Threshold Wind Velocity Research Articles

Field determination for roughness length above the different non-erodible surfaces

Non-erodible elements, for its disturbance to the near-surface airflow, have been widely used in arid and semi-arid regions to protect the surface from wind erosion. Roughness length was usually used to evaluate the protection effect of non-erodible elements from wind erosion. In this study, the wind profiles above five types of non-erodible surfaces including gravel, wheat straw checkerboard barriers, cotton stem checkerboard barriers, shrubs, and herbs were measured and analyzed. The wind velocities above these surfaces increased with height approximately in logarithmic functions. The roughness length of different non-erodible surfaces was calculated by the functions of wind profiles. The results reveal that:(1) Roughness length increased with wind velocity in given wind velocity ranges. (2) On vegetative surfaces, wind did not effectively bend the stems. The threshold wind velocity for bending the stems of Achnatherum splendens was 4 m/s, 10 m/s for Agropyron cristatum , and for Artemisia ordosica , no obvious bending of stems even for wind velocity reaching 12 m/s. (3) Correlation analysis results show that the vegetation's coverage and frontal area affect the roughness length more significantly than the other parameters. (4) The protective results of these non-erodible elements were evaluated. The checkerboard sand barriers made of cotton stem could provide more effective protection than that made of wheat straw. In the same coverage conditions, vegetation could provide more effective protection from wind erosion than gravel, and the blending of different non-erodible elements especially the combination of blending of vegeation and checkerboard sand barriers could provide more effective protection to the surface.

Sand Transport and Abrasion within Simulated Standing Vegetation

Abstract.Crop residues help protect topsoil from depletion and abrasion due to wind erosion. Limited studies have focused on the type and orientation of canopies that help minimize the effects of erosion by wind. In this study, a series of wind tunnel experiments was conducted to measure sand transport and abrasion energies within simulated standing vegetation. Wind speed profiles, relative abrasion energies, and rates of sand discharge were evaluated during 3 min test runs at two different vegetation heights (150 and 220 mm) for each of three densities of simulated vegetation (i.e., 100 × 200 mm, 200 × 200 mm, and 300 × 200 mm spacing). Tests were also conducted for a bare sand surface. As expected, vegetation density was directly related to threshold velocity and inversely related to sand discharge. The densest configuration (i.e., 100 × 200 mm spacing) increased the threshold velocity of bare sand from 5.9 to 10 m s-1. The presence of vegetation was found to be effective in minimizing the abrasion experienced by the standing vegetation models by lowering the saltation of sand particles that could impact the simulated plants. The coefficient of abrasion (Can), a measure of kinetic energy via the impact of saltating particles, was affected by saltation discharge, although this did not depend on wind speed. The values of Can for all configurations were significantly different (p < 0.05) from the bare sand surface . Keywords: Abrasion energy, Sand discharge, Standing vegetation, Threshold wind velocity, Wind erosion.

Barchan dunes on Pluto?

We show that the orientation and morphology of bedforms occurring on top of Pluto’s smooth ice coats are consistent with an aeolian origin under conditions of unidirectional flow. From scaling relations for dune size as a function of attributes of atmosphere and sediments, we find that the average diameter of the granular particles constituting such bedforms — assuming an aeolian origin — lies within the range 600 μ m m. Our findings show that, owing to the effect of hysteresis in the minimal threshold wind velocity for saltation, dune migration on Pluto can occur under wind speeds that are common to Earth and Mars.

Integrated spatial assessment of wind erosion risk in Hungary

Abstract. Wind erosion susceptibility of Hungarian soils was mapped on the national level integrating three factors of the complex phenomenon of deflation (physical soil features, wind characteristics, and land use and land cover). Results of wind tunnel experiments on erodibility of representative soil samples were used for the parametrization of a countrywide map of soil texture compiled for the upper 5 cm layer of soil, which resulted in a map representing threshold wind velocity exceedance. Average wind velocity was spatially estimated with 0.5′ resolution using the Meteorological Interpolation based on Surface Homogenised Data Basis (MISH) method elaborated for the spatial interpolation of surface meteorological elements. The probability of threshold wind velocity exceedance was determined based on values predicted by the soil texture map at the grid locations. Ratio values were further interpolated to a finer 1 ha resolution using sand and silt content of the uppermost (0–5 cm) layer of soil as spatial co-variables. Land cover was also taken into account, excluding areas that are not relevant to wind erosion (forests, water bodies, settlements, etc.), to spatially assess the risk of wind erosion. According to the resulting map of wind erosion susceptibility, about 10 % of the total area of Hungary can be identified as susceptible to wind erosion. The map gives more detailed insight into the spatial distribution of wind-affected areas in Hungary compared to previous studies.

