Abstract
On 22 July 2019, mesoscale convective systems (MCSs) with an abrupt heavy rainfall event (AHRE) hit Shuicheng County of Guizhou Province in Southwest China causing landslide and debris flow secondary disasters. The AHRE over the complex terrain of Shuicheng County had differences in location and intensity during two stages of the event. The two stages could be divided into different rainfall types (topographic rainfall and synoptic-weather-related rainfall) according to the spatiotemporal distribution and organization of MCSs based on surface and midlevel environmental field conditions. During the topographic rainfall stage, smaller meso-γ-scale (2–20 km) convective cells with lower echo-top heights (6–10 km) occurred along the windward slope of the primary mountain peak. During the synoptic-weather-related rainfall stage, a meso-β-scale (20–200 km) convective echo band with higher echo-top heights (10–14 km) occurred in the valley of the region. An adverse wind area (AWA) with distinct convergence of radar radial velocity existed over Shuicheng County. A formation mechanism analysis of the AHRE showed that topographic rainfall occurred in the warm and moist area, while synoptic-weather-related rainfall occurred due to local convergence and the intrusion of a cold tongue. Compared to the early stage, the cold tongue from the higher terrain superimposed over the warm sector at the base of major mountain ranges appeared to strengthen the rainfall.
Highlights
In Southwest China, an abrupt heavy rainfall event (AHRE) is defined as a period of 3 h of rainfall ≥ 50 mm with at least one 1 h rainfall period of ≥20 mm during the successive three-hour period [1,2]
Shuicheng County is located in the eastern part of the Yunnan–Guizhou Plateau and is characterized by local complex terrain due to the Wumeng Mountains
Shuicheng County is characterized by locally complex terrain in the eastern Yunnan–Guizhou
Summary
In Southwest China, an abrupt heavy rainfall event (AHRE) is defined as a period of 3 h of rainfall ≥ 50 mm with at least one 1 h rainfall period of ≥20 mm during the successive three-hour period [1,2]. The Yunnan–Guizhou Plateau of Southwest China is dominated by complex terrain, which often experiences landslide and debris flow disasters when AHREs happen [3,4,5]. Water 2020, 12, 2502 on the climatological aspects of these events, such as the occurrence frequency, intensity, diurnal variations, and synoptic conditions [6,7]; most climatological studies focus on the synoptic and meso-α-scale environmental conditions of this extreme heavy precipitation [8,9]. In addition to the large-scale environmental conditions, high-precipitation supercells caused by terrain-forced convection have been observed to produce flash floods [10]. Chen et al [13] determined that shallow low-level eastward airflow plays a key role in convective cell formation on the east side of Fanjing Mountain in Guizhou
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