Gust Events Research Articles

Extreme Convective Gusts in the Contiguous USA

Most damage to buildings across the contiguous United States of America (USA) is caused by gusts in convective events associated with thunderstorms. Design rules for structures to resist these events rely on the integrity of meteorological observations and the methods of assessment. These issues were addressed for the US Automated Surface Observation System (ASOS) in six preliminary studies published in 2022 and 2023, allowing this present study to focus on the analysis and reporting of gust events observed between 2000 and 2023 at 642 well-exposed ASOS stations distributed across the contiguous USA. It has been recently recognized that the response of buildings to convective gusts, which are non-stationary transient events, differs in character from the response to the locally stationary atmospheric boundary gusts, requiring gust events to be classified and assessed by type. This study sorts the mixture of all observed gust events exceeding 20 kn, but excluding contributions from hurricanes and tropical storms, into five classes of valid meteorological types and two classes of invalid artefacts. The valid classes are individually fitted to optimal sub-asymptotic models through extreme value analysis. Classes are recombined into a joint mixture model and compared with current design rules.

Synchronous high-speed measurements of a flexible structure under wind gust load

Simultaneously measuring the fluid flow around a flexible structure and the resulting deformations during short-term yet highly dynamic flow events is the focus of this fluid–structure interaction (FSI) study. These scenarios occur when a wind gust impacts a flexible structure, leading to extreme loads and significant deflections. To mimic such gusts, a specifically designed wind gust generator is used within a wind tunnel featuring an open test section. A high-speed particle-image velocimetry system records the flow field, while the digital-image correlation technique captures the structural deformations. That allows us to perform synchronized coupled fluid–structure measurements for a T-structure under wind gust load. The time-resolved measurements are repeated up to 104 times, allowing for phase-averaging of both the flow and the structural data, and to examine the convergence of the statistics. A comprehensive analysis of the instantaneous and phase-averaged data reveals that the flow field in the vicinity of the structure undergoes noticeable changes during the gust impact. The recirculation region behind the T-structures perceptibly increases when the gust hits the structure. A maximum deformation of about 10% of its height is observed during the highly dynamic gust event. Given (1) the availability of synchronously recorded data for both the fluid flow and the structure deformation, (2) the simplicity of the structure's geometry, and (3) the moderate Reynolds number of about 4×104, this case also serves as a well-suited benchmark test case for evaluating simulation methodologies for strongly coupled, highly dynamic FSI problems.

Two-year wind field measurements near the ground at a site of the Tibetan Plateau

A nearly two-year wind field measurement in the plateau has been conducted in the south of Tibet. High-frequency anemometric data of the distinctive plateau wind field was obtained. Combining the non-stationary model and test, wind samples are classified into three types of 10-min samples based on the level of stationarity. Analysis reveals the strong non-stationarity, turbulence intensity, gust factor, and integral length scale of the synoptic wind in the plateau, which differ from the ones at low altitudes. The stationary samples are recommended to represent the plateau synoptic wind for characterizing the fluctuating wind. At smaller time scales, high-frequency records capture some intense gust events. Based on the different influences of wind on the structures from the perspective of structural wind resistance, the plateau transient intense gust events are divided into thunderstorms and front, and short-rise-time gusts. Representative gust events are defined, sifted, and extracted. With the combination analysis of 10-min fluctuating wind characteristics and intense non-stationary gust events, the measurement data assist the structural wind-resistance design in the plateau.