Comparison of wind erosion based on measurements and SWEEP simulation: A case study in Kangbao County, Hebei Province, China

Farmland especially dry farmland managed in traditional ways has high wind erosion risk and contributes mainly to dust emission in arid area. Modeling predicting provides a general view to soil erosion susceptibility, and is very helpful for the understanding of potential spatial source of wind erosion. This study applied the Single-event Wind Erosion Evaluation Program (SWEEP) to predict soil wind erosion of farmland in the study area. SWEEP is a standalone version of the erosion sub-model from the Wind Erosion Prediction System (WEPS). It needs fewer calculation parameters than WEPS and is often used for single erosion events of limited size. The objective of this study was to test the feasibility of using SWEEP to estimate annual wind erosion of farmland over large areas (downwind distance >1600m) with limited wind data (2005–2011) from weather stations. We validated the simulation results by comparing them with field measurements and wind tunnel data for the same soils. The soil material eroded by wind included PM10, suspension, saltation, and creep particles. Suspension particles were the main component involved in the soil loss (averaged 61.8%). However, saltation and creep particles dominate the particle clouds for fields with a downwind length of less than 550m (averaged 56.6%), and the mass flux dominated by suspension particles stabilizes when this length is longer than 1000m (averaged 83.4%). PM 10 always has very low proportion (<2.3%). Our validation results suggest that it is feasible to use SWEEP for large areas with limited wind data. However, SWEEP could not simulate the small soil losses that occur especially at low wind velocities well. Many factors contribute to this problem, but the main one is overestimation of the threshold wind velocity. Previous research suggest that it will be difficult to replace SWEEP’s calculation algorithms for the threshold wind velocity, but both these algorithms and some SWEEP parameters must be improved to provide accurate predictions of soil erosion.

Effect of soil parameters on the threshold wind velocity and maximum eroded mass in a dry environment

The present study aims to investigate the relationships between several soil parameters (texture, organic matter and CaCO3 content) and the threshold wind velocity and erodibility of different soil types. Our aim was to determine the role of these soil parameters play in soil loss due to wind erosion and also to statistically evaluate these correlations. The erodibility studies were carried out in wind tunnel experiments, and the resulting data were analysed with multiple regression analysis and the Kruskal-Wallis test. We found that both the threshold wind speed and the erodibility of soils were mostly determined by silt fraction (0.05–0.02 mm), while sand fractions had a lesser effect on it. Our experiences with organic matter and CaCO3 similar, i.e. in spite of their correlation with the erosion, their contribution was not significant in the multivariate regression model. Consequently, based on mechanical composition of soils, one can predict threshold wind velocity and erodibility of soils.

가오리연의 매듭에 대한 수치해석 연구

대중적인 연에는 방패연과 가오리연 두 종류가 있다. 방패연은 전문가들에게 널리 사랑 받고 있는 반면, 초보자들에게는 가오리연이 더 익숙하다. 가오리연의 세 종류의 제품들에 대하여 목줄의 매듭을 조사하였다. 가오리 연에 작용하는 공기역학적 힘들을 Fluent를 사용하여 수치적으로 계산하였다. 각 종류의 매듭에 대한 비행 시뮬레이션을 수행함으로써, 기존보다 최소요구풍속이 더 낮은 새로운 매듭을 제안하였다. 최소요구풍속은 연이 날기 시작하는 한계 풍속이다. There is two popular kites, Bangpae and Gaori. While the Bangpae kite is being widely loved by experts, the Gaori kite is popular for kids and beginners. Three types of Gaori kite product have been survayed on the tow point. The aerodynamic force on Gaori kite is numerically calculated by using Fluent. Through flight simulations at the tow point of each kite type, the new tow point, at which the required minimum velocity is lower than those of existing tow points, has been proposed as a standard. The required minimum velocity is the threshold wind velocity at which the kite begins to fly.

Research progress on wind erosion control with polyacrylamide (PAM).

