
Jennifer Catto ◽  
Kevin Hodges ◽  
Ruth McDonald ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Storm Track ◽  
Storm Tracks ◽  
Extratropical Cyclones ◽  
Ocean Coupling ◽  
Coupled Climate Models ◽  
The Mean ◽  
The Impact

<p>Extratropical cyclones are the leading driver of the day-to-day weather variability and wintertime losses for Europe. In the latest generation of coupled climate models, CMIP6, it is hoped that with improved modelling capabilities come improvements in the structure of the storm track and the associated cyclones. Using an objective cyclone identification and tracking algorithm the mean state of the storm tracks in the CMIP6 models is assessed as well as the representation of explosively deepening cyclones. Any developments and improvements since the previous generation of models in CMIP5 are discussed, with focus on the impact of model resolution on storm track representation. Furthermore, large-scale drivers of any biases are investigated, with particular focus on the role of atmosphere-ocean coupling via associated AMIP simulations and also the influence of large-scale dynamical and thermodynamical features.</p>

Observed Patterns of Month-to-Month Storm-Track Variability and Their Relationship to the Background Flow*

2010 ◽  
Vol 67 (5) ◽  
pp. 1420-1437 ◽  
Author(s):  
Justin J. Wettstein ◽  
John M. Wallace
Keyword(s):  
Northern Hemisphere ◽  
Geopotential Height ◽  
Storm Track ◽  
Meridional Wind ◽  
Storm Tracks ◽  
Mean Flow ◽  
Annular Mode ◽  
The North ◽  
Jet Variability ◽  
The North Atlantic Oscillation

Abstract Month-to-month storm-track variability is investigated via EOF analyses performed on ERA-40 monthly-averaged high-pass filtered daily 850-hPa meridional heat flux and the variances of 300-hPa meridional wind and 500-hPa height. The analysis is performed both in hemispheric and sectoral domains of the Northern and Southern Hemispheres. Patterns characterized as “pulsing” and “latitudinal shifting” of the climatological-mean storm tracks emerge as the leading sectoral patterns of variability. Based on the analysis presented, storm-track variability on the spatial scale of the two Northern Hemisphere sectors appears to be largely, but perhaps not completely, independent. Pulsing and latitudinally shifting storm tracks are accompanied by zonal wind anomalies consistent with eddy-forced accelerations and geopotential height anomalies that project strongly on the dominant patterns of geopotential height variability. The North Atlantic Oscillation (NAO)–Northern Hemisphere annular mode (NAM) is associated with a pulsing of the Atlantic storm track and a meridional displacement of the upper-tropospheric jet exit region, whereas the eastern Atlantic (EA) pattern is associated with a latitudinally shifting storm track and an extension or retraction of the upper-tropospheric jet. Analogous patterns of storm-track and upper-tropospheric jet variability are associated with the western Pacific (WP) and Pacific–North America (PNA) patterns. Wave–mean flow relationships shown here are more clearly defined than in previous studies and are shown to extend through the depth of the troposphere. The Southern Hemisphere annular mode (SAM) is associated with a latitudinally shifting storm track over the South Atlantic and Indian Oceans and a pulsing South Pacific storm track. The patterns of storm-track variability are shown to be related to simple distortions of the climatological-mean upper-tropospheric jet.

Sensitivity of Perturbation Variance and Fluxes in Turbulent Jets to Changes in the Mean Jet

2004 ◽  
Vol 61 (21) ◽  
pp. 2644-2652
Author(s):  
Brian F. Farrell ◽  
Petros J. Ioannou
Keyword(s):  
Stochastic Model ◽  
Storm Track ◽  
Turbulent Jets ◽  
Static Stability ◽  
Structure Change ◽  
Synoptic Scale ◽  
Single Jet ◽  
The Mean ◽  
Arbitrary Change ◽  
Jet Structure

