High Wind Events Research Articles

Seasonal variation of aerosol composition in Orange County, Southern California

Southern California is an urban metropolis bordered by mountains to the north and east and the Pacific Ocean to the west. Its unique geography and climatological features lead to annual patterns in atmospheric aerosol content from natural and anthropogenic sources. Here we sought to determine the nitrogen (N, including NO3−, NH4+, and total N) content of Southern California particulate matter (PM2.5) collected in Orange County, CA, and to identify relevant sources and processes that affect PM2.5 abundance and chemistry in different seasons. PM2.5 carbon (C) and N isotopic compositions (δ13C and δ15N, respectively) suggested that the C content of the PM2.5 derived partly from the marine inversion layer that occurs in the months of May through July. The high N content and δ15N values of PM2.5 collected in summer suggest a contribution from anthropogenic emissions, which are likely trapped in the basin by the inversion layer. In contrast, winter PM2.5 had a lower N content per volume of air, and δ13C values indicated a greater terrestrial signal, consistent with easterly winds. This trend was particularly evident in samples collected during high velocity Santa Ana wind events, which bring terrestrial material from the Great Basin and mountainous regions to the east of Southern California. Based on these observations, we suggest that atmospheric deposition of N is more likely to affect terrestrial ecosystems in the summer, when N content is high and aerosols are trapped by the inversion layer, whereas coastal marine ecosystems are more likely to be affected in the winter when westward winds are more common.

Prescriptive Design Standards for Resilience of Canadian Housing in High Winds

High-wind events cause significant damage to structures and property; in particular, light-frame wood homes are especially vulnerable and are the most abundant housing type in North America. As with many regions, Canadian homes are built to prescriptive standards that are based on historical construction methods and have remained relatively unchanged structurally across several decades, even though energy requirements have changed substantially. The present work reviews existing recommendations and campaigns for wind resilience in other jurisdictions, assesses their relevance to the Canadian context, and evaluates current construction methods as well as proposed improvement alternatives. Components that are commonly observed to fail in Canadian tornado damage surveys are of primary interest; namely, roof sheathing, roof-to-wall connections, and discontinuities in wall-to-floor links. Limit states design-based calculations are completed to assess the adequacy of nailed components from an engineering design standpoint. Past work quantifying the inadequacy of roof sheathing provisions in the current version of the National Building Code of Canada is discussed, and new analyses are done for the other components. Sources of conservatism in design calculations are identified, and unfactored results are provided to describe more representative limit states. When the redundancy of load and resistance factors is removed, the results show that current prescriptive provisions for roof-to-wall fasteners are likely to be sufficient up to a failure wind pressure of about 0.6 kPa – this applies to most regions in Canada. The wall capacity calculations suggest significant vulnerability to uplift or sliding withdrawal of nailed connections; however, these results are considered to be especially conservative. Potential, non-structural sources of house capacity are discussed. In general, current prescriptive provisions are deemed suitable for the synoptic wind events that they are expected to face. However, concern is identified for houses in open terrain or those prone to tornado risk. Design recommendations are presented in the context of providing resistance to up to EF2 tornadoes.

A climatology of convective and non‐convective high‐wind events across the eastern United States during 1973–2015

AbstractThis study investigates convective and non‐convective high‐wind events (CWEs and NCWEs) across the eastern U.S. during a 43‐year climatological period (1973–2015) for spatial and temporal variations in wind speed and direction. Hourly surface wind observations were gathered from the National Centers for Environmental Information Data Center Integrated Surface Database (NCEI‐ISD). This dataset includes quality‐controlled wind observations from 391 first‐order weather stations in the eastern U.S. Findings show that high‐wind events (HWEs) meeting established National Weather Service criteria were most concentrated in the West North Central and South regions (High Plains) and fewer CWEs occurred during the study period compared to NCWEs. Gust CWEs increased significantly (1.95 days year−1) while sustained NCWEs decreased significantly (−0.58 days year−1). Mean wind directions were observed primarily in the southwest and northwest quadrants. Mean wind speed decreased at a statistically significant level for sustained CWEs, gust CWEs, and sustained NCWEs. Developing an extensive climatological understanding of convective and non‐convective high‐wind events is beneficial to mitigate damage and fatalities caused by these events.