Soil wind erosion is one of the main reasons for soil degradation in the northwest region of China. Polyacrylamide (PAM), as an efficient soil amendment, has gained extensive attention in recent years since it is effective in improving the structure of surface soil due to its special physical and chemical properties. This paper introduced the physical and chemical properties of PAM, reviewed the effects of PAM on soil wind erosion amount and threshold wind velocity, as well as the effect differences of PAM in soil wind erosion control under conditions of various methods and doses. Its effect was proved by comparing with other materials in detail. Furthermore, we analyzed the mecha-nism of wind erosion control with PAM according to its influence on soil physical characteristics. Comprehensive analysis showed that, although some problems existed in wind erosion control with (PAM), PAM as a sand fixation agent, can not only enhance the capacity of the soil resis-tance to wind erosion, but also improve soil physical properties to form better soil conditions. Besides, we proposed that combination of PAM and plant growth would increase the survival rate of plants greatly, control soil wind erosion in wind-erosive areas, and improve the quality of the ecological environment construction. Thus, PAM has practically important significance and wide application prospect in controlling soil wind erosion.

Threshold wind velocity dynamics as a driver of aeolian sediment mass flux

Abstract Horizontal (saltation) mass flux is a key driver of aeolian dust emission. Estimates of the horizontal mass flux underpin assessments of the global dust budget and influence our understanding of the dust cycle and its interactions. Current equations for predicting horizontal mass flux are based on limited field data and are constrained to representing transport-limited equilibrium saltation, driven by the wind momentum flux in excess of an entrainment threshold. This can result in large overestimation of the sediment mass flux. Here we compare measurements of the soil entrainment threshold, horizontal mass flux, and their temporal variability for five undisturbed dryland soils to explore the role of threshold in controlling the magnitude of mass flux. Average and median entrainment threshold showed relatively small variability among sites and relatively small variability between seasons, despite significant differences in soil surface conditions. Physical and biological soil crusts had little effect on the threshold value, and threshold appeared to play a minor role in determining the magnitude of sediment transport. Our results suggest that horizontal mass flux was controlled more by the supply limitation and abrasion efficiency of saltators present as loose erodible material or originating from neighboring soil sources. The omission of sediment supply and explicit representation of saltation bombardment from horizontal flux equations is inconsistent with the process representation in dust emission schemes and contributes to uncertainty in model predictions. This uncertainty can be reduced by developing greater process fidelity in models to predict horizontal mass flux under both supply- and transport-limited conditions.

Wind erosion prevention characteristics and key influencing factors of bryophytic soil crusts

Biological soil crusts (BSCs) are generally considered to reduce wind erosion, however, the extent of reductions is highly dependent on the vegetation type, soil moisture status, and their interactions in the field. The interrelationships between these factors or their combined effects are relatively unknown. The objectives of this study were to evaluate the contributions of the crust coverage (CC), associated with the soil moisture content (SMC), and the vegetation coverage (VC) to reduce wind-erosion and to provide a basis for the effective management of BSCs. We used an orthogonal design and large-scale wind tunnel simulations to determine the erosion-resistance characteristics of BSCs, and the effects of soil moisture content (SMC), vegetation coverage (VC) and crust coverage (CC) on its wind erosion reductions. Our results showed that 1) the medium SMC + low CC + high VC were the most effective contributors in decreasing the wind erosion modulus; 2) the high SMC + medium CC + low VC primarily reduced the sand-transport rate; 3) the medium SMC + high CC + low VC, with the smallest aeolian sand-flow structure index, resulted in the lowest level of aeolian sand-flow saturation; 4) the high SMC + high CC + medium VC exhibited the highest threshold wind velocity; and 5) the VC and CC were found to have significant effects on the surface roughness, but the SMC did not. BSCs should be strongly protected during dry and windy seasons in the spring and winter because of their value in reducing wind erosion. The BSC may be moderately disturbed during wet and weak wind seasons in the summer or autumn to ameliorate soil moisture conditions, especially in the sites with high vegetation coverage, without exacerbating wind erosion. Management that carefully considers the timing and disturbance of BSCs will help to determine the sustainable balance between the “protection” and “destruction” of BSCs and their effective use in reducing wind erosion.

