Wind Velocity (wind + velocity)

Distribution by Scientific Domains


Selected Abstracts


How internal waves influence the vertical distribution of zooplankton

FRESHWATER BIOLOGY, Issue 1 2007
KARSTEN RINKE
Summary 1. We present data with a high spatio-temporal resolution from a 72-h field survey in Bautzen Reservoir (Saxony, Germany). The aims of this survey were to observe hydrophysical processes during a period of unstable stratification in spring and investigate the effect of wind-induced internal waves on the vertical distribution of zooplankton. 2. Wind velocities up to 10 m s,1 caused a strong downwelling event of warm water at the sampling site and led to the generation of internal waves with an amplitude of 4 m. 3. The zooplankton community, which was dominated by Daphnia galeata, inhabited epilimnetic waters. Downwelling enlarged the thickness of the epilimnetic layer and, hence, led to high zooplankton abundances down to relatively deep water strata indicating lateral transport of zooplankton. As a consequence, area-specific zooplankton abundances increased considerably (max. fourfold) during downwelling. 4. We conclude that classical limnological field sampling, such as for monitoring purposes, can lead to severely biased estimates of zooplankton abundance due to the interfering effects of hydrophysical processes like internal waves. 5. Backscattering strengths measured by a simultaneously deployed Acoustic Doppler Current Profiler (600 kHz) were found to be correlated with estimated zooplankton abundances based on plankton samples. [source]


Wind effects on sediment transport by raindrop-impacted shallow flow: a wind-tunnel study

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2004
G. Erpul
Abstract In wind-driven rains, wind velocity and direction are expected to affect not only energy input of rains but also shallow ,ow hydraulics by changing roughness induced by raindrop impacts with an angle on ,ow and the unidirectional splashes in the wind direction. A wind-tunnel study under wind-driven rains was conducted to determine the effects of horizontal wind velocity and direction on sediment transport by the raindrop-impacted shallow ,ow. Windless rains and the rains driven by horizontal wind velocities of 6 m s,1, 10 m s,1, and 14 m s,1 were applied to three agricultural soils packed into a 20 by 55 cm soil pan placed on both windward and leeward slopes of 7 per cent, 15 per cent, and 20 per cent. During each rainfall application, sediment and runoff samples were collected at 5-min intervals at the bottom edge of the soil pan with wide-mouth bottles and were determined gravimetrically. Based on the interrill erosion mechanics, kinetic energy ,ux (Ern) as a rainfall parameter and product of unit discharge and slope in the form of qbSco as a ,ow parameter were used to explain the interactions between impact and ,ow parameters and sediment transport (qs). The differential sediment transport rates occurred depending on the variation in raindrop trajectory and rain intensity with the wind velocity and direction. Flux of rain energy computed by combining the effects of wind on the velocity, frequency, and angle of raindrop impact reasonably explained the characteristics of wind-driven rains and acceptably accounted for the differences in sediment delivery rates to the shallow ,ow transport (R2 , 0·78). Further analysis of the Pearson correlation coef,cients between Ern and qSo and qs also showed that wind velocity and direction signi,cantly affected the hydraulics of the shallow ,ow. Ern had a smaller correlation coef,cient with the qs in windward slopes where not only reverse splashes but also reverse lateral raindrop stress with respect to the shallow ,ow direction occurred. However, Ern was as much effective as qSo in the sediment transport in the leeward slopes where advance splashes and advance lateral raindrop stress on the ,ow occurred. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Internal loading: A new solution to an old problem in aquatic sciences

LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2004
Lars Håkanson
Abstract Internal loading has long been regarded as an ,Achilles heel' in aquatic science and management. Internal loading is of fundamental importance in large and shallow lakes, where even low wind velocities can cause a considerable resuspension of matter deposited on the lake bed. The resuspended matter, and the chemical substances bound to the resuspended matter, will influence almost all processes in the aquatic ecosystem, such as water clarity and depth of the photic zone, and hence, primary and secondary production. If the sediments are contaminated, it will increase the concentrations of harmful substances in water and sediments and the potential ecosystem effects related to such concentrations. This paper presents an overview of the processes regulating bottom dynamic conditions in lakes (erosion, transport, accumulation), provides examples on the role of internal loading within the context of limnology and water management, and presents a new, general approach to quantify internal loading from sediments in lakes. The new approach has been critically tested, being a key factor behind the increase in predictive power of a new generation of lake models meant to be used for practical water management. Internal loading of any water pollutant depends on sedimentation. Sedimentation in this approach is presented as a function of two substance-specific variables, including the fall velocity of the carrier-particles and the particulate fraction (which, by definition, is the only fraction of a water pollutant that can settle out on the lake bed), and three generic variables, including mean depth, suspended particulate matter and ET-areas (areas of erosion and transport). On ET-areas there is, by definition, a discontinuous sedimentation of materials that settles according to Stokes' law. Basically, internal loading is the sum of advective (resuspension) and diffusive transport from the sediments. Resuspension from ET-areas is given as a function of the lake form (a new algorithm based on the volume development) and the age of ET-sediments. [source]


Colliding stellar wind models with non-equilibrium ionization: X-rays from WR 147

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2007
Svetozar A. Zhekov
ABSTRACT The effects of non-equilibrium ionization are explicitly taken into account in a numerical model which describes colliding stellar winds (CSW) in massive binary systems. This new model is used to analyse the most recent X-ray spectra of the WR+OB binary system WR 147. The basic result is that it can adequately reproduce the observed X-ray emission (spectral shape, observed flux) but some adjustment in the stellar wind parameters is required. Namely (i) the stellar wind velocities must be higher by a factor of 1.4,1.6 and (ii) the mass loss must be reduced by a factor of ,2. The reduction factor for the mass loss is well within the uncertainties for this parameter in massive stars, but given the fact that the orbital parameters (e.g. inclination angle and eccentricity) are not well constrained for WR 147, even smaller corrections to the mass loss might be sufficient. Only CSW models with non-equilibrium ionization and equal (or nearly equal) electron and ion post-shock temperature are successful. Therefore, the analysis of the X-ray spectra of WR 147 provides evidence that the CSW shocks in this object must be collisionless. [source]


Woody Debris in the Mangrove Forests of South Florida1

BIOTROPICA, Issue 1 2005
Ken W. Krauss
ABSTRACT Woody debris is abundant in hurricane-impacted forests. With a major hurricane affecting South Florida mangroves approximately every 20 yr, carbon storage and nutrient retention may be influenced greatly by woody debris dynamics. In addition, woody debris can influence seedling regeneration in mangrove swamps by trapping propagules and enhancing seedling growth potential. Here, we report on line-intercept woody debris surveys conducted in mangrove wetlands of South Florida 9,10 yr after the passage of Hurricane Andrew. The total volume of woody debris for all sites combined was estimated at 67 m3/ha and varied from 13 to 181 m3/ha depending upon differences in forest height, proximity to the storm, and maximum estimated wind velocities. Large volumes of woody debris were found in the eyewall region of the hurricane, with a volume of 132 m3/ha and a projected woody debris biomass of approximately 36 t/ha. Approximately half of the woody debris biomass averaged across all sites was associated as small twigs and branches (fine woody debris), since coarse woody debris >7.5 cm felled during Hurricane Andrew was fairly well decomposed. Much of the small debris is likely to be associated with post-hurricane forest dynamics. Hurricanes are responsible for large amounts of damage to mangrove ecosystems, and components of associated downed wood may provide a relative index of disturbance for mangrove forests. Here, we suggest that a fine:coarse woody debris ratio ,0.5 is suggestive of a recent disturbance in mangrove wetlands, although additional research is needed to corroborate such findings. [source]


Wind effects on sediment transport by raindrop-impacted shallow flow: a wind-tunnel study

