2024 Volume 102 Issue 3 Pages 391-406
The impact of the directional propagation of mesoscale convective systems (MCSs) on precipitation structures during the pre-summer rainy season in South China remains unclear. Using multi-satellite datasets, this study aims to reveal the features and mechanisms of precipitation influenced by MCS propagation from the perspective of both cloud microphysics and diurnal forcing of land-atmospheric system. The study region mainly consists of three contiguous coastal regions (A1, B1, and C1 from southwest to northeast). Controlled by the steering flow, MCSs tend to move from region A1 to C1 with a direction parallel to the coastline with a speed of 50 km h−1. Although regions A1 and C1 are both hilly regions, the results show that region A1 is the only key region for initiation and development of MCS, while MCSs in region C1 mainly come from the upstream regions. The directional propagation of MCS causes the propagation of diurnal rainfall peaks, while strong precipitation may accelerate the dissipation of MCS in region C1. The activities of MCSs enhanced ice-phased precipitation processes by spreading more droplets and therefore near-surface rainfall in regions B1 and C1, whereas the hilly surface in region C1 further promoted liquid-phased processes by uplifting southerly low-level flow. Of all the thermodynamic parameters, the daytime vertically moistest layer above the boundary layer over the coastal regions plays a key role in the initiation and development of MCS. These results contribute to a deeper understanding of MCS-related precipitations over coastal regions.