A Mathematical Model for A Cladding Fastener to Estimate the Maximum Pull-Out Force Capacity

In the last few years, considerable attention has been paid to the roof cladding systems due to their progressive use in the construction of low-rise buildings. The design of such systems has been gaining importance since they are subjected to severe damage and failure caused by high wind events, particularly at their fastener connection points. To offer a solution for predicting the maximum pull-out force capacity of cladding fasteners, this article presents a mathematical model for a fastener made of high strength steel austenitic 316. In this model, the two basic parameters of the fastener, namely the thread depth and the thread angle are included as the main elements of the contact surface between threads and the low carbon mild steel batten/purlin sheets. This mathematical model will be proposed to estimate the maximum pull-out force capacity of the cladding fasteners made of cold-formed A2 316 stainless steel. After finding the parameters of the mathematical model by using an optimization method based on a genetic algorithm (GA), a comparison will be made between the mean estimation error of the new model and the formerly proposed ones.

Estimating Southern Ocean Storm Positions With Seismic Observations

AbstractSurface winds from Southern Ocean cyclones generate large waves that travel over long distances (>1,000 km). Wave generation regions are often colocated with enhanced air‐sea fluxes and upper ocean mixing. Ocean wave spectra contain information about storm wind speed, fetch size, and intensity at their generation site. Two years of seismic observations on the Ross Ice shelf, combined with modern optimization (machine learning) techniques, are used to trace the origins of wave events in the Southern Ocean with an accuracy of ±110 km and ±2 hr from a hypothetical point source. The observed spectral energy attenuated within sea ice and in the ice shelf but retains characteristics that can be compared to parametric wave models. Comparison with the Modern‐Era Retrospective Analysis for Research and Applications, Version 2, and ERA5 reanalyses suggests that less than 45% of ocean swell events can be associated with individual Southern Ocean storms, while the majority of the observed wave events cannot be matched with Southern Ocean high wind events. Reanalysis cyclones and winds are often displaced by about 350 km or 10 hr in Modern‐Era Retrospective Analysis for Research and Applications, Version 2, and ERA5 compared to the most likely positions inferred from the seismic spectra. This high fraction of displaced storms in reanalysis products over the South Pacific can be explained by the limited availability of remote sensing observations, primarily caused by the presence of sea ice. Deviation of wave rays from their great circle path by wave‐current interaction plays a minor role.

Spatial Particulate Fields during High Winds in the Imperial Valley, California

We examined windblown dust within the Imperial Valley (CA) during strong springtime west-southwesterly (WSW) wind events. Analysis of routine agency meteorological and ambient particulate matter (PM) measurements identified 165 high WSW wind events between March and June 2013 to 2019. The PM concentrations over these days are higher at northern valley monitoring sites, with daily PM mass concentration of particles less than 10 micrometers aerodynamic diameter (PM10) at these sites commonly greater than 100 μg/m3 and reaching around 400 μg/m3, and daily PM mass concentration of particles less than 2.5 micrometers aerodynamic diameter (PM2.5) commonly greater than 20 μg/m3 and reaching around 60 μg/m3. A detailed analysis utilizing 1 km resolution multi-angle implementation of atmospheric correction (MAIAC) aerosol optical depth (AOD), Identifying Violations Affecting Neighborhoods (IVAN) low-cost PM2.5 measurements and 500 m resolution sediment supply fields alongside routine ground PM observations identified an area of high AOD/PM during WSW events spanning the northwestern valley encompassing the Brawley/Westmorland through the Niland area. This area shows up most clearly once the average PM10 at northern valley routine sites during WSW events exceeds 100 μg/m3. The area is consistent with high soil sediment supply in the northwestern valley and upwind desert, suggesting local sources are primarily responsible. On the basis of this study, MAIAC AOD appears able to identify localized high PM areas during windblown dust events provided the PM levels are high enough. The use of the IVAN data in this study illustrates how a citizen science effort to collect more spatially refined air quality concentration data can help pinpoint episodic pollution patterns and possible sources important for PM exposure and adverse health effects.

