Shao Physics and Modelling of Wind Erosion

2. Auflage 2008
ISBN: 978-1-4020-8895-7
Verlag: Springer Netherland
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, 456 Seiten, Web PDF

Reihe: Earth and Environmental Science

Wind erosion occurs in many arid, semiarid and agricultural areas of the world. It is an environmental process in?uenced by geological and climatic variations as well as human activities. In general, wind erosion leads to land degradation in agricultural areas and has a negative impact on air quality. Dustemissiongeneratedbywinderosionisthelargestsourceofaerosolswhich directly or indirectly in?uence the atmospheric radiation balance and hence global climatic variations. Strong wind-erosion events, such as severe dust storms, may threaten human lives and cause substantial economic damage. The physics of wind erosion is complex, as it involves atmospheric, soil and land-surface processes. The research on wind erosion is multidisciplinary, covering meteorology, ?uid dynamics, soil physics, colloidal science, surface soil hydrology, ecology, etc. Several excellent books have already been written about the topic, for instance, by Bagnold (1941, The Physics of Blown Sand and Desert Dunes), Greeley and Iversen (1985, Wind as a Geological P- cess on Earth, Mars, Venus and Titan), Pye (1987, Aeolian Dust and Dust Deposits), Pye and Tsoar (1990, Aeolian Sand and Sand Dunes). However, considerable progress has been made in wind-erosion research in recent years and there is a need to systematically document this progress in a new book.

Zielgruppe

Research

Autoren/Hrsg.

Shao, Yaping

Inhaltsverzeichnis

Wind Erosion and Wind-Erosion Research.- Wind-Erosion Climatology.- Atmospheric Boundary Layer and Atmospheric Modelling.- Land-Surface Modelling.- Basic Aspects of Wind Erosion.- The Dynamics and Modelling of Saltation.- Dust Emission.- Dust Transport and Deposition.- Integrated Wind-Erosion Modelling.- Sand Dunes, Dynamics and Modelling.- Techniques for Wind-Erosion Measurements.- Concluding Remarks.

Leseproben

The world’s deserts show a variety of different types of sand dunes with fascinating shapes and patterns (Fig. 10.1). The focus of this chapter is on the dynamics and computational modelling of sand dunes and dune fields. This is again a complex problem, but in general the dynamics of sand dunes is governed by the interactions between (1) the atmospheric flow, (2) the motion of sand grains and (3) the dune morphological characteristics. We shall discuss these three topics in some detail.

The study on desert dunes has a history of more than a hundred years. Explorations on desert dunes began in the late 19th century, and by 1980 all major desert dune areas have been explored (Goudie, 1999). A comprehensive description of dune fields worldwide can be found in Wilson (1972). The number of basic dune forms is fairly small (Section 2), but a variety of combinations of dune types can occur. Dune combinations are mainly of two categories: (1) compound dunes made up of two or more dunes of the same basic type, coalescing or overlapping, and (2) complex dunes in which two or more different basic types are combined or superimposed (McKee, 1979). Recent advances in aircraft and satellite imagery have enabled a better classi.cation of sand-dune types, more reliable measures of large-scale desert morphology and development of hypotheses for the mechanisms of dune formation and evolution.

Studies on sand dunes have been made through wind-tunnel and field experiments, theoretical analysis and computational simulation. Wind-tunnel experiments are useful in studying flow over dunes and micro-scopic sand motions, but are not suitable for studying the dynamics of large-scale dune fields, because the requirement for dynamic similarity between the wind-tunnel and natural conditions are difficult to ful.l. Only a few field experiments on dune dynamics have been reported (e.g. McKenna Neuman et al. 1997, Nickling et al. 2002). Field experiments are time consuming and expensive to conduct and are limited to time periods much shorter than the time scale of dune field evolution. In general, there remains a lack of direct observations of flow structure, sand transport and deposition, which are critical to the understanding of dune dynamics. It is thus desirable to construct numerical models to simulate the behaviour of dunes and dune fields under varied atmospheric conditions and surface conditions (e.g. availability of sand supply) in order to predict their long-term evolutions. Computational simulation could play an important role to the understanding of dune dynamics, but so far few studies of this kind have been made, and the existing ones have been mainly limited to simple cases.

Most sand dunes are relatively low compared with their horizontal dimension and therefore, their aerodynamic characteristics are similar to those of low hills. Flow around low hills has been an active research topic in atmospheric boundary-layer studies and is reasonably well understood. During a wind-erosion event, the dune surface becomes mobile and therefore, the flow behaviour can be somewhat different from that around a low hill.

Über Autor(innen)

Yaping Shao is Professor of Meteorology at the Institute for Geophysics and Meteorology at the University of Cologne. After graduation from the Flinders University of South Australia in 1990, he worked in the Pye Laboratory of the Commonwealth Scientific and Industrial Research Organization of Australia and then in the School of Mathematics at the University of New South Wales. Shao has maintained a strong interest in Aeolian processes ever since the early 1990s. He has studied the physics of sand movement and dust emission by means of wind-tunnel experiments, worked on the theory of dust emission and developed numerical models for dust-storm predictions. His research aims to bridge the gaps between mathematics, computation, physics and observation in the studies on complex natural environmental problems.