Investigation on metal geochemical cycling in an anthropogenically impacted tidal river in Belgium

The geochemical behavior of metals in water and sediment was investigated in the tidal section of the Zenne River in Belgium. Twelve-hour sampling campaigns were performed in October 2013 and March 2021 at the mouth of the Zenne River, under dry and rainy weather conditions respectively. Water samples were collected every hour while the passive samplers of Diffusive Gradients in Thin-films (DGT) were deployed continuously during a tidal cycle. In addition, bottom sediments were sampled at the tidal station and water samples were taken upstream and downstream of that station to identify the metal sources. The highest concentrations of Fe, Mn, Pb, Cr, Ni and Zn appear at low tide, indicating the Zenner River as a main source. However, for Co, Cd and Cu, other sources including upstream transport may explain their behavior during a tidal cycle. Fe, Pb and Cr are essentially transported in the particulate phase (<10 % dissolved) while the other metals in the dissolved phase (20 to 90 %). Rainfall and wind gust events also play an important role in trace metal distribution, increasing sediment resuspension and metal desorption. A good agreement was found between the time-averaged dissolved and DGT-labile metal concentrations with the exception of Cu and Fe, which form strong organic Cu complexes and Fe colloids respectively. The sediments of the tidal Zenne are contaminated by trace metals, thus acting as a secondary pollution source to the river. The reductive dissolution of Mn and Fe oxyhydroxides and the release of associated trace metals are the main mobilization mechanisms. Knowledge of the upstream and downstream levels in the water column, the benthic fluxes, which are based on turbulent diffusion, and the partitioning between dissolved and particulate phases allow to explain the metal concentration variations during the tidal cycle.

An Overview of Extreme Storm Trends in Java Island using Storm Severity Index (SSI)

Extreme winds can lead to extreme storms, which are among the most frequent forms of extreme weather in Indonesia. With climate change predicted to increase the adverse impact of extreme weather, it is crucial to keep track of and gauge the severity of storm events. Storm Severity Index (SSI) can be used to measure the severity of storms, which is defined by their intensity, duration, and extent. SSI has been used in continental areas. However, the application of SSI in the maritime continent is still limited. This study explores the application of SSI to measure extreme storms in Indonesia based on wind gust speed. This study uses wind gust data in 1959-2021 from ERA5 reanalysis data and calculates the SSI based on the 98th percentile and the 50-year return value of the wind data. This study also explores the meteorological events that coincide with high SSI values. This study found the SSI able to capture high wind gust events in Java Island. This study finds high SSI value coincides with tropical cyclone events in the Indian Ocean. Topography affects the area on Java Island that has a high SSI value. Further study should evaluate the impact of the coastal and non-coastal areas to reduce the significant effect of sea-land breeze or mountain-valley breeze. In addition, future research also needs to address the significance level of the duration of events in a severe storm to enhance the information on severity.

Analysis and characterisation of extreme wind gust hazards in New South Wales, Australia

Extreme wind gusts cause major socioeconomic damage, and the rarity and localised nature of those events make their analysis challenging by either modelling or empirical approaches. A 23-year long data record from 29 automatic weather stations located in New South Wales (eastern Australia) is used to study the distribution, frequency and average recurrence intervals (ARIs) of extreme gusts via a peaks-over-threshold approach. We distinguish between gust events generated by synoptic phenomena (e.g. cyclones and frontal systems), hereafter called “synoptic events”, and convective phenomena (i.e. thunderstorms), hereafter called “convective events”, using the wind time series. For synoptic events the frequency of gusts >25 m/s decreases systematically inland from the coast, in contrast to convective gusts which are more uniformly distributed geographically and occur more often than synoptic gusts at nearly all inland locations. At inland locations the most extreme wind gusts are likewise dominated by convective events, whereas at coastal stations both gust types have similar intensities at low ARIs but convective events again dominate at the highest ARIs. Extreme gust directions were found to be predominantly westerly at inland locations and southerly at coastal ones, with more variable direction for convective than synoptic events. This study confirms the dominant role of thunderstorms in producing the most extreme gusts in the region, and shows that wind risk varies strongly with distance from the coast.