Vertical structure of ocean surface currents under high winds from massive arrays of drifters

Abstract. Very-near-surface ocean currents are dominated by wind and wave forcing and have large impacts on the transport of buoyant materials in the ocean. Surface currents, however, are under-resolved in most operational ocean models due to the difficultly of measuring ocean currents close to, or directly at, the air–sea interface with many modern instrumentations. Here, observations of ocean currents at two depths within the first meter of the surface are made utilizing trajectory data from both drogued and undrogued Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE) drifters, which have draft depths of 60 and 5 cm, respectively. Trajectory data of dense, colocated drogued and undrogued drifters were collected during the Lagrangian Submesoscale Experiment (LASER) that took place from January to March of 2016 in the northern Gulf of Mexico. Examination of the drifter data reveals that the drifter velocities become strongly wind- and wave-driven during periods of high wind, with the pre-existing regional circulation having a smaller, but non-negligible, influence on the total drifter velocities. During these high wind events, we deconstruct the total drifter velocities of each drifter type into their wind- and wave-driven components after subtracting an estimate for the regional circulation, which pre-exists each wind event. In order to capture the regional circulation in the absence of strong wind and wave forcing, a Lagrangian variational method is used to create hourly velocity field estimates for both drifter types separately, during the hours preceding each high wind event. Synoptic wind and wave output data from the Unified Wave INterface-Coupled Model (UWIN-CM), a fully coupled atmosphere, wave and ocean circulation model, are used for analysis. The wind-driven component of the drifter velocities exhibits a rotation to the right with depth between the velocities measured by undrogued and drogued drifters. We find that the average wind-driven velocity of undrogued drifters (drogued drifters) is ∼3.4 %–6.0 % (∼2.3 %–4.1 %) of the wind speed and is deflected ∼5–55∘ (∼30–85∘) to the right of the wind, reaching higher deflection angles at higher wind speeds. Results provide new insight on the vertical shear present in wind-driven surface currents under high winds, which have vital implications for any surface transport problem.

Effects of CME and CIR induced geomagnetic storms on low-latitude ionization over Indian longitudes in terms of neutral dynamics

This paper presents the response of the ionosphere during the intense geomagnetic storms of October 12–20, 2016 and May 26–31, 2017 which occurred during the declining phase of the solar cycle 24. Total Electron Content (TEC) from GPS measured at Indore, Calcutta and Siliguri having geomagnetic dips varying from 32.23°N, 32°N and 39.49°N respectively and at the International GNSS Service (IGS) stations at Lucknow (beyond anomaly crest), Hyderabad (between geomagnetic equator and northern crest of EIA) and Bangalore (near magnetic equator) in the Indian longitude zone have been used for the storms. Prominent peaks in diurnal maximum in excess of 20–45 TECU over the quiet time values were observed during the October 2016 storm at Lucknow, Indore, Hyderabad, Bangalore and 10–20 TECU for the May 2017 storm at Siliguri, Indore, Calcutta and Hyderabad. The GUVI images onboard TIMED spacecraft that measures the thermospheric O/N2 ratio, showed high values (O/N2 ratio of about 0.7) on October 16 when positive storm effects were observed compared to the other days during the storm period. The observed features have been explained in terms of the O/N2 ratio increase in the equatorial thermosphere, CIR-induced High Speed Solar Wind (HSSW) event for the October 2016 storm. The TEC enhancement has also been explained in terms of the Auroral Electrojet (AE), neutral wind values obtained from the Horizontal Wind Model (HWM14) and equatorial electrojet strength from magnetometer data for both October 2016 and May 2017 storms. These results are one of the first to be reported from the Indian longitude sector on influence of CME- and CIR-driven geomagnetic storms on TEC during the declining phase of solar cycle 24.

