scholarly journals Transient Tropical Diabatic Heating and the Seasonal-Mean Response to ENSO

2015 ◽  
Vol 72 (5) ◽  
pp. 1891-1907 ◽  
Author(s):  
Erik T. Swenson ◽  
David M. Straus
Keyword(s):  
Diabatic Heating ◽  
Grid Point ◽  
Low Frequency ◽  
Setup Time ◽  
Atmospheric Model ◽  
Frequency Component ◽  
Meridional Wind ◽  
Ensemble Member ◽  
Boreal Winter ◽  
Time Step

Abstract Boreal winter simulations of the Community Atmospheric Model, version 4.0, were carried out using observed sea surface temperature (SST) fields from the three El Niño events of 1982/83, 1991/92, and 1997/98 [control (CTL) runs] and from observed climatology (CLIM run). In each case, 50 ensemble members were run (1 November–31 March). The diabatic heating Q at every grid point, level, and day of the CTL runs in the Indo-Pacific region was stored and used in four additional suites of experiments, each of which parallels the appropriate CTL suite. In each suite, Q generated by the model is replaced by a specified subset of Q at every time step, grid point, and level spanning the Indo-Pacific. The Q subsets consist of the seasonal ensemble-CTL-mean Q for each ensemble member (suite FIX), the seasonal-mean Q from the appropriate ensemble member of the CTL (suite EFIX), the seasonal mean plus low-frequency component of Q (suite ESUBFIX), and the daily means of Q (suite DAYFIX). The midlatitude ENSO anomalies of the seasonal-mean upper-level height field and time-filtered meridional wind variance are enhanced in the FIX, EFIX, and ESUBFIX suites, with little change in patterns, compared to CTL anomalies. The enhancements have a smaller magnitude in ESUBFIX and especially in DAYFIX; qualitative differences are seen in DAYFIX. These differences are due to (i) the required setup time for midlatitude response, (ii) the altered relationship between vertical structure and vertically integrated heating, and (iii) the lack of midlatitude interactive influence on tropical heating in the experiments.

Forcing Processes of the Summertime Circumglobal Teleconnection Pattern in a Dry AGCM

2010 ◽  
Vol 23 (8) ◽  
pp. 2093-2114 ◽  
Author(s):  
Soichiro Yasui ◽  
Masahiro Watanabe
Keyword(s):  
Eastern Mediterranean ◽  
Eastern Mediterranean Region ◽  
Low Frequency ◽  
Atmospheric Model ◽  
Meridional Wind ◽  
Reanalysis Data ◽  
Teleconnection Pattern ◽  
Boreal Summer ◽  
Potential Predictability ◽  
Circumglobal Teleconnection

Abstract To better understand the predictability of the wavelike circumglobal teleconnection (CGT) pattern prevailing during boreal summer, two sets of experiments are performed using a nonlinear dry atmospheric model. Each experiment consists of a 10-member ensemble of 26-yr integrations driven by the diabatic heating derived from reanalysis data: one with the monthly climatological mean heating (CLIM) and the other with the monthly heating for 1979–2004 (HIST). Both do well in reproducing the observed summer mean state, as well as the low-frequency variance distribution. The CGT pattern identified in the monthly meridional wind anomalies at 200 hPa shows zonally oriented wave packets over Eurasia. The simulated CGT has a nearly identical phase structure with the observations and indicates little difference between the CLIM and HIST results. While this indicates that the origin of CGT lies in the internal dry dynamics, the ensemble mean of the CGT in HIST is partly controlled by the slow variation in the heating field, as indicated by the high potential predictability of the simulated CGT pattern. Diagnoses using the linearized model demonstrate that the heating anomaly most responsible for the CGT-like steady response is located over the eastern Mediterranean region, where the heating may be coupled with the CGT pattern. In addition to the heating near the CGT, remote heating and cooling anomalies over North America and equatorial Africa are found to be effective at exciting stationary Rossby waves trapped on the Atlantic and Asian jets. It is thus suggested that the mechanisms generating the heating anomalies over these regions are the key to the predictability of the CGT pattern.