Evidence of Strong Land Degradation by Wind Erosion as a Result of Rainfed Cropping in the Algerian Steppe: A Case Study at Laghouat

AbstractIn Algeria, overgrazing has long threatened the sustainable use of the nearly 20 million hectares of steppe lands. More recently, governmental policies favouring extensive rainfed cereal cropping in the steppe region have increased anthropic pressure on this fragile environment. Low rainfall, weak crop development and sandy soils lead to a high risk of wind erosion, yet no studies have been carried out in this region to this date to quantify the effect of steppe conversion on wind erosion. A 1·3‐ha field in the central steppe of Algeria (Laghouat) was converted to cropland (Hordeum Vulgare L.) and equipped with a weather station and Big Spring Number Eight sand straps to monitor climate‐related parameters and sediment fluxes over a 25‐month period. Threshold wind velocities (3·6 m height) varied between 6 and 7 m s−1 with a weak seasonal variation. More than 70% of the saltation‐producing winds originated from the NW. For these winds, a soil loss of 155 Mg ha−1 was measured. Half of the sediment loss occurred during a single, 12‐day period. Deposition of 26·5 Mg ha−1 was observed for SW winds. The measured erosion rates by far exceeded all norms of tolerable soil loss, indicating that rainfed cereal cropping is a highly unsustainable form of land use in the steppe region around Laghouat. National agricultural policies should be revised to take this into account. © 2014 The Authors. Land Degradation and Development published by John Wiley &amp; Sons, Ltd.

Operational field monitoring of interactive vortex-induced vibrations between two parallel cable-stayed bridges

An in-depth study was conducted on interference VIV between two parallel cable-stayed bridges with respect to the mutual motion of both decks downstream as well as upstream. The mechanical damping ratios of both bridges were estimated by the Natural Excitation Technique (NExT) combined with the Eigen Realization Algorithm (ERA) method. The test setup in a wind tunnel takes two wind directions as well as the identified damping ratios of both decks into consideration. The findings, based on parametric wind tunnel tests, suggest that interference VIV is possible, even in the downstream area of the bridge although this has not been reported before. However, the higher lock-in velocity as well as the higher damping ratio of the downstream bridge would be expected to decrease the possibility of VIV. The interactive behavior was further examined using field monitoring data and the results were in good agreement with the findings obtained in wind tunnel tests, in terms of the threshold wind velocity, the frequency components of the motion and the amplitude ratio between the two bridges. Unfortunately, however, a strong wind was not observed opposite to the main wind direction and it was not possible to confirm the interactive behavior for this situation.

Measurement of dust emission from a road construction using exposure-profiling method

Road construction is one example of heavy constructions that may have a substantial temporary impact on local air quality. Construction of Lule? Road during the summer of 2013 generated a great deal of dust emission. US EPA recommended exposure-profiling method was used to measure dust emission. Inexpensive BSNE dust samplers were used instead of high volume samplers. The objective was to give a general idea of the amount of dust generated due to the construction work. Dust generation related to weather was discussed under conditions. Estimated threshold wind velocities for road surface materials at the height of 2 m were 12.88 m/s, 12.88 m/s and 24.76 m/s which were lower measured wind velocities, indicating no dust generated from wind erosion. Dust masses for 7 sampling periods show dust generation had a close relation with moisture content of surface material. Wind speed, humidity had minor or no effect. The estimated dust emission rate in the construction work during the measuring period was 22.86 kg TSP/d, 6 kg/d was from construction work and 16.86 kg/d was generated due to traffic on temporary roads.

A Study on Dust Storms Using Wind Rose, Storm Rose and Sand Rose (Case Study: Tehran Province)

Sand and dust storms are natural events that occur widely around the world, mostly in dry and bare lands. Over thepast decade a large part of Iran has been affected by this phenomenon, and Tehran has not been excluded from thisevent. Therefore, having knowledge of spatiotemporal frequency variations can aid us in future management andstorm trajectory assessment. In this study the synoptic anemometric data of Tehran-Mehrabad stations over the past47 years were used. Annual and monthly wind and storm roses were drawn to determine the predominant winddirection. The primary results indicated that the prevailing wind direction is western, but in summer, it is southsoutheastern.According to the threshold wind velocity (6.5 ms-1) about 12% of recorded data was categorized intothe storm condition.. Results also indicated that western, northwestern, and southwestern winds have the three highestrates of sand drift potential (Dpt), respectively. The temporal variability of dust storms showed that between 1951 and2005, the largest number of days characterized by dust and thunderstorms was observed in the spring and summer.The average number of dusty days in spring and summer was four d/m, and the fastest winds ranged from 40 to 49m/s-1. An assessment of dusty days over the past five decades revealed that the average number of dusty days hassignificantly increased from 10 days to 80 days. It seems that cyclonic circulations in the Monsoon Trough togetherwith regional winds in central Iran are responsible for the transmission of dust particles over central Iran. Results anddata from this study can be helpful in determining and predicting the critical dust storm period and in formingmanagement strategies in order to minimize aftermath impacts.

