The Sichuan Basin (SCB) is located to the east of the Tibetan Plateau (TP) and features nocturnal precipitation. This study explores spatial variation of nocturnal precipitation during the warm season over the SCB using high spatiotemporal resolution merged precipitation products from 2008 to 2017. It is found that there is a prominent northeastward timing delay of precipitation peak over the SCB, that is, the diurnal peak of precipitation occurs in the midnight over the southwestern SCB whereas in the early morning over the northeastern SCB. This time delay is partly ascribed to a northeastward propagation of precipitation over the SCB, account for about 40% and 25% of the diurnal variation of precipitation over the central and northeastern SCB, respectively. Precipitation first occurs over the southwestern edge of the SCB at about 1900–2000 LST, and then propagates northeastward steered by the large‐scale mid‐tropospheric southwesterly airflow, which is consistent with the northeastward propagation of the large moisture convergence. The precipitation reaches the northeastern SCB in the early morning. The diurnal variation of 850‐hPa wind has strong easterly wind deviations in the early evening over the southwestern SCB, which favours for an initiation of precipitation by orographic lift of air. The diurnal variation of difference in equivalent potential temperature between 500 hPa and 850 hPa has a maximum negative deviation in the early evening over the southwestern SCB, which enhances the instability and therefore favours an initiation of precipitation. The Yunnan‐Guizhou Plateau (YGP) may play an important role in the initiation of precipitation over the southwestern SCB in the early evening.

中文翻译：

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四川盆地夜间降水向东北传播

四川盆地（SCB）位于青藏高原（TP）的东部，具有夜间降水。本研究利用高时空分辨率合并降水产物，探索了SCB夜间暖季夜间降水的空间变化，发现2008-2017年期间SCB的降水峰值向东北方向有明显的时间延迟，即昼夜降水峰值出现在西南SCB的午夜，而清晨出现在SCB的东北。该时间延迟部分归因于SCB上降水向东北传播，分别占SCB中部和东北降水日变化的40％和25％。大约在1900-2000 LST时，降水首先发生在SCB的西南边缘，然后在大尺度对流层西南气流的控制下向东北传播，这与大的水汽汇合向东北传播是一致的。降水在清晨到达东北SCB。850-hPa风的日变化在西南SCB傍晚有强烈的东风偏向，这有利于通过地形的空气升空引发降水。在500hPa和850hPa之间的等效电位温度差的昼夜变化在西南SCB的傍晚具有最大的负偏差，这增加了不稳定性，因此有利于降雨的开始。