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Downbursts are strong downdrafts that originate from thunderstorm clouds and create vigorous radial outflows upon hitting the ground. This study is part of the comprehensive experimental research on downburst outflows produced as large-scale impinging jets in the WindEEE Dome simulator at Western University, Canada. The 2800 tests carried out form the largest database of experimental measurements on downburst winds developed thus far, which is made available to the public in its whole and described in detail in a complementary study. Therefore, the current manuscript merely focuses on the data post-processing outcomes and interpretation of results from a selected subset of measurements. Impinging jets are here simulated as transient phenomena in which velocity time series are characterized by a sudden ramp-up of velocity, followed by the velocity peak, a short statistically stationary region, and the final velocity slowdown, as it is expected to occur in the actual downbursts. A dominant velocity peak that was systematically observed in all velocity records is associated with the radial advection of the primary vortex in the outflow. Depending on the radial distance from the downdraft, the primary vortex was sometimes preceded by a secondary, much smaller, vortex close to the surface. Vertical profiles of mean velocity and turbulence intensity are for the first time characterized through the extent of a downburst-like event in the spatiotemporal domain. Particularly, these profiles rapidly change in relation to the passage of the primary vortex and consequent variation of the surface layer thickness. This study lays out a foundation for an experimental model of non-stationary downburst outflows to come. Article highlights: Large experimental campaign and public database of measurements on transient downburst-like impinging jets. Characterization of the spatiotemporal evolution of wind speed and turbulence profiles. Measuring the effects of the primary and secondary vortices in the outflow on velocity and turbulence profiles. [ABSTRACT FROM AUTHOR]

The extreme value theory has been object of engineering studies for more than a century. The analysis of extreme winds plays a key role for complex civil structures and a driving role in different stages of wind turbines lifetime. Most of extremes probability models depend on the annual rate of independent events (ARIE) which has been traditionally considered a constant value. The authors have embraced a recent belief considering the ARIE as a function of the wind velocity. Even though a certain agreement has been achieved across the researches, some issues are still pending. In this regard, the paper shows that the annual, seasonal and daily fluctuations embedded in time series of the mean wind speeds, constrain its probability distribution and time correlation to be physically consistent. Besides, a new physical interpretation of the ARIE is presented, expressing how the independence across wind observations increases with the wind speed, up to the point that all yearly observations are independent if larger than a suitable speed value. Such a tendency is not revealed if the annual, seasonal and daily fluctuations are excluded by the analysis, leading to a deceitful shape of the ARIE. Finally, the paper shows how the velocity‐dependent ARIE model is consistent with the conventional asymptotic extreme value theory, if a sufficiently large left‐censorship applies to the dataset. The study of the ARIE presented in this paper is based on long‐term Monte Carlo simulation of the mean wind speed. [ABSTRACT FROM AUTHOR]

This paper describes the dataset of measurements collected and published in the context of the comprehensive experimental campaign on downburst-like outflows that was performed at the WindEEE Dome at Western University, Canada. Downbursts are strong downdrafts of air that originate from thunderstorm clouds and create vigorous radial outflows upon hitting the ground. Downbursts are here simulated as transient phenomena produced by large-scale impinging jet. Two jet velocities were adopted in the experiments. The three-component velocity measurements were recorded using 7 Cobra probes mounted on a vertical stiff mast and displaced at 10 radial positions in respect to the downdraft centerline. For every radial position, each experiment with the same initial condition was repeated 20 times to inspect the deterministic features of the signal. Overall, the total of 2800 tests (2 jet velocities × 20 repetitions × 10 radial positions × 7 heights) represent one of the largest experimental campaigns on downburst winds carried out in a wind tunnel facility thus far. Measurement(s) atmospheric wind speed Technology Type(s) Cobra Probe Factor Type(s) wind velocity Sample Characteristic - Organism wind flow Sample Characteristic - Environment wind tunnel [ABSTRACT FROM AUTHOR]

