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This study identifies daily Meiyu-like East Asian Summer Monsoon patterns that are linked to precipitation observations in the Poyang lake catchment. This analysis provides insight into the dynamics of strong, local precipitation events and has the potential to improve projections of precipitation from coarse-grid numerical simulations. Precipitation observations between 1960 and 1999 are taken from 13 rain gauges located in the Poyang lake catchment, which is a sub-catchment of the Yangtze River. The analysis shows that the observations are linked to daily patterns of relative vorticity at 850 hPa (Vo850) and vertical velocity at 500 hPa (W500) taken from the ERA-40 re-analysis data set. The patterns are derived by two approaches: (a) empirical orthogonal function (EOF) analysis and (b) rotated EOF analysis. Vo850 and W500 refer to geostrophic and ageostrophic processes, respectively. A logistic regression connects the large-scale dynamics to the local observations, whereby a forward regression selects the patterns best suited as predictors for the probability of exceeding thresholds of 24 h accumulated rainfall at the gauges. The regression model is verified by cross-validation. The spatial structure of the detected patterns can be interpreted in terms of well-known meso-α-scale disturbances called Southwest vortices. Overall, the proposed EOF and rotated EOF patterns are both related to physical processes and have the potential to work as predictors for exceedance rates of local precipitation in the Poyang catchment. [ABSTRACT FROM AUTHOR]

Numerous dams and reservoirs in the Yangtze River basin have been constructed. Thus understanding the variability of hydroclimatological time series is important for the development of an optimal reservoir management strategy. This is crucial for life in the densely populated basin known to be highly susceptible to floods and droughts. Time series of annual precipitation totals and precipitation totals from May to September (the rainy season) for the period from 1961 to 2002 were averaged within the subbasins of the Yangtze River. The resulting time series were analyzed for similarities and differences and continuous wavelet transforms were produced to identify inherent quasi-periodicity. The western subbasins have shown a diverse pattern of periods with high and low precipitation variance. We have detected prominent periods of high precipitation variance for the central and eastern subbasins in the 1980s and 1990s, respectively. [ABSTRACT FROM AUTHOR]