Automated classification of gust events in the contiguous USA

Automated classification of gust events in the contiguous USA

Analysis of extreme wind gusts using a high-resolution Australian Regional Reanalysis

The characterisation of extreme wind gust speeds has historically relied on data from observations, while numerically modelling these events is limited due to their rarity and localised nature. However, the ongoing increase in computational power now allows extreme events to be characterised in fine-scale numerical data. Extreme gust events are examined using 24 years of 1.5 km horizontal grid reanalysis data for eastern Australia, and compared to those based on 1-minute data from station observations. We estimate return values over long periods using the generalised Pareto distribution (GPD) peaks-over-threshold approach. An automated algorithm that selects an optimal threshold at each grid point is outlined and gives similar results to an approach based on pre-fixing the shape factor value similar to what is applied in Australian building design standards. We also present a decision tree model that skillfully distinguishes between convective (i.e., thunderstorm) and synoptic (e.g., frontal system and cyclone) gust events using only hourly reanalysis data. The reanalysis shows high synoptic gust intensities and frequencies along the coast, consistent with station observations, and that synoptic-type extreme gusts are enhanced by topography (higher occurrence frequencies in mountain areas) while convective-type events are less affected. The reanalysis systematically overestimates parameterised gust activity, while compensating for this at many locations by underestimating the resolved wind speed, thus often producing gusts close to observed. With the proviso that these issues are considered, we find that the information on wind gusts provided by reanalysis data may be quite useful especially in regions with low observational network coverage.

Large-eddy simulation of gusty wind turbulence over a travelling wave

Wind gustiness in the marine atmospheric boundary layer affects significantly the dynamics of air–sea interaction. To understand the impacts of wind gust events, we perform large-eddy simulation of wind turbulence over a travelling wave to investigate the response of the wind field to an impulsive wind speed increase or decrease. It is found that the turbulence fluctuations and the terms in the turbulent kinetic energy budget equation have a delayed response to the change in the mean flow, while the response of the wave-coherent motions is quasi-stationary. The wave-coherent motions are investigated quantitatively through comparison with a viscous curvilinear model developed by Cao et al. (J. Fluid Mech., vol. 901, 2020, A27) and Cao &amp; Shen (J. Fluid Mech., vol. 919, 2021, A38). We observe an asymmetric hysteresis between the growing wind and the decaying wind in the evolution of the form drag and the viscous drag. We find further that the variation of the wave growth rate during the wind gust is related closely to the contribution from the out-of-phase component of the vertical velocity. Our discoveries provide evidence for the necessity of improving non-equilibrium turbulence and wind input modelling to account for the wind gustiness effect in future studies.

Observational Analysis of a Wind Gust Event during the Merging of a Bow Echo and Mini-Supercell in Southeastern China

The merging of a fast-moving bow echo with a convective cell of a hook-echo signature was studied by using polarimetric radar detections. Gusts with wind speeds near 35 m s−1 were recorded by the surface station, which caused significant damage. A convective cell with a mesovortex signature, which is hereafter referred to as a mini-supercell, was observed over the northeast of the bow echo before the convective merging. It was found that the mesovortex possessed cyclonic circulation and resembled a supercell-like feature. The merging of the bow echo and the mini-supercell strengthened the updraft near the apex of the bow echo. The enhanced updraft was also demonstrated by the appearance of a differential reflectivity (ZDR) column with a topmost height of 4 km above the melting layer (~4 km). The bow was separated into northern and southern sectors after merging with the mini-supercell, leading to the gusty wind over the surface of the south sector.

Analysis of Jerk as a novel tree-fails hazard index: A case study applied to tree monitoring in the archaeological park of the Colosseum in Rome (Italy)