Thunderstorm outflows are usually analysed by decomposing their horizontal velocity into a slowly-varying mean part and a residual fluctuation; in this framework the wind direction is often examined qualitatively but disregarded quantitatively. This is incoherent with the traditional analysis of synoptic wind speeds, where the mean velocity and direction are first determined, then the fluctuations are decomposed in terms of longitudinal and lateral turbulence components. Aiming to overcome these shortcomings, a novel directional decomposition strategy is formulated here, which makes the study of thunderstorm outflows and synoptic winds fully coherent. The results provided by the classic and novel decomposition rules are first compared and elucidated with reference to a couple of real thunderstorm and synoptic wind velocity records. Later on, they are applied to a broad class of thunderstorm outflow records whose statistical properties are investigated. The novel approach is strategic to carry out directional analyses of the dynamic behaviour of structures in terms of alongwind and crosswind response. • The classical decomposition rule of thunderstorm outflows disregards wind direction. • Classical synoptic wind and thunderstorm outflow decomposition rules are incoherent. • A novel directional rule is formulated that overcomes the above shortcomings. • The novel rule is strategic to carry out directional analyses of the structural response. [ABSTRACT FROM AUTHOR]

Highlights • Design wind velocity and wind-induced damage are often related to thunderstorms. • Research on thunderstorm loading of structures is still fragmentary and uncertain. • Calibration and advance are provided of response spectrum technique and time-domain analysis. • The response spectrum technique is a suitable tool for engineering calculations. • Time-domain analysis is highly efficient with a limited computational burden. Abstract Thunderstorms are transient events. Design wind velocity and wind-induced damage are often related to them. Despite this, research on thunderstorm loading of structures is still fragmentary and uncertain due to their complexity, short duration and small size. These issues make it difficult to set physically realistic and simple models as well as to gather real data. This favoured the implementation of refined methods based on limited measurements. The European Projects "Wind and Ports" and "Wind, Ports and Sea" realised an extensive monitoring network from which many thunderstorm outflow records were extracted. They were analysed to inspect their characteristics and to formulate methods coherent with measurements. Firstly, the response spectrum technique conceived for earthquakes was extended to thunderstorms. Then, a hybrid simulation strategy was proposed and time-domain integrations of the structural response were applied. This paper provides a joint calibration and advancement of these two methods, leading to results that substantially agree, especially faced with their conceptual and operative diversities. This confirms the potential of the response spectrum technique to become a suitable tool for calculating the thunderstorm loading of structures and the efficiency of hybrid simulations and time-domain analyses to investigate, with a limited computational burden, advanced structural issues. [ABSTRACT FROM AUTHOR]

The meteorological services of mid-latitude countries record wind speeds averaged over 10 min or 1 h periods and peak wind speeds for the same averaging period or a full day. Design wind speeds based on the statistical analysis of this data in a mixed wind climate may prove to be imprecise and unsafe due to the occurrence of intense, small and rapid extreme wind events such as thunderstorm outflows. Considering the 6 year continuous high-frequency records registered in two Port areas of the Upper Tyrrhenian Sea, a preliminary but representative analysis of the extreme wind speed distribution has been carried out in a mixed wind climate area frequently struck by thunderstorms. Results show that wind speeds with a high return period are always related to thunderstorm outflows. The mixed extreme distribution asymptotically overlaps with that for thunderstorms for high return periods and always provides the highest wind speeds. Gathering the ensemble of all extreme values into a single set leads to underestimating of the extreme wind speed. The Italian code provides conservative estimates of the extreme wind speed that protect designers from thunderstorms as well. However, refined analyses of the local wind climate that ignore thunderstorm events may lead to severe underestimations of the design wind velocity. [ABSTRACT FROM AUTHOR]

Summary: This paper studies the wind load on 1,000 m‐high super‐tall buildings and provides basic reference for design, including the utilization of passive and active control devices. High‐frequency force balance wind tunnel tests of super‐tall buildings with different height are carried out to investigate the effects of building height and wind flow on the wind load. Both monsoon and typhoon climate wind flows are simulated based on target models suggested in literatures. The simulation of typhoon climate wind flows is carried out by a newly developed technique. The analysis of the experimental results confirms that the aerodynamic force is very sensitive to both building height and wind flow. In monsoon climate, the turbulence intensity decreases on increasing the height above ground. Thus, on increasing the building height, vortex shedding becomes increasingly intense and excites stronger structural vibrations in the across‐wind direction, though the across‐wind fluctuating overturning moment coefficient is almost the same. In typhoon climate, both the mean and the fluctuating overturning moment coefficients increase with the building height. This is mainly caused by the decreasing mean wind speed. The vortex excitation becomes weaker on increasing the building height, and this phenomenon is different from that observed in the monsoon climate. In order to better explain vortex‐shedding excitation, a new parameter referred to as the characteristic turbulence intensity is defined herein as a weighted mean value of the turbulence intensity in the range of the building height. It provides a robust interpretation of the vortex excitation of super‐tall buildings located in different wind flow and climate conditions. [ABSTRACT FROM AUTHOR]