Stratospheric modulation of the large‐scale circulation in the Atlantic–European region and its implications for surface weather events

AbstractExtreme states of the stratospheric polar vortex can have long‐lasting impacts on extratropical circulation patterns, such as the North Atlantic Oscillation (NAO). This provides windows of subseasonal predictability beyond the typical weather forecast horizon of about 10 days. Subseasonal forecasts of surface weather are of significant interest in weather‐dependent socio‐economic sectors. For example, demand and supply for electricity and gas are weather dependent and therefore accurate forecasts are important for the energy industry and energy trading. Here we investigate the subseasonal impact of stratospheric conditions on surface weather events relevant to the energy industry in five subregions of Europe in winter. We use a definition of seven Atlantic–European weather regimes to describe the variability of the large‐scale circulation on subseasonal time scales. Results indicate that weather events are often associated with more than one preferred weather regime. In turn, some weather regimes project onto a specific NAO phase, while others are independent of the NAO. As expected, anomalous stratospheric polar vortex states predominantly modulate the occurrence of regimes related to the NAO and affect the likelihood of their associated weather events. In contrast, the occurrence of weather regimes which do not project well onto the NAO is not affected by anomalous stratospheric polar vortex states. These regimes provide pathways to unexpected weather events in extreme stratospheric polar vortex states. For example, weak stratospheric polar vortex states enhance the likelihood of negative NAO. High wind events in Central Europe predominantly occur during the zonal regime, strongly projecting onto positive NAO. However, these events also occur during the Atlantic trough regime, which is unaffected by anomalous stratospheric polar vortex states and thus provides a pathway to Central European high wind events during weak stratospheric polar vortex states. A correct NAO prediction alone is therefore not sufficient to correctly predict surface weather after extreme stratospheric polar vortex states. Moreover, weather regime life cycles independent of the NAO also need to be forecast accurately.

Accelerated Springtime Melt of Snow on Tundra Downwind from Northern Alaska River Systems Resulting from Niveo-aeolian Deposition Events

It is well known that light-absorbing particulate matter (PM) enhances absorption of sunlight when deposited on ice and snow. Such increased absorption is due to a reduction in surface albedo, resulting in accelerated melt of frozen surfaces. In isolation, earlier melt enhances Arctic warming since dark surfaces underlying snow and ice are exposed and absorb additional solar energy. Here, we combine various observational tools to demonstrate that aeolian deposition of PM along fluvial features on the North Slope of Alaska resulted in a notable reduction of surface albedo in the spring of 2016, from values typical for snow (~0.8) to around 0.35 on average. This reduction resulted in accelerated snow and ice melt by up to three weeks compared to unaffected areas. This phenomenon was observed to some degree in 12 other years dating back to 2003. Deposition generally was found to occur near particular sections of the rivers, with several areas affected by events in multiple years. In all years, the deposition is attributed to high wind events. The extreme case in 2016 is linked to unusually strong and extraordinarily persistent winds during April. The deposited material is thought to be the natural sediment carried by the rivers, resulting in a seasonally replenished source of PM. These findings indicate a previously unreported impact of both fluvial and atmospheric processes on the seasonal melt of northern Alaska rivers.

The behaviour of Nitinol Wire Bundles for Structural Applications

Shape memory alloys (SMA) belong to a family of smart materials, which undergo diffusionless phase transformations when subjected to thermo-mechanical changes making them ideally suitable for utilization in several structural engineering applications. Within this class of materials, Ni-Ti (Nickel-Titanium) alloys are predominantly used due to their non-linear behaviour. Nitinol, one of the Ni-Ti alloys, possesses unique properties such as super-elasticity and shape- memory effect, which makes it suitable for damping vibrations transmitted to structures like buildings and bridges during high wind and seismic events. This paper presents selected results obtained from a series of tests conducted on Nitinol 55 wires and bundles made from wires having diameters of 0.25, 0.5, 0.55, and 1 mm. The tests conducted include microstructure analyses, static tensile tests, hysteresis tests, and cyclic dynamic tests performed on wire bundles of various diameters. It is demonstrated that wires having small diameters (0.25 and 0.5 mm) exhibit greater ultimate strength compared with the ones having a larger diameter (1 mm). The bundles produced from these wires displayed hysteretic behaviour under cyclic-dynamic testing conditions confirming their suitability in structural engineering applications.

