Gust Factors: Meteorologically Stratified Climatology, Data Artifacts, and Utility in Forecasting Peak Gusts

AbstractGust factors in Milwaukee, Wisconsin, are investigated using Automated Surface Observing System (ASOS) wind measurements from 2007 to 2014. Wind and gust observations reported in the standard hourly ASOS dataset are shown to contain substantial bias caused by sampling and reporting protocols that restrict the reporting of gusts to arbitrarily defined “gusty” periods occurring during small subsets of each hour. The hourly ASOS gust reports are found to be inadequate for describing the gust characteristics of the site and ill suited for the study of gust factors. A gust-factor climatology was established for Milwaukee using the higher-resolution, 1-min version of the ASOS dataset. The mean gust factor is 1.74. Stratified climatologies demonstrate that Milwaukee gust factors vary substantially with meteorological factors, with wind speed and wind direction exerting the strongest controls. A variety of modified gust-factor models were evaluated in which the peak wind gust is estimated by multiplying a gust factor by the observed, rather than forecast, wind speed. Errors thus obtained are entirely attributable to utility of the gust factor in forecasting peak gusts, having eliminated any error associated with the wind speed forecast. Results show that gust-factor models demonstrate skill in estimating peak gusts and improve with the use of meteorologically stratified gust factors.

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Meteorologically Stratified Gust Factors for Forecasting Peak Wind Gusts Across the United States

Bulletin of the American Meteorological Society ◽

10.1175/bams-d-21-0013.1 ◽

2021 ◽

pp. 1-17

Author(s):

Jonathan D. W. Kahl ◽

Brandon R. Selbig ◽

Austin R. Harris

Keyword(s):

United States ◽

Wind Speed ◽

Power Distribution ◽

The United States ◽

Wind Gust ◽

Average Wind Speed ◽

Gust Factor ◽

Wind Gusts ◽

Wide Range ◽

Gust Factors

AbstractWind gusts are common to everyday life and affect a wide range of interests including wind energy, structural design, forestry, and fire danger. Strong gusts are a common environmental hazard that can damage buildings, bridges, aircraft, and trains, and interrupt electric power distribution, air traffic, waterways transport, and port operations. Despite representing the component of wind most likely to be associated with serious and costly hazards, reliable forecasts of peak wind gusts have remained elusive. A project at the University of Wisconsin-Milwaukee is addressing the need for improved peak gust forecasts with the development of the meteorologically stratified gust factor (MSGF) model. The MSGF model combines gust factors (the ratio of peak wind gust to average wind speed) with wind speed and direction forecasts to predict hourly peak wind gusts. The MSGF method thus represents a simple, viable option for the operational prediction of peak wind gusts. Here we describe the results of a project designed to provide the site-specific gust factors necessary for operational use of the MSGF model at a large number of locations across the United States. Gust web diagrams depicting the wind speed- and wind direction-stratified gust factors, as well as peak gust climatologies, are presented for all sites analyzed.

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An Examination of Tropical and Extratropical Gust Factors and the Associated Wind Speed Histograms

Journal of Applied Meteorology ◽

10.1175/jam2199.1 ◽

2005 ◽

Vol 44 (2) ◽

pp. 270-280 ◽

Cited By ~ 45

Author(s):

B. M. Paulsen ◽

J. L. Schroeder

Keyword(s):