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2004
G. Erpul
Abstract In wind-driven rains, wind velocity and direction are expected to affect not only energy input of rains but also shallow ,ow hydraulics by changing roughness induced by raindrop impacts with an angle on ,ow and the unidirectional splashes in the wind direction. A wind-tunnel study under wind-driven rains was conducted to determine the effects of horizontal wind velocity and direction on sediment transport by the raindrop-impacted shallow ,ow. Windless rains and the rains driven by horizontal wind velocities of 6 m s,1, 10 m s,1, and 14 m s,1 were applied to three agricultural soils packed into a 20 by 55 cm soil pan placed on both windward and leeward slopes of 7 per cent, 15 per cent, and 20 per cent. During each rainfall application, sediment and runoff samples were collected at 5-min intervals at the bottom edge of the soil pan with wide-mouth bottles and were determined gravimetrically. Based on the interrill erosion mechanics, kinetic energy ,ux (Ern) as a rainfall parameter and product of unit discharge and slope in the form of qbSco as a ,ow parameter were used to explain the interactions between impact and ,ow parameters and sediment transport (qs). The differential sediment transport rates occurred depending on the variation in raindrop trajectory and rain intensity with the wind velocity and direction. Flux of rain energy computed by combining the effects of wind on the velocity, frequency, and angle of raindrop impact reasonably explained the characteristics of wind-driven rains and acceptably accounted for the differences in sediment delivery rates to the shallow ,ow transport (R2 , 0·78). Further analysis of the Pearson correlation coef,cients between Ern and qSo and qs also showed that wind velocity and direction signi,cantly affected the hydraulics of the shallow ,ow. Ern had a smaller correlation coef,cient with the qs in windward slopes where not only reverse splashes but also reverse lateral raindrop stress with respect to the shallow ,ow direction occurred. However, Ern was as much effective as qSo in the sediment transport in the leeward slopes where advance splashes and advance lateral raindrop stress on the ,ow occurred. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Airborne dust deposition in the Okavango Delta, Botswana, and its impact on landforms

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2004
M. Krah
Abstract This study investigated the local-scale generation and movement of dust in the seasonal swamps of the Okavango Delta, Botswana, with a view to examining possible transfer of material between ,ood plains and islands. It was found that most of the dust load was carried in the lowest 3 m of the air column, and consisted mainly of amorphous silica, indicating that dust was generated largely on the ,ood plains. Dust loads were found to be highest above the ,ood plains and lowest over the interiors of islands, probably due to the baf,ing effect of the island trees on wind velocity. The contrast in dust loads between islands and ,ood plains suggests that there is a net transfer of dust from ,ood plains to islands, but it was not possible to quantify this transfer. It is evident, however, that ,ood plains experience net erosion and islands net aggradation. A strong seasonality in dust loads was observed, with the maximum dust loads coinciding with maximum wind velocity in October. This also coincides with peak seasonal ,ooding in the delta, and only non-inundated ,ood plains are capable of generating dust. Years of low ,ood therefore appear to be more dusty. There may also be transfer of material from higher-lying to lower-lying ,ood plains, which may reduce the topographic contrast on the ,ood plains. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Meteorological factors affecting the diversity of airborne algae in an urban atmosphere

ECOGRAPHY, Issue 5 2006
Naveen K. Sharma
Aeroalgal sampling of Varanasi City, India, was done using a Tilak Rotorod sampler and exposing agarised Bold basal medium Petri plates during March 2003 to February 2005. Amongst the 34 airborne algal genera recorded, cyanobacteria dominated the aero-algal flora, followed by green algae and diatoms. The generic diversity of airborne algae as well as the constituting groups exhibited seasonal variation. The most favored period for the appearance of cyanobacteria in the air was summer, while winter favored green algae. Presence of diatoms was almost uniform throughout the year. The presence of algal particles in the air depended upon the abundance and dynamics of algal source and their release and dispersal in the atmosphere. Best model selection with Akaike information criteria indicated temperature, relative humidity, rainfall, wind velocity as the most important climatic factors determining algal diversity. These factors exert their effect both directly by influencing entrainment and dispersal of algae from the source, and indirectly by regulating the dynamics of the possible algal source (soil, water, plant body, wall and roof of the building) by supporting or inhibiting the algal growth. In a closed environment and at low altitude sampling site characteristic is also an important factor. Open area near to the countryside had maximal aero-algal diversity. [source]


