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  • American Geophysical Union (AGU)  (22)
  • 1
    Online Resource
    Online Resource
    Variations of the Intensity of the Siberian High During the Last Glacial Revealed by the Sorting Coefficient of Loess‐Paleosol Deposits in Eastern Central Asia
    American Geophysical Union (AGU) ; 2022
    In:  Paleoceanography and Paleoclimatology Vol. 37, No. 9 ( 2022-09)
    Details
    In: Paleoceanography and Paleoclimatology, American Geophysical Union (AGU), Vol. 37, No. 9 ( 2022-09)
    Abstract: Sorting coefficient is a more sensitive proxy for wind intensity than commonly used proxies of mean grain size and grain size fraction Antiphase relationship between the Siberian High (SH) and East Asian Summer Monsoon during the last glacial Our results support the great influence of the extent of Arctic sea ice on the intensity of the SH
    Type of Medium: Online Resource
    ISSN: 2572-4517 , 2572-4525
    URL: Article
    DOI: 10.1029/2022PA004468
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2022
    detail.hit.zdb_id: 2916554-4
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  • 2
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    Online Resource
    Coexistence of Two Dune Growth Mechanisms in a Landscape‐Scale Experiment
    American Geophysical Union (AGU) ; 2022
    In:  Geophysical Research Letters Vol. 49, No. 11 ( 2022-06-16)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 49, No. 11 ( 2022-06-16)
    Abstract: Dunes of different shapes and orientations develop and coexist under the same natural wind regime depending on sand availability The dynamics of pattern coarsening selects dune aspect‐ratio over short time There is a minimum size for dune elongation on a nonerodible bed, below which barchan or asymmetric barchan shapes are observed
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2021GL097636
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2022
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 3
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    Online Resource
    Wind velocity profiles with a blowing sand boundary layer: Theoretical simulation and experimental validation
    American Geophysical Union (AGU) ; 2007
    In:  Journal of Geophysical Research: Atmospheres Vol. 112, No. D19 ( 2007-10-16)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 112, No. D19 ( 2007-10-16)
    Abstract: Describing wind velocity profiles modified by the movement of blown sand is of continuing significance because they are thought to bear rich information about wind‐sand interaction in a blowing sand cloud. This paper treats the saltating cloud as a fluidized particle flow and develops a mathematical model of the wind‐sand interactions. The force exerted on the air by saltating particles is characterized by introducing a drag coefficient of the fluidized aeolian particle flow that is modified after the drag coefficients proposed for liquid fluidized particle flow. The resulting model was then used to simulate wind velocity profiles in the presence of a saltation cloud on the basis of the mean particle velocity and particle concentration profiles of the fluidized particle flow obtained from wind tunnel tests. The simulated velocity profiles agree well with those directly measured in the wind tunnel. The blowing sand boundary layer is divided into a saltation subboundary layer, in which saltating particles participate in momentum exchange with the wind, and an outer subboundary layer above the saltation subboundary layer. The wind velocity profiles within the saltation subboundary layer are characterized by convex‐upward curves in a log (height)‐linear (wind velocity) plot rather than the straight lines in the velocity profiles of clean wind. The upward convexity of the velocity profiles increases as wind velocity increases, suggesting that more wind momentum is absorbed by the saltating particles as the sand transport rate increases. The wind velocity profiles in the outer subboundary layer approach the Prandtl logarithmic law with the saltation subboundary layer providing increased aerodynamic roughness. Our results suggest that the wind shear velocity in the presence of a saltation cloud is a physical dimension that can reflect the effect of saltation.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2006JD007447
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2007
    detail.hit.zdb_id: 161666-3
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  • 4
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    Online Resource
    Defining the threshold wind velocity for moistened sediments
    American Geophysical Union (AGU) ; 2007
    In:  Journal of Geophysical Research: Solid Earth Vol. 112, No. B8 ( 2007-08)
    Details
    In: Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 112, No. B8 ( 2007-08)