This study shows the implementation of a new risk assessment monitoring tool, to be applied to prevent trees failure and significant damage to people and structures, in an urban archaeological site i.e. the Colosseum's Archaeological Park in Rome. Here, a network of ten TreeSavers has been recently installed to allow real-time continuous static and dynamic monitoring of the trees. These data, also linked with readings collected from a local weather station, are transmitted to an online data storage i.e. the cloud to be post-processed. The objective, in this post-processing phase, is that the online data storage system effectively works in autolearning capabilities to “become experts” in risk assessment and thus preventing dangerous situations. In this study we present the preliminary data, analyzed by relating the maximum acceleration on x-, y- and z-axis with maximum wind speed and gust events. The risk analysis was performed considering the Drag Coefficient CD and the Jerk values. The first represents the drag force generated on plants; the second describes the effect of accelerations on rigid bodies. This study has deepened the understanding of Jerk, as a novel hazard index, able to categorize the effect of accelerations on trees under dynamic wind loads for hazard control and prediction of the tree fails. Jerk has the potentiality to be an effective tool for early warning alarm which may reduce the risk of falling of trees with consequent reduction of damage to people and structures, especially in the urban archaeological sites.

Application of Self-organizing Maps to classify the meteorological origin of wind gusts in Australia

Across much of the world, wind gust data are continuously measured by Automatic Weather Stations (AWS). However, the meteorological origin of individual extreme gust events within these datasets are seldom automatically assigned. To overcome this, Self-Organizing Maps (SOM) are proposed here as an automated tool to classify gust events within 1-min AWS data. In this paper, this method is specifically used to distinguish between wind gust events of convective (often broadly termed non-synoptic or thunderstorm) and non-convective origin, with the latter events further sub-classified as either, wind only, transition, or other. The efficacy of a range of different SOMs and input variables were assessed, and it was found that those that utilised gust wind speed, temperature, and pressure generally outperformed other models when classifying wind gusts. Applying this approach in the Australian context, all wind gusts of convective origin greater than 70 ​km ​h−1 (19.4 ​m ​s−1) and 90 ​km ​h−1 (25 ​m ​s−1) were identified at 306 AWS across Australia and a climatology of seasonal and annual convective wind gust occurrence developed and discussed.

Surface wind gust prediction over Incheon international airport using the unified model

The unified model (Version: UM10.4) wind gust prediction system using rose nesting suite at 300 m resolution over the Incheon international airport (IIA) is carried out, and the prediction results of multiple domain nesting with input initial and lateral boundary conditions from the Korea meteorological administration (KMA) operational global data assimilation and prediction system (GDAPS) are compared with the operational local data assimilation and prediction system and the observed automated weather stations (AWS) dataset. The 300 m nested prediction system over the IIA is built from the 17 km GDAPS output in KMA; it is downscaled with a multiple nesting domains to 300 m resolution from the GDAPS, here after called as IIA-300 m. The model results are validated against the AWS to see the accuracy of the IIA-300 m model’s skill in predicting the wind gust over the IIA. The nesting suite is run with the default ancillary files created by the central ancillary program 9.0 (CAP 9.0) as well as modified ancillary files created by modifying the land points over IIA region using an ancillary editor. The UM model wind prediction is done with both ancillary files to see the improvements achieved by adding additional land points over the IIA domain. Further the vegetation fraction from the international geosphere-biosphere program (IGBP) data classified as 9 tiles in the ancillary file is replaced by the environmental-geographic information system (E-GIS) data to see the effect on the UM model’s wind gust predictions. The prediction of two wind gust events on 30-August-2016 and 02-October-2016 reveals only modest improvements in the prediction with respect to AWS observations, even after the modification of ancillaries with land points over the IIA domain, and only minor improvements are noted for the vegetation fraction replacement from IGBP to E-GIS vegetation dataset over the Incheon International Airport and exhibited only a marginal wind speed decrease due to warming up of the land part, particularly on the peripheries of the IIA-domain.

What are unsafe strategies to pick up a light load according to graduates/students in physiotherapy and medicine?

