Structure and Evolution of a Convective System with Bow Echo Associated with Terrain on Jeju Island, Korea

Abstract

On July 13, 2012, a bow echo was observed over the lee side of the Mt. Halla (1,950 m above sea level) on Jeju Island, Korea. Three-dimensional (3D) wind-field and surface observation analyses were carried out to understand the structure and evolution of convective systems with a bow echo on a bell-shaped terrain. A northeastward-moving convective system passed over the approximately bell-shaped isolated mountain with a mean speed of 17 m s. On the windward side of the mountain, the convective system developed by the inflow of unstable warm air from the ocean and terrain-induced upward motion, even with a low convective available potential energy value of 511 J kg. When passing the lee side of the mountain, a bow echo was formed in the convective system by the strongest winds behind the bow echo. Behind the leading edge of the bow echo, the strengthened rear-inflow jet descended with relatively dry air along the surface, resulting in enhancing evaporative cooling. The precipitation-induced downdrafts generated a cold pool on the lee side of the mountain. The development of an rear-inflow jet and cold pool formation both contributed to the evolution of the bow echo. In addition, the isolated bell-shaped terrain had a major indirect influence on the evolution of the convective system with a bow echo in this event.