Wind Speed ◽

Tropical Cyclones ◽

Deep Convection ◽

Transitional Flow ◽

Wind Gust ◽

Measuring Device ◽

Gust Factor ◽

Mean Wind Speed ◽

Landfalling Tropical Cyclones ◽

Gust Factors

Abstract A gust factor, defined as the ratio between a peak wind gust and mean wind speed over a period of time, can be used along with other statistics to examine the structure of the wind. Gust factors are heavily dependent on upstream terrain conditions (roughness), but are also affected by transitional flow regimes (specifically, changes in terrain and the distance from the upstream terrain change to the measuring device), anemometer height, stability of the boundary layer, and, potentially, the presence of deep convection. Previous studies have yielded conflicting results regarding differences in gust factors that might exist between winds generated by tropical cyclones and those generated by extratropical systems. Using high-resolution wind speed data collected from both landfalling tropical cyclones and extratropical systems, two databases of wind characteristics were developed. Gust factors from tropical cyclone and extratropical winds were examined, summarized, and compared. Further analysis was conducted to examine and compare the characteristics of the associated tropical and extratropical wind speed histograms. As expected, the mean gust factor was found to increase with increasing upstream surface roughness. Some differences were observed between data from the tropical environment and the extratropical environment. Mean gust factors from the tropical regime were found to be higher than mean gust factors from the extratropical environment within each roughness regime and the wind speed histograms generated from data from the two environments indicated some differences.

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Drifting-snow studies over an instrumented mountainous site: II. Measurements and numerical model at small scale

Annals of Glaciology ◽

10.3189/172756401781819364 ◽

2001 ◽

Vol 32 ◽

pp. 175-181 ◽

Cited By ~ 9

Author(s):

Jean-Luc Michaux ◽

Florence Naaim-Bouvet ◽

Mohamed Naaim

Keyword(s):

Wind Speed ◽

Numerical Model ◽

Small Scale ◽

Wind Gust ◽

Strong Wind ◽

Experimental Site ◽

In Situ Data ◽

Drifting Snow ◽

Mean Wind Speed ◽

Gust Factors

AbstractThe Érosion torrentielle, neige et avalanche (Etna) unit of CEMAGREF and the Centre d’Etudes de la Neige of Météo-France have been working on snowdrift for 10 years. A numerical model was developed at CEMAGREF to simulate snowdrift (Naaim and others, 1998). To validate this model on in situ data, a high-altitude experimental site was developed, located at 2700 m a.s.l. at the Lac Blanc Pass near the Alpe d’Huez ski resort. It is a nearly flat area and faces winds primarily from north and south. After describing the experimental site, we present the processed data of winter 1998/99. First, we analyze the data from CEMAGREF’s acoustic snowdrift sensor. It is sensitive to snow depth and snow-particle type, so additional calibration is necessary. Nevertheless, it allowed us to study non- stationary aspects of drifting snow. An analysis of gust factors for wind and drifting snow indicates that strong wind-gust factors exist in the mountains, and that drifting snow is more important during a regular and strong wind episode than during high wind-gust periods. Therefore, the numerical model presented here uses only the recorded mean wind speed. The model, which attempts to reproduce several days of storm, takes into account the modification of input parameters (e.g wind speed) as a function of time. The comparison between numerical results and measurements for a given meteorological event shows good agreement.

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Effects of Sensor Response and Gust Duration on Maximum Wind Gust Measurements and Data Homogenisation

10.5194/egusphere-egu2020-12298 ◽

2020 ◽

Cited By ~ 1

Author(s):

Amir Ali Safaei Pirooz ◽

Richard G.J. Flay ◽

Lorenzo Minola ◽

Cesar Azorin-Molina ◽

Deliang Chen

Keyword(s):