The installation of small wind turbines and solar photovoltaic (PV) modules in the built environment requires a detailed understanding of wind resources to maximise turbine power output and minimise damage due to wind loading. While urban sites are known to be highly turbulent, less is known about the composition and frequency of gust events. To date a number of catastrophic wind turbine and solar PV structural failures have resulted from inadequate design for extreme gust events. In this study a 12 month wind resource measurement campaign was undertaken at an urban site. Gust events that satisfied the IEC 61400.2–2013 definition of an annual extreme operating gust were found to occur 100 times during the 12 months interval. These events had a 23% higher mean amplitude, and 21% shorter rise-and-fall time than that assumed by the standard. In addition, a site gust factor of 1.76 was determined, a value 26% higher than given in IEC 61400.2–2013. Consequently, IEC 61400.2–2013 appears not to predict the frequency and amplitude of extreme gust events at this given site suggesting there exists a risk that structural components may be under-designed for installation in urban sites.

Simulating the response of a small horizontal-axis wind turbine during wind gust using FAST

Small wind turbines are often erected close to their load and in urban environments where the mean velocity is lower than ideal, and the turbulence level is high. Urban environments experience wind gust events with published results indicating the number of gust events greatly exceeding the number of events assumed in International Electrotechnical Commission (IEC) standard IEC 61400.2-2013. The work presented in this paper has analysed detailed wind measurements from a site in an urban environment to identify wind gust events and has used these wind gust events as an input into a FAST model of a 5 kW horizontal-axis wind turbine. The FAST model predicted the turbine power extracted from the measured gusts are lower than the power extracted during the assumed IEC gust. The maximum energy extracted by the turbine during a gust is at least 36% lower for a measured gust event than for the assumed ideal gust event.

Enhancement of DFIG LVRT Capability During Extreme Short-Wind Gust Events Using SMES Technology

Wind energy is one of the premier renewable energy sources that have gained popularity during the last decade. Among the currently available wind energy conversion systems (WECS), doubly fed induction generator-based technology has been widely employed due to its superior advantageous. The key features of the DFIG-based WECS include its ability to capture more wind energy and support the grid with large reactive power during short disturbance events. On the other hand, DFIG is very sensitive to grid faults which affect its fault ride through (FRT) capability. Furthermore, extreme wind gust even for short durations may lead to the violation of the low voltage ride through (LVRT) threshold limits set by worldwide transmission line operators. This situation cannot be mitigated by the turbine blades pitch controller since the response of the pitch mechanical control is much slower than the rapid dynamic change in the wind speed during short duration of wind gust events. While DFIG FRT capability has been discussed in several papers in the literature, not much attention was given to the mitigation of the effects of extreme wind gust of short duration on the DFIG performance. In this paper, the effect of various levels of wind gust on the performance of a DFIG-based wind energy conversion grid-connected system is investigated and mitigated using a new controller for superconducting magnetic energy storage (SMES) unit. A combination of hysteresis current and fuzzy logic controllers is employed to control the voltage source converter and the DC-DC chopper interfacing the SMES coil with the investigated system. Simulation results reveal the effectiveness of the proposed SMES controller that can be easily implemented within existing as well as new WECS installations.

Measured gust events in the urban environment, a comparison with the IEC standard

The installation of small wind turbines and solar photovoltaic (PV) modules in the built environment requires a detailed understanding of wind resources to maximise turbine power output and minimise damage due to wind loading. While urban sites are known to be highly turbulent, less is known about the composition and frequency of gust events. To date a number of catastrophic wind turbine and solar PV structural failures have resulted from inadequate design for extreme gust events. In this study a 12 month wind resource measurement campaign was undertaken at an urban site. Gust events that satisfied the IEC 61400.2–2013 definition of an annual extreme operating gust were found to occur 100 times during the 12 months interval. These events had a 23% higher mean amplitude, and 21% shorter rise-and-fall time than that assumed by the standard. In addition, a site gust factor of 1.76 was determined, a value 26% higher than given in IEC 61400.2–2013. Consequently, IEC 61400.2–2013 appears not to predict the frequency and amplitude of extreme gust events at this given site suggesting there exists a risk that structural components may be under-designed for installation in urban sites.

