Physics and Modelling of Wind Erosion

Abstract

Wind erosion occurs in many arid, semiarid and agricultural areas of the world. It is an environmental process influenced 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. Dust emission generated by wind erosion is the largest source of aerosols which directly or indirectly influence 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, fluid 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 Process 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. There are three other reasons which motivated me to write this book. Firstly, in most existing books, there is a general lack of rigor in the description of wind-erosion dynamics; secondly, the emphasis of the existing books appears to be placed primarily on sand-particle motion, while topics related to the modelling of dust entrainment, transport and deposition have not been presented in great detail and thirdly, the results presented in the existing books appear to be mainly experimental and lacking in documentation of the computational modelling effort involved. My intention is to provide a summary of the existing knowledge of wind erosion and recent progress in that research field. The basic contents of the book include the physics of particle entrainment, transport and deposition and the environmental processes that control wind erosion. It is intended to treat the physics of wind erosion as rigorously as possible, from the viewpoint of fluid dynamics and soil physics. A considerable proportion of the book is devoted to the computational modelling of wind erosion. I hope that this book can be used as a reference point for both wind-erosion researchers and postgraduate students. My basic consideration is that wind erosion can only be understood from a multidisciplinary viewpoint and the computational modelling of wind erosion should focus on the development of integrated simulation systems. Such a system should tightly couple dynamic models, such as atmospheric prediction models and wind-erosion schemes, with real data that characterises soil and surface conditions. In the introductory chapter of the book, this basic concept is reiterated, while in Chapter 9 examples of the advocated modelling approach are given. Chapter 2 provides a summary of wind-erosion climatology in the world and selected regions. Chapters 3 and 4 are devoted to the description of atmospheric modelling and land-surface modelling, as these are the prerequisite for the modelling of wind erosion. Chapter 5 is a description of the basic aspects of wind-erosion theory, while Chapters 6, 7 and 8 are dedicated to the entrainment, transport and deposition of sand and dust particles. In Chapter 9, the integrated wind-erosion modelling system and the data requirement are described. The concluding remarks are given in Chapter 12.