Vertical Spectra Research Articles

Latitudinal and Seasonal Variations of Vertical Wave Number Spectra of Three‐Dimensional Winds Revealed by Radiosonde Observations

AbstractAiming at investigating the vertical wave number spectral features of three‐dimensional winds in the lower atmosphere as well as their latitudinal and seasonal variations, we analyzed 11 year (1998–2008) radiosonde data from 92 United States stations in the Northern Hemisphere. The spatiotemporal variation of the horizontal wind spectral amplitude agrees well with that of the inertial gravity wave energy, revealing that the observed horizontal wind spectra are mainly attributed to the inertial gravity waves. The horizontal wind spectral slope is systematically and climatologically less negative than the canonical value of −3. For the first time we found that the vertical wind spectrum is much shallower than the horizontal wind spectrum over a wide latitude region, with slopes varying in −1.1 to −0.2 (−0.6 to 0.1) in the troposphere (lower stratosphere). Besides the slopes, the height, latitudinal, and seasonal variations of the vertical wind spectral showed evident difference from those of the horizontal wind spectrum. These differences are due to the horizontal and vertical wind spectra that might be constituted mainly by low and high frequency waves, respectively. Both the horizontal wind and vertical wind spectra exhibit evident universal features, which are more prominent in the lower stratosphere than in the troposphere, where it is thought to be the main source region of gravity waves, implying that the dynamical processes in the wave propagation might be the main cause of the universal spectrum. The background wind was found to have significant impact on the horizontal wind spectrum but has only weak impact on the vertical wind spectrum.

Testing of the EPOS LHC, QGSJET01, QGSJETII-03 and QGSJETII-04 hadronic interaction models via help of the atmospheric vertical muon spectra

The recent results of the very precise measurements of the primary cosmic protons and helium nuclei energy spectra by AMS-02 and some rather accurate estimates of these energy spectra generated in SNR allow us to elaborate the new approximation of the pimary nucleon energy spectra. As the acuracy of this approximation is rather high we can use it to test various models of hadronic interactions with the help of atmospheric muon energy spectra. The atmospheric vertical muon energy spectra have been calcullated in terms of the EPOS LHC, QGSJET01, QGSJETII-03 and QGSJETII-04 models in the energy range 102 ÷ 105 GeV with help of the CORSIKA package and this new approximation of the primary nucleon spectrum. The comparison of calculations with the muon spectra observed by collaborations L3+Cosmic, LVD and MACRO has shown that all models predict approximately two times lower intensity of the muon energy spectra. As these muons are products of decays of the most energetic π± and K± mesons in the atmosphere, we can conclude that production of these π± and K± mesons is underestimated by EPOS LHC, QGSJET01, QGSJETII-03 and QGSJETII-04 models.

VULNERABILITY INDEX ASSESSMENT USING NEURAL NETWORKS (VIANN): A CASE STUDY OF NICOSIA, CYPRUS

Abstract. Many scholars have used microtremor applications to evaluate the vulnerability index. In order to reach fast and reliable results, microtremor measurement is preferred as it is a cost-effective method. In this paper, the vulnerability index will be reviewed by utilization of microtremor measurement results in Nicosia city. 100 measurement stations have been used to collect microtremor data and the data were analysed by using Nakamura’s method. The value of vulnerability index (Kg) has been evaluated by using the fundamental frequency and amplification factor. The results obtained by the artificial neural network (ANN) will be compared with microtremor measurements. Vulnerability Index Assessment using Neural Networks (VIANN) is a backpropagation neural network, which uses the original input microtremor Horizontal Vertical Spectrum Ratio (HVSR) spectrum set. A 3-layer back propagation neural network which contains 4096 input, 28 hidden and 3 output neurons are used in this suggested system. The output neurons are classified according to acceleration sensitivity zone, velocity zones, or displacement zones. The sites are classified by their vulnerability index values using binary coding: [1 0 0] for the acceleration sensitive zone, [0 1 0] for the velocity sensitive zone, and [0 0 1] for the displacement sensitive zone.