The analysis of wind actions and effects on structures involves the knowledge of the parent population and extreme value distributions of the mean wind velocity. In spite of an impressive amount of measurements, refined probabilistic models and detailed applications to the study of specific sites, there is an equally disheartening lack of available probabilistic information at the territorial scale, and, therefore, of tools effectively applicable in the engineering and codification sectors. Almost all of the international standards and codes report sufficiently reliable maps of the mean wind velocity with 50-year return periods. On the other hand, there are still few regulations that provide the distribution of the yearly maximum value of the mean wind velocity or such value as a function of the return period. Furthermore, no regulations provide the distribution of the parent population of the mean wind velocity that may be very important for serviceability and fatigue analyses. This paper introduces a joint representation of the parent population and extreme value distributions of the mean wind velocity of synoptic extratropical cyclones; starting from this model, simple but reliable expressions are derived, directly applicable in the engineering and codification sectors, aimed at bridging the gap described. The obtained expressions are critically examined, pointing out their advantages but also some apparent critical issues. A preliminary application of these expressions is carried out with reference to the Italian territory. [ABSTRACT FROM AUTHOR]

The study aims to estimate the maximum dynamic response of linear elastic SDOF systems subjected to thunderstorm outflows. Starting from a recently developed Evolutionary Power Spectral Density (EPSD) model for the wind velocity, the dynamic response is decomposed into a time-varying mean and a non-stationary random fluctuation. The EPSD and the Non-Geometrical Spectral Moments (NGSMs) of the random fluctuation are derived both accounting and neglecting the transient dynamics due to the modulating function of the load. The mean value of the maximum nonstationary fluctuating component of the response is estimated based on the definition of an equivalent stationary process following an approach proposed in the literature. In order to mitigate the overestimations of the maximum dynamic response due to the Poisson approximation, analogously to the formulation developed by Der Kiureghian for withe noise excitation, an equivalent expected frequency is introduced for thunderstorm excitation. Finally, the maximum dynamic response to thunderstorms is estimated as the sum of the maximum mean and fluctuating parts and a numerical validation of the results against real recorded thunderstorms is provided, highlighting the reliability of adding up the mean and fluctuating contributions and the advantages and limits of neglecting the transient dynamics. • Response is derived starting from a consistent EPSD model of thunderstorm velocity. • The expected value of the maximum response is derived trough equivalent parameters. • A correction for the overestimations due to Poisson approximation is introduced. • The approach is validated against time-domain solutions from recorded thunderstorms. • Neglecting the transient dynamics may be overconservative. [ABSTRACT FROM AUTHOR]

Wind-induced fatigue is a crucial topic in the design of wind-sensitive structures. Despite this, methods proposed in literature are mainly addressed to research, or they are too simplified for engineering applications. Thus, suitable engineering and standards procedures are almost totally lacking, which is a major shortcoming in structural and wind engineering. Starting from a closed-form solution (CFS) recently proposed by the authors, this paper develops a novel engineering approach to evaluate the alongwind-induced fatigue of structures and structural elements. This approach is based on a hierarchy of hypotheses that lead to a progressive simplification of the basic formulation. Two classes of formulas, referred to as Levels I and II CFSs, are obtained and critically discussed with special concern for input parameters. Level I CFS implies three further simplifications joined together by the common aim of providing refined approximations of the reference target solution. Level II CFS implies three different simplifications joined together by the common aim of providing easy solutions on the safe side. This set of CFSs is framed within a general procedure that any country, society, or engineer can easily personalize to a situation and requirement, ranging from numerical tools to manual engineering calculations and code provisions. [ABSTRACT FROM AUTHOR]

