scholarly journals Climatology of Three-Dimensional Eliassen–Palm Wave Activity Fluxes in the Northern Hemisphere Stratosphere from 1981 to 2020

Climate ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 124
Author(s):  
Indrė Gečaitė
Keyword(s):  
Northern Hemisphere ◽  
Extreme Values ◽  
Time Lag ◽  
Three Dimensional ◽  
Reanalysis Data ◽  
Wave Activity ◽  
Initial State ◽  
Eddy Heat Flux ◽  
Key Factor ◽  
Two Parameters

Based on the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) reanalysis data from 1981 to 2020, the climatological features of the vertical components of three-dimensional Eliassen–Palm (EP) wave activity fluxes (WAF) were investigated. The parameter is related to eddy heat flux and is a key indicator of the upward and downward propagation of quasi-stationary planetary-scale waves. Northern Hemisphere data from a 30 km height (or about a 10-hPa level) were used for the analysis. We evaluated the extreme values (daily maxima and minima) of the vertical WAFs, the probability of their recurrences, and their interannual and daily variability observed over the last four decades. The correlation between the upward EP WAF maxima and the 10-hPa stratosphere temperature anomalies were examined. The results show that very close relationships exist between these two parameters with a short time lag, but the initial state of the stratosphere is a key factor in determining the strength of these relationships. Moreover, trends over the last 40 years were evaluated. In this research, we did not find any significant changes in the extreme values of the vertical WAFs. Finally, the dominant spatial patterns of upward and downward extreme WAFs were evaluated. The results show that there are three main regions in the stratosphere where extremely intensive upward and downward WAFs can be observed.

scholarly journals Influence of Early Winter Upward Wave Activity Flux on Midwinter Circulation in the Stratosphere and Troposphere

2004 ◽  
Vol 17 (22) ◽  
pp. 4443-4452 ◽  
Author(s):  
Alexei Karpetchko ◽  
Grigory Nikulin
Keyword(s):  
Heat Flux ◽  
Reanalysis Data ◽  
Wave Activity ◽  
Heat Fluxes ◽  
Early Winter ◽  
Polar Night ◽  
Wave Refraction ◽  
Eddy Heat Flux ◽  
Wave Flux

Abstract Using NCEP–NCAR reanalysis data the authors show that the November–December averaged stratospheric eddy heat flux is strongly anticorrelated with the January–February averaged eddy heat flux in the midlatitude stratosphere and troposphere. This finding further emphasizes differences between early and midwinter stratospheric wave flux behavior, which has recently been found in long-term variations. Analysis suggests that the intraseasonal anticorrelation of stratospheric heat fluxes results from changes in the upward wave propagation in the troposphere. Stronger (weaker) upward wave fluxes in early winter lead to weaker (stronger) upward wave fluxes from the troposphere during midwinter. Also, enhanced equatorward wave refraction during midwinter (due to the stronger polar night jet) is associated with weak heat flux in the early winter. It is suggested that the effect of enhanced midwinter upward wave flux from the troposphere in the years with weak early winter heat flux overcompensates the effect of increased equatorward wave refraction in midwinter, leading to a net increase of midwinter upward wave fluxes into the stratosphere.

The evolution mechanisms of Ural blocking from the lens of local finite-amplitude wave activity budget analysis 

2021 ◽  
Author(s):  
Mengling Wang ◽  
Yang Zhang ◽  
Jian Lu
Keyword(s):  
Diabatic Heating ◽  
Activity Budget ◽  
Finite Amplitude ◽  
Reanalysis Data ◽  
Wave Activity ◽  
Amplitude Wave ◽  
Budget Analysis ◽  
Eddy Heat Flux ◽  
Formation And Evolution ◽  
Finite Amplitude Wave Activity

