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Lanzhou University (2022)

The Formation Mechanism and Evolution Modeling of the Tallest Sand Dunes ——A Case Study from the Badain Jaran Sand Sea,china

牛震敏

Titre : The Formation Mechanism and Evolution Modeling of the Tallest Sand Dunes ——A Case Study from the Badain Jaran Sand Sea,china

Auteur : 牛震敏

Grade : Doctoral Dissertation 2022

Université : Lanzhou University

Résumé partiel
The total area of deserts in China is more than one tenth of the total area of the country,thus,the study of aeolian geomorphology is an important part of geomorphology research in China.Sand dune morphology and its evolution is one of the major parts of aeolian geomorphology research.The formation mechanism of different types of sand dunes has been relatively well studied,but the research on the factors influencing dune height growth,the formation and limitation of the maximum dune height is still insufficient.The Badain Jaran Sand Sea is considered to have the tallest dune in the world,and about 110 perennial lakes locate in the interdunal area of the mega-dunes.Various hypotheses have been proposed about the causes of these mega-dunes,each one partially explains the formation mechanism of the mega-dunes from different perspectives,but a unified understanding has not yet been formed,especially for the special spatial distribution pattern of the tallest dunes concentrated in the lake group area.Some researchers have recognized that mega-dune formation may be related to moisture conditions,but the understanding of the mechanisms and pathways of lake-dune interactions is still highly controversial.Numerical simulation is an important way to study dune evolution,but existing models are mostly focused on the relationship between the formation of different types of dunes and the related wind regimes and sand supply.The evolution of dune height is not sufficiently studied,and there are few models that can both simulate the evolution of complex dune fields and provide spatial and temporal linkages to real dunes.Models which have a real time and length are either too complex,which will bring unnecessary complexity to the dune height evolution researches,or too simple to simulate a complex dune field.So,a suitable model for dune height evolution remains to be developed.In terms of the formation mechanism of the existing mega-dunes,we developed a dune height and slope algorithm based on digital elevation model(DEM),and obtained the maximum dune heights of 32 major sand seas worldwide.Then,we focused on the spatial distribution of dune heights and slopes in the Badain Jaran Sand Sea.Based on the high-resolution images from Google Earth,the location and area of the lakes in the Badian Jaran Sand Sea were obtained.Based on the in situ meteorological observation of the Badain Jaran Sand Sea and the shallow water content samples at different time and in different heights,the spatial and temporal distribution of shallow water content in the lake group area of the Badain Jaran Sand Sea were discovered and its influencing factors were studied.Combining previous studies on deeper water content and water isotope results,a new viewpoint of lake-dune water interaction is proposed,and the spatial distribution of lake area,dune height and dune slope is combined to propose a "lake-dune" pattern model to explain the coexist of the tallest dunes in the lake group area.In order to further investigate the evolution pattern and growth limitation of dune height,a two-dimensional cellular automata model was developed with reference to the Werner model,that can well reproduce the two-dimensional dune evolution process under different wind conditions and has advantages in matching spatial and temporal scales to the reality.

Mots clés : dune height ;dune evolution ;Badain Jaran ;sand layer water content ;numerical simulation ;

Présentation (CNKI)

Page publiée le 15 octobre 2022