A climatology of high‐wind events for the eastern United States

AbstractThis study examines the spatial and temporal characteristics of high‐wind events (HWEs) based on the National Weather Service high‐wind criteria for 391 first‐order weather stations in the eastern United States from 1973 to 2015. A geographical analysis on the frequency of sustained and gust HWEs shows that the highest occurrences were reported in the Great Plains and Great Lakes, while the lowest number of observations occurred in the Mid‐South and Southeast. Linear trends show that the yearly frequency of sustained and gust HWEs are significantly decreasing (−0.579 days/year) and increasing (0.943 days/year) respectively during the 43‐year study period. These trends do not persist when the HWE data are normalized (long‐term mean is removed from the yearly count), but shows a cyclical anomaly pattern for both sustained and gust winds. Overall, 90 and 82% of all sustained and gust HWEs occur from the northwest or southwest quadrant, but when interpreted from a spatial perspective the mean wind direction of HWEs can be classified into specific regional wind groupings. However, this persistent southwesterly wind direction has gradually shifted to a more southerly (northerly) orientation for sustained (gust) HWEs over the study period.

Evaluating historical trends and influences of meteorological and seasonal climate conditions on lake chlorophyll a using remote sensing

Hansen CH, Burian SJ, Dennison PE, Williams GP. 2019. Evaluating historical trends and influences of meteoorological and seasonal climate conditions on lake chlorophyll a using remote sensing. Lake Reserv Manage. 36:45–63.Evaluations of long-term water quality trends and patterns in lakes and reservoirs are often inhibited by irregular historical records. This study uses historical Landsat satellite imagery to construct a more complete historical record of algal biomass (measured via chlorophyll a [Chl-a]) and presents a framework for developing seasonal algal estimation models using open source tools for processing and model development. This approach is both physically based (using observed patterns of variability and algal succession in the lake) and data driven (relying on statistical methods for model development). We use a generalized linear regression modeling technique to develop lake-specific, seasonal models for each lake in the multilake Great Salt Lake system in Utah. The 32-yr constructed history of estimated Chl-a enables analysis of long-term trends within the lake system as well as evaluations of local climate influences on Chl-a concentrations. The estimated historical record exhibits a shift in seasonality (i.e., maximum Chl-a occurs earlier in the growing season), as well as increasing trends of extreme Chl-a concentrations. We also evaluated relationships between meteorological conditions and Chl-a using the enhanced historical record and found localized sensitivity to short-term weather events such as high wind, high temperatures, or precipitation events. Seasonal climate conditions including high winter precipitation, summer temperatures, and early spring snow water equivalent are consistent with higher Chl-a extremes in the historical record. Improved understanding of the trends and climate influences provides useful context and guidance for future monitoring efforts and management strategies.

Investigations of a Southerly Non-Convective High Wind Event in Turkey and Effects on PM10 Values: A Case Study on April 18, 2012

On 18 April 2012, a cyclone originating in the Central Mediterranean caused a southerly non-convective high wind event, gusts ≥ 50 kn and not associated with thunderstorms, in the western and interior regions of Turkey. Dust events occurred because of dust plumes that rose from the Sahara Desert and from the interior regions of Turkey. The particle matter profile (PM10) on 18 April 2012 was the result of dust transport that appeared in conjunction with a non-convective high wind event, which is investigated in this study. The main objective of this research is to describe the conditions that prevailed before or during the event that occurred over airports and the long-range (intercontinental) trans-boundary transport of PM10 in Turkey. The dust transport trajectories were adjusted to determine the trajectories of long-range dust particles and/or dust particles that moved from interior regions of Turkey using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and by calculating the backward trajectories of airports that experienced dust occurrences. Furthermore, dust RGB and MODIS satellite pictures, CALIPSO images, BSC-DREAM8b outputs, Global Forecast System analysis outputs, and surface chart analysis outputs were used for various analyses. On 18 April 2012, Turkey’s largest average hourly value of PM10 was observed to be 844 µg/m3 at Kayseri 1 Air Quality Observation Station. Consequently, it was concluded that the Sahara Desert is the main source of dust transport in Turkey.