<p>Understanding the formation and evolution mechanisms of Ural blocking (UB) is of great importance for the prediction of UB and relevant extremes in east Asia. Using the 6-hourly ERA-Interim reanalysis data, this study quantifies the conservative and nonconservative processes in the lifecycle of UB through the lens of the hybrid Eulerian-Lagrangian local finite-amplitude wave activity (LWA) diagnostics. It is found that (i) as a wave activity source, eddy heat flux works to not only initiate the UB, but also prevent the wave activity of the blocking from dispersing downstream---the key characteristic of blocking; (ii) both the wave propagation and wave advection mechanisms are indispensable for the evolution of UB, playing a tug-of-war on the downstream development of wave activity; (iii) throughout the lifespan of UB, diabatic heating provides the most important damping mechanism for the wave activity both upstream and downstream.</p>

Vertical extent related characteristics of the explosive cyclones in the Northern Hemisphere: A 40-yr climatology study based on the ERA-I reanalysis

2020 ◽  
Author(s):  
Shenming Fu ◽  
Lizhi Jiang ◽  
Jianhua Sun
Keyword(s):  
Northern Hemisphere ◽  
Three Dimensional ◽  
Reanalysis Data ◽  
Dimensional System ◽  
Weather System ◽  
New Findings ◽  
Explosive Cyclones ◽  
Northern Atlantic ◽  
Northern Pacific ◽  
Three Dimensional System

<p>The explosive cyclone (EC), which is the most destructive subcategory of the extratropical cyclone, has been a research center for decades. Many key features of this type of cyclone have been shown, however, as a three-dimensional system, their vertical extents and associated important characteristics still remain vague. This study attempts to fill this vacancy by focusing on ECs’ vertical extents related features in the Northern Hemisphere on the basis of the ERA-I reanalysis data during a 40-yr period. Some new findings are reached: (i) overall, the EC is a type of deep weather system, as more than 63% of them reach an upmost level above 300 hPa, whereas only less than 12% of them maintain below 500 hPa during their whole life spans. (ii) ECs’ vertical extents show remarkable latitude dependent features (maximum vertical extents appear in the zone of 55oN-65oN), and they also show obvious seasonal changes, with the minimum vertical extents appeared in January. (iii) ECs’ maximum vertical extents show a significant positive correlation with their minimum central pressure, whereas, their maximum vertical extents show no obvious relationship to the ECs’ maximum deepening rates and maximum 10-m winds. (iv) in general, ECs over the northern Pacific Ocean have larger intensity, longer life spans, and thicker vertical extents than those of the ECs over the northern Atlantic Ocean.</p>

Sensitivity of the Stratospheric Circulation to the Latitude of Thermal Surface Forcing*

2011 ◽  
Vol 24 (20) ◽  
pp. 5397-5415 ◽  
Author(s):  
Barbara Winter ◽  
Michel S. Bourqui
Keyword(s):  
Surface Temperature ◽  
Northern Hemisphere ◽  
Ozone Concentration ◽  
Planetary Wave ◽  
Wave Generation ◽  
Wave Activity ◽  
High Latitudes ◽  
Thermal Forcing ◽  
Eddy Heat Flux ◽  
Low Latitudes

Abstract Using the chemistry climate model Intermediate General Circulation Model–Fast Stratospheric Ozone Chemistry (IGCM-FASTOC), the authors analyze the response in the Northern Hemisphere winter stratosphere to idealized thermal forcing imposed at the surface. The forcing is a 2-K temperature anomaly added to the control surface temperature at all grid points within a latitudinal window of 10° or 30°. The bandwise forcing is applied systematically throughout all latitudes of the Northern Hemisphere. Thermal forcing applied anywhere equatorward of 20°N, or continuously from the equator to 30°N, increases planetary-wave generation in the troposphere and enhances the flux of wave activity propagating vertically into the stratosphere. Consequently, a greater flux of wave activity breaks in the polar vortex, increasing the Brewer–Dobson circulation and leading to a warm anomaly in the polar stratosphere. Ozone concentration increases at high latitudes and decreases at low latitudes. Thermal surface forcing imposed between 30° and 60°N has the reverse effect—decreased planetary-wave generation in the lower troposphere and reduced vertically propagating wave flux entering the stratosphere—and leads to a stronger and colder vortex. Thermal forcing applied poleward of 60°N has little effect on the tropospheric mean state but nonetheless decreases the planetary-scale eddy heat flux from the surface to the tropopause, resulting in a sufficient decrease of the vertical flux of wave activity for the vortex to be anomalously strong and cold. When surface forcing is imposed only poleward of 30°N, ozone concentration decreases at high latitudes but is not affected at low latitudes. Combining the forcing in an equatorial and an extratropical band leads to a response similar to that of the equatorial forcing, demonstrating that the subtropical surface temperature changes determine the sign of the surface-driven response in the vortex.

