A radar-based investigation of precipitation growth and decay in South Korea

Understanding precipitation growth and decay (GD) is necessary to improve the predictability of precipitation. Investigating the precipitation GD has been mostly based on an Eulerian approach, which examines the physical characteristics in a fixed coordinate system. In contrast, a Lagrangian approach provides a way to monitor the temporal evolution following the motion of the precipitation system. In this study, we employ a semi-Lagrangian advection framework to quantitatively retrieve radar-based GD of precipitation in South Korea. Additionally, we explore the dependence of GD on the following factors: flow direction, flow speed, and relative geographical location to the topography and land–ocean boundary. Our findings reveal that the flow direction significantly influences the spatial distribution of GD. The growth generally tends to occur on the windward side of the mountain range and vice versa on the lee side. The flow speed affects the intensity of GD. Furthermore, we examine the diurnal variability of GD. Due to strong orographic forcing on the diurnal variation, the unique geographical features of South Korea created diurnal patterns near Seoul by land–ocean breeze circulation and on the windward side of the mountain ranges (inland) by solar heating. The GD in South Korea exhibits two diurnal peaks of growth: an early morning peak over the ocean and an afternoon peak on the land. A monthly variation is also observed, with the most intense growth taking place in August. The findings of this study will aid in improving nowcasting algorithms that account for growth and decay, while also supporting forecasters in their predictive efforts.