inscription
PORTAIL D'INFORMATION GÉOGRAPHIQUE

Résultats de la recherche (575 résultats)

Affinez votre recherche

Par Collection Par Auteur Par Date Par Sujet Par Titre
  • Interannual variability of wind speed and wind power at five tall-tower sites in Minnesota (1996-2001)
  • Interannual variability ; Methodology ; Minnesota ; United States of America ; Wind ; Wind energy ; Wind speed ; Years 1990-99
  • The AA. use wind speed measurements from 1996-2001 at 70 m above ground (a typical wind turbine height) to investigate interannual variability in wind speed and wind power at 5 sites in Minnesota, and to determine whether the sites have similar
  • patterns of variability. They use the standard deviation (computed from mean hourly data) as a measure of within-year variability because squared differences emphasize the effects of the long tails of the wind speed and wind power distributions.
  • Relations of sand trapping efficiency and migration speed of transverse dunes to wind velocity
  • Aeolian features ; Aeolian transport ; Dune ; Earth surface processes ; Model ; Wind speed
  • A self-consistent model which describes transverse dune migration in equilibrium is introduced. It shows that an equilibrium expression for dune migration speed (Cd) must take into account sand trapping efficiency (Te), and that Te is strongly
  • related to the wind speedup over the windward surface.
  • Proneness of soils to wind erosion as a function of moisture content and wind speed
  • Arid land;Arid environment ; Eolian erosion;Wind erosion ; Soil erosion ; Soil moisture ; Wind ; Wind speed
  • The effect of single vegetation elements on wind speed and sediment transport in the Sahelian Zone of Burkina Faso
  • Arid area ; Burkina ; Sahel ; Scrub ; Sediment transport ; Soil erosion ; Tree ; Vegetation ; Wind erosion ; Wind speed
  • The aim of this study was to determine the effects of a single tree and shrub on wind speed and sediment transport in the Sahelian zone of Burkina Faso. First an overview will be given of the effects of sparse vegetation and single vegetation
  • elements on wind speed and sediment transport as known from the literature. Subsequently, results of experimental work that was done in the north of Burkina Faso on the pattern of wind speed and sediment transport around single trees and shrubs
  • Energy;Power ; Romania ; Wind ; Wind energy ; Wind speed
  • The AA. utilize monthly and annual means of the wind speed for 15 years of observations at two meteorological stations, pointing out the maximum and minimum speeds and the frequency of the different classes of speed. It is discussed, also
  • , the efficiency of the generators of energy based on the wind.―(M. Vârlan).
  • Spatial coherence and decay of wind speed and power in the north-central United States
  • Annual variation ; Climatology ; Interannual variability ; Methodology ; Spatial analysis ; Spatial autocorrelation ; United States of America ; Wind ; Wind speed
  • of spatial analyses of near-surface wind speed and power. Spatial autocorrelation functions calculated at a number of timescales : annual, monthly, daily, hourly, and mean absolute differences are used to characterize the spatial coherence and decay of wind
  • speed and power. Methods for improving the spatial analysis of wind also are discussed.
  • Hourly wind data from a network of climate stations in the north-central United States (drawn from the states of Illinois, Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, South Dakota, and Wisconsin) are analyzed to evaluate the efficacy
  • Influence of wind speed on rainsplash erosion
  • Denmark ; Experiment plot ; Model ; Precipitation ; Soil erosion ; Splash ; Wind speed
  • induced by wind speed. A digital raingauge with a high output resolution was used to measure precipitation. Erositivity indexes were worked out based on the assumption that those minutes with the highest energy input in an event are decisive for soil
  • Interaction between wind and sand surface
  • Sand transport takes place when the wind speed is higher than some critical value. When the wind speed is not too high and the sand has a monodisperse size distribution it is possible that ripples are formed. Simple relationships are derived between
  • Directional characteristics of potentially damaging wind gusts in the southeast United States
  • Climatology ; Damage ; Forecast ; Natural hazards ; United States of America ; Wind ; Wind speed
  • and speeds of high winds. The results will provide a preliminary guide to the zones around trees that are most threatened by blowover from high winds.
  • In this study, this wind gust data is analyzed from a network of 20 weather stations in the southeastern United States. From this analysis, the AA. develop a short-term climatology that summarizes regional variations in the prevailing directions
  • Spatial modeling of wind speed around windbreaks
  • Wind erosion in Europe. Special issue
  • Aeolian features ; England ; Forecast ; Geographical information system ; Model ; Spatial analysis ; United Kingdom ; Wind erosion ; Wind speed
  • is modeled in terms of friction velocity reduction, which is a function of wind speed and direction, distance from the barrier, windbreak height, porosity, width, and orientation. A first application of the model was conducted at a study area
  • This paper presents a model to integrate windbreak shelter effects into a Geographic Information System (GIS). The GIS procedure incorporates the 1999 version windbreak sub-model of the Wind Erosion Prediction System (WEPS). Windbreak shelter
  • Alföld ; Climate ; Energy;Power ; Hungary ; Wind ; Wind energy ; Wind speed
  • The paper analyses the wind conditions and the location of old windmills on the Great Hungarian Plain, delimiting the areas where the amount of wind power is sufficient to operate wind converters of smaller capacity. - (JS)
  • Spatial distribution of wind erosion and its driving factors in China
  • Aeolian features ; Arid area ; China ; Desertification ; Geographical information system ; Land use ; Remote sensing ; Spatial distribution ; Vegetation index ; Wind erosion ; Wind speed