Vertical ductility demand and residual displacement of roof-type steel structures subjected to vertical earthquake ground motions

The vertical component of seismic ground motions (VGM) may induce severe responses in roof-type structures such as mega canopies, large floors, etc. This paper proposes a ductility-based approach for estimating the inelastic responses of roof-type steel structures under VGMs. Due to the pre-loaded gravity, a roof-type steel structure exhibits obvious asymmetric hysteresis properties in the vertical direction. Accordingly, this kind of structure could be idealized as “one-side yielding” systems which only yield in the lower side of vibration, wherein the gravity effect and the VGM effect positively super-positions with each other. Based on the idealized model, the vertical ductility demand spectra and the vertical residual displacement spectra for roof-type steel structures are computed using 53 recorded strong near-fault VGMs. Taking into account the vertical strength reduction factor and the vertical post-yielding stiffness ratio, a vertical ductility demand model in the μ-T format is proposed for roof-type steel structures under VGMs. Meanwhile, the vertical residual displacement model is derived from the vertical ductility demand model, since the vertical residual displacement could be computed as the peak vertical displacement subtracted by the recoverable elastic displacement. An application of these proposed models is given in the paper. The vertical seismic responses of a large-span steel floor under VGMs are predicted based on the proposed models, and the obtained results (including both the peak and the residual responses in the vertical direction) show good accuracy as compared with the results given by nonlinear response history analysis.

Seismic microzonation by using microtremor method in Pandan volcano, Bojonegoro, East Java

Pandan volcano geographically is located in the north of Madiun and Nganjuk district, and south Bojonegoro district. The status of this volcano is longer not active, but it still emerges hot spring in some areas. This research aims to understand the distribution of the natural frequency value, the amplification factor value, and the vulnerability index value by using mictrotremor horizontal to vertical spectrum ratio (HVSR) method, that is believed to have an important contribution to earthquake disaster mitigation. There are 19 measurement sites where geographically ranges between 7°26′36.60″–7°27′16.49″S and 111°46′31.76″– 111°47′11.98″E. The survey used portable seismograph 3-components SL07 SARA single station. For each site of measurement needs 30 minutes of ambient noise recording with a sampling rate of 100 Hz. The data processing was done by HVSR analysis method on Easy HVSR software. The natural frequency (fo) value ranges between 1,1 and 9,95 Hz, and amplification factor (Ag) value varies from 2,1 to 7,2. The vulnerability index (Kg) value ranging from 0,48 to 25,34. The highest risk index is located in the north part of the research area where have high potential to damage when the earthquake happens.

The low-lying doublet electronic excited states of ZrO2−: A symmetry adapted cluster–configuration interaction (SAC-CI) study

The low-lying doublet excited states of ZrO2− were studied using the SAC-CI method. The vertical excitation spectrum of ZrO2− was calculated and compared with that of TiO2−. Similar to that for TiO2−, ZrO2− also have a dipole-bound state. The ground electronic state (X2A1) and the excited states having bound characters (22A1, 12B1, and dipole-bound states) were optimized to C2v structures. The adiabatic electronic affinity of ZrO2 and the adiabatic excitation energies of the three bound excited states were obtained at the SAC-CI level.

Vertical spectra of stratified turbulence at large horizontal scales

Stably stratified turbulence is investigated with the aim of increasing our limited understanding of the vertical structure of this type of turbulent flow. For strongly stratified turbulence there ...

Simultaneous observation of gravity waves at PMC altitude from AIM/CIPS experiment and PANSY radar over Syowa (69°S, 39°E)

Simultaneous observation of gravity waves (GWs) in the polar summer mesosphere over Syowa (69°S, 39°E) by a ground-based radar and satellite instrument are presented. On 21 January 2016, at 2.3 UT, the CIPS instrument on the AIM satellite observed Polar Mesospheric Clouds (PMCs) with GW structures over Syowa. The orientation of the wave crests suggests north-west propagation direction. A periodogram analysis indicates GWs with horizontal wavelengths of 105 ± 5 and 60 ± 5 km. Cross-spectral analysis of the PANSY radar horizontal wind components at the same time, location, and altitude indicate two dominant waves with apparent periods of 15 and 9 h, with respective horizontal wavelengths of 100 ± 5 km and 302 ± 130 km. At the PMC altitude of ∼83 km, the mean zonal component of the vertical momentum flux spectra of the observed GWs is westward and the meridional component is northward. The comparable horizontal wavelengths of the 15 h wave observed by PANSY radar and the CIPS instrument, along with the agreement between the direction of vertical flux of horizontal momentum from PANSY, the propagation direction estimated from the cross-spectral analysis, and the orientation of the wave crests from CIPS i.e. north-west propagation direction suggests that the same wave is observed by both instruments. This simultaneous observation of the same wave by CIPS and PANSY radar provide a distinctive view of both the horizontal and vertical extent of a GW in the Antarctic summer mesosphere.