Global‐scale attribution of anthropogenic and natural dust sources and their emission rates based on MODIS Deep Blue aerosol products

Our understanding of the global dust cycle is limited by a dearth of information about dust sources, especially small‐scale features which could account for a large fraction of global emissions. Here we present a global‐scale high‐resolution (0.1°) mapping of sources based on Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue estimates of dust optical depth in conjunction with other data sets including land use. We ascribe dust sources to natural and anthropogenic (primarily agricultural) origins, calculate their respective contributions to emissions, and extensively compare these products against literature. Natural dust sources globally account for 75% of emissions; anthropogenic sources account for 25%. North Africa accounts for 55% of global dust emissions with only 8% being anthropogenic, mostly from the Sahel. Elsewhere, anthropogenic dust emissions can be much higher (75% in Australia). Hydrologic dust sources (e.g., ephemeral water bodies) account for 31% worldwide; 15% of them are natural while 85% are anthropogenic. Globally, 20% of emissions are from vegetated surfaces, primarily desert shrublands and agricultural lands. Since anthropogenic dust sources are associated with land use and ephemeral water bodies, both in turn linked to the hydrological cycle, their emissions are affected by climate variability. Such changes in dust emissions can impact climate, air quality, and human health. Improved dust emission estimates will require a better mapping of threshold wind velocities, vegetation dynamics, and surface conditions (soil moisture and land use) especially in the sensitive regions identified here, as well as improved ability to address small‐scale convective processes producing dust via cold pool (haboob) events frequent in monsoon regimes.

A field experiment on dust emission by wind erosion in the Taklimakan Desert

Dust emission by wind erosion in surface is a serious problem in many arid regions around the world, and it is harmful to the ecological environment, human health, and social economy. To monitor the characteristics of saltation activity and to calculate the threshold wind velocity and sediment discharge under field conditions have significance on the research of dust emission by wind erosion. Therefore, a field experiment was conducted over the flat sand in the hinterland of the Taklimakan Desert. One sampling system was installed on the flat sand surface at Tazhong, consisting of a meteorological tower with a height of 2 m, a piezoelectric saltation sensor (Sensit), and a Big Spring Number Eight (BSNE) sampler station. Occurrence of saltation activity was recorded every second using the Sensit. Each BSNE station consisted of five BSNE samplers with the lowest sampler at 0.05 m and the highest sampler at 1.0 m above the soil surface. Sediment was collected from the samplers every 24 h. It is found that saltation activity was detected for only 21.5% of the hours measured, and the longest period of saltation activity occurring continuously was not longer than 5 min under the field conditions. The threshold wind velocity was variable, its minimum value was 4.9 m s−1, the maximum value was 9.2 m s−1, and the average value was 7.0 m s−1. The threshold wind velocity presented a positive linear increase during the measurement period. The observation site had a sediment discharge of 82.1 kg m−1 over a period of 24 h. Based on hourly saltation counts, hourly sediment discharge was estimated. Overall, there was no obvious linear or other functional relationship between the hourly sediment discharge and wind velocity. The results show that the changes of sediment discharge do not quite depend on wind velocity.

An aerodynamic roughness length map derived from extended Martian rock abundance data

Many boundary layer processes simulated within a Mars General Circulation Model (MGCM), including the description of the processes controlling dust rising from the Martian surface, are highly sensitive to the aerodynamic roughness length z0. On the basis of rock‐size frequency distributions inferred from different Martian landing sites and Earth analog sites, we have first established that lognormal‐modeled rock‐size frequency distributions are able to reproduce correctly the observed Martian rock populations. We have validated the hypothesis that the rock abundance ζ of a given area could be estimated at a first order from its thermophysical properties, namely its thermal inertia I and its albedo α. We have demonstrated the possibility of using rock abundance ζ to estimate the roughness density λ on Mars and to retrieve subsequently the aerodynamic roughness length by using semi‐empirical relationships based on terrestrial wind‐tunnel and field measurements. By combining our methodology with remote sensing measurements of the Thermal Emission Spectrometer aboard Mars Global Surveyor, we have derived a global map of the aeolian aerodynamic roughness length with a 1/8° × 1/8° resolution over the entire Martian surface. Contrary to what is often assumed, the Martian aeolian aerodynamic roughness length is spatially highly heterogeneous. At the fullest resolution, the Martian aerodynamic roughness length varies from 10−3 cm to 2.33 cm. About 84% of the Martian surface seems to be characterized by an aeolian aerodynamic roughness length value lower than 1 cm, the spatially uniform value that most of the MGCMs simulations have assumed recently. Since the aerodynamic roughness length z0 is a key parameter in deriving the erosion threshold wind velocities, we anticipate a significant impact of our findings on the efficiencies for lifting dust in future MGCMs.

