Storm Surges Congress, Hamburg, Germany 13–17 September 2010 SSC2010-57 © Author(s) 2010 Analysis of Anomalous Storm Surge around West Coast of the Sea of Japan S.Y. Kim (1), Y. Matsumi (2), T. Yasuda (3), and H. Mase (3) (1) Dept of Social Management, Tottori University, 4-101 Koyama-Minami, Tottori 680-8552, Japan. [email protected], +81-857-31-5311, (2) Dept of Social Management, Tottori University, 4-101 Koyama-Minami, Tottori 680-8552, Japan. , (3) Disaster Prevention Research Inst., Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan. Introduction Maximum surges occur after typhoons pass at Sakai Minato in west coasts of the Sea of Japan instead of the typhoons’ peak at the site. The time lag is more evident from the time series of measured water levels during the Typhoon Songda in 2004 and predicted tides by Japan Meteorological Agency. It denotes that the maximum surge was delayed 15 hours after the typhoon passed. Understanding of such anomalous storm surges is poor in the west coast of the Sea of Japan. The anomalous storm surges are characterized by the fact that typhoon centers are far from the coast. The present study examines the mechanisms of anomalous surges from viewpoints of external meteorological forces and induced currents at Sakai Minato during Typhoon Songda (2004). Numerical analysis of storm surge A coupling model of surge, wave and tide (called SuWAT), developed by Kim et al. (2008)), was employed in the present study by using six level grid system (nesting scheme). Two types of external wind and pressure es- timations were used: one is those from an empirical model by Fujii and Mitsuta (referring to FM); another is those from Weather Research and Forecasting model (WRF) by Skamarock et al. (2008). FM typhoon model gives symmetric wind and pressure fields without considering the terrain effects; while WRF model gives more realis- tic meteorological fields influenced by topography than FM output. WRF was run by a two-way nesting with 12 km - 1.3 km grid sizes for six grid regions with the 4D data assimilation method: 1) nudging with the reanalysis FNL data (NCEP/NCAR) in the outer most domain (referring to WRF-NF); and 2) nudging in all nested domains (WRF-NA). In the storm surge simulations two different drag coefficients were used: one is the wave dependent drag (WDC); another is the empirical drag coefficients (EDC) to estimate the wind stresses. Results and discussion The maximum pressure depression of FM model is close to the measurement at Sandozaki. The time series by WRF-NF and WRF-NA outputs agree well to the measurement although their maximum pressure depressions are a little smaller than the measurement. On the other hand, the wind speed estimated by the FM model are considerably larger than the measurement at Mihonoseki, while those predicted by WRF-NF and WRF-NA are close to the measurement. The surge heights in the second sea level rise using WRF-NF estimations agree well with the measured sea level rise. The storm surge heights using WRF-NA estimations are under-predicted for the secondary sea level rise. The storm surge heights cannot present the measurement when using estimations by FM model. From the storm surge simulations with and without Coriolis force, it is found that Coriolis force is an important factor for the anomalous storm surge at Sakai Minato as well as the accurate estimations of external forces of winds and pressures. REFERENCES Fujii, T. and Mitsuta, Y., 1986. Synthesis of a stochastic typhoon model and simulation of typhoon winds. Annuals of Disas. Prev. Res. Inst., Kyoto Univ., 29, B-1: 229-239. Kim, S.Y., Yasuda, T., Mase, H., 2008. Effects of Tidal Variation on Storm Surges and Waves, Applied Ocean Research, 30, 311-322. Skamarock, W.C., Klemp, J.B., Dudhia, J., Gill, D.O., Barker, D.M., Duda, M.G., Huang, X.Y., Wang, W., Powers, J.G., 2008. A description of the Advanced Research WRF Version 3, NCAR/TN-475+STR, 113p..