Statistical analysis of temperature impact on daily hospital admissions: analysis of data from Udine, Italy

ENVIRONMETRICS, Issue 1 2006
Francesco Pauli
Abstract This article is devoted to the analysis of the relationship between the health status of an urban population and meteorological variables. The analysis considers daily number of hospital admissions, not due to surgery, regarding the population resident in the Municipality of Udine, aged 75 and over. Hourly records on temperature, humidity, rain, atmospheric pressure, solar radiation, wind velocity and direction recorded at an observation site located near the center of Udine are considered. The study also considers hourly measures of pollutant concentrations collected by six monitoring stations. All data are relative to the summer periods of years 1995,2003. Generalized additive models (GAM) are used in which the response variable is the number of hospital admissions and is assumed to be distributed as a Poisson whose rate varies as a possibly non-linear function of the meteorological variables and variables allowing for calendar effects and pollutant concentrations. The subsequent part of the analysis explores the distribution of temperature conditional on the number of daily admissions through quantile regression. A non-linear (N-shaped) relationship between hospital admissions and temperature is estimated; temperature at 07:00 is selected as a covariate, revealing that nighttime temperature is more relevant than daytime. The quantile regression analysis points out, as expected, that the distribution of temperature on days with more admissions has higher q -quantiles with q near unity, while a clear-cut conclusion is not reached for q quantiles with q near 0. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Bootstrap simulations for evaluating the uncertainty associated with peaks-over-threshold estimates of extreme wind velocity

ENVIRONMETRICS, Issue 1 2003
M. D. Pandey
Abstract In the peaks-over-threshold (POT) method of extreme quantile estimation, the selection of a suitable threshold is critical to estimation accuracy. In practical applications, however, the threshold selection is not so obvious due to erratic variation of quantile estimates with minor changes in threshold. To address this issue, the article investigates the variation of quantile uncertainty (bias and variance) as a function of threshold using a semi-parametric bootstrap algorithm. Furthermore, the article compares the performance of L-moment and de Haan methods that are used for fitting the Pareto distribution to peak data. The analysis of simulated and actual U.S. wind speed data illustrates that the L-moment method can lead to almost unbiased quantile estimates for certain thresholds. A threshold corresponding to minimum standard error appears to provide reasonable estimates of wind speed extremes. It is concluded that the quantification of uncertainty associated with a quantile estimate is necessary for selecting a suitable threshold and estimating the design wind speed. For this purpose, semi-parametric bootstrap method has proved to be a simple, practical and effective tool. Copyright © 2003 John Wiley & Sons, Ltd. [source]


Diffusion Characteristics of VOCs Indoors

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2010
Shin-ichi Shibata Student Member
Abstract Diffusion characteristics of volatile organic compounds (VOCs) were investigated indoors using tin oxide gas sensors. The chemicals cause various kinds of symptoms in humans, for example, the sick house syndrome. In this study, eight sensors were installed in a vertical direction and on a plane surface. These sensors were of the same type. The VOC is placed in a generation source, and the sensor output increases as the chemical diffuses. The sensor output becomes higher as the concentration increases. The following chemicals were tried as air pollutants: formaldehyde, toluene, and xylene. The sensor output changes in short, quick steps by slight fluctuations of the wind velocity. Therefore, the differential characteristic of the sensor output was adopted and the noise component was removed as far as possible. A threshold time tth to the characteristic was set up. It is assumed that the examining chemical reaches the installed sensor point in a time greater than this time. The new speed of arrival is proposed using the threshold time. The speed s [cm/min] is indicated using the distance d and the reaching time tth, namely, s = d/tth. Here, d means the distance between the sensor position and the polluting source. As a result, the speed for the sensor that is installed near the ceiling (at a height of 260 cm from the floor) is the highest. And, it became obvious that s was larger for the chemical with a smaller molecule. The speed of formaldehyde for the sensor installed near the ceiling was 700 cm/min and that for the sensor installed at the height of 100 cm from the floor was 370 cm/min. There is almost a two times difference in the speed. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]