Applications of Scanning Microscopy in Biomedical Research

1968 ◽  
Vol 26 ◽  
pp. 354-355
Author(s):  
T. L. Hayes
Keyword(s):  
Information Content ◽  
Biomedical Research ◽  
Biomedical Applications ◽  
Three Dimensional ◽  
Dental Enamel ◽  
Resolving Power ◽  
Whole Mount ◽  
Two Parameters ◽  
Content Information ◽  
Sectioned Tissue

Biomedical applications of the scanning electron microscope (SEM) have increased in number quite rapidly over the last several years. Studies have been made of cells, whole mount tissue, sectioned tissue, particles, human chromosomes, microorganisms, dental enamel and skeletal material. Many of the advantages of using this instrument for such investigations come from its ability to produce images that are high in information content. Information about the chemical make-up of the specimen, its electrical properties and its three dimensional architecture all may be represented in such images. Since the biological system is distinctive in its chemistry and often spatially scaled to the resolving power of the SEM, these images are particularly useful in biomedical research.In any form of microscopy there are two parameters that together determine the usefulness of the image. One parameter is the size of the volume being studied or resolving power of the instrument and the other is the amount of information about this volume that is displayed in the image. Both parameters are important in describing the performance of a microscope. The light microscope image, for example, is rich in information content (chemical, spatial, living specimen, etc.) but is very limited in resolving power.

scholarly journals Seasonal prediction of the boreal winter stratosphere

2021 ◽  
Author(s):  
Alice Portal ◽  
Paolo Ruggieri ◽  
Froila M. Palmeiro ◽  
Javier García-Serrano ◽  
Daniela I. V. Domeisen ◽  
...  
Keyword(s):  
Southern Oscillation ◽  
Polar Vortex ◽  
Seasonal Prediction ◽  
Wave Activity ◽  
Boreal Winter ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Eddy Heat Flux ◽  
Prediction Systems ◽  
Model Database

AbstractThe predictability of the Northern Hemisphere stratosphere and its underlying dynamics are investigated in five state-of-the-art seasonal prediction systems from the Copernicus Climate Change Service (C3S) multi-model database. Special attention is devoted to the connection between the stratospheric polar vortex (SPV) and lower-stratosphere wave activity (LSWA). We find that in winter (December to February) dynamical forecasts initialised on the first of November are considerably more skilful than empirical forecasts based on October anomalies. Moreover, the coupling of the SPV with mid-latitude LSWA (i.e., meridional eddy heat flux) is generally well reproduced by the forecast systems, allowing for the identification of a robust link between the predictability of wave activity above the tropopause and the SPV skill. Our results highlight the importance of November-to-February LSWA, in particular in the Eurasian sector, for forecasts of the winter stratosphere. Finally, the role of potential sources of seasonal stratospheric predictability is considered: we find that the C3S multi-model overestimates the stratospheric response to El Niño–Southern Oscillation (ENSO) and underestimates the influence of the Quasi–Biennial Oscillation (QBO).

scholarly journals The Changing Paradigm in the Treatment of Structural Heart Disease and the Need for the Interventional Imaging Specialist

2016 ◽  
Vol 11 (2) ◽  
pp. 135
Author(s):  
Nina C Wunderlich ◽  
Harald Küx ◽  
Felix Kreidel ◽  
Ralf Birkemeyer ◽  
Robert J Siegel ◽  
...  
Keyword(s):  
Heart Disease ◽  
Heart Diseases ◽  
Three Dimensional ◽  
Structural Heart Disease ◽  
Percutaneous Treatment ◽  
Interventional Imaging ◽  
Key Factor ◽  
Structural Heart Diseases ◽  
Specialist Standard ◽  
Contrast Ventriculography

