Precipitation enhancement of Typhoon Khanun (2012) by orographic effect of Mt.Halla in Jeju Island, Korea

Typhoon Khanun (2012) passed over Jeju Island (width 78 km, length 35 km) from the south to north side of the Island from 1700 to 2200 LST on 18 July 2012, resulting localized intense rainfall over 226 mm around a central mountain peak (Mt. Halla height; 1950 m). In contrast, the relatively-weak rainfall (< 30 mm) was recorded on the southern coastal region of the island and moderate rainfall (< 100 mm) was accumulated on the northern slope. The enhancement mechanism of Khanun, which generated the localized heavy rainfall on the mountain peak was investigated using S-band Dual-Doppler radar data analysis and a cloud-resolving storm simulator (CReSS). The precipitating region of Khanun was classified into 1) two rain bands (RB1 and RB2) and 2) inner core (IC), based on the reflectivity distribution at 2 km height. As the RB1 passed from the southern to the northeastern side of the island, the leading part of the RB1 was enhanced around the mountain peak. During the enhancement, the reflectivity (> 40 dBZ) was intensified along the southern slope of the island from surface to 2 km height. RB2 moved from the southwestern to eastern side of the island, and it was shortly enhanced before its arrival on the top of mountain. As the IC passed from the western to northeastern side of the island, the area of reflectivity larger than 45 dBZ was considerably enlarged and the leading part of the IC was enhanced above 2 km height over the mountain. All three precipitation region (RB1, RB2 and IC) showed the rainfall enhancement on the southern slope of the mountain.

To clarify the dynamical and microphysical features of Khanun, we performed numerical simulation experiments under the condition with different terrain heights. The orographic effect of Mt.Halla associated with factors such as microphysics, vertical wind, and convergence. More detail analysis will be presented in the conference.