Wind Speed ◽

Wind Tunnel ◽

Turbulence Intensity ◽

Moving Average ◽

Wind Gust ◽

Gust Factor ◽

Wind Speeds ◽

Research Areas ◽

Factor Ratios ◽

Cup Anemometer

<p>Wind speed data recorded using different signal-processing procedures can introduce errors in the wind speed measurements. This study aims to assess the effects of a set of various moving average filter durations and turbulence intensities on the recorded maximum gust wind speeds. For this purpose, a series of wind-tunnel experiments was carried out at the University of Auckland, New Zealand, on the widely-used Vaisala WAA151 cup anemometer. The variations of gust and peak factors, and turbulence intensities measured by the cup anemometer as a function of the averaging duration and turbulence intensity are presented. The wind-tunnel results are compared with values computed from a theoretical approach, namely random process and linear system theory, and the results were also validated against values reported in the literature where possible.</p><p>To summarise, the major findings of this experimental study are:</p><ol><li>The results show that increasing the effective gust duration reduces both the gust and peak factors, resulting in an underestimation of maximum gust wind speeds and an overestimation of minimum gust wind speeds.</li> <li>The maximum difference between gust factors obtained for high (e.g. 3-s to 5-s) and low (raw, unfiltered measurements) gust durations reached values of 25% &#8211; 30% for the high turbulence conditions, and up to 5% &#8211; 10% for low turbulence intensities.</li> <li>Gust factor ratios, an important parameter that allow the measurements from a specific gust duration to be converted to other gust durations of interest, are reported for various gust durations as a function of turbulence intensity.</li> <li>The differences and gust factor ratios computed in this study can be applied directly to full-scale measurements, and can be used in several research areas, including analysing and homogenisation of historical wind speed time series, comparing gust climatologies of countries where different gust durations have been adopted, and so on. These factors clearly play an essential role in meteorological, climatological and wind engineering studies.</li> </ol>

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A two-year intercomparison of CW focusing wind lidar and tall mast wind measurements at Cabauw

10.5194/amt-2020-304 ◽

2020 ◽

Author(s):

Steven Knoop ◽

Fred C. Bosveld ◽

Marijn J. de Haij ◽

Arnoud Apituley

Keyword(s):

Wind Speed ◽

Wind Direction ◽

Continuous Wave ◽

Data Availability ◽

Horizontal Wind ◽

Horizontal Wind Speed ◽

Low Clouds ◽

Wind Measurements ◽

Wind Lidar ◽

The Mean

Abstract. A two-year measurement campaign of the ZephIR 300 vertical profiling continuous-wave (CW) focusing wind lidar has been carried out by the Royal Netherlands Meteorological Institute (KNMI) at the Cabauw site. We focus on the (height-dependent) data availability of the wind lidar under various meteorological conditions and the data quality through a comparison with in situ wind measurements at several levels in the 213-m tall meteorological mast. We find an overall availability of quality controlled wind lidar data of 97 % to 98 %, where the missing part is mainly due to precipitation events exceeding 1 mm/h or fog or low clouds below 100 m. The mean bias in the horizontal wind speed is within 0.1 m/s with a high correlation between the mast and wind lidar measurements, although under some specific conditions (very high wind speed, fog or low clouds) larger deviations are observed. The mean bias in the wind direction is within 2°, which is on the same order as the combined uncertainty in the alignment of the wind lidars and the mast wind vanes. The well-known 180° error in the wind direction output for this type of instrument occurs about 9 % of the time. A correction scheme based on data of an auxiliary wind vane at a height of 10 m is applied, leading to a reduction of the 180° error below 2 %. This scheme can be applied in real-time applications in case a nearby, freely exposed, mast with wind direction measurements at a single height is available.

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Whole Process Wind Characteristics Field Measurements of a Strong Wind

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.5094 ◽

2011 ◽

Vol 243-249 ◽

pp. 5094-5100 ◽

Cited By ~ 1

Author(s):

Ke Yang ◽

Wen Hai Shi ◽

Zheng Nong Li

Keyword(s):

Wind Speed ◽

Turbulence Intensity ◽

Field Measurements ◽

Integral Length Scale ◽

Length Scale ◽

Strong Wind ◽

Gust Factor ◽

Mean Wind Speed ◽

Wind Characteristics ◽

The Mean

This paper presents field measurement results of boundary layer wind characteristics over typical open country during the passages of typhoon Fung-wong passed by Wenzhou in July 2008. The field data such as wind speed and wind direction were measured from two propeller anemometers placed at the height of about 30m. The measured wind data are analyzed to obtain the information on mean wind speed and direction, turbulence intensity, gust factor, turbulence integral length scale and spectra of wind speed fluctuations. The results clearly demonstrate that the turbulence intensity and gust factor of typhoon Fung-wong are larger than normal, and there is a tendency for the turbulence intensities to decrease with the increase of the mean wind speed, however, there is another tendency for the turbulence integral length scale to increase with the increase of the mean wind speed. The power spectral densities of fluctuating wind speed in longitudinal and lateral directions obtained from the measured wind speed data roughly fit with Von Karman spectra. The results presented in this paper are expected to be of use to researchers and engineers involved in design of low-rise buildings.