• A mathematical model to evaluate motion-induced forces on slender structures subjected to thunderstorm outflows is proposed. • Time-varying aerodynamic damping matrix and aerodynamic stiffness matrix of the system are defined. • Three levels of analysis are addressed, according to the characteristics of the wind event. • The classical solution for synoptic winds is found as a particular case. • Suitable wind fields compatible with single-point records are rebuilt and applied on two configuration of a structure, estimating the motion-induced forces. • The effects of the transient aeroelasticity are analysed and critically commented. • Motion-induced forces are evaluated on slender real structures. Literature is rich about studies which concern the insurgence of instability of structural systems under the action of steady flows, which have led to well-consolidated methods to assess the structural safety with regard to aeroelastic phenomena induced by synoptic winds. On the other hand, there are no clear references regarding aeroelasticity induced by the effect of thunderstorm outflows, events characterised by irregular variations of the wind speed and direction in a limited duration of time, which prevent the furnishing of a long time interval for the structure and the fluid to synchronise. This paper, based under the hypothesis of applicability of the classic strip and quasi-steady theory, illustrates a mathematical model able to consider the aeroelastic effects of thunderstorm outflows into the dynamic response of slender structures, from which the methodology for synoptic winds may be found as a particular case. After defining three different levels of analysis, applications regarding the Endless Column by Constantin Brâncuși under the action of ten thunderstorm outflows are proposed, whose outcomes are critically analysed and commented. [ABSTRACT FROM AUTHOR]

Abstract: Monte Carlo simulation is becoming a fundamental tool for the design of complex and important wind-excited structures. A common application regards the time-domain dynamic analysis of multi-dof nonlinear structures whose excitation is calculated on the base of simulated wind velocity time-histories. The present paper describes a methodology for the simulation of wind velocity fields over large domains, possibly in zones characterised by complex topography. The modelling of turbulence in non-homogeneous flow condition and some computational aspects related to its simulation are discussed, proposing some strategies for reducing the calculation time. The simulation procedure is applied to the case of the Messina Strait bridge for which the three components of turbulence are simulated over a domain composed by 351 nodes. [Copyright &y& Elsevier]

The urban atmospheric boundary layer (UABL) is complex due to the heterogeneous underlying city surface. The nine anemometers installed at different heights along the 325 m meteorological tower provide an opportunity to carry out a refined study of wind properties in the UABL in central Beijing, China. Based on the recent 5-year high-resolution measured data, in total, 229,488 10-min length segments of wind records related to each anemometer are reliable for further analyses. Accordingly, the statistical properties of the wind speed and direction are first analyzed to present the local wind climate in a comprehensive way. Moreover, the pattern of the wind profiles related to two typical synoptic intense events are illustrated in order to give a preliminary perspective, then the statistical properties corresponding to a series of intense windstorms are described. Here, the deviations in the wind direction occur between 200 m and 280 m of the atmosphere, which might be due to the existence of an Ekman spiral; besides this, the laws of wind profiles based on open terrain are not suitable for the UABL, and the aerodynamic characteristic parameters of the UABL based on vertical stratified structures have to be considered. The results contribute to the establishment of revised models for the wind profile and are useful for the further understanding of the structure of UABL wind. [ABSTRACT FROM AUTHOR]

This paper presents a new approach for modelling the evolutionary power spectral density (EPSD) of thunderstorm outflows based on a database of 129 real-scale thunderstorm time-histories. Two equivalent methods of decomposition of the wind velocity are investigated, outlining the derivation of the EPSD. The analyses are based on the hypothesis that the residual turbulent fluctuations can be treated as a uniformly modulated process, whose reliability is verified studying the steadiness of its up-crossing rate. The assumption of considering a constant turbulence intensity is checked through the evaluation of the dynamic response of a set of SDOF systems in time-domain and through the response spectrum technique. Two models for the time-modulating function of the EPSD are proposed that include the parameters characteristic of both the thunderstorm event and the background wind. Finally, the steps for the derivation of the EPSD are outlined pointing out the limits of the representation of the PSD of the reduced turbulent fluctuations through spectral models commonly adopted in wind engineering. The final aim of this research is finalising a triad of complementary methods for evaluating the dynamic response of structures to thunderstorm outflows - EPSD, time-domain and response spectrum - consistent with real-scale time-history records. • The non-stationarity of turbulent fluctuations is analysed through their up-crossing rate. • The residual turbulent fluctuations can be dealt with a uniformly modulated process. • Assuming steady turbulence intensity causes overestimations in the dynamic response. • The models proposed for the time-modulating functions encase a physical meaning. • Two different ways of modelling the evolutionary power spectral density are outlined. [ABSTRACT FROM AUTHOR]

