Wavelet analysis of Amazon hydrological regime variability

Labat, David; Ronchail, Josyane; Callède, Jacques; Guyot, Jean‐Loup; Oliveira, Eurides de; Guimarães, Waldemar

doi:10.1029/2003gl018741

Cited by 65 publications

(47 citation statements)

References 27 publications

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“…Wang and Eltahir (1999), Tawfik (2003) and Eldaw et al (2003) have corroborated the Nile discharge-SOI association. Labat et al (2004Labat et al ( , 2005 using wavelet techniques showed that the Amazon, Parana, Orinoco and Congo river flows were influenced by the SOI on a 3-6-year time-scale in keeping with the earlier study of Amarasekera et al (1997), while longer term variability was influenced by a combination of the Pacific Decadal Oscillation and the North Atlantic Oscillation. Whitaker et al (2001), concentrating on the Ganges, found a relatively strong relationship at the 95% significance level between annual river flow and indices of the extremes of El Niño-Southern Oscillation (ENSO) and also whether the trend of the SOI was increasing or decreasing, suggesting that there existed a basis for prediction.…”

Section: Introductionsupporting

confidence: 83%

Large‐scale controls on Ganges and Brahmaputra river discharge on intraseasonal and seasonal time‐scales

Jian

Webster

Hoyos

2009

Quart J Royal Meteoro Soc

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Reliable water supply from the Ganges and Brahmaputra is of critical importance to the sustainability of the agricultural societies of India and Bangladesh. But, the flow in both basins is highly variable on time-scales ranging from days to years, creating challenges for the optimization of agricultural practices, water resource management and disaster mitigation. The following questions are addressed. Is intraseasonal monsoon variability related to the subseasonal variability of river flow? Do variations in the large-scale tropical sea-surface temperature (SST) located both regionally and remotely promote seasonal and interannual variations of river discharge? And, if these relationships do exist, are they determinable with sufficient lead-times to allow useful predictions for user communities in South Asia? We examine these questions using 50 years of daily river discharge data for both rivers calculated at the points where they enter Bangladesh, and with SST data in the Indo-Pacific region. We also examine the question of determining the impact of man-made dams, diversions and barrages on the data record, especially that of the Ganges. A comparison of discharge prior to 1974 (the time of the construction of the largest barrage) shows no statistical difference that cannot be explained by basin-wide rainfall distributions. Changes that do occur are restricted to the dry-season months.Subseasonal river discharge is found to be strongly tied to the monsoon intraseasonal cycle resulting in a near-inphase timing of Ganges and Brahmaputra discharge. A basin isochrone analysis is used to couple stream-flow variability and intraseasonal precipitation during the different phases of the intraseasonal cycle. On longer time-scales, statistically significant correlations are found between mean monthly equatorial Pacific SST and the boreal summer Ganges discharge with lead times of 2-3 months. These relationships are tied to El Niño-Southern Oscillation (ENSO) oscillations in addition to SST variability in the southwest and northwest Pacific that also seems to be related to ENSO. The Brahmaputra discharge, on the other hand, shows somewhat weaker relationships with tropical SST. Strong lagged correlation relationships are found with SST in the Bay of Bengal but these are the result of very warm SSTs and exceptional Brahmaputra discharge during the summer of 1998. When this year is removed from the time series, relationships with SST anomalies weaken everywhere except in the northwest Pacific for the June discharge and in areas of the central Pacific straddling the Equator for the July discharge. In addition, the northwest Pacific relationship changes polarity for June and July discharges. Although the relationships are weaker than those found for the Ganges, they are persistent from month to month and suggest that two different and sequential factors influence Brahmaputra river flow.

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Section: Introductionsupporting

confidence: 83%

Large‐scale controls on Ganges and Brahmaputra river discharge on intraseasonal and seasonal time‐scales

Jian

Webster

Hoyos

2009

Quart J Royal Meteoro Soc

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“…Gaucherel (2002) detected and explained the 'Short March Summer' meteorological phenomenon over the Guyana Shield using wavelet analysis of the Guyanian watershed discharge series. Labat et al (2004) proposed a wavelet analysis of the annual rainfall over the Amazon basin and of the annual regime of the Amazon discharge at Obidos, in relationship to climatic drivers.…”

Section: The Wavelet Transform In Geosciencesmentioning

confidence: 99%

Recent advances in wavelet analyses: Part 1. A review of concepts

Labat

2005

Journal of Hydrology

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510

299

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“…Earlier applications of wavelets to discharge time series already allows to detect climatic oscillation [21,23,27]. The reader is referred to Ghil et al [12] and Labat et al [25] for a more complete bibliography on the applications of wavelets in geosciences.…”

Section: Overview Of Wavelet Analysismentioning

confidence: 98%