Diurnal variations of precipitation during the warm season over China

Abstract

ABSTRACT:The spatial distribution and seasonal change of diurnal variations of precipitation during the warm season (May-September) over China were analysed using hourly data from 62 rain gauges during 1954-2001. Nocturnal precipitation predominates for the stations over the Tibetan Plateau as well as in south-west and north-west China. For stations to the east of about 110°E, daytime precipitation predominates in the northern and southern parts, whereas nocturnal precipitation predominates in the middle and lower reaches of the Yangtze River and the North China Plain. Further, the magnitude of diurnal variations first decreases and then increases from the south towards the north. Two stations located close to the Bohai Bay manifest morning maxima. The significant diurnal variations in vertical circulation (stronger during the day and weaker at night), the meso-local-scale mountain-valley winds, and the nighttime cooling of cloud tops could be the processes behind the nocturnal rain in the western part of China (to the west of about 110°E). Daytime precipitation in the eastern part of China (to the east of about 110°E) could be attributed to the moist convection connected with solar heating. The morning peaks for stations in the middle and lower reaches of the Yangtze River and the North China Plain and the magnitude changing pattern in the eastern part seem to be connected with the advance and retreat of the East Asian summer monsoon. The morning maxima at coastal stations may be mainly attributed to the local land-sea breeze. The seasonal changes of diurnal variations for the western part of China are relatively small, with nighttime precipitation maxima remaining fairly constant during the warm season. This part is not directly influenced by the monsoon. For most of the stations in the eastern part, morning peaks tend to be strengthened/weakened along with the East Asian monsoon's advancing/retreating.

Maintenance mechanisms for the early‐morning maximum summer rainfall over southeast China

“…Power spectrum analyses of P SEC and LIS SEC variations during the 1998-2009 summer periods also show the diurnal and semi-diurnal as the two dominant oscillation periods (Figure 2(a) and (b) respectively). Yin et al (2009) suggested that the hourly rainfall records from 62 selected rain gauges over China can be well explained by their S1 and S2 harmonics with a 90% confidence threshold. Consistent with Yin et al (2009), it is found that ∼97% and 98% of the variance of P SEC and LIS SEC respectively (thick grey solid line in Figure 2(c) and (d) respectively) is explained by the variance of their combining S1 and S2 harmonics (thin solid line with open circles).…”

“…Yin et al (2009) suggested that the hourly rainfall records from 62 selected rain gauges over China can be well explained by their S1 and S2 harmonics with a 90% confidence threshold. Consistent with Yin et al (2009), it is found that ∼97% and 98% of the variance of P SEC and LIS SEC respectively (thick grey solid line in Figure 2(c) and (d) respectively) is explained by the variance of their combining S1 and S2 harmonics (thin solid line with open circles). In addition, it is also noted from Figure 2(c) and (d) that the variance of S2(P) SEC and S2(LIS) SEC contributes to ∼30% and 35% of the variance of P SEC and LIS SEC respectively.…”

“…For stations located west of 110 • E, diurnal rainfall in the summer tends to peak at midnight or in the early morning (Asai et al, 1998;Wang et al, 2004;Yu et al, 2007a;Li et al, 2008). Such a feature also predominates in some areas east of 110 • E, including the middle and lower reaches of the Yangtze River, the North China Plain, and the coastal regions of China (Peacock, 1952;Chan and Ng, 1993;Yin et al, 2009;Chen et al, 2010). In contrast, the northern and southern parts of areas east of 110 • E are dominated by daytime precipitation (Chen et al, 1999Yu et al, 2007a).…”

“…It was noted from rain gauge observations that the hourly rainfall over SEC (hereafter, P SEC ) frequently consists of two peaks within a day (e.g. Ramage, 1952;Yin et al, 2009). Generally, a major maximum peak of P SEC occurs in the afternoon and a minor maximum peak appears in the early morning (Figure 1(c)).…”

“…The tidal waves evolve with periods of 24 and 12 h and are commonly referred to as the diurnal and semidiurnal oscillations respectively (e.g. Wallace and Hartranft, 1969;Hamilton, 1980;Deser and Smith, 1998;Yin et al, 2009). Because the semi-diurnal harmonic component of P SEC , i.e.…”