Small Scale Aeolian Processes and Landform Response

When the wind blows across a surface with erodible grains, it exerts a shear stress on the surface. When the strength of the wind increases, those grains on the surface can be moved. The transported grains exchange momentum with fluid flow, interact with the surface, and then finally settle down when the wind strength becomes too weak to maintain their motion. The deposited grains produce various landforms from centimeter-scale sand ripples to meter- or kilometer-scale dunes and dune fields on terrestrial and extraterrestrial surfaces. In this dissertation, I investigated three subjects concerning small-scale aeolian processes and landforms: 1) the mechanisms of the low-energy creep mode of sand motion, especially the proportion of creep relative to the total transport within the aeolian system; 2) a method to efficiently delineate grainflow boundaries from a dune slipface; and 3) grainflow morphology characteristics on dunes of different sizes. To address these understudied topics, I integrated field data, signal and image processing techniques, and remote sensing and GIS techniques, to elucidate questions and arguments relevant to the study of aeolian processes and landforms.This dissertation focuses on aeolian landforms that respond quickly to forcing processes by studying creep motion and grainflow morphology. We reviewed the literature on aeolian creep and found a fundamental deficit in the understanding of the sand transport system. We argued for an agreement on creep definition and accompanying measurement methods. We developed an algorithm to objectively and efficiently delineate grainflow boundaries. It is an essential tool to study aeolian processes on slipfaces and is also applicable to the broader family of geophysical flows. we addressed grainflow morphology on two relatively large dunes. The quantification and classification of grainflow morphology showed that grainflow shapes were dune-size dependent. The findings of this dissertation are relevant to the formation and evolution of aeolian landforms with associated processes.

Grantor dc:publisher

University of Alabama Libraries

Year dc:date.issued

2022

Author dc:creator

• Zhang, Pei

Advisor dc:contributor.advisor

• Sherman, Douglas J.

Contributors dc:contributor

• Liu, Hongxing
• Parteli, Eric J.
• Ellis, Jean T
• Cohen, Sagy

Statement dc:rights

• All rights reserved by the author unless otherwise indicated.

Language dc:language.iso

en_US, English

Dc Identifier Other

http://purl.lib.ua.edu/186480
u0015_0000001_0004439
Zhang_alatus_0004D_14908

OAI identifier oai:identifier

oai:ir.ua.edu:123456789/9466