    Abstract: The moisture of surface sediments is one of the most significant factors governing the initiation of particle movement by the wind and hence the aeolian transport rate. This paper develops an equation for the threshold shear velocity of moistened sediments based more soundly on physics by means of the moment balance method, taking account of the interparticle cohesive forces produced by moisture. The equation relates threshold shear velocity directly to moisture content and contains three simple coefficients that need be determined from experiments. The threshold equation for moistened sediments basically follows Bagnold's threshold equation for loose, dry sediments but with a proportionality coefficient that accounts for the effect of moisture. Previously published data on the threshold shear velocities of moistened sediments from wind tunnel tests are used to determine the coefficients contained in the threshold equation, and it proves that the new equation describes the threshold velocities of moistened sediments reasonably well. Comparing the threshold shear velocity predicted using the new equation with the results of Belly's and Hotta et al.'s empirical equations reveals that the predicted results differed greatly. These differences can be attributed to differences in the definition of threshold velocity and moisture content in the physical and chemical properties of the sediment samples and in the experimental methods. Further theoretical and experimental investigation is required to fully understand the effects of sediment moisture content on threshold wind velocity. We also suggest that methodological improvement itself is also a topic of future research.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2006JB004476
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2007
    detail.hit.zdb_id: 161666-3
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  • 5
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    Online Resource
    A wind tunnel simulation of the effects of stoss slope on the lee airflow pattern over a two‐dimensional transverse dune
    American Geophysical Union (AGU) ; 2007
    In:  Journal of Geophysical Research: Earth Surface Vol. 112, No. F3 ( 2007-09)
    Details
    In: Journal of Geophysical Research: Earth Surface, American Geophysical Union (AGU), Vol. 112, No. F3 ( 2007-09)
    Abstract: Secondary airflow plays an important role in dune formation and development. The lee airflow pattern over transverse dunes is important in determining the shape, alignment, and spacing of dunes and is influenced significantly by the lee slope angle. In this paper we present the results of scaled wind tunnel simulations of the effects of stoss slope on the mean lee airflow patterns of transverse dunes. The leeward velocity field was measured nonintrusively using particle image velocimetry to assess the airflow pattern. We found that the flow separated over the dunes with a leeward angle close to the slip face angle of natural transverse dunes and was insensitive to stoss angle. Separation cells were characterized by a back eddy. Reattachment distance, height, area, and aspect ratio were used to characterize the separation cell. The first three parameters increased with increasing stoss angle for angles less than 15° but remained constant or decreased slightly with angles greater than 15°. On the basis of the leeward velocity profiles, six flow regions corresponding to those in previous models were recognized. These regions are initially bounded by kinks but gradually transition downwind and merge to recover a uniform velocity profile after a significant distance. We suggest that the separation cell is most developed when the angle of stoss slope reaches 15°, but the significance of this angle in the evolution of transverse dunes needs further exploration.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2006JF000686
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2007
    detail.hit.zdb_id: 161666-3
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  • 6
    Online Resource
    Online Resource
    Mean airflow patterns upwind of topographic obstacles and their implications for the formation of echo dunes: A wind tunnel simulation of the effects of windward slope
    American Geophysical Union (AGU) ; 2011
    In:  Journal of Geophysical Research Vol. 116, No. F4 ( 2011-12-09)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 116, No. F4 ( 2011-12-09)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2011JF002020
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2011
    detail.hit.zdb_id: 161666-3
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Aerodynamic roughness of fixed sandy beds
    American Geophysical Union (AGU) ; 2001
    In:  Journal of Geophysical Research: Solid Earth Vol. 106, No. B6 ( 2001-06-10), p. 11001-11011
    Details
    In: Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 106, No. B6 ( 2001-06-10), p. 11001-11011
