Nat Hazards (2009) 51:151–162 DOI 10.1007/s11069-009-9395-y ORIGINAL PAPER Simulation of atmospheric states for a storm surge on the west coast of Korea: model comparison between MM5, WRF and COAMPS Ki-Young Heo Æ Jeong-Wook Lee Æ Kyung-Ja Ha Æ Ki-Cheon Jun Æ Kwang-Soon Park Æ Jae-Il Kwon Received: 20 July 2008 / Accepted: 7 April 2009 / Published online: 22 April 2009 Ó Springer Science+Business Media B.V. 2009 Abstract High-quality informations on sea level pressure and sea surface wind stress are required to accurately predict storm surges over the Korean Peninsula. The storm surge on 31 March 2007 at Yeonggwang, on the western coast, was an abrupt response to meso- cyclone development. In the present study, we attempted to obtain reliable surface winds and sea level pressures. Using an optimal physical parameterization for wind conditions, MM5, WRF and COAMPS were used to simulate the atmospheric states that accompanied the storm surge. The use of MM5, WRF and COAMPS simulations indicated the devel- opment of high winds in the strong pressure gradient due to an anticyclone and a meso- cyclone in the southern part of the western coast. The response to this situation to the storm surge was sensitive. A low-level warm advection was examined as a possible causal mechanism for the development of a mesocyclone in the generating storm surge. The low- level warm temperature advection was simulated using the three models, but MM5 and WRF tended to underestimate the warm tongue and overestimate the wind speed. The WRF simulation was closer to the observed data than the other simulations in terms of K.-Y. Heo Á J.-W. Lee Á K.-J. Ha (&) Division of Earth Environmental System, Pusan National University, Busan 609-735, Republic of Korea e-mail: [email protected] K.-Y. Heo e-mail: [email protected] J.-W. Lee e-mail: [email protected] K.-C. Jun Á K.-S. Park Á J.-I. Kwon Climate Change and Coastal Disaster Research Department, Korea Ocean Research and Development Institute, Ansan, Republic of Korea K.-C. Jun e-mail: [email protected] K.-S. Park e-mail: [email protected] J.-I. Kwon e-mail: [email protected] 123 152 Nat Hazards (2009) 51:151–162 wind speed and the intensity of the mesocyclone. It can be concluded that the magnitude of the storm surge at Yeonggwang was dependent, not only on the development of a meso- cyclone but on ocean effects as well. Keywords Storm surge Á Mesocyclone Á Sea surface wind Á MM5 Á WRF Á COAMPS 1 Introduction On 31 March 2007, a storm surge struck Yeonggwang (35.3°N, 126.5°E). The storm surge that originated in the Yellow Sea resulted in flooding and significant coastal damage in the vicinity of Yeonggwang. As a result of the surge, about 38 families or approximately 87 people were made homeless and 4 died in the area. Property damage in the Yeonggwang area was estimated to exceed 1.6 million dollars. Seventy-two fishing boats were destroyed and 79 marine product facilities were submerged. The intensity of the disaster, calculated using a factor of 1.8 by the method of Feng and Hong (2008), indicates that it was a very small disaster. The invading storm surge was accompanied by a high tide and the recorded sea level reached 703 cm. This corresponds to a sea level that is 102.6 cm higher than the Yeonggwang high tide (Fig. 1) on 1631UTC 30 March 2007. The wind speed increased substantially about 1 h prior to the storm surge. Moon et al. (2003) noted that Yeonggwang is located on the west coast of Korea, which is one of the strongest tidal areas in the world. They also concluded that the sea levels can be higher than when the tides are average if the astronomically enhanced tide levels coincide with the passage of a cyclone. Figure 2 shows the surface weather chart and the QuikSCAT sea surface wind (SSW) for this time period. On 09 UTC 30 March 2007, a mesoscale cyclone and an anticyclone were located off the west coast of Korea (Fig. 2a). In the weather map, the storm surge is assumed to be developing with the mesoscale cyclone. The cyclone was generated rapidly, as shown in the black box of Fig. 2b on 15 UTC 30 March 2007 when the storm surge occurred. Storm surges occur frequently, due to the presence of typhoons over the west or Fig. 1 Temporal variation in observed sea level height (solid