Wind Field Research Articles (Page 1)

Abstract Orbital precession modifies the intensity of the annual cycle at millennial time scales and is a major external driver of El Niño–Southern Oscillation (ENSO) variability in both proxy records and climate model simulations. We examine precession’s influence on ENSO through a subtropical pathway, the Pacific meridional mode (PMM), using a suite of NCAR Community Earth System Model, version 1.2 (CESM1.2), experiments that simulate five precessional extremes: perihelion at autumnal equinox (AE), winter solstice (WS), vernal equinox (VE), summer solstice (SS), and zero eccentricity (E0). We investigate mechanisms that may moderate the PMM’s influence on ENSO such as the strength of midlatitude stochastic forcing via the North Pacific Oscillation, changes in the climatological mean state, and the wind–evaporation–sea surface temperature (SST) (WES) feedback. We find that orbital precession strongly influences PMM variability, the PMM’s ability to trigger El Niño events, and ENSO diversity. Precessional extremes characterized by a more southerly intertropical convergence zone (ITCZ) and stronger trade winds (WS and AE) have more variable PMM behavior and a PMM that is more effective at triggering El Niño events, particularly central Pacific events. Precessional extremes characterized by a more northerly ITCZ and weaker trade winds (SS and VE) have reduced PMM variability and a PMM that is a less-reliable precursor to El Niño events. The PMM response to precession is driven by variations in surface wind fields that moderate the strength of WES feedback, the mechanism by which PMM anomalies grow and propagate. Understanding the sensitivity of ENSO to subtle shifts in the mean state contextualizes past variability and aids in anticipating future change. Significance Statement Orbital precession alters the seasonal distribution of solar insolation around Earth and has vast impacts on the climate system including El Niño–Southern Oscillation (ENSO). Here, we examine how precession influences ENSO through a subtropical ENSO precursor: the Pacific meridional mode (PMM). We use climate models to test how the influence of warm PMM events on El Niño events may vary under extreme states of orbital precession. We find precession moderates the variability of the PMM, the ability of the PMM to trigger El Niño events, and the spatial diversity of El Niño events. These results help us to interpret past climatic changes and understand the sensitivity of the tropical Pacific to small variations in external forcing.

Abstract. An unphysical stripe pattern is identified in low-level wind field in China Meteorological Administration Global Forecast System (CMA-GFS), characterized by meridional stripes in u-component and zonal stripes in v-component. This stripe noise is primarily confined to the planetary boundary layer over land. The structural mismatch between static field variations and the observed 2Δx noise amplitude suggests that locally forced mechanisms from surface inhomogeneity alone cannot explain the wind stripe patterns. Meanwhile, pure dynamical core simulations exhibit no such noise, confirming that the dynamical core itself does not generate these patterns. These results suggest that staggered-grid mismatch in physics-dynamics coupling is likely the primary mechanism. Idealized two-dimensional experiments demonstrate that combining one-dimensional dynamic-core advection and physics-based vertical diffusion on a staggered grid generates 2Δx-wavelength spurious waves when surface friction is non-uniform. One-dimensional linear wave analysis further confirms that staggered-grid coupling between dynamic advection and inhomogeneous damping forcing induces dispersion errors in wave solutions. Sensitivity tests validate that eliminating grid mismatch in physics-dynamics coupling removes this stripe noise. These findings collectively indicate that while staggered grids benefit the dynamic core's numerical stability and accuracy, their inherent grid mismatch with physics parameterizations requires specialized coupling strategies to avoid spurious noise. Potential solutions to remedy this issue are discussed.

Coronal mass ejections (CMEs) are the main drivers of disturbances in the solar heliosphere because they propagate and interact with the magnetic field of the solar wind. It is crucial to investigate the evolution of CMEs and their deformation for understanding the interaction between the solar wind and CMEs. We quantify the effect of the dynamic solar wind on the propagation of a CME in the heliosphere with a hydrodynamic plasma cloud-cone model and a linear force-free spheromak model at various locations in the heliosphere. We chose a CME event that launched on SOL2021-09-23T04:39:45 and was observed by multiple spacecraft, namely BepiColombo, Parker Solar Probe, Solar Orbiter, Stereo A and ACE. The solar wind was modelled in the steady and dynamic regimes in the Icarus model. The CME parameters were approximated for the selected event, and two CME models (spheromak and cone) were launched from the inner heliosphere boundary. The obtained synthetic in situ measurements were compared to the observed in situ measurements at all spacecraft. The internal magnetic field of the flux rope was better reconstructed by the spheromak model than by the cone CME model. The cone CME model maintained a nearly constant longitudinal angular extension while somewhat contracting in the radial direction. In contrast, the spheromak model contracted in the longitudinal direction while expanding in the radial direction. The CME sheath and magnetic cloud signatures were better reproduced at the four spacecraft clustered around the CME nose by the spheromak CME model. The dynamic solar wind caused a greater deceleration of the modelled CME than the steady-state solar wind solution. Because the background was homogeneous, the modelled CME properties were only mildly affected by the solar wind regime, however.