Abstract Synoptic-scale eddy variance and fluxes of heat and momentum in midlatitude jets are sensitive to small changes in mean jet velocity, dissipation, and static stability. In this work the change in the jet producing the greatest increase in variance or flux is determined. Remarkably, a single jet structure change completely characterizes the sensitivity of a chosen quadratic statistical quantity to modification of the mean jet in the sense that an arbitrary change in the jet influences a chosen statistical quantity in proportion to the projection of the change on this single optimal structure. The method used extends previous work in which storm track statistics were obtained using a stochastic model of jet turbulence.

scholarly journals The Role of Mannose-Binding Lectin Serum Level in Tubotympanic Chronic Suppurative Otitis Media

2018 ◽  
Vol 2018 ◽  
pp. 1-4
Author(s):  
Anton Budhi Darmawan ◽  
Marsetyawan H. N. E. Soesatyo ◽  
Ratna Dwi Restuti ◽  
Agus Surono
Keyword(s):  
Serum Level ◽  
Otitis Media ◽  
Control Group ◽  
Suppurative Otitis Media ◽  
Mannose Binding ◽  
The Mean ◽  
And Control ◽  
Binding Lectin ◽  
Mbl Deficiency

Background. Chronic suppurative otitis media (CSOM) is a common public health problem worldwide and a major cause of hearing impairment especially in developing countries. The role of Mannose-Binding Lectin (MBL), a component of innate immunity, in CSOM has not been studied. The aim of the study was to examine whether MBL deficiency was more frequently present in cases group of tubotympanic CSOM patients rather than healthy subjects. Material and Methods. This was an analytic observational study. Subjects were enrolled in the Otorhinolaryngology Clinic at Margono Soekarjo Hospital, Purwokerto, Indonesia. An independent t-test was used to compare the mean of MBL serum concentration between tubotympanic CSOM subjects and control. Results. From 36 tubotympanic CSOM patients, there were 8 (22.22%) patients with MBL deficiency (MBL level < 100 ng/ml), while no deficiency was found in the control group. The mean of MBL level in cases group was 354.88 ng/ml, with the lowest level being 0.001 ng/ml and the highest level 690.24 ng/ml, while in the control group MBL level mean was 376.27 with the lowest level being 188.71 and the highest level 794.54 ng/ml. Conclusion. There was no significant difference of MBL serum level between tubotympanic CSOM and control group. However, the presence of subjects with MBL deficiency in the tubotympanic CSOM group might be considered as playing a role in the tubotympanic CSOM.

scholarly journals An Idealized Nonlinear Model of the Northern Hemisphere Winter Storm Tracks

2006 ◽  
Vol 63 (7) ◽  
pp. 1818-1839 ◽  
Author(s):  
Edmund K. M. Chang
Keyword(s):  
Heat Release ◽  
Storm Track ◽  
Storm Tracks ◽  
Iterative Approach ◽  
Latent Heat Release ◽  
Mean Flow ◽  
Winter Storm ◽  
Climate Anomalies ◽  
Hemisphere Winter ◽  
Northern Hemisphere Winter

Abstract In this paper, a nonlinear dry model, forced by fixed radiative forcing alone, has been constructed to simulate the Northern Hemisphere winter storm tracks. A procedure has been devised to iterate the radiative equilibrium temperature profile such that at the end of the iterations the model climate closely resembles the desired target climate. This iterative approach is applied to simulate the climatological storm tracks in January. It is found that, when the three-dimensional temperature distribution in the model resembles the observed distribution, the model storm tracks are much too weak. It is hypothesized that this is due to the fact that eddy development is suppressed in a dry atmosphere, owing to the lack of latent heat release in the ascending warm air. To obtain storm tracks with realistic amplitudes, the static stability of the target climate is reduced to simulate the enhancement in baroclinic energy conversion due to latent heat release. With this modification, the storm tracks in the model simulation closely resemble those observed except that the strength of the Atlantic storm track is slightly weaker than observed. The model, when used as a forecast model, also gives high-quality forecasts of the evolution of observed eddies. The iterative approach is applied to force the model to simulate climate anomalies associated with ENSO and the interannual variations of the winter Pacific jet stream/storm tracks. The results show that the model not only succeeds in simulating the climatology of storm tracks, but also produces realistic simulations of storm track anomalies when the model climate is forced to resemble observed climate anomalies. An extended run of the control experiment is conducted to generate monthly mean flow and storm track statistics. These statistics are used to build a linear statistical model relating storm track anomalies to mean flow anomalies. This model performs well when used to hindcast observed storm track anomalies based on observed mean flow anomalies, showing that the storm track/mean flow covariability in the model is realistic and that storm track distribution is not sensitive to the exact form of the applied forcings.

