Diurnal Variations of Warm-Season Precipitation East of the Tibetan Plateau over China

Abstract

This study explores the diurnal variations of the warm-season precipitation to the east of the Tibetan Plateau over China using the high-resolution NOAA/Climate Prediction Center morphing technique (CMORPH) precipitation data and the Global Forecast System (GFS) gridded analyses during mid-May to mid-August of 2003-09. Complementary to the past studies using satellite or surface observations, it is found that there are strong diurnal variations in the summertime precipitation over the focus domain to the east of the Tibetan Plateau. These diurnal precipitation cycles are strongly associated with several thermally driven regional mountain-plains solenoids due to the differential heating between the Tibetan Plateau, the highlands, the plains, and the ocean. The diurnal cycles differ substantially from region to region and during the three different month-long periods: the pre-mei-yu period (15 May-15 June), the mei-yu period (15 June-15 July), and the post-mei-yu period (15 July-15 August).In particular, there is a substantial difference in the propagation speed and eastward extent of the peak phase of the dominant diurnal precipitation cycle that is originated from the Tibetan Plateau. This diurnal peak has a faster (slower) eastward propagation speed, the more (less) coherent propagation duration, and thus covers the longest (shortest) distance to the east during the pre-mei-yu (post-mei-yu) period than that during the mei-yu period. The differences in the mean midlatitude westerly flow and in the positioning and strength of the western Pacific subtropical high during different periods are the key factors in explaining the difference in the propagation speed and the eastward extent of this dominant diurnal precipitation cycle.

Diurnal Variation of Rainfall Associated with Tropical Depression in South China and its Relationship to Land-Sea Contrast and Topography

“…The time step is set to 30 s. As is known to meteorologists around the world, it is very difficult to obtain an accurate track and rainfall simulation for a 10-day TD through continuous model integration, despite some successful studies that have conducted long-time numerical simulations to investigate the diurnal rainfall cycle [9,26]. Considering the fact that the observed features of the diurnal rainfall cycle are obtained by averaging hourly TRMM-estimated or surface rain-gauge rainfall [8,13,45], an alternative method is adopted in this study. Ten simulations have been done in this study to cover the 10-day period of the case, with each simulation being initialized at 2000 BLT (1200 UTC) and integrated for 36 h. The last 24-h results are used for analysis, while the first 12-h results are discarded to alleviate the model spin-up impacts.…”

“…Regional and/or seasonal differences of diurnal rainfall patterns not only occur in China [8,[18][19][20], but also exist in other regions of the world, like in Japan [21], island regions in Asia [22,23], the Asian monsoon region [10][11][12], marine continental islands [24,25], northwest South America [26], the United States Great Plains [27], the Andes in South America [28,29], Africa [30] and even the global tropics [31,32]. The convective rainfall maximum late at night or in the early-morning hours over oceans can be explained by radiation-convection interaction theory [33,34].…”

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

“…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).…”

“…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).…”

“…And the diurnal variation of the solenoid circulation may contribute to the longevity and propagation of episodes in the vicinity of the eastern TP. Bao et al (2011) employed the theory of mountain-plain solenoid propagation (may refer to Tripoli and Cotton 1989;Carbone and Tuttle 2008) to understand the phenomena of eastward delayed phase for precipitation in the Sichuan Basin. Chen et al (2010) and Yuan et al (2011) suggested that the summertime nocturnal precipitation was attributed to the decreasing stability caused by the low-tropospheric convergence and upward motion, accompanied by a long wave radiative cooling at the cloud top and the weak cold advection from the TP.…”