  • Based on remote sensing and geographic information system, the spatial distribution of nation-wide wind erosion is studied, and the 1:100 000 national map of soil erosion by wind in China is made. Wind speed, soil dryness, NDVI, soil texture
  • and the slope of land surface are the key factors to wind erosion. The relations between wind erosion and each factor are discussed. The method of principal component is used to pick up the information included in the 5 factors, and the wind erosion dynamic
  • index (WEDI) is established. Its comparison with the RS/GIS derived data shows that WEDI can reflect the potential capacity of soil erosion by wind.
  • History of strong winds in the Czech lands : causes, fluctuations, impacts
  • Climatology ; Czech Republic ; Global change ; Impact ; Sixteenth Century ; Storm ; Tornado ; Twentieth Century ; Wind ; Wind speed
  • Problems of wind speed measurements are analysed. The climatology of strong winds in the Czech Republic during the period 1961-1990 is presented. The main groups of strong winds are characterised according to their origin. The accuracy of historical
  • written reports of strong winds and to their impacts in the pre-instrumental period are discussed. The chronology of strong damaging winds in the Czech lands from A.D. 1500-1929 is presented with a division into gales on the one hand and strong winds
  • connected with convective storms on the other. Cases of gales of the century are described. The impact of strong winds is discussed, with special attention being paid to forest damage.
  • Measuring the erositivity of the wind
  • Aeolian features ; Methodology ; Model ; Soil ; Soil erosion ; Soil properties ; Suspended load ; Wind ; Wind erosion ; Wind speed
  • Measuring wind erosion is difficult as it requires the coincidence of a rare wind event with soil conditions that allow erosion. There is not necessarily a distinct threshold velocity; the relative force of the wind and the fluffiness of the soil
  • determine whether erosion will occur. The relative importance of stable/unstable surface elements may be determined by analysing the wind profile. Lastly, a model of suspension with saltation has evolved; it suggests that saltation is not distinctly
  • Wind effects on sediment transport by raindrop-impacted shallow flow : a wind-tunnel study
  • Belgium ; Experimentation ; Overland flow ; Raindrop erosion ; Rainfall simulation ; Roughness ; Sediment transport ; Soil erosion ; Splash ; Water erosion ; Wind ; Wind speed
  • In this study, sediment transport rates by raindrop-impacted shallow flow were measured under wind-driven rain. By comparing the results from windward and leeward slopes, the AA aimed to clarify the effects of wind velocity and direction
  • on the transport process. The study was conducted in a wind tunnel rainfall simulator facility at Ghent University, Belgium.
  • Aeolian features ; Aeolian transport ; Arid area ; China ; Dune ; Friction velocity ; Gansu ; Grain size distribution ; Mars planet ; Quantitative analysis ; Sand ; Simulation ; Wind speed
  • Based on quantitative simulations on the formation and evolution of aeolian dune fields, a semi-analytical equation describing the migration of aeolian sand dunes with respect to dune height, annual wind regime, frictional wind speed, and sand grain
  • , and it can be applied to describe the migration of underwater sand dunes and aeolian snow dunes on Earth, as well as that of aeolian sand dunes on other planets, for example Martian sand dunes. In addition, the A-W (annual wind regime-wind speed) method
  • proposed by this paper can also be used to determine the annual wind regime and wind speed in dune fields for given dune speed and sand diameter.
  • diameter is proposed in this paper through analyzing the migration speeds of aeolian sand dunes with different heights in a dune field. The migration speeds of aeolian sand dunes on Earth predicted by the equation is consistent with field observations
  • Wind velocity and algal crusts in dune blowouts
  • Aeolian features ; Algae ; Coastal environment ; Dune ; Eolian deflation ; Model ; Netherlands (The) ; Spatial distribution ; Wind speed
  • The frequency distribution of the general wind at Valkenburg is analysed and combined with the horizontal wind velocity pattern within blowouts. A simulation model, producing the spatial distribution of the wind power shows that the prevalence
  • of algal crusts at the SW side of blowouts agrees well with the location which reaches the lower wind power values. In other parts of the blowouts algal crusts are damaged by moving sand at times of high wind velocity.
  • Aeolian features ; Aeolian transport ; Model ; Numerical model ; Sand ; Simulation ; Wind speed
  • variations in wind speed. The wind velocity is varied with an unsteady upper boundary condition. The model predicts different transient behaviour for different heights of the simulation, i.e. different wind tunnel heights.
  • One-dimensional simulations of the unsteady saltation process show that the transport rate's response depends on the amplitude and frequency of the wind fluctuations. The numerical model presented in this paper is capable of simulating temporal
  • Wind tunnel and field calibration of five aeolian sand traps
  • Aeolian features ; Aeolian transport ; Experimentation ; Grain size distribution ; Methodology ; Wind speed
  • is independent of wind speed.
  • The efficiency of 5 aeolian sand samplers was tested via wind tunnel experiments and field measurements : the Big Spring Number Eight (BSNE) sampler, the Modified Wilson and Cooke (MWAC) sampler, the Suspended Sediment Trap (SUSTRA), the Pollet
  • Aeolian features ; Arid area ; Model ; Nevada ; Roughness ; Shear stress ; United States of America ; Vegetation ; Wind erosion ; Wind speed
  • model of Raupach et al. (1993) over a range of wind speeds. As well, this study will provide a data set for comparison with other field and wind tunnel studies.
  • The purpose of this investigation is to provide direct measurements of wind force components over surfaces of various roughnesses in the field in order to assess the protective role of sparse vegetation and to evaluate the shear stress partitioning