Long-term trends of synoptic-scale breaking Rossby waves in the Northern Hemisphere between 1958 and 2001

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2008
F. Isotta
Abstract Breaking synoptic-scale Rossby waves are frequent features of the upper troposphere and lower stratosphere (UTLS) which affect both global- and regional-scale dynamics. Furthermore, they directly influence ozone distribution through meridional transport of ozone-rich air towards the south and ozone-poor air towards the north. Here, trends in the frequency of these breaking waves are assessed by analysing a 44-year climatology (1958,2002) of potential vorticity (PV) streamers on isentropic surfaces from 310 to 350 K. These streamers are viewed as breaking Rossby waves, whereby stratospheric (tropospheric) streamers indicate southward (northward) breaking waves. Two complementary techniques are used to analyse the trends. First, linear trends are computed using the least-squares regression technique. Statistically significant linear trends are found to vary in location and magnitude between isentropic levels and the four seasons. In winter significant trends are detected in the eastern Pacific between 340 and 350 K. A positive trend of stratospheric streamers in the Tropics is related to an increase of total column ozone, whereas the positive trend of tropospheric streamers in the mid-latitudes is associated with a decrease of total ozone. Secondly, a nonlinear trend analysis is performed using the seasonal-trend decomposition procedure based on Loess (STL). With this technique, the low-frequency variability of the time series is analysed during the 44-year period. For instance, over the eastern Atlantic on 350 K, a phase of decreasing PV streamer frequencies in the 1950s and 1960s is followed by a positive streamer tendency after the 1970s. Additionally, trends of the zonal wind are investigated. One prominent outcome of this analysis is the observation that equatorial easterlies over the Atlantic are weakening. A dynamically meaningful link exists between the trends observed in both wind velocity and PV streamers. Copyright © 2008 Royal Meteorological Society [source]


Changes in spring weather conditions and atmospheric circulation in Estonia (1955,95)

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2003
Sirje Keevallik
Abstract An analysis has been undertaken at Tiirikoja Meteorological Station to investigate changes in the main weather elements in late winter and spring during the period 1955,95. The relationship between these changes and the trends in the atmospheric circulation above Estonia have also been analysed. The latter was estimated from wind speed and direction data recorded at Tallinn Aerological Station at two isobaric levels (500 and 850 hPa). These data permitted the analysts to calculate zonal and meridional components of wind velocity at both levels. Linear trends were fitted to time series of monthly averages of all parameters under consideration. The results indicate that significant changes in meteorological parameters took place in March. These changes are statistically related to the changes in the average airflow in the free atmosphere above Estonia. In March the wind speed at the 500 and 850 hPa isobaric levels increased and the average airflow turned from WNW or NW to SW or WSW. Such changes in the atmospheric circulation can only partly be attributed to the intensification of the North Atlantic oscillation. Copyright © 2003 Royal Meteorological Society [source]


Implications of seasonal and diurnal variations of wind velocity for power output estimation of a turbine: a case study of Grenada