This paper discusses different strategies for the extraction of the time-varying mean from wind speed time histories. Due to the advantage of allowing analytical evaluations, the attention is focused on kernel regression techniques, considering different weighting functions, namely a constant, a Gaussian and a cardinal sine weighting function. The problem is firstly treated analytically, and the frequency-domain properties of the filter associated to different kinds of weighting functions in the definition of the slowly varying mean through kernel regression are analysed. Then, different weighting functions are adopted for the analysis of digitally-simulated stationary wind speed time histories and for the time histories of thunderstorm outflows recorded by a tri-axial anemometer. The consequences of the adoption of different weighting functions on the harmonic content and statistical properties of turbulence are studied. The same features are found also for thunderstorm outflow records. • Kernel regression techniques for the time-varying mean extraction are studied. • The properties of the filter associated to various weighting functions are analysed. • The statistical moments of the reduced turbulent fluctuation are estimated. • Applications to stationary and nonstationary wind speed time histories are provided. [ABSTRACT FROM AUTHOR]

Wind actions are crucial for the safety and sustainability of structures. The wind climate of Europe and many other parts of the world is dominated by synoptic extra-tropical cyclones and mesoscale thunderstorms. Thunderstorms are frequent events that cause wind speeds and damage often greater than those of cyclones. This paper describes a wide research activity including an extensive monitoring network, an unprecedented database of transient wind speed recordings, a broad spectrum of numerical tools for elaborating data and extracting their statistical properties relevant to the wind loading of structures, the development of wind tunnel tests and CFD simulations, investigations on weather scenarios and damage surveys aiming to complete the information provided by field measurements. Based on these resources, a new generation of wind loading models is being developed – response spectrum technique, time-domain integration, evolutionary spectral density - robustly coherent with measured data and intrinsically coherent with each other. These studies are being carried out in the framework of the project THUNDERR, funded by the European Research Council (ERC) with an Advanced Grant 2016 in order to produce outcomes physically correct, transferable to design and standards, suitable to modify the current wind loading format and make constructions wind-safer and cost-efficient. • THUNDERR project studies thunderstorm outflows and their impact on structures. • Outflows are studied by real measurements, CFD simulations and wind tunnel tests. • New wind loading models are being developed to account for thunderstorm effects. • Design practices will benefit of THUNDERR outcomes to make constructions wind-safer. [ABSTRACT FROM AUTHOR]

The statistical modeling of the extreme mean wind speed is a very controversial subject. Several models are currently being applied in the literature, based on different assumptions and supplying quite different results. This paper takes a step back towards the common root of many extreme value models: the Annual Rate of Independent Events (ARIE). Starting from an analysis of large datasets of synthetic wind observations, the ARIE is inspected from a new point of view and some features so far hidden are brought to light. Based on that, a new effective approach to model the distribution of the extreme mean wind speed is proposed. The reliability of the proposed model is discussed processing both large datasets of synthetic wind observations, and small-sized datasets representative of real conditions. ARIE sensitivity to uncertainties in the parent distribution is also evaluated and critically discussed. [ABSTRACT FROM AUTHOR]