Percutaneous interventions in structural heart diseases are emerging rapidly. The variety of novel percutaneous treatment approaches and the increasing complexity of interventional procedures are associated with new challenges and demands on the imaging specialist. Standard catheterisation laboratory imaging modalities such as fluoroscopy and contrast ventriculography provide inadequate visualisation of the soft tissue or three-dimensional delineation of the heart. Consequently, additional advanced imaging technology is needed to diagnose and precisely identify structural heart diseases, to properly select patients for specific interventions and to support fluoroscopy in guiding procedures. As imaging expertise constitutes a key factor in the decision-making process and in the management of patients with structural heart disease, the sub-speciality of interventional imaging will likely develop out of an increased need for high-quality imaging.

scholarly journals The Effect of Different Mixed Organic Solvents on the Properties of p(OPal-MMA) Gel Electrolyte Membrane for Lithium Ion Batteries

2018 ◽  
Vol 8 (12) ◽  
pp. 2587 ◽  
Author(s):  
Lanlan Tian ◽  
Mengkun Wang ◽  
Lian Xiong ◽  
Haijun Guo ◽  
Chao Huang ◽  
...  
Keyword(s):  
Specific Capacity ◽  
Mixed Solvents ◽  
Three Dimensional ◽  
Lithium Ion ◽  
Transference Number ◽  
Polymer Membrane ◽  
Electrochemical Performances ◽  
Electrolyte Membrane ◽  
Phase Inversion Technique ◽  
Key Factor

A solvent is a key factor during polymer membrane preparation, and it is directly related to application performance as a separator for lithium ion battery (LIB). In this study, different mixed solvents were employed to prepare polymer (p(OPal-MMA)) membranes by the phase inversion technique. The polymer membrane then absorbed liquid electrolytes to obtain gel electrolytes (GPEs). The surface morphologies and porosities of these membranes were investigated, and lithium ion transferences and electrochemical performances of these GPEs were also measured. The membrane displayed an interconnected three-dimensional framework structure with uniformly distributed pores when using DMF as a porogen. When combined with acetone as the component solvent, the prepared GPE displayed the largest lithium ion transference number (0.706), the highest porosity (42.6%) and ion conductivity (3.99 × 10−3 S/cm). Even when assembled as Li/GPE/LiFePO4 cell, it exhibited the highest initial specific capacity of 167 mAh/g and retained most capacity (162 mAh/g) after 50 cycles. The results presented here probably provide reference for choosing an appropriate mixed solvent in fabricating polymer membranes.

scholarly journals Identifying global patterns of stochasticity and nonlinearity in the Earth System

2016 ◽  
Author(s):  
Fernando Arizmendi ◽  
Marcelo Barreiro ◽  
Cristina Masoller
Keyword(s):  
Time Series ◽  
Extreme Values ◽  
Surface Air Temperature ◽  
Reanalysis Data ◽  
Earth System ◽  
Entropy Analysis ◽  
Solar Forcing ◽  
The Earth ◽  
Geographical Regions ◽  
Global Patterns

Abstract. By comparing time-series of surface air temperature (SAT, monthly reanalysis data from NCEP CDAS1 and ERA Interim) with respect to the top-of-atmosphere incoming solar radiation (the insolation), we perform a detailed analysis of the SAT response to solar forcing. By computing the entropy of SAT time-series, we also quantify the degree of stochasticity. We find spatial coherent structures which are characterized by high stochasticity and nearly linear response to solar forcing (the shape of SAT time-series closely follows that of the isolation), or vice versa. The entropy analysis also allows to identify geographical regions in which there are significant differences between the NCEP CDAS1 and ERA Interim datasets, which are due to the presence of extreme values in one dataset but not in the other. Therefore, entropy maps are a valuable tool for anomaly detection and model inter-comparisons.

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