Thermodynamic effects on particle movement: Wind tunnel simulation results

Sand/dust storms are some of the main hazards in arid and semi-arid zones. These storms also influence global environmental changes. By field observations, empirical statistics, and numerical simulations, pioneer researchers on these natural events have concluded the existence of a positive relationship between thermodynamic effects and sand/dust storms. Thermodynamic effects induce an unsteady stratified atmosphere to influence the process of these storms. However, studies on the relationship of thermodynamic effects with particles (i.e., sand and dust) are limited. In this article, wind tunnel with heating was used to simulate the quantitative relationship between thermodynamic effects and particle movement on different surfaces. Compared with the cold state, the threshold wind velocity of particles is found to be significantly decrease under the hot state. The largest decrease percentage exceedes 9% on fine and coarse sand surfaces. The wind velocity also has a three-power function in the sand transport rate under the hot state with increased sand transport. Thermodynamic effects are stronger on loose surfaces and fine particles, but weaker on compacted surfaces and coarse particles.

Identifying sensitive areas to wind erosion in the Xilingele grassland by computational fluid dynamics modelling

In order to identify the areas in the Xilingele grassland which are sensitive to wind erosion, a computational fluid dynamics model (CFD-WEM) was used to simulate the wind fields over a region of 37km2 which contains different topography and land use types. Previous studies revealed the important influences of topography and land use on wind erosion in the Xilingele grassland. Topography influences wind fields at large scale, and land use influences wind fields near the ground. Two steps were designed to implement the CFD wind simulation, and they were respectively to simulate the influence of topography and surface roughness on the wind. Digital elevation model (DEM) and surface roughness length were the key inputs for the CFD simulation. The wind simulation by CFD-WEM was validated by a wind data set which was measured simultaneously at six positions in the field. Three scenarios with different wind velocities were designed based on observed dust storm events, and wind fields were simulated according to these scenarios to predict the sensitive areas to wind erosion. General assumptions that cropland is the most sensitive area to wind erosion and heavily and moderately grazed grasslands are both sensitive etc. can be refined by the modelling of CFD-WEM. Aided by the results of this study, the land use planning and protection measures against wind erosion can be more efficient. Based on the case study in the Xilingele grassland, a method of regional wind erosion assessment aided by CFD wind simulation is summarized. The essence of this method is a combination of CFD wind simulation and determination of threshold wind velocity for wind erosion. Because of the physically-based simulation and the flexibility of the method, it can be generalised to other regions.

Continental wind patterns associated with Colorado alpine dust deposition: An application of the BLM/USFS RAWS network

The winter and early spring of 2008-2009 brought an unusually high number of alpine dust deposition events to the Rocky Mountains of Colorado. The greatest dust accumulations were observed in the San Juan Mountains of southwestern Colorado. Significant dust accumulation was even observed along the Continental Divide in northern Colorado. The primary source for this dust has previously been identified as the Colorado Plateau. Analysis using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) atmospheric trajectory model along with satellite imagery showed that dust from the 2009 events also originated from the Colorado Plateau, especially from areas in and around northeastern Arizona that were experiencing abnormally dry conditions that spring. The study utilized data from the BLM/USFS Remote Automated Weather Station (RAWS) network in the southwestern U.S. to identify periods of high winds corresponding to documented Colorado dust events. The RAWS database, once considered to be brief and unsuitable as a climate resource, is quickly approaching 30 years of record and provides a valuable resource for application to various climate questions. Analysis of wind data from these RAWS sites during known dust events show that a minimum threshold wind velocity exists before dust storm generation occurs, and that this threshold velocity occurs from a southwesterly direction. Threshold velocity for the daily mean speed was found to be 15 mph and 44 mph for daily maximum gusts. Wind speeds for the study region were then evaluated for the period January 1 A joint research project through the Bureau of Land Management and the Colorado Climate Center