Compression and Decay of Hillslope Topographic Variance in Fourier Wavenumber Domain
Compression and Decay of Hillslope Topographic Variance in Fourier Wavenumber Domain
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傅里叶波数域山坡地形方差的压缩与衰减
DOI：
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
D. Furbish
中科院分区：
文献类型：
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作者：
T. Doane;D. Roth;J. Roering;D. Furbish
坡面泥沙输移的数学模型有三种：线性扩散、非线性扩散和非局部输移。每一种理论都有不同的理论支持，但每一种理论都包含地表坡度作为核心要素。因此，所有这三种模式的陆面演变在很大程度上是相似的，地形高点退化，低点填充。然而，陆面形态的细节揭示了陆面线性或非线性行为的诊断线索。我们将陆面演化转换为波数（傅立叶）域，有效地将信号分离为陆面形态的粗尺度和细尺度元素，例如山坡-山谷序列和坑丘特征。在波数域线性扩散导致垂直谱衰减，这与地形变直和尖锐凹陷的平滑有关。非线性扩散导致频谱向低波数方向压缩，这与地形延长有关，类似于斜坡置换。非定域过程共享线性或非线性的元素，但被粒子行进距离分布的特定形式所修改。最终，所有的过程都趋向于零地形变化，但在波数域中显示出明显不同的风格。非线性过程的光谱压缩可以导致在某些光谱波段上的暂时光谱增长，并被解释为某些地貌的非线性过程的特征。这些特征来自于地形细节的演变，具有尖锐凹陷的地形突出了这种行为，而具有低凹陷的地形掩盖了这些诊断行为。
Three mathematical models of hillslope sediment transport are common: linear diffusion, nonlinear diffusion, and nonlocal transport. Each of these is supported by a different theory, but each contains land‐surface slope as a central ingredient. As such, land‐surface evolution by all three of these models is largely similar in that topographic highs degrade and lows fill in. However, details of land‐surface form reveal diagnostic clues to linear or nonlinear behavior of the land surface. We cast land‐surface evolution into wavenumber (Fourier) domain, which effectively separates signals into coarse‐ and fine‐scale elements of land‐surface form, such as hillslope‐valley sequences and pit‐mound features, respectively. In wavenumber domain linear diffusion results in vertical spectral decay, which is associated with landform straightening and smoothing of sharp concavities. Nonlinear diffusion results in spectral compression toward low wavenumbers, which is associated with landform lengthening and is similar to slope replacement. Nonlocal processes share elements of linearity or nonlinearity but are modified by the particular form of the distribution of particle travel distance. Ultimately, all processes tend toward zero topographic variance, but by distinctly different styles as revealed in wavenumber domain. Spectral compression by nonlinear processes can result in temporary spectral growth over certain spectral bands and is interpreted as a signature of nonlinear processes for certain landforms. The signatures come from the evolution of topographic details and landforms with sharp concavities highlight this behavior, whereas landforms with low concavities obscure these diagnostic behaviors.
影响因子：
3.9
作者：
Hurst, Martin D.;Mudd, Simon M.;Yoo, Kyungsoo
通讯作者：
Yoo, Kyungsoo