On tridimensional rip current modeling

A potent mechanism for the generation of low-frequency atmospheric variability on vortex basic states consisting of a single potential vorticity jump, or contour, separating two regions of uniform equivalent barotropic potential vorticity is described. Such basic states represent in a simple manner the potential vorticity distribution of the extratropical upper troposphere. It is shown that the group velocity for stationary waves propagating on such states can vanish for realistic zonal variations in the basic-state flow along the vortex edge, leading to local exponential disturbance growth due to the accumulation of wave action. Further, pseudo-energy stability criteria are derived that suggest that exponentially growing global disturbances are possible for sufficiently strong zonal variations in the flow along the vortex edge. These predictions are examined using linear and nonlinear initial value problem calculations. For wavenumber-1 flow variations in the basic-state zonal flow along the vortex edge, no global instability occurs. However, strong local disturbance growth in response to weak stationary forcing does occur and can lead to irreversible deformation of the vortex. For wavenumber-2 and higher variations in the basic-state zonal flow along the vortex edge, global instability occurs if the stability criteria is violated. These instabilities have peak dimensional e-folding times on the order of one week, with faster growth rates corresponding to stronger zonal variations in the flow along the vortex edge. Quantization of the zonal scale of amplifying disturbances occurs, indicating disturbance resonance with the underlying zonal variations in the basic-state flow along the vortex edge. In the nonlinear regime, longer wavelength disturbances lead to large amplitude periodic fluctuations of the vortex. Intermediate wavelength disturbances are shown to yield suprisingly realistic blocking events, while short wavelength disturbances saturate at amplitudes too small to change the overall structure of the vortex. The pervasiveness of instability in this simple system suggests similar processes may be important for blocking transitions and the generation of low-frequency variability in the extratropical atmosphere. Preliminary results from the National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis show that the climatological 330-K isentropic potential vorticity is accurately characterized as the time average of a fluctuating single-contour vortex. Wave action conservation on basic states constructed using dynamical fields on the 330-K isentropic surface reproduces observed shifts in low-frequency variability that occur during the El Niño cycle. Further, these shifts lead to transient-driven time mean flow anomalies that have a teleconnection pattern-like structure, despite the fact that meridional propagation of waves is forbidden in this system. The ability of this system to accurately simulate diverse atmospheric phenomena as well as explain certain aspects of upper-tropospheric dynamics suggests that it may provide a powerful new paradigm with which to view low-frequency dynamics in the climate system.

[This corrects the article DOI: 10.1371/journal.pone.0204267.].

Three-dimensional linearized nonlinear electromagnetic inversion is developed for revealing the subsurface conductivity structure using isolated very low frequency (VLF) and VLF-resistivity anomalies due to conductors that may be arbitrarily directed towards the measuring profiles and the VLF transmitter. We described the 3D model using a set of variables in terms of geometric and physical parameters. These model parameters were then optimized (parametric inversion) to obtain their best estimates to fit the observations. Two VLF transmitters, i.e., the Hx, Ey (“E”) and the Hy, Ex (“H”) polarizations, respectively, can be considered jointly in inversion. After inverting several noise-free and noisy synthetic data, the results revealed that the estimated model parameters and the functionality of the approach were very good and reliable. The inversion procedure also worked well for the field data. The reliability and validity of the results after the field data inversion have been checked using data from a shear zone associated with uranium mineralization.

The mechanisms generating high- frequency (HF) and low-frequency (LF) blood pressure variability (BPV) are reasonably well understood. However, little is known about the origin of very low-frequency (VLF) BPV. We tested the hypothesis that VLF BPV is generated by L-type Ca(2+) channel-dependent mechanisms. In conscious rats, arterial blood pressure was recorded during control conditions (n = 8) and ganglionic blockade (n = 7) while increasing doses (0.01-5.0 mg.100 micro l(-1).h(-1)) of the L-type Ca(2+) channel blocker nifedipine were infused intravenously. VLF (0.02-0.2 Hz), LF (0.2-0.6 Hz), and HF (0.6-3.0 Hz) BPV were assessed by spectral analysis of systolic blood pressure. During control conditions, nifedipine caused dose-dependent declines in VLF and LF BPV, whereas HF BPV was not affected. At the highest dose of nifedipine, VLF BPV was reduced by 86% compared with baseline, indicating that VLF BPV is largely mediated by L-type Ca(2+) channel-dependent mechanisms. VLF BPV appeared to be relatively more dependent on L-type Ca(2+) channels than LF BPV because lower doses of nifedipine were required to significantly reduce VLF BPV than to reduce LF BPV. Ganglionic blockade markedly reduced VLF and LF BPV and abolished the nifedipine-induced dose-dependent declines in VLF and LF BPV, suggesting that VLF and LF BPV require sympathetic activity to be evident. In conclusion, VLF BPV is largely mediated by L-type Ca(2+) channel-dependent mechanisms. We speculate that VLF BPV is generated by myogenic vascular responses to spontaneously occurring perturbations of blood pressure. Other factors, such as sympathetic nervous system activity, may elicit a permissive effect on VLF BPV by increasing vascular myogenic responsiveness.