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2003
D. Weisser
Abstract This case study highlights the importance of taking into consideration diurnal variations of wind velocity for wind energy resources assessment. Previous studies of wind energy distribution that are based on the two-parameter Weibull density function have so far neglected to consider time of day fluctuations in wind speed, instead concentrating primarily on seasonal deviations. However, this has serious implications where such a wind energy model is the underpinning of calculations for the potential power production from a wind turbine and in particular where the timing of the energy output is essential to meet electricity loads. In the case of Grenada the energy output from a wind turbine during the day is approximately two times the output at night thereby fluctuating enormously around the seasonal mean distribution. When this is not taken into account the economic and technological viability of a wind turbine project may be overestimated or not even be identified. This work shows how a wind energy resources assessment based on the Weibull distribution model can be done and how the power output of a horizontal axis turbine is calculated. An analysis of the recorded wind data confirms the application of the Weibull density function as a suitable tool for modelling wind regimes. Copyright © 2003 John Wiley & Sons, Ltd. [source]


How do wind velocity and light intensity influence host-location success in Cotesia glomerata (Hym., Braconidae)?

JOURNAL OF APPLIED ENTOMOLOGY, Issue 3 2001

Wind and light are major climatic factors which affect host-location process in parasitoids, but these environmental effects have not been studied thoroughly. Wind-tunnel experiments were designed to dissect how changes in wind velocity and light intensity influence flight initiation, flight orientation and host-searching efficiency in Cotesia glomerata. This study uncovers the influences of changes in wind velocity and light intensity on different phases of host-location process in the parasitoid. These results suggest that a cloudy and/or windy weather may reduce the success of host location by C. glomerata because such conditions suppress flight initiation, cause failure to orientate flights to the herbivore-infested plant and hamper host-searching activity on the plant. [source]


Distribution of infestation by lentil gall midge Contarinia lentis (Dipt., Cecidomyiidae) in lentil fields: statistical model

JOURNAL OF APPLIED ENTOMOLOGY, Issue 1 2000
P. Kolesik
The horizontal distribution of infestation by Contarinia lentis in lentil fields, not subjected to chemical control was recorded and analysed in Slovak Republic during outbreaks of this pest in 1986,89. Infestation level was defined as the percentage of galls form the total number of galls, pods, and flowers. The highest level of infestation were found along the edges and the lowest levels in the centres of fields. The distribution of the infestation between the edge and the centre has been described for 18 fields using a nonlinear function containing two parameters. The first parameter represents the infestation level at the edge. The second parameter represents the rate of decreas of infestation from the edge towards the centre of the field. The relationship between the first parameter and the distance to the adult midge emerge site and the relationship between second parameter and the mean velocity of winds caryring females from the emergence site is described using exponential functions. The results indicate that (1) the longer the distance to the midge emergence site, the lower the infestation at the edge; and (2) the gretaer the wind velocity, the weaker the decrese in infestation from the edge towards the centre of a field. [source]


A LARGE ELECTRONIC WEIGHING LYSIMETER SYSTEM: DESIGN AND INSTALLATION,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2002
Gholam-Abbas Barani
ABSTRACT: To measure crop evapotranspiration, a large double tank, electronic weighting lysimeter system was designed and installed at the Shahid Bahonar University farm, Kerman, Iran. The system was installed in a 50 m2 underground building. It includes two tanks of 3.00 m in diameter and 1.75 m deep. The weighing mechanism for each tank is a set of three compression strain gage load cells, which are fixed on 1.20 m height column above the floor. According to the specification of the load cells, the maximum possible weighing error may be about 0.01 percent of total mass, which is equivalent to 0.28 mm of water, but the measured error was equal to 1 kg mass, which is equivalent to 0.14 mm of water. The load cell data from each tank and the on-site environmental data (temperature, humidity, and wind velocity and direction) are automatically recorded and saved in a personal computer hard disk for further use and analysis. [source]


Threshold wind velocity as an index of soil susceptibility to wind erosion under variable climatic conditions