Abstract. Metal layer forms as a result of meteoric ablation and exist as a layer of metal elements between approximately 80 and 105 km altitude, and it provides information about the physics and chemistry of the boundary between the atmosphere and space. There are some studies about the wind field disturbances in Mesosphere and Low Thermosphere (MLT) region and the plasma variations in ionospheric E-region during magnetic storms, but no study on the impact of storms on the metal atom layers in mesosphere. During the super substorm on 4 November 2021, the atmospheric metal layers were observed to decrease by observations from three lidars at the mid-latitudes of China. The Na, Ca and Ni densities on the storm day were significantly lower than in other days in October and November. The O/N2 column density ratio observed by the Global Ultraviolet Imager (GUVI) on the storm day was much higher than on quiet days, and the numerical simulation results demonstrate a substantial increase in atomic oxygen density at the heights of the metal layer. The increase in oxygen density may lead to the formation of more metal compounds, thus more metal atoms are consumed. This is an interesting phenomenon that magnetic storm can perturb the atmospheric metal layer through chemical reactions.

The numerical analysis technique is one of the primary methods for the design and development of floating offshore wind turbines (FOWTs). This study presents a detailed investigation into the influences of fully coupled and decoupled numerical analysis methods on the dynamic responses of a floating offshore wind turbine. The fully coupled analysis is implemented via bidirectional FAST-OrcaFlex co-simulation, considering the dynamic interaction between rotor operation and platform motions. The decoupled analysis is conducted using OrcaFlex for wave-induced response analysis, incorporating unidirectional imported FAST-based thrust time series. First, the numerical tools used for simulating fully coupled numerical model of OC5 DeepCwind are verified against published model test data, including free-decay test, white noise wave test and working condition test. Then, the fully coupled and decoupled numerical models are compared under wind fields of different turbulence intensities and wind speeds to reveal the dynamic coupling effects. The results indicate that the predictions of the decoupled model are more aligned with the experimental data compared to those of the fully coupled model under conditions of combined wave and steady winds. The differences between the fully coupled and decoupled models are minor under wave-only condition. However, under turbulent condition, the decoupled model overestimates surge by up to 10% and mooring tension by less than 5%, while pitch deviations can reach 17%. These findings support the use of the decoupled method in preliminary design stages—especially for mooring system optimal design—to save computational cost and time. For detailed designs involving turbulent winds, low-frequency structure response analysis or pitch-sensitive performance, the fully coupled approach is recommended to ensure accuracy. This study could offer practical guidance for selecting suitable numerical methods in FOWT design and analysis.

Abstract This study investigates the impact of vertical wind shear (VWS) on vortex size expansion using a series of idealized numerical experiments. A control experiment (CTL) without ambient flow is compared with the experiments with 6 m s −1 (SH6) and 12 m s −1 (SH12) westerly VWS imposed after a 36-h vortex spin-up. In SH6, the low-level wind field expands coherently in a quasi-axisymmetric manner, similar to that in CTL. However, SH12 exhibits a 12-h stagnation in size expansion before re-expansion. This stagnation is primarily associated with outer wind deceleration in the downshear-left (DSL) quadrant, where the vortex tilt and asymmetric convection are locked. In the DSL downwind section, the stratiform precipitation develops, impeding vortex tilt precession and increasing tilt magnitude. Diabatic cooling related to the stratiform precipitation enhances midlevel descending inflow (MDI), locally strengthening tangential winds in the DSL downwind section by enhancing the radial flux of absolute vorticity. As a result, a sharp azimuthal wind gradient forms to generate negative tangential advection of tangential wind that decelerates quadrant-averaged wind speed and halts overall size expansion. Later, the low-level radial outflow in the upshear quadrants deflects the MDI-induced descending parcels outward, limiting their return to the DSL updraft region and thus weakening the convection, stratiform precipitation, and MDI. As the stratiform precipitation and MDI dissipate, the wind field asymmetry diminishes, and the vortex tilt precession and size expansion resume. These results reveal that strong VWS–induced asymmetric convection can not only impede TC intensification but also temporarily halt size expansion.