Research on Compilation Method of Multi-Axial Loading Spectrum for Cylindrical Shock Absorber

The main failure mode of cylindrical shock absorbers (CSAs) used by taxis in China’s Zhejiang Province is oil leakage because of a large horizontal force loaded on the cylinder wall by a questionnaire survey. The previous CSA durability bench test methods, which do not involve the interaction between horizontal load and vertical load and do not consider the user road spectrum, cannot simulate the real fatigue phenomena of it. In order to preferably reproduce the failure mode and accurately to predict the failure time of the CSA used in the area, a compilation method of multi-axial loading spectrum is proposed based on the road spectrum. The vertical loading spectrum is compiled by using the way of sine on sine, in which high frequency (HF) signal superimposed on low frequency (LF) signal. The LF is determined by the half-power bandwidth theory, which can reflect the power spectral density distribution of the random road spectrum. The HF is determined by the maximum line velocity principle to effectively reduce test time. The loading cycles and amplitudes of them are determined by using the rain-flow counting method. In addition, the horizontal loading force is taken into consideration in the multi-axial loading spectrum. To prove the validation and efficiency of the method described in this paper, the compiled multi-axial loading spectrum was used to conduct the durability bench test. The results show that the mean failure mileage of specimens is close to the mean mileage time of field samples. The failure modes of the specimens are the same as those of field samples. Thus the proposed method can be used as a reference for durability bench test of CSA. The test data can also be used to accurately study the reliability of CSA.

Global linear stability analysis of jets in cross-flow

The stability of low-speed jets in cross-flow (JICF) is studied using tri-global linear stability analysis (GLSA). Simulations are performed at a Reynolds number of 2000, based on the jet exit diameter and the average velocity. A time stepper method is used in conjunction with the implicitly restarted Arnoldi iteration method. GLSA results are shown to capture the complex upstream shear-layer instabilities. The Strouhal numbers from GLSA match upstream shear-layer vertical velocity spectra and dynamic mode decomposition from simulation (Iyer & Mahesh, J. Fluid Mech., vol. 790, 2016, pp. 275–307) and experiment (Megerian et al., J. Fluid Mech., vol. 593, 2007, pp. 93–129). Additionally, the GLSA results are shown to be consistent with the transition from absolute to convective instability that the upstream shear layer of JICFs undergoes between $R=2$ to $R=4$ observed by Megerian et al. (J. Fluid Mech., vol. 593, 2007, pp. 93–129), where $R=\overline{v}_{jet}/u_{\infty }$ is the jet to cross-flow velocity ratio. The upstream shear-layer instability is shown to dominate when $R=2$, whereas downstream shear-layer instabilities are shown to dominate when $R=4$.

Highly entangled photon pairs generated from the biexciton cascade transition in a quantum-dot–metal-nanoparticle hybrid system

The entanglement between photon pairs generated from the biexciton cascade transition in a semi- conductor quantum dot located in the vicinity of a metal nanoparticle is theoretically investigated. In the model scheme, the biexciton-exciton and exciton-ground state transitions are assumed to be coupled to two principal plasmon modes of orthogonal polarizations. For a broad spectral window, because the horizontal and vertical spectra are overlapped, the biexciton and exciton photons are degenerate in energy. This allows us to overcome the natural splitting between the intermediate exciton states. Moreover, the degree of entanglement depends on the geometrical parameters of the system. i.e., the radius of the metal nanoparticle and the distance between the quantum dot and the nanoparticle. The results reveal that such a hybrid system profoundly modifies the photon entanglement even in the absence of strong coupling between the emitter and the metal nanosphere.