High-resolution simulation of an isolated tornadic supercell in Poland on 20 June 2016

On 20 June 2016, a convective cell, which developed on the Polish-Slovakian border, under favorable kinematic and thermodynamic conditions, evolved into a supercell. It moved for 500 km, heading northeast, and remained isolated during its entire lifecycle. The storm was responsible for producing multiple large hail (up to 7.5 cm) and severe wind gust events. At around 1700 UTC (+/− 5 min), a tornado was reported near Sulów, and after moving for 21 km it dissipated near Skawinek (Lubelskie Voivodeship). Based on the damage survey, the peak intensity of the tornado was estimated at F1/T3 in the Fujita/TORRO scale. In this paper, we perform two simulations using the WRF model to evaluate the possibilities of predicting this event. The first simulation is a WRF base run, while the second version uses well established data assimilation techniques applied to the model domain with high spatial resolution. The surface observational data, together with the atmospheric soundings, are assimilated in the second model run. Three one-way nested domains were defined, with spatial resolutions of 9 km, 3 km and 1 km. Observations from meteorological stations, severe weather reports, and radar reflectivity from the POLRAD network are compared with the simulations to assess their quality. An additional parameter of an updraft helicity track is used to analyze the lifecycle of a simulated supercell. Results indicate a slight overestimation of temperature, dew point and wind speed. Our findings confirm that downscaling to convection-permitting resolution makes it possible to successfully predict tornadic supercells. Data assimilation, applied to the second model run, improved the model's performance. The model's errors, calculated by comparing the results with meteorological observation, were reduced if compared to the base run. Additionally, the number of convective cells and storm tracks was appropriate.

Aerosol particles during the Innsbruck Air Quality Study (INNAQS): The impact of transient fluxes on total aerosol number exchange

Air quality in the city of Innsbruck, Austria, is affected by transalpine traffic and mountainous terrain, which is characterized by a pronounced mountain – valley wind system often favouring high pollution levels. To contribute to a better understanding of urban air pollution mechanisms in an Alpine valley, eddy covariance (EC) measurements with a condensation particle counter (CPC) were performed at an urban site in Innsbruck in the framework of the Innsbruck Air Quality Study (INNAQS). Emission fluxes of 10.6⋅107 m−2 s−1 (median) were observed during daytime and up-valley flow, whereas fluxes during reversal periods of the valley wind system were more variable and partly negative.Sporadic gust-like motions of vertical wind and concurrently measured large changes in particle number concentration (termed particle gusts) significantly biased total particle fluxes, reflecting, however, rather local fluxes at the measurement height. The particle gust events were identified by applying the median absolute deviation (MAD) method to particle fluxes. The particle flux was reconstructed by means of a continuous wavelet transform (CWT) to confirm the validity of the EC calculations during particle gusts. Their origin could not clearly be identified, but they indicate the presence of poorly mixed air parcels which are strongly enriched with particles. Due to the episodic yet large contribution to particle fluxes in Innsbruck, the potential impact of particle gusts on turbulent particle exchange should also be evaluated at other urban and non-urban sites.

Aerodynamic modelling of wind turbine blade loads during extreme deflection events

Long, flexible wind turbine blades experience significant deflections during operation. Historically, the blade element momentum model in Bladed assumed that the blade is split into a set of radial aerodynamic sections which are aligned perpendicular to the pitch axis, and that any rotation of the sections due to deflection, pre-bend or pre-sweep in the blade can be ignored. For modern-day flexible rotor blades, under extreme loading conditions, this assumption no longer holds. Including this rotation when calculating inflow velocities and angle of attack, and when resolving the resultant forces at the element, causes a significant change in axial force (Fz) along the pitch axis, and therefore the blade out of plane bending moment (My). This in turn drives a change in overturning moments on the hub (which is driven by differences in bending moments between blades). An example 160m rotor shows an increase of 68% in hub overturning moment during an extreme gust event when aerofoil rotation due to deflection is included. This is verified through comparison to the alternative free vortex wake rotor model in Bladed. DNV GL Bladed includes the rotation of aerofoils by default at version 4.8.