This study investigated characteristics of atmospheric environmental fields in the occurrence of quasi-stationary convective bands (QSCBs) in Kyushu, western Japan during the July 2020 heavy rainfall event. We performed case studies of extreme rainfall subevents in the Kumamoto and Kagoshima prefectures on 3-4 July (2020KK) and northern Kyushu on 6-7 July 2020 (2020NK), compared with two heavy rainfall events in northern Kyushu in 2017 and 2018.

Nine QSCBs were objectively extracted during the July 2020 heavy rainfall event, causing hourly precipitation amounts exceeding 100 mm twenty times. In 2020KK, the environmental field with extremely large precipitable water due to low-level and middle-level humidity was affected by the upper-level cold airflow, which resulted in favorable condition for the deep convection development. Consequently, the lightning activity became high, and cloud tops were the highest in comparison to previous events. QSCBs in 2020KK and 2020NK were located along a low-level convergence line/zone associated with an inflow that had extremely large water vapor flux on the south side of the mesoscale Baiu frontal depressions. In most of the QSCB cases in 2020, mesoscale depressions were observed and enhanced horizontal winds, which led to extremely large low-level water vapor flux to produce short-term heavy rainfall.

这项研究调查了2020年7月强降雨事件期间日本西部九州发生准平稳对流带（QSCB）时大气环境场的特征。我们对7月3-4日（2020KK）的熊本县和鹿儿岛县以及2020年7月6日至2020年7月6日的九州北部（2020NK）进行了极端降雨子事件的案例研究，而2017年和2018年在九州北部发生了两次强降雨事件。

在2020年7月的强降雨事件中，客观地提取了9个QSCB，导致每小时降水量超过100毫米达20倍。2020KK，高空冷气流影响了低空和中空湿度导致可降水量极大的环境领域，为深对流发展提供了有利条件。因此，雷电活动变得很高，与以前的事件相比，云顶最高。2020KK和2020NK的QSCBs沿着一条与流入有关的低层汇合线/区域，该流入在中尺度的贝乌额陷的南侧具有极大的水蒸气通量。在2020年的大多数QSCB案例中，观测到中尺度的凹陷并增强了水平风，