Influence of vibronic contribution on light harvesting efficiency of NKX-2587 derivatives with oligothiophene as π-conjugated linker

Based on the NKX-2587 molecule we designed ten sensitizers with 1–10 thiophene moieties to investigate how the number of thiophene unit in the spacer influences the absorption spectra of sensitizer in dye sensitized solar cells (DSSCs). The parameters of short-circuit current density (Jsc), open circuit voltage (Voc), the light harvesting efficiency (LHE), injection driving force (∆Ginject), and transferred electron number (nc), were calculated and discussed in detail. Results indicated that the increasing of thiophene units makes for the enhancement of oscillator strengths (f), although the red shift of vertical electronic absorption spectra is small. For the designed sensitizers with 1–5 thiophene units, their ΔGinject and nc raise gradually with the increasing of thiophene number. However, for those sensitizers with 6–10 thiophene units, the ΔGinject and nc decrease continuously with the increasing of thiophene units. In order to study how the oligothiophene as π-conjugated linker affects light harvesting efficiency of DSSCs, the vibrationally resolved electronic spectra of five metal-free NKX-2587 derivatives with 1–5 thiophene units were simulated within the Franck-Condon approximation including the Herzberg-Teller and Duschinsky effects. The present theoretical results provided helpful guidance for understanding the sources of spectral intensities of dye molecules, and a valuable method for rational design of new molecules to improve the energy conversion efficiency (η) of DSSCs.

Erratum to: A model for predicting vertical component peak ground acceleration (PGA), peak ground velocity (PGV) and 5% damped pseudospectral acceleration (PSA) for Europe and the Middle East

In this study, we present a ground-motion model for the vertical component of peak ground acceleration, peak ground velocity, and 5% damped pseudo acceleration response spectra at periods ranging from 0.01 to 4 s. The vertical model is based on the ground-motion models previously developed for the horizontal component and vertical-to-horizontal ratio of ground motion by Akkar et al. (Bull Earthq Eng 12:359–387, 2014a; 517–547, 2014b) rather than on an independent regression analysis of strong-motion data available for Europe and the Middle East. The proposed ground-motion model includes formulations for the median values as well as for the aleatory within-event, between-event, and total standard deviation values of the vertical ground motion. We validate the proposed model by comparing it against the strong-motion database of Europe and the Middle East. Our vertical ground-motion model is applicable for moment magnitudes ranging from 4.0 to 8.0, for source-to-site distances ranging from 0 to 200 km, average shear-velocity down to 30 m (Vs30) values ranging from 150 to 1200 m/s and for reverse, normal and strike-slip styles of faulting as is the case for the underlying horizontal component and vertical-to-horizontal ratio ground-motion models of Akkar et al. (2014a, b). Within the scope of this study, a method to develop a vertical spectrum that is fully consistent with the corresponding horizontal uniform hazard spectrum is also proposed.

Digital soil map of the Ussuri River basin

On the basis of digital soil, topographic, and geological maps; raster topography model; forestry materials; and literature data, the digital soil map of the Ussuri River basin (24400 km2) was created on a scale of 1: 100000. To digitize the initial paper-based maps and analyze the results, an ESRI ArcGIS Desktop (ArcEditor) v.10.1 (http://www.esri.com) and an open-code SAGA GIS v.2.3 (System for Automated Geoscientific Analyses, http://www.saga-gis.org) were used. The spatial distribution of soil areas on the obtained digital soil map is in agreement with modern cartographic data and the SRTM digital elevation model (SRTM DEM). The regional soil classification developed by G.I. Ivanov was used in the legend to the soil map. The names of soil units were also correlated with the names suggested in the modern Russian soil classification system. The major soil units on the map are at the soil subtypes that reflect the entire vertical spectrum of soils in the south of the Far East of Russia (Primorye region). These are mountainous tundra soils, podzolic soils, brown taiga soils, mountainous brown forest soils, bleached brown soils, meadow-brown soils, meadow gley soils, and floodplain soils). With the help of the spatial analysis function of GIS, the comparison of the particular characteristics of the soil cover with numerical characteristics of the topography, geological composition of catchments, and vegetation cover was performed.