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A 2-year intercomparison of continuous-wave focusing wind lidar and tall mast wind measurements at Cabauw

Atmospheric Measurement Techniques ◽

10.5194/amt-14-2219-2021 ◽

2021 ◽

Vol 14 (3) ◽

pp. 2219-2235

Author(s):

Steven Knoop ◽

Fred C. Bosveld ◽

Marijn J. de Haij ◽

Arnoud Apituley

Keyword(s):

Wind Speed ◽

Wind Direction ◽

Continuous Wave ◽

Data Availability ◽

Horizontal Wind ◽

Horizontal Wind Speed ◽

Low Clouds ◽

Wind Measurements ◽

Wind Lidar ◽

The Mean

Abstract. A 2-year measurement campaign of the ZephIR 300 vertical profiling continuous-wave (CW) focusing wind lidar has been carried out by the Royal Netherlands Meteorological Institute (KNMI) at the Cabauw site. We focus on the (height-dependent) data availability of the wind lidar under various meteorological conditions and the data quality through a comparison with in situ wind measurements at several levels in the 213 m tall meteorological mast. We find an overall availability of quality-controlled wind lidar data of 97 % to 98 %, where the missing part is mainly due to precipitation events exceeding 1 mm h−1 or fog or low clouds below 100 m. The mean bias in the horizontal wind speed is within 0.1 m s−1 with a high correlation between the mast and wind lidar measurements, although under some specific conditions (very high wind speed, fog or low clouds) larger deviations are observed. The mean bias in the wind direction is within 2∘, which is of the same order as the combined uncertainty in the alignment of the wind lidars and the mast wind vanes. The well-known 180∘ error in the wind direction output for this type of instrument occurs about 9 % of the time. A correction scheme based on data of an auxiliary wind vane at a height of 10 m is applied, leading to a reduction of the 180∘ error below 2 %. This scheme can be applied in real-time applications in the situation that a nearby freely exposed mast with wind direction measurements at a single height is available.

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Forecasting Peak Wind Gusts Using Meteorologically Stratified Gust Factors and MOS Guidance

Weather and Forecasting ◽

10.1175/waf-d-20-0045.1 ◽

2020 ◽

Vol 35 (3) ◽

pp. 1129-1143

Author(s):

Jonathan D. W. Kahl

Keyword(s):

Wind Speed ◽

Weather Forecasting ◽

Factor Model ◽

Model Performance ◽

The United States ◽

Gust Factor ◽

Wind Gusts ◽

Skill Improvement ◽

Model Output Statistics ◽

Gust Factors

Abstract Gust prediction is an important element of weather forecasting services, yet reliable methods remain elusive. Peak wind gusts estimated by the meteorologically stratified gust factor (MSGF) model were evaluated at 15 locations across the United States during 2010–17. This model couples gust factors, site-specific climatological measures of “gustiness,” with wind speed and direction forecast guidance. The model was assessed using two forms of model output statistics (MOS) guidance at forecast projections ranging from 1 to 72 h. At 11 of 15 sites the MSGF model showed skill (improvement over climatology) in predicting peak gusts out to projections of 72 h. This has important implications for operational wind forecasting because the method can be utilized at any location for which the meteorologically stratified gust factors have been determined. During particularly windy conditions the MSGF model exhibited skill in predicting peak gusts at forecast projections ranging from 6 to 72 h at roughly half of the sites analyzed. Site characteristics and local wind climatologies were shown to exert impacts on gust factor model performance. The MSGF method represents a viable option for the operational prediction of peak wind gusts, although model performance will be sensitive to the quality of the necessary wind speed and direction forecasts.

