The Mekong River in Southeast Asia thanks its regular annual flood to thesouthwest monsoon. At longer time scales, the monsoon is a spatially andtemporally variable circulation, with different annual to millennialvariation for different regions. In this paper, the Indian and the WesternPacific components of the monsoon were analyzed to draw a light on theinterannual flood variability of the Mekong River.The focus is on the variance of flood season flows at 8 stations on theMekong River, as well as on well-known climate indexes that reflect thedynamics of the monsoon circulation and ocean temperature anomalies. Aneffort was made to identify the temporal resolution that contains most of theinterannual variability of both flood regime of the Mekong and monsoonintensity.We found a close connection between the Western Pacific monsoon and thedischarge in Kratie and other stations in the Southern Mekong region. In thefrequency domain, the interannual to decadal variance of the Mekong dischargeclosely follows that of the Western Pacific monsoon. More importantly, thewell-known regime shift of 1976 in the North Pacific is detectable in thefrequency domain for flood discharge and monsoon intensity. This suggests arelationship between Pacific sea surface temperature and monsoon variance,which is a good predictor for flood variance. This dependence influences theprobability of occurrence of floods in the Mekong Delta.
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