LAND DEGRADATION AND DEVELOPMENT, Issue 1 2009
Laura A. de Oro
Abstract Wind erosion starts when the threshold wind velocity (µt) is exceeded. We evaluated the sensitivity of µt to determine the wind erosion susceptibility of soils under variable climatic conditions. Three years field data were used to calculate µt by means of the equation µt,=,, - , ,,1 (,), where , is the mean wind speed (m,s,1), , the , standard deviation (m,s,1), , the saltation activity and , the standard normal distribution function of ,. Saltation activity was measured with a piezoelectric sensor (Sensit). Results showed that , of the whole studied period (3·41 m,s,1) was lower than µt (7·53,m,s,1), therefore, wind erosion was produced mainly by wind gusts. The µt values ordered in the sequence: Winter (6·10 m,s,1),<,Spring (8·22,m,s,1),=,Summer (8·28,m,s,1),<,Autumn (26·48,m,s,1). Higher µt values were related to higher air humidity and lower wind speeds and temperatures. The µt values did not agree with the erosion amounts of each season, which ordered as follows: Summer (12·88,t ha,1),>,Spring (3·11,t ha,1),=,Winter (0·17,t ha,1),=,Autumn (no erosion). Low µt and erosion amounts of Winter were produced by a scarce number of gusts during eroding storms. We concluded that µt is useful as an index of soil susceptibility to wind erosion of different climatic periods. The use of a unique µt value in wind erosion prediction models can lead to erroneous wind erosion calculations. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Processing of turbulent-layer wind speed with Generalized SCIDAR through wavelet analysis

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006
B. García-Lorenzo
ABSTRACT We describe a new method involving wavelet transforms for deriving the wind velocity associated with atmospheric turbulent layers from Generalized SCIDAR measurements. The algorithm analyses the cross-correlation of a series of scintillation patterns separated by lapses of ,t, 2,t, 3,t, 4,t and 5,t using wavelet transforms. Wavelet analysis provides the position, direction and altitude of the different turbulent layers detected in each cross-correlation. The comparison and consistency of the turbulent-layer displacements in consecutive cross-correlations allow the determination of their velocities and avoid misidentifications associated with noise and/or overlapping layers. To validate the algorithm, we have compared the velocity of turbulent layers derived on four nights with the wind vertical profile provided by balloon measurements. The software is fully automated and is able to analyse huge amounts of Generalized SCIDAR measurements. [source]


Combustion Model for Pyrophoric Metal Foils

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2003
Caroline
Abstract A model for the combustion of pyrophoric metal foils has been developed. The diffusive mass transport, heat transport, and chemical reactions of porous iron foils have been described. The temperature and radiated energy of these materials has been predicted as a function of the physical characteristics of the material (porosity, pore size, specific surface area) for different atmospheric conditions (temperatures and oxygen concentrations varied with altitude and wind velocity). [source]


Impact of weather on off-flavour episodes at a Louisiana commercial catfish farm

AQUACULTURE RESEARCH, Issue 5 2009
Barry K Hurlburt
Abstract The catfish aquaculture industry is hampered by off-flavour events that affect timely fish sales. In this study, weather data were correlated with geosmin and 2-methylisoborneol (2-MIB) levels in 21 commercial pond's water samples. Samples were collected weekly for 44 weeks. The off-flavour compounds, geosmin and 2-MIB, were quantified using gas chromatography,mass spectrometry. Weather data were collected near the catfish farm and included maximum and minimum air temperature, rainfall, average wind velocity, maximum and minimum humidity, and maximum and minimum soil temperature. Geosmin was weakly and positively correlated with air and soil temperatures, and weakly and negatively correlated with wind velocity. 2-MIB was strongly and positively correlated with air and soil temperatures, moderately and negatively correlated with wind velocity, and weakly and positively correlated with maximum humidity. There were no bivariate relationships between rainfall, minimum humidity or pond size, and levels of either off-flavour compound. Using logistic regression, the best predictors for off-flavour status based on geosmin levels included minimum soil temperature, rainfall and minimum humidity. The best predictors for off-flavour status based on 2-MIB levels included minimum soil temperature and average wind velocity. Soil temperature and rainfall were risk factors for off-flavour, while humidity and wind velocity were protective factors. [source]