The authors have recently developed a Monte Carlo simulation algorithm able to generate thousands of years of synthetic wind speed values. In this study, however, two points have not received adequate attention: the presence of underlying periodic deterministic components embedded into the time series of the velocity and the generation of time series having exactly the desired marginal distribution. In principle, both these issues may have relevant consequences on the distribution of extreme values. This paper investigates and discusses the presence of underlying deterministic components in the wind records, develops a refined simulation algorithm for non-Gaussian colored wind speed stationary processes, and finally inspects how much these advances affect the analysis of extreme values. An extensive simulation consisting of more than 12,740 years of synthetic wind speeds is performed, based on the synoptic wind climatology of the central part of Italy. The results demonstrate that the use of a refined simulation algorithm improves the quality of extreme values analysis. On the other hand, it is not easy to express a definite opinion on the random or deterministic nature of some periodic cycles; it is shown, however, that dealing with such cycles as random or deterministic has very limited consequences on extreme values analysis. [ABSTRACT FROM AUTHOR]

Abstract: This study proposes a novel methodology to create a large sized synthetic dataset of wind velocities and adopts this to discuss the probability distributions commonly used for extreme winds. A large number of long-term time series of mean wind speed are generated by a numerical procedure that faithfully reproduces the macro-meteorological component of wind velocity, while guaranteeing sample functions with random extremes. Through application of this technique, a large sized dataset of synthetic extreme wind observations has been extracted, of a size unprecedented in literature. Commonly applied extreme value (EV) methods are then used to process the dataset produced. In the first instance, the effectiveness of these models is tested to exclude any false effects due to the limited period covered by current wind measurements. Following this, interval estimations of design wind speeds are derived by analyzing EVs from records of different lengths in order to explore the applicability of EV distributions to real situations. The comparison between analytical and numerical results provides many interesting and intriguing points of discussion, and opens the way to new research horizons in EV analysis. [Copyright &y& Elsevier]

Abstract: This paper introduces a procedure for the simulation of long-term time series of the mean wind speed. A series of meteorological records are used to describe the probabilistic distribution and the spectrum of the process to be simulated. In particular, a complete description of the macro-meteorological spectrum of the wind speed is obtained, piecing together spectral portions deriving from different records. Then, an advanced simulation algorithm is introduced, based on existing iterative methods for simulating non-Gaussian processes via memoryless transformations, revised in order to obtain random extreme values of the simulated time-histories. The outlined procedure is finally applied for generating sample functions of the mean speed process. The availability of a large number of realizations permits the ability of the new algorithm to produce functions with desired features to be investigated in terms of ensemble statistics. This robust database could be useful for further studies. [Copyright &y& Elsevier]

A "downburst" is defined as a diverging wind system that occurs when a strong downdraft induces an outflow of damaging winds on or near the ground. Severe wind damage in many parts of the world are often due to thunderstorm outflows and their knowledge is therefore relevant for structural safety and design wind speed evaluation. Nevertheless, there is not yet a shared model for thunderstorm outflows and their actions on structures. In this paper, an analytical model that simulates the horizontal mean wind velocity originated from a travelling downburst is proposed. The horizontal wind velocity is expressed as the vector summation of three independent components: the stationary radial velocity generated by an impinging jet over a flat surface, the downdraft translating velocity, which corresponds to the parent cloud motion, and the boundary layer background wind field at the surface where the downburst is immersed. A parametric analysis is also developed and coupled with the analytical model aiming to investigate two observed downburst events and extract their main parameters – e.g. downdraft diameter, touch-down position, translating downdraft speed and direction, intensity and decay period - in order to reconstruct the space-time evolution of these events and validate the model itself. • An analytical model is developed to simulate thunderstorm outflows. • Downburst parameters are estimated through a parametric analysis. • Two real-scale thunderstorm outflows are simulated. [ABSTRACT FROM AUTHOR]

The study of thunderstorm outflows and their actions on structures is a dominant topic of wind engineering. This paper contributes to knowledge in this field through a systematic analysis of the thunderstorm outflows recorded by 9 anemometers installed at different heights along the 325 m high Beijing Meteorological Tower. Analyses are carried out through a directional decomposition strategy. The characteristics of a wide dataset of thunderstorm signals are analysed in a statistical environment coherent with the traditional one for synoptic winds; in this stage of the research, estimations of the mean wind speed and direction, the turbulence parameters and gust factor are carried out considering the records as disjoint from each other. Based on this choice, the results are compared with those obtained in the northern Mediterranean, providing a preliminary answer to the crucial question whether thunderstorms have similar properties in different areas, or, better, what of their properties are similar and what depend on the area itself. Besides to previous researches, the time evolution of the wind speed and direction profile is investigated with reference to a thunderstorm test case event. The systematic analysis of the full dataset of thunderstorm outflow fields is postponed to future researches. • A series of thunderstorm outflow records are detected in Beijing urban area. • A novel directional decomposition strategy recently formulated is implemented. • The characteristics of a wide dataset of thunderstorm signals are analysed in a statistical environment. • The results are compared with those obtained in the northern Mediterranean preliminarily. • The time evolution of the wind speed and direction profile is investigated condidering a test case. [ABSTRACT FROM AUTHOR]