The Lightning Electromagnetic Pulse Coupling Effect Inside the Shielding Enclosure With Penetrating Wire

Frequenz ◽  
2017 ◽  
Vol 71 (11-12) ◽  
Author(s):  
Xue Jiao ◽  
Bo Yang
Keyword(s):  
Electromagnetic Pulse ◽  
Coupling Effect ◽  
Fdtd Method ◽  
Current Source ◽  
Low Frequency ◽  
Frequency Component ◽  
Lightning Current ◽  
Proper Size ◽  
Practical Engineering ◽  
Difference Time

AbstractTo study the lightning electromagnetic pulse (LEMP) coupling and protection problems of shielding enclosure with penetrating wire, we adopt the model with proper size which is close to the practical engineering and the two-step finite-difference time-domain (FDTD) method is used for calculation in this paper. It is shown that the coupling voltage on the circuit lead inside the enclosure increases about 34 dB, when add 1.0 m long penetrating wire at the aperture, comparing with the case without penetrating wire. Meanwhile, the waveform, has the same wave outline as the lightning current source, shows that the penetrating wire brings a large number of low frequency component into the enclosure. The coupling effect in the enclosure will reduce greatly when penetrating wire has electrical connection with the enclosure at the aperture and the coupling voltage increase only about 12 dB than the case without penetrating wire. Moreover, the results show that though the waveguide pipe can reduce the coupling effect brought by the penetrating wire, the exposing part of penetrating wire can increase the coupling when the penetrating wire outside the enclosure is longer than the waveguide pipe and the longer the exposing part is, the stronger the coupling is.

Low-frequency component electric microfield distributions in plasmas governed by W. Ebeling potential

2021 ◽  
Author(s):  
Sara Kobbi ◽  
Salima Guerricha ◽  
Smaïl Chihi ◽  
Abdallah Bekkouche ◽  
Mohammed Tayeb Meftah
Keyword(s):  
Low Frequency ◽  
Frequency Component

scholarly journals Electron acoustic solitons in the Earth's magnetotail

2004 ◽  
Vol 11 (2) ◽  
pp. 215-218 ◽  
Author(s):  
S. G. Tagare ◽  
S. V. Singh ◽  
R. V. Reddy ◽  
G. S. Lakhina
Keyword(s):  
Electron Beam ◽  
Small Amplitude ◽  
Low Frequency ◽  
Frequency Component ◽  
Magnetized Plasma ◽  
Cold Electron ◽  
Ion Plasma ◽  
Electron Acoustic ◽  
Two Temperature ◽  
Perpendicular Polarization

Abstract. Small amplitude electron - acoustic solitons are studied in a magnetized plasma consisting of two types of electrons, namely cold electron beam and background plasma electrons and two temperature ion plasma. The analysis predicts rarefactive solitons. The model may provide a possible explanation for the perpendicular polarization of the low-frequency component of the broadband electrostatic noise observed in the Earth's magnetotail.

scholarly journals The Tangential Force Affecting the Radial Baffles in a Stirred Vessel: Analysis of the Macro-instability Related Component

10.14311/450 ◽  
2003 ◽  
Vol 43 (4) ◽  
Author(s):  
P. Hasal ◽  
I. Fořt ◽  
J. Kratěna
Keyword(s):  
Experimental Data ◽  
Spectral Analysis ◽  
Tangential Force ◽  
Low Frequency ◽  
Frequency Component ◽  
Relative Magnitude ◽  
Tangential Component ◽  
Vertical Position ◽  
Total Force ◽  
Rushton Turbine

Experimental data obtained by measuring the tangential component of the force affecting radial baffles in a flat-bottomed cylindrical mixing vessel stirred with a Rushton turbine impeller is analysed. Spectral analysis of the experimental data demonstrated the presence of its macro-instability (MI) related low-frequency component embedded in the total force. Two distinct dimensionless frequencies (both directly proportional to the impeller speed of rotation N) of the occurence of the MI component were detected: a lower frequency of approximately 0.025N and a higher frequency of about 0.085N. The relative magnitude QMI of the MI-related component of the total tangential force was evaluated by a combination of proper orthogonal decomposition (POD) and spectral analysis. The values of magnitude QMI varied in the interval [rom approximately 0.05 to 0.30. The magnitude QMI takes maximum values at low Reynolds number values (in laminar and transitional regions). In the turbulent region (ReM >20000) the QMI value is low and practically constant. The dependence oj the QMI values on vertical position in the vessel is only marginal. The results suggest that the magnitude of the MI component of the force is significantly influenced by the liquid viscosity and density.

