Rainy-Season Precipitation over the Sichuan Basin and Adjacent Regions in Southwestern China

Abstract

The spatial variability and diurnal propagation of mean precipitation in the summer rainy seasons (from 2003 to 2010) over the Sichuan basin (SCB) and adjacent mountainous regions are examined using high spatiotemporal resolution satellite-derived precipitation estimates. The SCB is located just east of the Tibetan Plateau (TP) and is prone to heavy precipitation that often peaks over nighttime and early morning. The large-scale environment over the SCB during the rainy season is characterized by weak low- to midtropospheric convergence in the lee of the TP and by the upper-tropospheric jet stream to the north. Under this flow configuration, the study links the unique diurnal variations in the precipitation pattern and propagation to the unique topography in this region. It is found that during the rainy season, the local diurnal precipitation maximum moves primarily downslope and southeastward, from over the TP in the daytime to SCB at night. A secondary maximum moves northeastward downslope of the Yunnan–Guizhou Plateau toward the SCB from late evening to the early morning. The movement of precipitation over the SCB and the adjacent regions is closely tied to multiple regional-scale mountain–plain solenoids because of the large contrast in terrain heights between the basin and surrounding mountain ranges.

What Is the Main Cause of Diurnal Variation and Nocturnal Peak of Summer Precipitation in Sichuan Basin, China? The Key Role of Boundary Layer Low‐Level Jet Inertial Oscillations

“…Nocturnal precipitation has been found to account for up to 70% of the total precipitation in SB (Zheng et al, ), which is usually called “Bashan Yeyu” (nocturnal precipitation in Bashan Mountains; Lv, ). Both rain gauge and satellite observations reveal that, from pre‐Meiyu season to midsummer, precipitation peak usually occurs at night and early morning in SB (Bao et al, ; G. Chen et al, ; Qian et al, ; Shen & Zhang, ; Xu & Zipser, ; Yin et al, ; Yu, Xu, et al, ; Yu, Zhou, et al, ; Yuan et al, ). Within the basin, there are also diurnal changes in the precipitation distribution.…”

“…Convection tends to first appear on the eastern slope of the TP around noon, and propagates eastward into the basin by late evening (Jin et al, ). After midnight and through the early morning hours, the precipitation area tends to cover the entire SB (Qian et al, ).…”

“…Precipitations over China have been studied extensively using numerical simulations (Shen & Zhang, ; Yuan, ). Most studies, however, focus on the precipitation in central eastern China (G. Chen et al, , ; H. L. Huang et al, ; Shen & Zhang, ; Xu & Zipser, ; Yuan, ), while only a few studies focus on SB precipitation (Jin et al, ; Qian et al, ). Often, large discrepancies exist between the simulated and observed precipitation in SB, including their spatial pattern, intensity, and timing (Zhou et al, ).…”

“…Both rain gauge and satellite observations reveal that, from pre-Meiyu season to midsummer, precipitation peak usually occurs at night and early morning in SB (Bao et al, 2011;G. Chen et al, 2013;Qian et al, 2015;Shen & Zhang, 2011;Xu & Zipser, 2011;Yin et al, 2009;Yu, Xu, et al, 2007;Yuan et al, 2012). Within the basin, there are also diurnal changes in the precipitation distribution.…”

“…Convection tends to first appear on the eastern slope of the TP around noon, and propagates eastward into the basin by late evening (Jin et al, 2012). After midnight and through the early morning hours, the precipitation area tends to cover the entire SB (Qian et al, 2015). 2010; H. L. Huang et al, 2010;Shen & Zhang, 2011;Xu & Zipser, 2011;Yuan, 2013), while only a few studies focus on SB precipitation (Jin et al, 2012;Qian et al, 2015).…”