Abstract The screening current problem is one of the most critical challenges in high-temperature superconducting (HTS) coated conductors, severely degrading both the magnetic field magnitude and the stability of HTS inserts in high-field superconducting magnets. A promising strategy to mitigate screening current is the application of a shaking field perpendicular to the penetrating field. However, existing studies lack an effective computational model for the vortex shaking process and a comprehensive investigation into the unique characteristics of no-insulation (NI) coils under a shaking field. In this paper, a T-A formulation considering the coil thickness is used to simulate the electromagnetic behavior of NI coils during the shaking process. By combining simulations and experiments, the reduction of the screening current-induced field (SCIF) under varying coil parameters and operation conditions is investigated. The results indicate that the radial current has a dominant influence on the SCIF in NI coils with low contact resistivity. The rapid change in radial current induced by the shaking field leads to a sharp mitigation in the screening current within a short period, exhibiting a strong dependence on the shaking duration and coil’s contact resistivity. Moreover, this study demonstrates the effectiveness of the shaking field in accelerating radial current decline, and evaluates the additional AC losses induced by shaking field. These findings offer insights into the different mechanisms of the shaking field on SCIF reduction and radial current decline in NI coils, contributing to a better understanding of strategies for mitigating large screening current in REBCO magnets.

Abstract Super intense storms are unique, and their impacts are remarkable. The present study focuses on the super intense geomagnetic storms (SYM‐H ≤ −300 nT) in solar cycles 23 and 25 to address critical questions such as what made a geomagnetic storm a super intense one, and the pivotal role of solar wind and interplanetary magnetic field parameters. The storms with significant steepening of SYM—H are examined, a factor P dyn .B z is introduced and correlation coefficient analysis is carried out. To address the complexity of storms, the correlations of solar wind energy input (Einj) with P dyn .Bz and Esw are investigated and are found to be well correlated with coefficients of 0.94 and 0.89, respectively. The time integrated values of SYM‐H during the storm period provide a higher correlation with VB z and P dyn .B z than peak SYM‐H values. The ideal combination of high values of P dyn and VB z , that is, P dyn ≥ 10 nPa and VB z ≥ 5 mV/m and duration play a major role in developing steep SYM‐H (<−400 nT) as seen for the super intense geomagnetic storms. We can clearly state that the combination of high P dyn and steady southward B z is a key factor in deciding the intensity of the storm as the longer the duration of the combination led to larger peak values of SYM‐H. MHD simulations have evidently shown that the crucial role of high solar wind density values for longer duration contributes to the steepening of SYM‐H leading to super‐intense geomagnetic storms.

Dynamic control of multiple stratospheric airships in time-varying wind fields for communication coverage missions

Modelling and application of fluid-structure interaction in the study of wind fields and crops interaction: A review

Galloping mitigation of ice-coated conductors with hybrid nutation dampers under stochastic wind fields

Experimental investigation on the vortex-induced vibration of a rectangular 4:1 cross-section continuous girder bridge in natural wind field

A self-attention convolutional long and short-term memory network for correcting sea surface wind field forecasts to facilitate sea ice drift prediction

Optimisation of STEP poloidal field coils with superconducting coil constraints in STEP-Bluemira power plant design framework

Automated Testing of Rotor Faults in Wound Field Synchronous Motors for EV Applications

In this study, the outdoor space of an aged residential community in Zhangjiakou, China, where strong winds frequently occur during the spring season, was investigated for environmental modifications. The study employed Rayman software to analyze the acceptable outdoor wind comfort range for residents, and utilized EDDY 3D simulation software to simulate and assess the current outdoor wind environment in the district. The analysis revealed that wind comfort was inadequate in several outdoor activity areas. The study suggests that the combination of landscape walls, enclosed spaces, and windbreak plants can effectively enhance wind environment conditions. The results indicate that: (1) The opening at the bottom of the wind-blocking wall can improve the static wind area at the corner, promote air circulation, and prevent pollutant accumulation. The larger the opening, the broader the influence of the wind shadow area and the greater the wind comfort area. (2) In cubic outdoor enclosed spaces, the degree of enclosure affects wind field conditions. Among these, the primary factor in enhancing the wind comfort area is the level and quantity of shelters perpendicular to the wind direction; the wind velocity variation in the wind shadow area is positively correlated with the degree of space enclosure. (3) Among the combinations of windbreak plants, the landscape configurations featuring equal height and gradient elevation arrangements. (4) After implementing the above three strategies to renovate the outdoor space of aged residential community, a computer simulation indicated that, under prevailing spring wind conditions, the wind-comfortable outdoor area increased from 40.26% to 79.84% demonstrate superior wind protection efficacy.

