The characteristic and seasonal variation of mesoscale convective systems' precipitation over North China

Using an iterative rain-cell tracking method to identify and track mesoscale convective system (MCS) precipitation during the warm seasons (May-October) of 2015-2020, we reveal the seasonal variation in the spatiotemporal distribution, rainfall characteristics, and the life cycle of MCS precipitation in different months over North China. Notable MCS precipitation centers are located around mountain slopes and downstream areas. The diurnal peak of MCS rainfall is manifested as a southeastern delay from afternoon in mountainous regions to midnight or morning over downstream plains. In May and June, MCS rainfall is distributed on the hillside of Taihang-Yan mountains and the Shandong Peninsula. MCS precipitation gets an early evening peak on mountain slopes and a nocturnal maximum over the North China Plain (NCP). In July and August, the MCS activities extend to NCP, and another MCS precipitation center exists over the Luliang Mountains in western North China, under the seasonal march of the monsoon flow. The local diurnal peaks to the east of 114 degrees E are generally later than in May and June, and MCS precipitation gets a peak during midnight to early morning over the NCP. MCSs in July and August feature the strongest intensity. In September and October, the MCS precipitation shifts to high terrain of the Taihang Mountains and its west, with an early afternoon peak. MCSs have the largest size and the fastest propagation speed in September and October, but with the weakest intensity. Compared with short-lived MCSs, long-lived MCSs have stronger precipitation intensity, larger rainfall area, and faster propagation speed. In addition, the life cycle of long-lived MCS precipitation represents asymmetric development and decay. Long-lived MCSs occur with more pronounced upper troposphere warming and low-level anomalous southwesterlies. Meanwhile, higher specific humidity in the low- and mid-level troposphere provides a more favorable environment for the maintenance of MCS precipitation.