The wavelet packet transform: A technique for investigating temporal variation of river water solutes
The wavelet packet transform: A technique for investigating temporal variation of river water solutes
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DOI：
10.1016/j.jhydrol.2009.09.038
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发表时间：
2009-12
影响因子：
6.4
通讯作者：
A. Milne;C. Macleod;P. Haygarth;J. Hawkins;R. Lark
中科院分区：
文献类型：
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作者：
A. Milne;C. Macleod;P. Haygarth;J. Hawkins;R. Lark
了解影响河流水质的因素日益重要。我们现在能够集中监测水变量，从而产生大的时间序列，这可以用来促进这种理解。这些时间序列代表了由外部因素驱动的许多复杂过程的集合，发生在不同的时间尺度上。挑战在于利用时间序列来阐明在每个时间尺度（或频率）上发生的主要气候、水文和生物地球化学过程。时间序列是典型的非平稳的，所以经典的方法，如傅里叶分析，是不合适的。在本文中，我们证明了离散小波包变换（DWPT）及其自适应（最大重叠DWPT - modwpt）是分析这些复杂信号的合适工具。我们通过考虑硝酸盐和氯化物浓度、温度和英国德文郡陶河的排放量来举例说明这一点。小波分析能够区分频率特定行为以及在原始时间序列中不明显的间歇性事件。我们为其他工作人员对类似系统的观察发现了支持性证据，并进行了一些额外的观察。我们得出结论，MODWPT是一个重要的工具，可以帮助水文学家和生物地球化学家深入了解流域系统的复杂行为。
Understanding factors influencing river water quality is of increasing importance. We are now able to intensively monitor water variables resulting in large time series which can be used to facilitate this understanding. These time series represent the aggregation of many complex processes driven by external factors and occurring at different temporal scales. The challenge is to use the time series to elucidate the dominant climatic, hydrological and biogeochemical processes occurring at each temporal scale (or frequency). The time series are typically non-stationary and so classical methods, such as Fourier analysis, are not suitable. In this paper we demonstrate that the Discrete wavelet packet transform (DWPT) and an adaptation of this (the Maximal Overlap DWPT—MODWPT) are appropriate tools for analysing these complex signals. We exemplify this by considering measurements of nitrate and chloride concentration, temperature and discharge from the Taw River, Devon, UK. The wavelet analysis is able to distinguish frequency specific behaviour as well as intermittent events that were not visually apparent in the original time series. We find supporting evidence for observations made on similar systems by other workers and make some additional observations. We conclude that the MODWPT is an important tool which can help hydrologists and biogeochemists gain insight into the complex behaviour of catchment systems.