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Probabilistic Wind Gust Forecasting Using Nonhomogeneous Gaussian Regression

Monthly Weather Review ◽

10.1175/mwr-d-11-00075.1 ◽

2012 ◽

Vol 140 (3) ◽

pp. 889-897 ◽

Cited By ~ 26

Author(s):

Thordis L. Thorarinsdottir ◽

Matthew S. Johnson

Keyword(s):

Wind Speed ◽

Linear Function ◽

Location Parameter ◽

Maximum Wind Speed ◽

Wind Gust ◽

Probabilistic Forecasting ◽

Maximum Wind ◽

Gaussian Regression ◽

Gust Speed ◽

Wind Speed Forecast

Abstract A joint probabilistic forecasting framework is proposed for maximum wind speed, the probability of gust, and, conditional on gust being observed, the maximum gust speed in a setting where only the maximum wind speed forecast is available. The framework employs the nonhomogeneous Gaussian regression (NGR) statistical postprocessing method with appropriately truncated Gaussian predictive distributions. For wind speed, the distribution is truncated at zero, the location parameter is a linear function of the wind speed ensemble forecast, and the scale parameter is a linear function of the ensemble variance. The gust forecasts are derived from the wind speed forecast using a gust factor, and the predictive distribution for gust speed is truncated according to its definition. The framework is applied to 48-h-ahead forecasts of wind speed over the North American Pacific Northwest obtained from the University of Washington mesoscale ensemble. The resulting density forecasts for wind speed and gust speed are calibrated and sharp, and offer substantial improvement in predictive performance over the raw ensemble or climatological reference forecasts.

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Wind Characteristics Investigation on The Roofs of Three Adjacent High-Rise Buildings in a Coastal Area during Typhoon Meranti

Applied Sciences ◽

10.3390/app9030367 ◽

2019 ◽

Vol 9 (3) ◽

pp. 367 ◽

Cited By ~ 4

Author(s):

Chequan Wang ◽

Zhengnong Li ◽

Qizhi Luo ◽

Lan Hu ◽

Zhefei Zhao ◽

...

Keyword(s):

Wind Speed ◽

Turbulence Intensity ◽

Wind Direction ◽

Time Interval ◽

Integral Scale ◽

High Rise ◽

Wind Turbulence ◽

Mean Wind Speed ◽

The Mean ◽

Gust Factors

This paper presents the study of the pulsating characteristics of three adjacent high-rise buildings A, B, and C under typhoon ‘Moranti’ (2016) based on the measurement of the actual top wind speed. The studied pulsating characteristics included mean wind speed and direction, turbulence intensity, gust factor, turbulence integral scale, wind speed spectrum and correlation. The relationships between each pulsating parameter and the relationship between the pulsating parameter and gust duration have been investigated. Results show that the mean wind speed and wind direction of three buildings are close. When U ≥ 10 m/s in three different sites at the same time, the turbulence intensity variation of three buildings is consistent and decreases when mean wind speed increases. Once only two locations are acquired simultaneously and the wind angle between 35° and 45°, the mean values of the along-wind and cross-wind turbulence of building A and building C are close. The along-wind turbulence of the three buildings is greater than the predicted Chinese codes for various terrains. The turbulence intensity and gust factors obtained through the analysis of the samples with the mean wind speed U ≥ 10 m/s are reasonable. The turbulence integral scales of buildings A and C are equal to the predicted values of ASCE-7 and AIJ-2004, whereas the turbulent integral scale of building B is evidently small. The gust factors of three buildings increase when the turbulence intensity increases; these two characteristics have a linear relationship. At the same time interval, building B has the maximum along-wind turbulence intensity and gust factors during the low wind speed period and building C achieves the minimum values. Building A acquires the maximum and building C obtains the minimum values in the high wind speed period. The turbulence intensity and gust factors of building B show a certain pulsation. Results show that turbulence intensity and gust factors are mainly affected by the short-term fluctuation of wind. The longitudinal wind speed spectrum of three buildings conforms well to the von Karman model. The correlation of along-wind speed depends on the wind speed, whereas the correlation of cross-wind direction is independent of wind speeds. The measured data and statistical parameters provide useful information for the wind resistance design of high-rise buildings in typhoon-prone areas.

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