Changes in the Extratropical Storm Tracks in Response to Changes in SST in an AGCM

2012 ◽  
Vol 25 (6) ◽  
pp. 1854-1870 ◽  
Author(s):  
Lise Seland Graff ◽  
J. H. LaCasce
Keyword(s):  
Boundary Conditions ◽  
General Circulation ◽  
Lower Boundary ◽  
Storm Track ◽  
Circulation Model ◽  
Hadley Circulation ◽  
Meridional Overturning Circulation ◽  
Storm Tracks ◽  
Poleward Shift ◽  
The Mean

Abstract A poleward shift in the extratropical storm tracks has been identified in observational and climate simulations. The authors examine the role of altered sea surface temperatures (SSTs) on the storm-track position and intensity in an atmospheric general circulation model (AGCM) using realistic lower boundary conditions. A set of experiments was conducted in which the SSTs where changed by 2 K in specified latitude bands. The primary profile was inspired by the observed trend in ocean temperatures, with the largest warming occurring at low latitudes. The response to several other heating patterns was also investigated, to examine the effect of imposed gradients and low- versus high-latitude heating. The focus is on the Northern Hemisphere (NH) winter, averaged over a 20-yr period. Results show that the storm tracks respond to changes in both the mean SST and SST gradients, consistent with previous studies employing aquaplanet (water only) boundary conditions. Increasing the mean SST strengthens the Hadley circulation and the subtropical jets, causing the storm tracks to intensify and shift poleward. Increasing the SST gradient at midlatitudes similarly causes an intensification and a poleward shift of the storm tracks. Increasing the gradient in the tropics, on the other hand, causes the Hadley cells to contract and the storm tracks to shift equatorward. Consistent shifts are seen in the mean zonal velocity, the atmospheric baroclinicity, the eddy heat and momentum fluxes, and the atmospheric meridional overturning circulation. The results support the idea that oceanic heating could be a contributing factor to the observed shift in the storm tracks.

scholarly journals Editorial: Scholarly communications and corporate governance research

2019 ◽  
Vol 17 (1) ◽  
pp. 162-164
Author(s):  
Alexander Kostyuk
Keyword(s):  
Corporate Governance ◽  
American Economic Review ◽  
Theory And Practice ◽  
Final Approval ◽  
Critical Commentary ◽  
Scholarly Communications ◽  
The Mean ◽  
And Control ◽  
To Receive

The role of scholarly conferences as a method of scholarly communications cannot be overestimated. Thus, Torgler and Piatti (2013) found that in 1974, only 19 per cent of papers published in American Economic Review had been presented at one or more conferences, workshops or seminars, for critical commentary prior to publication. On average, the number of presentations was 0.24 per paper. Twenty-five years later, 73 percent of the papers accepted for publication have been previously presented, and the mean number of pre-publication presentations was 4.73. Personal editorial and reviewing experience give a right to conclude that papers previously presented at the conferences have more serious scholarly content, solid empirical fundamentals and relevance. Scholarly journal reviewers are more favourable about such papers and it takes less time to receive the final approval of the reviewers for further publishing. Discussing the papers in an open manner at the conferences is welcome both by the authors of the papers as well as the commenting scholars adding more enthusiasm for further research. International conference "New Challenges in Corporate Governance: Theory and Practice"1 took place in Naples on October 3-4, 2019.2 About 80 experts from America, Europe, Asia, Africa and Oceania gathered at the conference venue to discuss relevant issues of corporate governance, ownership and control, share their most recent research and come up with the solutions of the existing corporate governance research.