Previously, we demonstrated that very low-frequency (VLF) blood pressure variability (BPV) depends on voltage-gated L-type Ca(2+)-channels, suggesting that autoregulation of blood flow and/or myogenic vascular function significantly contributes to VLF BPV. To further substantiate this possibility, we tested the hypothesis that the frequency response characteristic of whole body autoregulation of blood flow is consistent with the frequency range of VLF BPV (0.02-0.2 Hz) in rats. In anesthetized rats (n = 11), BPV (0.016-0.5 Hz) was induced by computer-regulated cardiac pacing while blood pressure, heart rate, and cardiac output (CO) were recorded during control conditions (NaCl, 1 ml/h iv) and during alpha(1)-adrenergic receptor stimulation (phenylephrine, 1 mg.ml(-1).h(-1) iv) that has been reported to facilitate myogenic vascular function. Baroreceptor-heart rate reflex responses were elicited to confirm a functional baroreflex despite anesthesia. During control conditions, transfer function analyses between mean arterial pressure (MAP) and CO, and between MAP and total vascular conductance (CO/MAP) indicated autoregulation of blood flow at 0.016 Hz, passive vascular responses between 0.033 and 0.2 Hz, and vascular responses compatible with baroreflex-mediated mechanisms at 0.333 and 0.5 Hz. Stimulation of alpha(1)-adrenergic receptors extended the frequency range of autoregulation of blood flow to frequencies up to 0.033 Hz. In conclusion, depending on sympathetic vascular tone, whole body autoregulation of blood flow operates most effectively at frequencies below 0.05 Hz. This frequency range overlaps with the lower end of the frequency band of VLF BPV in rats. Baroreceptor reflex-like mechanisms contribute to LF (0.2-0.6 Hz) but not VLF BPV-induced vascular responses.

A new framework for multi-site stochastic rainfall generator based on empirical orthogonal function analysis and Hilbert-Huang transform

<strong class="journal-contentHeaderColor">Abstract.</strong> The Tropical Pacific Ocean is characterized by its dominant zonal flow, strong climate dependence on the El Ni&ntilde;o Southern Oscillation (ENSO) and abundant tuna stocks. Tuna fisheries in the West and Central Pacific Ocean accounted for 55 % of world-wide tuna catch in 2019 and are one of the main sources of income in many Pacific island nations. One of the dominant fishing methods in this region relies on the use of drifting Fish Aggregating Devices (dFADs): rafts with long underwater appendages (on average 50 m deep) that attract and aggregate fish. Although currents such as the North Equatorial Countercurrent (NECC) and South Equatorial Current (SEC) in the tropical Pacific Ocean vary strongly with ENSO, little is known about the impact of this variability in flow on dFAD dispersion. In this study, virtual Lagrangian particles are tracked for the period 2006 to 2021 over the domain in a 3D hydrodynamic model and are advected in simulations with only surface flow as well as simulations using a depth-averaged horizontal flow over the upper 50 meters. The particle trajectories are used to determine zonal displacements, eddy-like behaviour and ENSO variability for drifters that are subjected to either surface or depth-averaged currents. It was found that virtual particles that are advected by only surface flow are displaced up to 35 % farther than those subjected to a depth-averaged flow, but no other major differences are found in dispersion patterns. Strongest correlations between ENSO and dFAD dispersion for the assessed variables were found in the West Pacific Ocean, with Pearson correlation coefficients up to 0.59 for dFAD displacement. Connections between ENSO and eddy-like behaviour were found in the western part of the SEC, indicating more circulation and meandering during el Ni&ntilde;o. These findings may be useful for improving sustainable deployment strategies during ENSO events, and understanding the ocean processes driving the distribution of dFADs.

