Recent advances in wavelet analyses: Part 2—Amazon, Parana, Orinoco and Congo discharges time scale variability
Recent advances in wavelet analyses: Part 2—Amazon, Parana, Orinoco and Congo discharges time scale variability
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DOI：
10.1016/j.jhydrol.2005.04.004
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发表时间：
2005-11
影响因子：
6.4
通讯作者：
D. Labat;J. Ronchail;J. Guyot
中科院分区：
文献类型：
--
作者：
D. Labat;J. Ronchail;J. Guyot
本文致力于阐述水文学领域中的新小波分析方法。新的小波指标应用于长期水文和气候代理。它们首先应用于四个大西洋大河的月流量（亚马逊河、巴拉那河、奥里诺科河和刚果河），然后应用于两个著名的长期气候指数：南方涛动和北大西洋涛动。这种方法使得对时间尺度依赖关系提出物理解释成为可能。除巴拉那河外，所有河流都存在六个月的变化。在刚果河中，该信号接近静止，具有很强的熵。这一规模的强度与 1920 年之前较高的流量变异性以及 1940 年至 1955 年间流量值较高的奥里诺科河流域相一致。所有河流都存在年周期，但在拥有大型热带盆地的河流（如亚马逊河和奥里诺科河）中，年周期和熵要强得多。这种年度信号在刚果并不是永久性的，而在巴拉那州则更加间歇性，那里的年度补给量显得非常不规律。所有赤道地区河流都存在明显的准两年变化，并且 SOI 和亚马逊流量之间几乎存在永久性的 2 年一致性。在所有河流中都观察到典型的 ENSO 变化的 3-6 年振荡。它是间歇性的，1930 年之前在所有河流中都观察到，1980 年之后主要在亚马逊河中观察到。这些活动峰值对应于 SOI 主要变化的时期。巴拉那河在 1940 年之前和 1970 年左右的 8 年变化尤其强烈，奥里诺科河在 1940 年至 1970 年低 NAO 指数期间的变化程度较小。刚果河在 1970 年左右表现出这种时间尺度。在巴拉那和刚果排放中观察到 SOI、NAO 和南大西洋环流共有的 13 年变化。在所有河流中，在双十年和多十年时间尺度上观察到最大的熵，与 NAO 和 SOI 具有最大的一致性。 1970 年左右的大部分系列都观察到近 20 年的时间尺度，尽管亚马逊和巴拉那放电最强。最后，观察到 1940 年至 1970 年之间的 30 年时间尺度。值得注意的是，所有河流中大多数时间尺度的主导活动可能受到 1940 年至 1970 年左右太平洋和大西洋发生的年代际变化的影响。因此，在本论文中，新的小波指标（组合连续和多分辨率分析、小波熵、小波相干性、小波互相关）的应用导致了对这些全球水文信号波动及其相互时变关系的分析的一些改进。结果表明，小波应该比经典傅里叶分析更系统地使用，特别是在水文学中。
This paper is devoted to illustrating new wavelet analysis methods in the field of hydrology. New wavelet indicators are applied to long-term hydrological and climatologic proxies. They are first applied to four Atlantic large river monthly discharges (Amazon, Parana, Orinoco and Congo) and then applied to two well-known long-term climatologic indexes: the Southern Oscillation and the North Atlantic Oscillation. This approach makes it possible to suggest physical explanations for time–scale dependant relationships. Six-month variability is present in all the rivers except in the Parana. In the Congo River this signal is near stationary with strong entropy. The strength of this scale coincides with higher discharge variability before 1920 and over the Orinoco basin with higher discharge values between 1940 and 1955. An annual cycle is present in all the rivers but is much stronger, along with the entropy, in the rivers with a large tropical basin, as in the Amazon and the Orinoco. This annual signal is not permanent in the Congo and much more intermittent in the Parana where the annual recharge appears as very irregular. A quasi biennial variability is apparent in all the equator ward rivers and a nearly permanent 2-year coherence is found between SOI and the Amazon discharge. A 3–6-year oscillation typical of ENSO variability is observed in all the rivers. It is intermittent, observed before 1930 in all the rivers and after 1980 mostly in the Amazon River. These peaks of activity correspond to periods of major SOI variability. An 8-year variability is particularly strong in the Parana River before 1940 and around 1970 and to a lesser extent in the Orinoco River during the low NAO index period, between 1940 and 1970. The Congo River exhibits that time–scale around 1970. A 13-year variability common to SOI, NAO and the South Atlantic Ocean circulation is observed in the Parana and Congo discharges. In all the rivers the greatest entropy is observed at bi and multi decadal time scales with the greatest coherence with both NAO and SOI. A near 20-year time–scale is observed in most of the series around 1970, although it is strongest in Amazon and Parana discharges. Finally, a 30-year time–scale is observed between 1940 and 1970. It is to be noted that most of the time–scale dominant activities, in all the rivers, may have been influenced by the interdecadal shifts that took place around 1940 and 1970 in the Pacific and in the Atlantic. Therefore, in this contribution, the application of new wavelet indicators (combined continuous and multi-resolution analysis, wavelet entropy, wavelet coherence, wavelet cross-correlation) leads to several improvements in the analysis of these global hydrological signal fluctuations and of their mutual time varying relationships. It is demonstrated that wavelets should be used more systematically in preference to the classical Fourier analysis, notably in hydrology.