Role of large eddies in the breakdown of the Reynolds analogy in an idealized mildly unstable atmospheric surface layer

While the breakdown in similarity between turbulent transport of heat and momentum (or Reynolds analogy) is not disputed in the atmospheric surface layer (ASL) under unstably stratified conditions, the causes of this breakdown are still debated. One reason for the breakdown is differences between how coherent structures transport heat and momentum, and their differing responses to increasing instability. Monin—Obukhov Similarity Theory (MOST), which hypothesizes that only local length‐scales play a role in ASL turbulent transport, implicitly assumes that large‐scale structures are inactive, despite their large energy content. Widely adopted mixing‐length models also rest on this assumption in the ASL. The difficulty of characterizing low‐wavenumber turbulent motions with field measurements motivates the use of high‐resolution Direct Numerical Simulation (DNS), which is free from subgrid‐scale parametrizations and adhoc assumptions near the boundary. Despite the low Reynolds number and idealized geometry of the DNS, DNS‐estimated MOST functions are consistent with ASL field experiments, as are low‐frequency features of the spectra. Parsimonious spectral models for MO stability correction functions for momentum (φm) and heat (φh) are derived, based on idealized vertical velocity variance and buoyancy variance spectra fit to the corresponding DNS spectra. For φm, a spectral model, based only on local length‐scales, matches DNS and field measurements well. In contrast, for φh, the model is substantially biased unless contributions from larger length‐scales are also included. These results are supported by sensitivity analyses based on field measurements that are independent of the DNS. They show that ASL heat transport is not MO‐similar, even under mild stratification, and in the absence of entrainment, non‐stationarity and canopy effects. It further suggests that the breakdown of the Reynolds analogy is at least partially caused by the influence of large eddies on turbulent heat transport.

Response of greenhouse tomato to different vertical spectra of LED lighting under overhead high pressure sodium and plasma lighting

Different light spectra trigger different plant growth processes. Therefore, the optimum light spectrum for various plant growth processes such as leaf and fruit growth may be different. Greenhouse mini-cucumber (Cucumis sativus L.) is a tall crop, with most leaf growth occurring in the top and middle canopy while fruit growth occurs in the middle and bottom canopy. Therefore, optimized vertical light spectral distribution profiles could be developed for improving both vegetative and fruit growth. In this study, we investigated the effects of different vertical spectra of light-emitting diodes (LED) lighting under high-pressure sodium (HPS) and plasma overhead lighting on plant growth and fruit yield of mini-cucumber. The study was conducted from October 2014 to April 2015 in a large greenhouse divided into 4 sections (50 m2 growing area in each section). Two sections were installed with plasma overhead light and the other two sections with HPS light, with both of them providing the same amount of overhead light (165 μmol m-2 s-1). Four vertical LED regimes (the top far red with bottom blue; the top blue with bottom far red; the top far red with bottom red; the top red with bottom far red) were applied to 4 plots inside each of the 4 sections. The blue or red LED each provided 10 µmol m-2 s-1, while the far red LED provided 8 µmol m-2 s-1 of light. The vertical LED treatments resulted in more than a 10% difference in fruit yield despite the small amount of light, indicating that the vertical light distribution had a large influence on plant growth. Top blue LED reduced leaf size and plant height in the early growth period which reduced total fruit yield for the plants grown under plasma light but not under HPS. Far red LED placed at the top of the canopy increased fruit yield, in comparison to bottom canopy placement, for plants grown under plasma light. This study has demonstrated that vertical light spectral distribution can have a large influence on plant growth and development, and optimized light distribution should and can be developed for year-round greenhouse vegetable production with supplemental lighting.

