Abstract
Located in the eastern edge of the Sichuan Basin (SCB) in the southwest China, Chongqing is a mountainous region with typical complex topographic features. Using the hourly rainfall observation data of high-density 1686 meteorological stations in Chongqing during warm season from 2009 to 2016, we investigated the diurnal characteristics of precipitation affected by complex topography. The complex mountainous terrain has a significant impact on diurnal variations and distinct regional features of rainfall amount, frequency, and intensity. The stations located in the higher complex mountainous areas have greater rainfall amount, frequency, and intensity than those in the lower surrounding areas. In addition, the detailed characteristics of the rainfall amount and frequency in the four study regions further show that the rainfall amount and frequency significantly increase with the rise of elevation, especially in the area that terrain height sharply increases along the mountain extending direction. The diurnal variation of the rainfall amount is characterized by a bimodal structure with a dominant early-morning peak occurring at approximately 0700 LST (23 UTC) and a weaker secondary late-afternoon peak at approximately 1600 LST (08 UTC), while the rainfall frequency has a single early-morning peak. The terrain height has a significant impact on the proportions of the early-morning rainfall. With the elevation increasing in the four study regions, the proportions of rainfall amount (frequency) that occurs during early-morning period decrease.
Highlights
The complex topography plays a significant role in the inhomogeneous spatial and temporal distributions of rainfall patterns, and most previous researches have shown that the mechanisms of the orographic influences are complex (Smith 1979; Jiang and Smith 2003; Colle 2004; Smith and Barstad 2004; Roe 2005; Rotunno and Houze 2007; Kirshbaum 2011; Houze 2012; Couto et al 2016; DeHart and Houze 2017; Purnell and Kirshbaum 2018; Kang et al 2019)
From the above discussion of the spatial variations of the rainfall over four focus regions, the results show that the rainfall amount and frequency at higher elevations are larger than those at lower elevations, and the rainfall amount and frequency significantly increases as the terrain height sharply increase, which indicates that mountainous terrain has a remarkable enhancing effect on precipitation in the four study regions
Based on the hourly rain gauge data of high-density stations in Chongqing during the warm season (May to September) from 2016 to 2020, the overall features and regional differences in the diurnal variations of rainfall affected by complex terrain are identified, and the detailed influences of the gauge elevations on the diurnal variations of rainfall are investigated
Summary
The complex topography plays a significant role in the inhomogeneous spatial and temporal distributions of rainfall patterns, and most previous researches have shown that the mechanisms of the orographic influences are complex (Smith 1979; Jiang and Smith 2003; Colle 2004; Smith and Barstad 2004; Roe 2005; Rotunno and Houze 2007; Kirshbaum 2011; Houze 2012; Couto et al 2016; DeHart and Houze 2017; Purnell and Kirshbaum 2018; Kang et al 2019). The topography in China has complex and various with diverse mountain ranges and plateaus; the influence of terrain on precipitation is more complex (Tao 1980; Peng et al 1995; Liao et al 2007; Yu et al 2014). The influences on rainfall in the high Tibetan Plateau (TP) region are closely related to the spatiotemporal distributions of rainfall in the local and the surrounding areas (Liu et al 2009; Xu and Zipser 2011; Jin et al 2013; Guo et al 2014, 2016; Cuo and Zhang 2017; Li 2017; Chen et al 2018), and to diurnal variations of rainfall in the faraway
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