New Geophysical Model Function for Ocean Emissivity at 89 GHz Over Arctic Waters

New empirical geophysical model functions (GMFs) have been developed to interpret 89-GHz brightness temperature measurements over cold Arctic seas. Careful data screening is applied to the Advanced Microwave Scanning Radiometer 2 (AMSR2) multifrequency measurements to exclude atmospheric scattering and large absorption impacts, to estimate the 89-GHz sea surface emissivity and its relative changes with surface wind speed (SWS). Matched-up wind speeds are directly derived from the AMSR2 low-frequency measurements. The GMFs are obtained from the AMSR2 level 1R 89 GHz measurements corrected for the atmospheric impact with physical models and atmospheric parameters derived from the AMSR2 data. A carefully selected database encompasses mostly cold sea conditions (<4 °C) and a large range of wind speed conditions, including extratropical cyclone and polar low high-wind events over the Nordic Seas. Resulting GMFs contrast with previously proposed ones manifesting larger SWS signal at horizontal and positive SWS signal at vertical polarization.

Wind Climatology for Alaska: Historical and Future

Wind is a climate variable with major impacts on humans, ecosystems and infrastructure, especially in coastal regions with cold climates. Climate-related changes in high-wind events therefore have major implications for high-latitude residents, yet there has heretofore been no systematic evaluation of such changes in a framework spanning historical and future timeframes. In this study, hourly winds from surface station reports and from dynamical downscaling of winds simulated by two different global climate models have been synthesized into historical and future wind climatologies for Alaska. Quantile mapping procedures are used to calibrate wind simulations driven by an atmospheric reanalysis, and the calibrated winds are then used to bias-adjust the full distributions of historical and future winds downscaled from the global climate models. In the resulting climatologies, winds are generally stronger at coastal and offshore (island) locations than at interior sites, where calm conditions are frequent in winter. The season of peak wind speed varies from winter in the coastal and offshore locations to summer in interior areas. High-wind events determined from the hourly data are most frequent during winter at coastal locations. Projected changes for the late 21st century are statistically significant at many locations, and they show a qualitatively similar seasonality in the output from the two models: an increase of mean wind speeds in the cold season and a decrease of mean wind speeds in the warm season. High-wind events are projected by both models to become more frequent in the northern and western Alaska coastal regions, which are precisely the regions in which the protective sea ice cover has decreased (and is projected to decrease further), pointing to increased risks of coastal flooding and erosion.

Extreme Wind Events Influence Seed Rain and Seedling Dynamics of Guam’s Serianthes nelsonii Merr

The seasonal aspects of Guam’s Serianthes nelsonii seed rain quantity, new seedling emergence, and lifespan of newly emerged seedlings were determined by direct observations. Two high wind events in January and September 2013 generated 63% of the annual number of new seeds collected in litterfall. A defoliating tropical cyclone in May 2015 generated an abrupt increase in seedling emergence with 17% of the annual new seedling count emerging during the 4-week period after the tropical cyclone. Of the annual count of seedlings that lived longer than 2 weeks, 8% of them emerged during the 7 months prior to the tropical cyclone in May 2015. In contrast, 92% of these long-lived seedlings emerged during the 5 months immediately after the tropical cyclone. Mitigating the limitations to regeneration and recruitment of Serianthes nelsonii will likely require a change in approach for species recovery such that holistic habitat restoration becomes the goal rather than species recovery per se.