With the development of mountain areas, more wind-sensitive infrastructures are constructed. In the design of these infrastructures, the wind loading cannot be accurately obtained from the code based on the flat area. Hence, it is of great importance to study the mountain wind characteristics. In this study, the wind field measurement was initiated in a mountain area of western China. After the examination of the measured data, two typical wind events including the thunderstorm wind and thermally developed wind are highlighted. To extract and separate these wind events, an automatic classification method is proposed. The thunderstorm wind is analyzed in order to capture the rapid variation of its maximum wind speed, mean temperature and mean humidity through the boxplot method while the analysis of thermally developed winds relies on the correlation between the mean wind speed and mean temperature. Since the thunderstorm wind is relatively more important for wind engineering, its wind characteristic is focused hereafter and analyzed in detail based on the ultrasonic anemometer data. The characteristics of the thermally developed wind and other wind will be the matter of further studies and investigations. Results show that the characteristics of the thunderstorm wind measured in the mountainous area have no significant difference in comparison with those in the flat area. Due to the limited data, the above results deserve further investigations when more measurements become available. • Field measurement was conducted to study intense wind characteristics in mountain. • Thunderstorm and thermally developed winds (TW, TDW) are spotted in mountain. • TW and TDW are separated out by the proposed automatic classification method. • Transient characteristics of TW in mountain area are well discussed. • Characteristics of TW in mountain area are found to be similar to those in flat area. [ABSTRACT FROM AUTHOR]

Abstract: The separation and classification of intense wind events into homogeneous families is a key topic to study the wind-excited response of structures and to determine the distribution of extreme wind velocities and extreme wind-induced effects. This paper deals with the management of large sets of wind velocity data, in order to separate and classify independent extreme wind events through a semi-automated procedure involving a suitable mix of systematic quantitative controls and specific qualitative judgments. The proposed method is applied to an extensive dataset of continuous wind measurements provided by a wide and high quality monitoring network realized in the five main ports of the Northern Tyrrhenian Sea – namely Genova, Savona, La Spezia, Livorno and Bastia – in the framework of the European Project “Wind and Ports”. [Copyright &y& Elsevier]

Detection of thunderstorms is important to the wind hazard community to better understand extreme wind field characteristics and associated wind-induced load effects on structures. This paper contributes to this effort by proposing an innovative course of research that uses machine learning techniques, independent of wind statistics-based parameters, to autonomously identify thunderstorms from large databases containing high-frequency sampled continuous wind speed data. In this context, the use of Shapelet transform is proposed to identify key individual attributes distinctive to extreme wind events based on similarity of the shape of their time series signature. This shape-based representation, when combined with machine learning algorithms, yields a practical event detection procedure with minimal domain expertise. In this paper, the shapelet transform along with Random Forest classifier is employed for the identification of thunderstorms from 1-year of data from 14 ultrasonic anemometers that are a part of an extensive in-situ wind monitoring network in the Northern Mediterranean ports. A collective total of 240 non-stationary records associated with thunderstorms were identified using this method. The results lead to enhancing the pool of thunderstorm data for a more comprehensive understanding of a wide variety of thunderstorms that have not been previously detected using conventional gust factor-based methods. • The use of Shapelet Transform (ST) based machine learning is proposed to detect thunderstorms from wind velocity measurements. • This method is independent of wind statistics-based parameters so that a wide variety of thunderstorms can be identified. • Data from 14 ultrasonic anemometers in the Northern Mediterranean ports are used • A collective total of 240 non-stationary records associated with thunderstorms are autonomously identified using this method. [ABSTRACT FROM AUTHOR]