On the Diurnal Cycle of Heavy Rainfall over the Sichuan Basin during 10–18 August 2020
On the Diurnal Cycle of Heavy Rainfall over the Sichuan Basin during 10–18 August 2020
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2020年8月10日至18日四川盆地强降雨日周期分析
DOI：
10.1007/s00376-021-1118-7
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发表时间：
2021-11
影响因子：
5.8
通讯作者：
Rudi Xia
中科院分区：
文献类型：
--
作者：
Rudi Xia
摘要2020年8月10-18日，四川盆地发生了一次持续性强降雨过程，除第一天外，降雨量日变化明显，夜间峰值和下午最小值。结果表明，西太平洋副热带高压异常偏强的向西伸，有利于维持西南偏南的低空急流，有利于水汽输送的持续，有利于降水量的异常偏高。流域降水的日变化与低空急流在风速和风向上的周期性振荡密切相关，而低空急流的周期性振荡是由惯性振荡和地形热力强迫共同作用引起的。对流增强的降水主要是由盆地西南部的潮湿对流产生的，那里有高对流可用位能和较潮湿的近地面潮湿空气。对流的发生是由于来自川西高原降水云的冷空气或一股较大规模的偏北气流与来自南方的暖湿气流相遇。这是暖湿气流在冷空气上方倾斜上升的结果，西南涡和准地转上升经常促成了这一过程，从而释放了对流不稳定并产生了暴雨。
Abstract A sustained heavy rainfall event occurred over the Sichuan basin in southwest China during 10–18 August 2020, showing pronounced diurnal rainfall variations with nighttime peak and afternoon minimum values, except on the first day. Results show that the westward extension of the anomalously strong western Pacific subtropical high was conducive to the maintenance of a southerly low-level jet (LLJ) in and to the southeast of the basin, which favored continuous water vapor transport and abnormally high precipitable water in the basin. The diurnal cycle of rainfall over the basin was closely related to the periodic oscillation of the LLJ in both wind speed and direction that was caused by the combination of inertial oscillation and terrain thermal forcing. The nocturnally enhanced rainfall was produced by moist convection mostly initiated during the evening hours over the southwest part of the basin where high convective available potential energy with moister near-surface moist air was present. The convective initiation took place as cold air from either previous precipitating clouds from the western Sichuan Plateau or a larger-scale northerly flow met a warm and humid current from the south. It was the slantwise lifting of the warm, moist airflow above the cold air, often facilitated by southwest vortices and quasi-geostrophic ascent, that released the convective instability and produced heavy rainfall.
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