    Abstract: The nature of interactions between surface winds and sand surfaces that can be characterized by aerodynamic roughness length has important implications for aeolian sediment transport. Here we report the wind tunnel results of systematic tests of the aerodynamic roughness lengths of different sized fixed sand beds at different free‐stream wind velocities. The results suggest that there are complex variations of aerodynamic roughness length. Wind is an active factor in determining the aerodynamic roughness length of fixed sand beds. The so‐called 1/30 law in aeolian research proposed by Bagnold more than a half century ago for sand surfaces is found to suffer some limitations. Some multivariate models relating aerodynamic roughness length and other factors are provided. The differences between the aerodynamic roughness of fixed and mobile beds are discussed, and it is implied that mobile surfaces adapt to the wind by changing roughness. The similarities between aerodynamic roughness and hydraulic roughness are compared. Aerodynamic roughness is divided into aerodynamically smooth, transitional, and completely rough regimes.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2001JB900009
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2001
    detail.hit.zdb_id: 161666-3
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  • 8
    Online Resource
    Online Resource
    Analysis of the mass flux profiles of an aeolian saltating cloud
    American Geophysical Union (AGU) ; 2006
    In:  Journal of Geophysical Research: Atmospheres Vol. 111, No. D16 ( 2006-08-27)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 111, No. D16 ( 2006-08-27)
    Abstract: Aeolian researchers have recognized the importance of measuring the height profile of aeolian saltating flux and devoted a lot of effort to reliable measurement. In this paper, the height profiles of aeolian saltation flux are reconstructed on the basis of the profiles of mean particle velocity and relative particle concentration obtained by particle image velocimetry, a nonintrusive technique, in a wind tunnel. The results suggest that the mean particle velocity increases with an increase in wind velocity and height but decreases with an increase in particle size. The height profile of mean particle velocity can be expressed by a power function, essentially in agreement with previous studies. Particle concentration decays exponentially with the square root of height rather than height itself as proposed in most previous studies. Mass flux profiles are derived by multiplying the mean particle velocity and concentration profiles. The reconstructed mass flux profiles are characterized by three sections. In the near‐surface layer, mass flux increases with height. In the upper layer, mass flux decays exponentially with height. Between the near‐surface and upper layers is a peak flux zone whose height above the surface increases with an increase in wind velocity but decreases with an increase in particle size. The reconstructed mass profiles are essentially in reasonably good agreement with those measured by a segmented sand sampler in a wind tunnel. Two significant parameters, average saltation height and relative decay factor, are proposed to characterize variation with height of aeolian saltating flux. They are well correlated and imply that saltating particles can reach higher levels as wind velocity increases and particle size decreases and that mass flux decays more rapidly as wind velocity decreases and particle size increases.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2005JD006630
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2006
    detail.hit.zdb_id: 161666-3
    SSG: 16,13
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  • 9
    Online Resource
    Online Resource
    High‐Altitude Aeolian Research on the Tibetan Plateau
    American Geophysical Union (AGU) ; 2017
    In:  Reviews of Geophysics Vol. 55, No. 4 ( 2017-12), p. 864-901
    Details
    In: Reviews of Geophysics, American Geophysical Union (AGU), Vol. 55, No. 4 ( 2017-12), p. 864-901
    Abstract: Aeolian processes were active in many areas of the Tibetan Plateau in the geologic past and continue today Aeolian research on the plateau is conducted in the general framework of aeolian science but addresses issues specific to the plateau that result from its low air temperature, low air density, and the presence of a cryosphere Recent decades have witnessed increasing interest in aeolian research on the plateau, resulting in encouraging research achievements
    Type of Medium: Online Resource
    ISSN: 8755-1209 , 1944-9208
    URL: Issue
    URL: Article
    DOI: 10.1002/rog.v55.4
    DOI: 10.1002/2017RG000585
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2017
    detail.hit.zdb_id: 2035391-1
    detail.hit.zdb_id: 209852-0
    SSG: 16,13
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  • 10
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    Online Resource
    Aeolian transport in the field: A comparison of the effects of different surface treatments
    American Geophysical Union (AGU) ; 2012
    In:  Journal of Geophysical Research: Atmospheres Vol. 117, No. D9 ( 2012-05-16)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 117, No. D9 ( 2012-05-16)
    Abstract: Aeolian transport on three field plots of different type is discussed The flux density profiles are defined in terms of surface type and wind speed Transport rate is well correlated to drift potential
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2012JD017538
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2012
    detail.hit.zdb_id: 161666-3
    SSG: 16,13
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