Airborne Wind Lidar Measurements of Vertical and Horizontal Winds for the Investigation of Orographically Induced Gravity Waves

AbstractAirborne coherent Doppler wind lidar measurements, acquired during the Gravity Wave Life-Cycle (GW-LCYCLE) I field campaign performed from 2 to 14 December 2013 in Kiruna, Sweden, are used to investigate internal gravity waves (GWs) induced by flow across the Scandinavian Mountains. Vertical wind speed is derived from lidar measurements with a mean bias of less than 0.05 m s−1 and a standard deviation of 0.2 m s−1 by correcting horizontal wind projections onto the line-of-sight direction by means of ECMWF wind data. The horizontal wind speed and direction are retrieved from lidar measurements by applying a velocity–azimuth display scan and a spectral accumulation technique, leading to a horizontal resolution of about 9 km along the flight track and a vertical resolution of 100 m, respectively. Both vertical and horizontal wind measurements are valuable for characterizing GW properties as demonstrated by means of a flight performed on 13 December 2013 acquired during weather conditions favorable for orographic GW excitation. Wavelet power spectra of the vertical wind speed indicate that the horizontal GW wavelengths lay mainly between 10 and 30 km and that the GW amplitude above the mountain ridge decreases with increasing altitude. Additionally, the perturbations of the horizontal wind speed are analyzed, showing horizontal wavelengths in the excitation region of 100–125 km with upwind-tilted wave fronts. By means of elevation power spectra, it is revealed that vertical wind power spectra are dominated by the short-wave elevation part, whereas horizontal wind perturbations are dominated by the long-wave part.

Lidar observations of stratospheric gravity waves from 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 1. Vertical wavelengths, periods, and frequency and vertical wave number spectra

AbstractFive years of atmospheric temperature data, collected with an Fe Boltzmann lidar by the University of Colorado group from 2011 to 2015 at Arrival Heights, are used to characterize the vertical wavelengths, periods, vertical phase speeds, frequency spectra, and vertical wave number spectra of stratospheric gravity waves from 30 to 50 km altitudes. Over 1000 dominant gravity wave events are identified from the data. The seasonal spectral distributions of vertical wavelengths, periods, and vertical phase speeds in summer, winter, and spring/fall are found obeying a lognormal distribution. Both the downward and upward phase progression gravity waves are observed by the lidar, and the fractions of gravity waves with downward phase progression increase from summer ~59% to winter ~70%. The seasonal and monthly mean vertical wavelengths and periods exhibit clear seasonal cycles with vertical wavelength growing from summer ~5.5 km to winter ~8.5 km, and period increasing from summer ~4.5 h to winter ~6 h. Statistically significant linear correlations are found between the monthly mean vertical wavelengths/periods and the mean zonal wind velocities from 30 to 50 km. Assuming horizontal phase speeds independent of month, the monthly mean horizontal wavelengths, intrinsic periods, and group velocities are estimated for stratospheric gravity waves. The slopes of wave frequency spectra change from −1.9 at 30–60 km to −1.45 around 60–65 km. The vertical wave number spectra show the power spectral density at vertical wavelengths of 5–20 km decreasing from winter maximum to summer minimum. Several aforementioned features are observed for the first time in Antarctica.

The low-lying doublet electronic excited states of TiO2−: A symmetry adapted cluster–configuration interaction (SAC-CI) study

The low-lying doublet excited states of the singly charged TiO2 anion (TiO2−) were investigated by the SAC-CI method. The vertical excitation spectrum of TiO2− was calculated at the SAC-CI/aug-cc-pVTZ levels. The ground electronic state (X2A1) and the lowest two valence excited states (22A1 and 12B1) having bound characters were optimized to stable C2v structures. A dipole-bound state (2A1) was found and optimized to a C2v structure. The adiabatic energies of the 22A1, 12B1, and dipole-bound states were obtained.

Calculating vertical atmospheric muon energy spectra for energies ranging from 102 to 105 GeV

New calculations of the atmospheric vertical muon energy spectra for energies ranging from 102 to 105 GeV are performed using an original approach and the CORSIKA 7.4 software package. The intensity of the atmospheric muon flux calculated using the SIBYLL 2.1 and QGSJET II-03 models for muon energies of ~(103–105) GeV is 1.7 times lower than the intensity predicted by L3+Cosmic, MARO and LVD collaborations on the basis of experimental data. For the energy range of ~(102–103) GeV, this reduction is as high as ~2.2 for the QGSJET II-03 model; for the SIBYLL 2.1 model, it falls to 2.1. If we assume that the first generation of charged π± and K ± mesons makes the greatest contribution to the most energetic muon flux, the generation of mesons is underestimated by 1.7 times in the abovementioned models.