Seasonal Variation of the Diurnal Cycle of Rainfall in Southern Contiguous China

Abstract

Hourly station rain gauge data are employed to study the seasonal variation of the diurnal cycle of rainfall in southern contiguous China. The results show a robust seasonal variation of the rainfall diurnal cycle, which is dependent both on region and duration. Difference in the diurnal cycle of rainfall is found in the following two neighboring regions: southwestern China (region A) and southeastern contiguous China (region B). The diurnal cycle of annual mean precipitation in region A tends to reach the maximum in either midnight or early morning, while precipitation in region B has a late-afternoon peak. In contrast with the weak seasonal variation of the diurnal phases of precipitation in region A, the rainfall peak in region B shifts sharply from late afternoon in warm seasons to early morning in cold seasons. Rainfall events in south China are classified into short-(1-3 h) and long-duration (more than 6 h) events. Short-duration precipitation in both regions reaches the maximum in late afternoon in warm seasons and peaks in either midnight or early morning in cold seasons, but the late-afternoon peak in region B exists during February-October, while that in region A only exists during May-September. More distinct differences between regions A and B are found in the long-duration rainfall events. The long-duration events in region A show dominant midnight or early morning peaks in all seasons. But in region B, the late-afternoon peak exists during JulySeptember. Possible reasons for the difference in the diurnal cycle of rainfall between the two regions are discussed. The different cloud radiative forcing over regions A and B might contribute to this difference.

The quasi-stationary feature of nocturnal precipitation in the Sichuan Basin and the role of the Tibetan Plateau

“…Such studies use either rain-gauge measurements (e.g. Fujinami et al 2005;Zhao et al 2005;Yu et al 2007a, b;Li et al 2008) or satellite data Chen et al 2009;Yu et al 2009;He and Zhang 2010). The nocturnal precipitation in the Sichuan Basin in summer, i.e.…”

“…The nocturnal precipitation in the Sichuan Basin in summer, i.e. the precipitation reaches its diurnal peak around midnight, becomes a hot topic in the recent decade (Li et al 2008;Yu et al 2007aYu et al , 2009Chen et al 2010;Huang et al 2010;Bao et al 2011;Yuan et al 2011). This phenomenon has been observed and documented since long time (Lu 1942;Ye and Gao 1979;Zeng et al 1994).…”

“…Dai et al 2007;Yu et al 2007a). Yu et al (2007b) and Li et al (2008) showed that the summertime nocturnal precipitation in the Sichuan Basin is contributed mainly by long-duration precipitating systems. In addition, the diurnal cycle of precipitation presents an eastward delayed diurnal phase from the east of the Tibetan Plateau (TP) down to the Yangtze River valley in central China Huang et al 2010;Bao et al 2011;Yuan et al 2011).…”

“…Li et al (2003Li et al ( , 2008 suggested that it may be caused by a weakening of the mid-level inversion layer at night in summer. A numerical modeling study by Huang et al (2010) on an individual event revealed that the eastern TP acts as a heat source for convection and a thermal driven diurnal solenoid circulation results in an ascendance over the Sichuan Basin in nighttime, which favors the nocturnal precipitation.…”

Diurnal phase of late-night against late-afternoon of stratiform and convective precipitation in summer southern contiguous China

“…Their results show that long-duration rainfall events tend to have their maximum hourly rainfall around the early morning, while short-duration rainfall events tend to peak around the late afternoon. The seasonal variation of rainfall diurnal cycle in the southern contiguous China was also examined by Li et al (2008) and it is both regional and durational dependent.…”