A first characterization of high winds that affect the energy distribution system of Uruguay and their related effects

UTE is the company that delivers electric power to all Uruguay, serving almost a million and a half clients and 99.3% of Uruguayan homes.When direct wind effects on energy distribution systems are simulated, usually studying the action of wind on sections of these systems, it is generally assumed that high winds are of synoptic type, as e.g. those generated by hurricanes or winter storms. In Uruguay, high wind events are sometimes generated by synoptic winds, usually due to the passage of intense extratropical cyclones, but non-synoptic winds generated by severe convective activity are more frequent and intense in comparison, and are the cause of many incidences and damage to different economic sectors in the country.This paper presents results from the first academic research conducted on wind effects on the energy distribution system of Uruguay. Its aims were to characterize the main outages that occur in this system at national and management levels and their associated meteorological conditions, to explore the relative importance of synoptic and non-synoptic winds as causes of these incidences, and the possibility that different regions of the country exhibit different behavior in relation to the related weather conditions.

The Effect of Fallow Tillage Management on Aeolian Soil Losses in Semiarid Central Anatolia, Turkey

Core Ideas Eliminating fallow tillage increased the natural plant cover at the soil surface. Increased natural plant cover did not significantly decrease the aeolian soil losses. Event‐based vertical distribution of soil losses were related to the upwind plant characteristics. Accounting for plant configuration improved the prediction of vertical soil flux distribution. In semiarid Central Anatolia Turkey, winter wheat (Triticum aestivum L.) planted under a conservation tillage system undergoes a no‐till fallow phase to reduce aeolian soil losses by maintaining the natural plant cover. This research was conducted to investigate the effectiveness of natural vegetation cover in relation to tillage‐induced soil surface properties in reducing the wind erosion during the fallow periods. Climatic parameters at experimental plots subjected to no fallow tillage (NFT) and conventional fallow tillage (CFT) (disk) managements were measured and friction velocity (u*) and aerodynamic roughness (z0) over four high wind events (wind velocities &gt;5.7 ms−1 at 2 m high) were determined. Sediment fluxes at each management were measured using 20 sampling posts each holding five vertically placed sediment traps. Spatial dynamics of soil fluxes were related to the soil surface properties and the vegetation characteristics (coverage and configuration). Spatial variations in upwind vegetation characteristics were significantly (p &lt; 0.05) related to the mass fluxes up to 40 cm above the soil surface. However, greater vegetation cover in NFT did not result in significant reductions in mass transport rate compared with CFT. This can be explained by substantially greater (&gt;360%) loose material in NFT due to the dissipation of wheat residue during the early fallow period (23% in late March) and longer transport distance due to a lower surface roughness. These results corroborate that the elimination of fallow tillage alone may not generate sufficient natural vegetation cover to effectively reduce aeolian soil losses in fallow periods of winter wheat cropping systems.

Pull-through capacities of cold-formed steel roof battens considering loading rate sensitivity

Static and fatigue pull-through failures of thin steel roof battens in the vicinity of batten to rafter screw connections are part of the major premature connection failures which lead to severe roof failures during high wind events. As wind speed and thereby wind uplift loading rate on a building roof varies over a wide range, the loading rate which should be used to conduct prototype roof tests is a moot point. Current wind loading standards and guidelines recommend a wider range of loading rates/frequencies in simulating static and cyclic wind loads. This could adversely affect the test results of loading/strain rate sensitive materials. Since cold-formed steels appear to be sensitive to loading rate, it is necessary to investigate the effect of loading rate on both static and fatigue pull-through capacities of cold-formed steel roof battens. Therefore, a series of static and cyclic pull-through tests was conducted at various loading rates on roof battens made of two grades (G300 and G550) and two thicknesses (0.75/0.80 and 0.95/1.00 mm). Test results showed that both static and fatigue pull-through capacities increase with increasing loading rate. To understand the loading rate sensitivity of roof battens, the effect of loading rate on the ultimate tensile strength of cold-formed steels was also investigated through a series of tensile coupon tests. Based on both pull-through and tensile coupon test results, suitable modifications and recommendations have been made to the current pull-through capacity equations and the current Low-High-Low (LHL) cyclic test loading frequency. A suitable material model is also proposed to determine the dynamic mechanical properties of cold-formed steels.