scholarly journals Impaired vagal activity to meal in patients with functional dyspepsia and delayed gastric emptying

2017 ◽  
Vol 46 (2) ◽  
pp. 792-801 ◽  
Author(s):  
W-J Guo ◽  
S-K Yao ◽  
Y-L Zhang ◽  
S-Y Du ◽  
H-F Wang ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Gastric Emptying ◽  
Functional Dyspepsia ◽  
Delayed Gastric Emptying ◽  
Low Frequency ◽  
Treatment Method ◽  
Frequency Component ◽  
High Frequency Component ◽  
Vagal Activity ◽  
Nervous Function

Objective This study was performed to investigate impaired vagal activity to meal in patients with functional dyspepsia (FD) with delayed gastric emptying (GE). Methods Eighty-five patients were studied. GE parameters, including those in the overall and proximal stomach, were measured by GE functional tests at the Department of Nuclear Medicine. Autonomic nervous function was tested by spectral analysis of heart rate variability (HRV). The vagal activity and sympathetic activity were analyzed by recording the power in the high-frequency component (HF), low-frequency component (LF), and LF/HF ratio. Results Overall and proximal GE were delayed in 47.2% and 50.9% of the patients, respectively. Spectral analysis of HRV showed that the HF in patients with delayed proximal GE was significantly lower and that the LF/HF ratio was significantly higher than those in patients with normal proximal GE after a meal. Conclusion Delayed proximal GE might be caused by disrupted sympathovagal balance as a result of decreased vagal activity after a meal. Improvement in vagal activity may constitute an effective treatment method for patients with FD.

The Influence of Air-Bearing Surface Geometry on the Dynamics of Sliders

1992 ◽  
Vol 114 (1) ◽  
pp. 26-31 ◽  
Author(s):  
M. Suk ◽  
T. Ishii ◽  
D. Bogy
Keyword(s):  
Surface Defect ◽  
Laser Interferometer ◽  
Low Frequency ◽  
Frequency Component ◽  
Flying Height ◽  
Disk Drives ◽  
Bearing Surface ◽  
Surface Geometry ◽  
Spacing Variation ◽  
Slider Motion

We investigate the influence of crown on slider dynamics during the takeoff stages of disk drives using the multi-channel laser interferometer. We show that a two-dimensional analysis of slider dynamics during takeoff/landing cannot explain all the observed phenomena. We also examine the crown effect on slider motion while it is flying on a thin film disk with a crater-like surface defect. Finally, we measure the spacing variation of the slider as a function of disk speed. It is observed that the initial motion of negative crown sliders during takeoff can be quite similar to positive crown sliders, although the process is quite different. Furthermore, the results suggest that the negative crown sliders may lead to more disk wear due to longer sliding distances. We observed that during steady flying conditions the craterlike surface defect on the disk produced significantly larger motions for negative crown sliders than positive crown sliders. Lastly, we found that both the waveform and magnitude of the low frequency component of the spacing fluctuation is independent of the slider flying height.

Research on Combined Prediction Model for Busy Telephone Traffic

2014 ◽  
Vol 610 ◽  
pp. 789-796
Author(s):  
Jiang Bao Li ◽  
Zhen Hong Jia ◽  
Xi Zhong Qin ◽  
Lei Sheng ◽  
Li Chen
Keyword(s):  
Prediction Model ◽  
Prediction Accuracy ◽  
Low Frequency ◽  
Prediction Method ◽  
Pso Algorithm ◽  
Frequency Component ◽  
Least Square ◽  
High Frequency Component ◽  
Support Vector ◽  
Telephone Traffic

In order to improve the prediction accuracy of busy telephone traffic, this study proposes a busy telephone traffic prediction method that combines wavelet transformation and least square support vector machine (lssvm) model which is optimized by particle swarm optimization (pso) algorithm. Firstly, decompose the pretreatment of busy telephone traffic data with mallat algorithm and get low frequency component and high frequency component. Secondly, reconfigure each component and use pso_lssvm model predict each reconfigured one. Then the busy telephone traffic can be achieved. The experimental results show that the prediction model has higher prediction accuracy and stability.

