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Duration is a key feature of rainfall events that is closely related to rainfall mechanisms and influences. This study analyzes the decadal change in the duration-related characteristics of late-summer (July-August) precipitation over eastern China during 1966-2005. Accompanying the southern-flooding and northern-drought (SFND) pattern of rainfall amount over the eastern China in recent decades, the duration-related rainfall structure also experienced significant changes. In North China, the frequency of short duration rainfall events decreased and their intensity increased. The decadal decreases of rainfall amount over North China are largely contributed by long duration rainfall events, especially those occurring between midnight and morning. In the mid-to-lower reaches of the Yangtze River valley, both the frequency and amount of long duration precipitation have significantly increased. The mean and maximum duration time of late-summer precipitation has increased 0.85 and 7.61 h, respectively. Considerable increases of rainfall amount of two kinds of precipitation, the short and medium duration rainfall events in the late afternoon and the long duration rainfall events in the early morning, contribute to the 'southern-flooding.' Despite the differences between the northern and southern region, there is a common feature of their decadal precipitation changes that the intensity of short duration rainfall in the late afternoon has shown an increasing trend. [ABSTRACT FROM AUTHOR]

Hourly observational records and 6-hourly reanalysis data were used to investigate the influences of large-scale forcings on the diurnal variation of summer rainfall along the Yangtze River (YR). The results show that long-duration (more than six hours) rainfall events dominate the summer rainfall along the YR. These events tend to start during the night and to peak after several hours of development. The eastward-delayed initiation of the nocturnal long-duration rainfall events is thought to be due to the diurnal clockwise rotation of the low-tropospheric circulation, especially the accelerated nocturnal southwesterlies. In the early evening, the anomalous easterly flow toward the Tibetan Plateau (TP) causes low-level convergence over the Plateau’s eastern slope that induces the formation of rainfall in the upper YR valley. The anomalous wind sequentially rotates clockwise to a southerly flow at midnight and accelerates the meridional wind in the middle valley, resulting in the initiation of rainfall between 2300 and 0300 LST. In the early morning, the accelerated southwesterlies in southern China, when combined with decelerated winds in the north of the YR, causes a strong convergence along the YR and contributes to the early morning rainfall in the lower valley. Furthermore, the development of the convection systems is suppressed in the afternoon by the mid- and low-level warm advection downstream from the TP. This helps explain why long-duration events do not typically start in the afternoon in the upper YR valley. [ABSTRACT FROM AUTHOR]