<strong class="journal-contentHeaderColor">Abstract.</strong> The Tropical Pacific Ocean is characterized by its dominant zonal flow, strong climate dependence on the El Ni&ntilde;o Southern Oscillation (ENSO) and abundant tuna stocks. Tuna fisheries in the West and Central Pacific Ocean accounted for 55 % of world-wide tuna catch in 2019 and are one of the main sources of income in many Pacific island nations. One of the dominant fishing methods in this region relies on the use of drifting Fish Aggregating Devices (dFADs): rafts with long underwater appendages (on average 50 m deep) that attract and aggregate fish. Although currents such as the North Equatorial Countercurrent (NECC) and South Equatorial Current (SEC) in the tropical Pacific Ocean vary strongly with ENSO, little is known about the impact of this variability in flow on dFAD dispersion. In this study, virtual Lagrangian particles are tracked for the period 2006 to 2021 over the domain in a 3D hydrodynamic model and are advected in simulations with only surface flow as well as simulations using a depth-averaged horizontal flow over the upper 50 meters. The particle trajectories are used to determine zonal displacements, eddy-like behaviour and ENSO variability for drifters that are subjected to either surface or depth-averaged currents. It was found that virtual particles that are advected by only surface flow are displaced up to 35 % farther than those subjected to a depth-averaged flow, but no other major differences are found in dispersion patterns. Strongest correlations between ENSO and dFAD dispersion for the assessed variables were found in the West Pacific Ocean, with Pearson correlation coefficients up to 0.59 for dFAD displacement. Connections between ENSO and eddy-like behaviour were found in the western part of the SEC, indicating more circulation and meandering during el Ni&ntilde;o. These findings may be useful for improving sustainable deployment strategies during ENSO events, and understanding the ocean processes driving the distribution of dFADs.

Using a new functional analysis tool, multiscale window transform (MWT), and the MWT-based localized multiscale energetics analysis and canonical transfer theory, this study reconstructs the Kuroshio system on three scale windows, namely, the mean flow window, the interannual-scale (low-frequency) window, and the transient eddy window, and investigates the climatological characteristics of the intricate nonlinear interactions among these windows. Significant upscale energy transfer is observed east of Taiwan, where the mean Kuroshio current extracts kinetic energy from both the interannual and eddy windows. It is found that the canonical transfer from the interannual variability is an intrinsic source that drives the eddy activities in this region. The multiscale variabilities of the Kuroshio in the East China Sea (ECS) are mainly controlled by the interaction between the mean flow and the eddies.The mean flow undergoes mixed instabilities (i.e., both barotropic and baroclinic instabilities) in the southern ECS, while it is barotropically stable but baroclinically unstable to the north. The multiscale interactions are found to be most intense south of Japan, where strong mixed instabilities occur; both the canonical transfers from the mean flow and the interannual scale are important mechanisms to fuel the eddies. It is also found that the interannual-scale energy mainly comes from the barotropically unstable jet, rather than the upscale energy transfer from the high frequency eddies.

A method to rapidly construct 3D canopy scenes for maize and their spectral response evaluation

A pilot study of the effects of suboccipital fascial release on heart rate variability in workers in the clothing industry: Randomized clinical trial

The potential of the Madden-Julian Oscillation (MJO) to influence the climate and weather in both tropical and extratropical regions is of utmost importance for the global warming and climate change discussion. In this context, understanding how the MJO responds to the warming of the planet is a necessary step to build our physical comprehension on the way in which global warming influences extreme events of precipitation and temperature fields. Here we address the issue of the MJO response to global warming by means of a toy model of the MJO activity based on a single nonlinear triad interaction involving two convectively coupled equatorial wave modes, namely a Rossby and a Kelvin wave, and a barotropic Rossby mode. The two equatorial modes are known to play an important role in the planetary-scale circulation features associated with the MJO within the tropics, while the barotropic Rossby mode is related to its tropical-extratropical teleconnection. In addition, since moisture convergence is also known to play an important role in the MJO dynamics, here we mimic this effect by representing the coupling between the equatorial waves and moist convection in terms of the wave-CISK formulation. We also analyze in this formulation the role of the diurnal cycle of the moisture field, which can resonantly couple the equatorial Rossby mode of the triad with a high-frequency inertio-gravity wave. The inertio-gravity mode is thought of as representing the high-frequency convective systems embedded in the MJO. The effect of global warming is analyzed by changing the maximum value of the moisture field. The results show that an enhanced moisture can allow the equatorial wave modes to get in resonance with the barotropic Rossby mode, making the wave triad to undergo stronger energy modulations. This stronger energy modulation of the triad interaction might suggest a stronger MJO activity under a moister (warmer) environment. Also, our results indicate that an increased moisture content renders possible the MJO low frequency envelope to excite a high frequency gravity mode. We further show by changing the amplitude of gravity mode that the energy modulation of the triad becomes more intense, with an enhanced back and forth energy transfer between the equatorial gravity and Rossby modes, affecting also the kelvin wave. This indicates a strong necessity of a better representation of gravity waves in GCMs in order to properly simulate the effect of global warming on the MJO.

