Regional features of topographic relief over the Loess Plateau, China: evidence from ensemble empirical mode decompositi
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RESEARCH ARTICLE
Regional features of topographic relief over the Loess Plateau, China: evidence from ensemble empirical mode decomposition Yongjuan LIU1,3, Jianjun CAO (✉)2,3,4, Liping WANG1, Xuan FANG2,3, Wolfgang WAGNER4 1 School of Environment Science and Spatial Informatics, China University of Mining and Technology, Xuzhou 221116, China 2 School of Geography Science/Key Laboratory of Virtual Geographic Environment of Ministry of Education, Nanjing Normal University, Nanjing 210023, China 3 School of Environmental Science, Nanjing Xiaozhuang University, Nanjing 211171, China 4 Department of Geodesy and Geoinformation, Vienna University of Technology, Vienna 1040, Austria
© Higher Education Press 2020
Abstract Landforms with similar surface matter compositions, endogenic and exogenic forces, and development histories tend to exhibit significant degrees of selfsimilarity in morphology and spatial variation. In loess hill–gully areas, ridges and hills have similar topographic relief characteristics and present nearly periodic variations of similar repeating structures at certain spatial scales, which is termed the topographic relief period (TRP). This is a relatively new concept, which is different from the degree of relief, and describes the fluctuations of the terrain from both horizontal and vertical (cross-section) perspectives, which can be used for in-depth analysis of 2-D topographic relief features. This technique provides a new perspective for understanding the macro characteristics and differentiation patterns of loess landforms. We investigate TRP variation features of different landforms on the Loess Plateau, China, by extracting catchment boundary profiles (CBPs) from 5 m resolution digital elevation model (DEM) data. These profiles were subjected to temporal-frequency analysis using the ensemble empirical mode decomposition (EEMD) method. The results showed that loess landforms are characterized by significant regional topographic relief; the CBP of 14 sample areas exhibited an overall pattern of decreasing TRPs and increasing topographic relief spatial frequencies from south to north. According to the TRPs and topographic relief characteristics, the topographic relief of the Loess Plateau was divided into four types that have obvious regional differences. The findings of this study enrich the theories and methods for digital terrain data Received September 10, 2019; accepted February 14, 2020 E-mail: [email protected]
analysis of the Loess Plateau. Future study should undertake a more in-depth investigation regarding the complexity of the region and to address the limitations of the EEMD method. Keywords catchment boundary profile, topographic relief period, ensemble empirical mode decomposition, Loess Plateau
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Introduction
Landform morphology is the most basic and important geographic parameter. Landforms such as mountains, hills, plains, and basins are the result of complex processes, during which the Earth’s surface undergoes changes directed by the effects of endogenic and exogenic forces (Mac
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