scholarly journals The Role of Volume, Conductivity, Scatter Changes of Neutrophils and Monocytes in Diagnosis of Megaloblastic Anemia

2020 ◽  
Vol 7 (12) ◽  
pp. A563-569
Author(s):  
Deepa Sowkur Anandarama Adiga ◽  
Debarshi Saha ◽  
Karthick R G ◽  
Vishnu Priya M ◽  
Purnima S Rao ◽  
...  
Keyword(s):  
Vitamin B12 ◽  
Megaloblastic Anemia ◽  
Serum Vitamin ◽  
Volume Conductivity ◽  
Degree Of Certainty ◽  
Normochromic Anemia ◽  
The Mean ◽  
The Difference ◽  
And Control

Background: Megaloblastic anemias are macrocytic normochromic anemia with mean corpuscular volume (MCV) of 100 fl-140 fl and caused by deficiency of either cobalamin (vitamin B12) or folate. However, increased MCV is not specific for megaloblastic anemia, nor is Vitamin B12 assay by chemiluminescence. We undertook this study to evaluate the possible role of Volume, Conductivity and Scatter (VCS) of WBCs derived from standard hematology analyzer to indicate megaloblastic anemia. Methods: We performed a case control study comparing data of 60 patients with low serum vitamin B12 or folate levels with 60 healthy volunteers. Comparison of the volume, conductivity and scatter parameters for neutrophils and monocytes of cases and control were done. Result: The mean neutrophil volume of cases (158.37±18.13fl) was significantly higher (p= 0.0001) compared to controls (141.26±4.22fl). Similarly, mean monocyte volume of cases (183.34±16.90fl) was significantly (p=0.0001) higher compared to controls (166.55±8.66fl). The difference in the mean conductivity of both neutrophils and monocytes between cases and controls were insignificant (p=0.43). Conclusion: Our study suggests analysis of VCS parameters for neutrophils and monocytes was a simple and objective method that substantiates the existence of subclinical deficiency of vitamin B 12 and folate with fair degree of certainty.

scholarly journals Performance of Turbulence Models in Simulating Wind Loads on Photovoltaics Modules

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3290 ◽  
Author(s):  
Mireille B. Tadie Fogaing ◽  
Arman Hemmati ◽  
Carlos F. Lange ◽  
Brian A. Fleck
Keyword(s):  
Energy Transport ◽  
Turbulence Models ◽  
Wind Loads ◽  
Turbulence Energy ◽  
Pressure Gradients ◽  
Mean Flow ◽  
Velocity Gradients ◽  
Large Pressure ◽  
The Mean ◽  
Recirculation Length

The performance of five conventional turbulence models, commonly used in the wind industry, are examined in predicting the complex wake of an infinite span thin normal flat plate with large pressure gradients at Reynolds number of 1200. This body represents a large array of Photovoltaics modules, where two edges of the plate dominate the flow. This study provided a benchmark for capabilities of conventional turbulence models that are commonly used for wind forecasting in the wind energy industry. The results obtained from Reynolds Averaged Navier-Stokes (RANS) k - ε , Reynolds Normalization Group (RNG) k - ε , RANS k - ω Shear Stress Transport (SST) and Reynolds Stress Model (RSM) were compared with existing Direct Numerical Simulations (DNS). The mean flow features and unsteady wake characteristics were used as testing criteria amongst these models. All turbulence models over-predicted the mean recirculation length and under-predicted the mean drag coefficient. The major differences between numerical results in predicting the mean recirculation length, mean drag and velocity gradients, leading to deficits in turbulence kinetic energy production and diffusion, hint at major difficulties in modeling velocity gradients and thus turbulence energy transport terms, by traditional turbulence models. Unsteadiness of flow physics and nature of eddy viscosity approximations are potential reasons. This hints at the deficiencies of these models to predict complex flows with large pressure gradients, which are commonly observed in wind and solar farms. The under-prediction of wind loads on PV modules and over-estimation of the recirculation length behind them significantly affects the efficiency and operational feasibility of solar energy systems.

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