scholarly journals Synoptic-Scale Variability and Its Relationship with Total Ozone and Antarctic Vortex Displacements

2005 ◽  
Vol 133 (8) ◽  
pp. 2374-2386 ◽  
Author(s):  
Paula K. Vigliarolo ◽  
Carolina S. Vera ◽  
Susana B. Díaz
Keyword(s):  
South America ◽  
Total Ozone ◽  
Lower Stratosphere ◽  
Meteorological Data ◽  
Atmospheric Model ◽  
Meridional Wind ◽  
Department Of Energy ◽  
Synoptic Scale ◽  
Austral Spring ◽  
Anomaly Pattern

Abstract The main synoptic-scale circulation anomaly pattern over extratropical South America during the austral spring (September–November) is identified by means of rotated extended empirical orthogonal function techniques, applied to the meridional wind perturbation time series at 300 hPa. The dataset is based on 15 spring seasons (1979–93) of meteorological data from the National Centers for Environmental Prediction–Department of Energy Atmospheric Model Intercomparison Project version-2 daily averaged reanalyses, given in 17 vertical levels from 1000 to 10 hPa. The total-ozone daily measurements for the same period are from the Total Ozone Mapping Spectrometer instrument (version 7). The principal synoptic-scale anomaly pattern is associated with an anticyclone–cyclone pair evolving eastward along subpolar latitudes (and hence it is termed the subpolar mode), with a typical length scale of 5000 km and a phase velocity of 8 m s−1. The subpolar-mode waves, which display the main characteristics of midlatitude baroclinic waves, typically maximize near or above the tropopause and propagate upward into the lower stratosphere, showing large amplitudes even at 50 hPa and above. Subpolar-mode-related circulation anomalies are found to be responsible for large total-ozone daily fluctuations near southern South America and nearby regions. In the positive phase of the subpolar mode, total-ozone fluctuations, which are negative, adopt a sigmoid structure, with a zonal scale as large as the anticyclone–cyclone pair. Moreover, it is herein shown that the associated anticyclone produces a local ozone-column decrease to the north and east of its center, due to adiabatic uplift of air parcels in the upper troposphere and lower stratosphere. At the same time, the downstream cyclonic disturbance is responsible for large negative total-ozone anomalies to the west and south of its center. As the cyclone develops in the lower stratosphere, it promotes the northward incursion of the Antarctic vortex up to about 55°S, along with air masses of highly depleted ozone levels.

scholarly journals Influence of the 2015–2016 El Niño on the record-breaking mangrove dieback along northern Australia coast

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Abhik ◽  
Pandora Hope ◽  
Harry H. Hendon ◽  
Lindsay B. Hutley ◽  
Stephanie Johnson ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Low Frequency ◽  
Multiple Linear Regression Model ◽  
Frequency Component ◽  
Enso Cycle ◽  
Northern Australia ◽  
Climate Conditions

AbstractThis study investigates the underlying climate processes behind the largest recorded mangrove dieback event along the Gulf of Carpentaria coast in northern Australia in late 2015. Using satellite-derived fractional canopy cover (FCC), variation of the mangrove canopies during recent decades are studied, including a severe dieback during 2015–2016. The relationship between mangrove FCC and climate conditions is examined with a focus on the possible role of the 2015–2016 El Niño in altering favorable conditions sustaining the mangroves. The mangrove FCC is shown to be coherent with the low-frequency component of sea level height (SLH) variation related to the El Niño Southern Oscillation (ENSO) cycle in the equatorial Pacific. The SLH drop associated with the 2015–2016 El Niño is identified to be the crucial factor leading to the dieback event. A stronger SLH drop occurred during austral autumn and winter, when the SLH anomalies were about 12% stronger than the previous very strong El Niño events. The persistent SLH drop occurred in the dry season of the year when SLH was seasonally at its lowest, so potentially exposed the mangroves to unprecedented hostile conditions. The influence of other key climate factors is also discussed, and a multiple linear regression model is developed to understand the combined role of the important climate variables on the mangrove FCC variation.

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