Interannual variation is a year-to-year variation which is defined as a deviation from the climatological annual cycle of a meteorological quantity. It can be caused by a variation of an external forcing of the atmospheric circulation system, or can be generated internally within the system. On the other hand, intraseasonal variation is a low-frequency variation within a season, and it is basically considered to be a result of internal processes which may exist even under constant external conditions. In this article, some observational facts on the intraseasonal and interannual variations of the polar stratosphere are presented, and the use of a hierarchy of numerical models to understand the stratospheric variations is reviewed systematically. Numerical models can be roughly divided into three classes based on their complexity; simple low-order models, medium mechanistic circulation models, and complex general circulation models. In order to understand the stratospheric variations, a hierarchy of stratosphere-only models have been used under an assumption of “slave stratospheric-variations” or “independent stratospheric-variations”. Parameter sweep experiment, in which many trials of computations in parameter space are done by sweeping the value of a control parameter, is a powerful method to understand complex behavior in the models. Recently, however, the importance of the coupled variability of the troposphere and the stratosphere was pointed out for the intraseasonal and interannual variations. In addition to numerical studies with simple or complex models, we have done some parameter sweep experiments with three-dimensional mechanistic circulation models to understand the troposphere-stratosphere coupled variability. All the effects of external forcings that might cause interannual variations can be excluded in the numerical experiments to focus only on internally generated variations within the coupled system. The obtained intraseasonal and interannual variations have some similar characteristics of the real atmosphere in some realistic parameter ranges. Roles of the interannual variations of the external forcings are discussed, which might be significant even if the amplitude is small.

Static electromagnetic braking (EMBr) fields affect greatly the turbulent flow pattern in steel continuous casting, which leads to potential benefits such as decreasing flow instability, surface defects, and inclusion entrapment if applied correctly. To gain a fundamental understanding of how EMBr affects transient turbulent flow, the current work applies large eddy simulations (LES) to investigate the effect of three EMBr ruler brake configurations on transient turbulent flow through the bifurcated nozzle and mold of a liquid-metal GaInSn model of a typical steel slab-casting process, but with deep nozzle submergence and insulated walls with no solidifying shell. The LES calculations are performed using an in-house graphic-processing-unit-based computational-fluid-dynamics code (LES-CU-FLOW) on a mesh of ~7 million brick cells. The LES model is validated first via ultrasonic velocimetry measurements in this system. It is then applied to quantify the mean and instantaneous flow structures, Reynolds stresses, turbulent kinetic energy and its budgets, and proper orthogonal modes of four cases. Positioning the strongest part of the ruler magnetic field over the nozzle bottom suppresses turbulence in this region, thus reducing nozzle well swirl and its alternation. This process leads to strong and focused jets entering the mold cavity making large-scale and low-frequency (<0.02 Hz) flow variations in the mold with detrimental surface velocity variations. Lowering the ruler below nozzle deflects the jets upward, leading to faster surface velocities than the other cases. The double-ruler and no-EMBr cases have the most stable flow. The magnetic field generates large-scale vortical structures tending toward two-dimensional (2-D) turbulence. To avoid detrimental large-scale, low-frequency flow variations, it is recommended to avoid strong magnetic fields across the nozzle well and port regions.

Climate Dynamic Geophysical Mon Copyright 2010 b 10.1029/2008GM Structure and dynamics of the Northern Hemisphere planetary waves, which cause geographically fixed longitudinal dependence to the climate, are examined through dynamical diagnoses applied tomodern global data sets. Summertime planetarywave signature in the Western Hemisphere includes surface maritime subtropical anticyclones, for which pronounced land-sea thermal contrasts across the west coasts of subtropical continents are important as thermal forcing. Its Eastern Hemisphere counterpart is dominated by continental-scale cyclone and anticyclone in the lower and upper troposphere, respectively, associated with Asian monsoon. Wintertime planetary waves are forced orographically and thermally in middle/subpolar latitudes, with pronounced land-sea thermal contrasts, including a contribution from diabatic heating along oceanic “storm tracks.” Wave activity thus generated propagates southeastward, maintaining an upper-level vorticity dipole over the Atlantic with an eddy-driven polar-front jet (PFJ) separated from a subtropical jet (STJ). Its Pacific counterpart is in the opposite sense with a predominant single jet with PFJ-STJ hybrid characteristics. Stationary circulation anomaly patterns that cause regional climate variability are strong in winter over the midlatitude ocean basins, extracting kinetic energy effectively from diffluent westerly jets and with feedback forcing by transient eddies along storm tracks. In the summertime Asian STJ exit, a stationary baroclinic anomaly pattern is dominant, maintaining itself by extracting potential energy from the jet and negating it by anomalous cumulus activity. Each of these patterns thus bears characteristics of a dynamical mode. Generation of shallow, cold surface anticyclones is discussed from a viewpoint of interaction of stationary Rossby waves with surface baroclinic zones.