Observation and numerical prediction of torrential rainfall over Korea caused by Typhoon Rusa (2002)

Abstract

[1] On landfall in 2002, Typhoon Rusa caused record-breaking rainfall (870.5 mm/d) in Gangneung at the foot of the Taebaek Mountain range, Korea. In this study, the predictability of the torrential rainfall associated with the typhoon and the detailed mesoscale precipitation distribution were investigated through numerical simulation. The weather research and forecasting (WRF) model successfully simulates the mesoscale rainfall distibution and timing. With a 10 km (3.3 km) horizontal grid, the model predicted 830.8 mm (1307.9 mm) of rain with some uncertainty in the observed local maximum in coverage. This study shows that the complexity of forecasting is associated with the interactions between environmental flows, typhoon flow, and topography. In bogus and 1-day-earlier initial-time experiments, the typhoon track and intensity are substantially improved, although this has little impact on successful rainfall simulation. The interaction between the large-scale features and the proper vertical structure of the typhoon is key. The simulated rainfall at the cloud-resolving spacing of 3.3 km is greater than that at 10 km because of the increased terrain height and not the greater resolution. Analysis of observed and simulated data shows that the torrential rainfall had two different causes with two peaks in the hourly rainfall at Gangneung. The first peak links to a mesoscale frontal structure, characterized by strong moisture and thermal gradients formed by the intrusion of cold, dry northerly air from a midlatitude trough and moist southerly air from the typhoon. The second peak results from the direct effect of the typhoon and the lifting of the moisture-laden typhoon winds.

Long‐term trends in tropical cyclone tracks around Korea and Japan in late summer and early fall

“…Such environmental changes, along with changes in the associated synoptic fields, could affect the characteristics of TC, which can subsequently alter the damage caused by them in Korea and Japan. For example, Typhoon Rusa in 2002 caused 4.5 billion USD worth of damage in Korea due to record‐breaking heavy rainfall, and Typhoon Songda in 2004 resulted in about 9 billion USD worth of damage in Japan due to flooding and strong winds (Lee and Choi, ; Re, ). These two typhoons caused severe damage in Korea and Japan in the early fall season.…”

Dependency of tropical cyclone risk on track in South Korea

“…We have to utilize a climate model with a fine resolution of at least less than 10 km for realistic simulation of active hazards, i.e. wind and rainfall (Park and Lee, 2007;Lee and Choi, 2010), which is a difficult task and requires high computing power. Hence, active hazards seem not to be optimal for risk forecasting to help emergent decision making, as well as climate change research with large spatiotemporal scale.…”

Environmental interactions during the extreme rain event associated with ex-tropical cyclone Oswald (2013)

“…Interestingly, they tend to focus on either the extratropical transition (ET, Evans et al 2017) of TCs (e.g. Klein et al 2000;Harr and Elsberry 2000;Jones et al 2003;Elsberry 2003, 2007;Anwender et al 2008;Keller et al 2019;Pohorsky et al 2019) or the antecedent rainfall well ahead of TCs (Cote 2007;Stohl et al 2008;Srock and Bosart 2009;Galarneau et al 2010;Lee and Choi 2010;Bosart et al 2012;Baek et al 2013;Moore et al 2013). Oswald was not a well-defined ET event, since the circulation had made landfall and had weakened below TC intensity before any interaction took place.…”