Atmospheric Factors for the Orographic Precipitation Enhancement over Mt. Jiri, Korea

During summertime, heavy rainfall induced by mesoscale convective systems and typhoons occurs frequently in the Korean Peninsula. Rainfall distributions are highly variable because mountain areas cover more than 70% of the Korean territory. Heavy rainfall in mountain areas tends to be caused by a low-level warm, humid air that is lifted to the level of free convection (LFC) by a forcing driven by mountains. To mitigate and prevent disasters in mountain areas, it is necessary to understand the formation and maintenance mechanisms of orographic precipitation and rainfall distributions around mountain areas.

In order to examine vertical structure of radar reflectivity and winds (especially vertical velocity) within the precipitation systems moving over Mt. Jiri, we performed dual-Doppler radar analyses to retrieve three-dimensional wind fields. Also, numerical simulations of orographic rainfall systems with surface observation data from rain gauges, Parsivel disdrometers, ultrasonic anemometers (measuring winds), and radiosondes launched in this complex terrain area were conducted in order to investigate important atmospheric factors affecting the orographic rainfall enhancement. Low-level convergence and upward motions induced by the terrain were found to be the most important factors contributing to heavy rainfall.

The primary purpose of this study is to investigate contributing atmospheric factors for the orographic precipitation systems through radar and surface observations and numerical modeling using the numerical model of Cloud-Resolving Storm Simulator (CReSS) at a 1-km horizontal grid size. Sensitivity experiments by modifying the terrain height of Mt. Jiri and environmental factors are performed. With regard to the development of convective systems and rainfall, physical processes and interactions between environmental airflow and topography of Mt. Jiri are also presented in this study.

Acknowledgements

This work was financially supported by the Development and application of Cross governmental dual-pol. Radar harmonization (WRC-2013-A-1) and the BK21 plus Project of the Graduate School of Earth Environmental Hazard System.