Spatial Variation of Z-R Relationship the Hallasan Mountain, Korea During the Typhoon Nakri in 2014

The Typhoon Nakri passed the Jeju Island in Korea (August, 1-3, 2014) and recorded one-day rainfall of 1,182 mm at the Witse-Oreum of the Hallasan Mountain (Oreum is a small vocanic cone). This one-day rainfall amount was the highest rainfall ever recorded in Korea. As the hight of the Witse-Oreum is 1,673 m from the sea-level, it was believed that the orographic effect enhanced the rainfall depth significantly. It is also argued that the maximum rainfall could be recorded in some another locations in the Hallasan Mountain. In this study, the rainfall event due to the Typhoon Nakri in the Jeju Island was analyzed fully using the radar and rain gauge data collected during this rainfall event. Fortunately, two radars (Seongsan and Gosan radars) are available on the eastern and western side of the Jeju Island. The entire Hallasan Mountain is covered by these two radars. A total of 23 rain gauges are also available in the Jeju Island. As a first step, the Z-R relationship was derived for every 250 m interval from the sea-level. The derived Z-R relationship was then spatially analyzed to investigate the orographic effect of the Hallasan Mountain as well as the storm direction.