With the growing demand for wind turbines in deep offshore regions, frequent typhoon disasters at sea have impeded the continued development of the wind power industry. To address the problem of typhoons destroying offshore wind power facilities, this paper investigates the aeroelastic characteristics of long flexible blades on ultra-large offshore wind turbines under typhoon loads. The WRF numerical model is employed for high-precision simulations of Typhoon Mangkhut (No. 1822). By optimizing parameterization schemes and incorporating 3DVAR data assimilation techniques, typhoon wind speed profiles in the target sea area are obtained. Based on IEA 15 MW offshore wind turbine data, 3D unsteady CFD models and full-scale finite element models of the blades are established to acquire the aerodynamic loads and structural responses of the blades in typhoon environments. The results indicate that, under extreme typhoon loads and considering wind shear and tower shadow effects, the forces near the blade root are greater; the maximum out-of-plane aerodynamic force occurs at the 14% span position of the blade at 90° azimuth, and the maximum torsional aerodynamic moment is experienced at the 26.5% span position of the blade at 270° azimuth. When the blade pitch angle and rotor yaw angle do not reach ideal states, the deflection of ultra-long flexible blades can increase by up to 3.26 times. These findings overcome the limitations of traditional uniform wind field studies and provide a theoretical basis for subsequent coping strategies for offshore blades under typhoon conditions.

The South China Sea (SCS) has undergone multiple marine heatwaves (MHWs) over the past few decades. Daily reanalyzed sea surface temperature (SST) data are applied to identify major MHWs in the northwest SCS over 1982–2021. The MHWs have increased in frequency, intensity, and spatial extent during recent decades, but the strongest 2015/2016 winter MHWs occurring in our study region have not been fully explained. In situ observations revealed a strong dependence of the formation of MHWs on interannual variability, i.e., the El Niño. A prominent difference in SST was identified in winters between the El Niño (2015/2016) and a normal year (2016/2017), as well as marine dynamical processes in wind and current. Due to the teleconnections of extreme El Niño, the weakened monsoon wind led to reduced basin-scale wind field anomalies and vertical currents, acting as pre-conditioning for extreme MHW events. Additionally, local oceanographic dynamics, especially upper ocean circulation and mesoscale eddies, play an important role in different MHWs during their formation and intensification by driving horizontal currents and advection. In particular, the northward flow from the tropics is favorable for the generation of MHWs. A heat budget analysis was performed, which agrees with observations, showing both enhanced solar radiation and weakened wind depressed oceanic turbulent mixing, leading to more heat being concentrated in a shallower mixed layer and resulting in the record-breaking MHW. The in situ observations offer a comprehensive insight into the formation of extreme MHWs in the SCS.

Unique research aircraft observations were conducted within an Arctic fjord in Svalbard during three days in March 2013. Wijdefjorden is 110 km long, 5–15 km wide and has a north–south axis. Two-thirds of the fjord were covered by land-fast sea ice, but the northern part of the fjord was open. On two days the flow over the fjord was largely controlled by orographic channelling of the north-easterly wind, and on all three days a cold-air mass accumulated over the sea ice in the fjord and gradually propagated towards the open sea in the north. An ice breeze (analogous to land breeze) circulation, due to a strong temperature gradient across the sea-ice edge, was a key driver of the southerly near-surface wind over the fjord. On two days, the cold-air mass reached the open sea and the near-surface air mass warmed rapidly by several Kelvins. On one day, the channelled northerly flow pushed the cold-air mass to the south, from where it gradually propagated back to the north after the channelled flow had weakened. The results suggest that the channelling of the large-scale flow in the fjord can suppress the ice breeze to a shallow near-surface layer and even push the cold-air mass far south of ice edge. The near-surface air temperature and wind fields that were based on the Copernicus Climate Change Service Arctic Regional Reanalysis (CARRA) data set included large errors because CARRA did not have any sea ice in the fjord.

Magnets in the accelerator interaction region (IR) present significant challenges because of high field requirements and limited available space. Conical-shaped magnets offer advantages in these environments by allowing closer placement to the interaction point while maintaining clearance from synchrotron radiation. Interestingly, numerical studies have shown that conical canted-cosine-theta (CCT) designs produce a constant field distribution along the axial direction in the IR quadrupoles for the Electron-Ion Collider (EIC) at Brookhaven National Laboratory. However, the field harmonics generated by conical CCT windings are not yet fully understood. This paper presents an analytical approach to describe the magnetic field produced by a conical surface current and proposes a method for designing conical CCT magnets for accelerator applications. First, we begin with a surface current sheet having a general cosine-theta distribution in spherical coordinates and solve the vector potential using the Green’s function. The magnetic fields generated by the conical current sheet are expressed using associated Legendre polynomials. These results are then related to circular field harmonics and integral field harmonics for designing a coil that produces a pure multipole field. Next, a single layer of the conical CCT winding path is produced based on the cosine-theta current distribution. Finally, the magnetic field quality of dipole and quadrupole conical CCT coils with multiple layers is verified using the Biot-Savart law.