line, cm) and wind speed (dashed line, ms-1) at the Yeonggwang station 123 Nat Hazards (2009) 51:151–162 153 Fig. 2 Observed surface weather map on a 0900 UTC 30 March 2007, b 1500 UTC 30 March 2007, and observed sea surface wind by QuikSCAT on c 1012 UTC 30 March 2007 and d 2124 UTC 30 March 2007 south coast of the Korean Peninsula. However, this is an exceptional case, in that a meso-b scale cyclone was generated, with a centre pressure of 1010 hPa at Yeonggwang, near the west coast of Korea (Fig. 2b). In order to accurately predict a storm surge, precise data on sea level pressure (SLP) and SSWs are required. Figure 2c and d shows the SSW obtained from the QuikSCAT satellite at 1012 UTC and 2124 UTC, respectively. The high-wind speed over the Yellow Sea had strengthened, which corresponds with the enhanced pressure gradient between a cyclone and an anticyclone (Fig. 2b). Cyclonic circulation occurs around 35°N, 125°E in Fig. 2b. 123 154 Nat Hazards (2009) 51:151–162 Very few studies can be found in the literature (Seo and Chang 2003; Kim et al. 2006; Heo et al. 2008) concerning the simulation of SSWs using regional models near the Korean coastline. Seo and Chang (2003) analyzed the characteristics of monthly mean SSWs and wind waves near the Korean marginal seas in the year 2002, based on predictions of SSWs using the MM5/KMA (Fifth-generation Mesoscale Model/Korean Meteorological Administration) model. Kim et al. (2006) carried out a sensitivity experiment for SSWs based on PBL schemes (Medium-range Forecast, MRF and Mellor-Yamada-Janjic, MYJ) and dynamic frames of MM5 and Weather Research and Forecasting model (WRF). Heo et al. (2008) reported on optimal combinations for parameterization for simulating SSWs using MM5 and WRF for cases of strong winds, such as the Typhoon Shanshan (0613) and the development of mesocyclones in the winter of 2006. It was also found that PBL parameterization plays a crucial role in mesoscale simulation and has a significant influ- ence on the magnitude of simulated wind speeds. In this study, we attempted to select the optimal physics combination for a high wind (Davis and Low-Nam 2001; Ivanov and Palamarchuk 2007) using the MM5 and the WRF. In order to investigate the atmospheric states that lead to a storm surge, MM5 and WRF the optimal physics, and the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) model were compared in terms of the time evolution of a surface wind and SLP. Finally, we investigate the causes of mesocyclone development and the role of this phenomenon in the generation of a storm surge along the west coast of Korea using the COHERENS (COastal Hydrodynamical Ecological Model for REgioNal Shelf seas) model. 2 Models 2.1 Atmospheric model MM5 version 3.7, WRF version 2.2 and COAMPS version 3.1 were used in this study. The nested domains over the centre of 35.0°N and 129.0°E are covered with 115 (in longi- tude) 9 124 (in latitude) grids in the 27-km mesh and 175 (in longitude) 9 238 (in lati- tude) grids in the 9-km mesh systems, respectively. The initial and boundary conditions are based on the NCEP Final Analysis (FNL) for MM5 and WRF. Initial and boundary conditions for COAMPS were obtained from NOGAPS and several sets of GOES satellite data, QuikSCAT and SSMI. The simulations were executed from 00 UTC 30 March 2007. In order to select the physics options for MM5 and WRF, three sets of experiments (EXP1, EXP2 and EXP3) were carried out for high-wind conditions. EXP1 and EXP2 used Eta PBL (Janjic 1990; Mellor and Yamada, 1982) and EXP3 used MRF PBL (Hong and Pan, 1996). EXP1 and EXP2 are recommended to be the best physical parameterizations for tropical cyclone prediction (Davis and Low-Nam 2001) and EXP3 arose from the best optimal parameterization scheme sets for atmospheric variables such as temperature and geopotential height (Ivanov and Palamarchuk 2007). It has been reported that the MRF PBL scheme (Hong and Pan 1996) tends to produce boundary layers that are too deep and dry outside the eye wall of mature hurricanes (Braun and Tao 2000) but may be adequate if the storms are weak. For the cumulus scheme, EXP1, EXP2 and EXP3 used the Betts– Miller scheme (Betts 1986; Betts and Miller 1993; Janjic 1994), Grell scheme (Grell 1993) and Kain–Fritsch scheme (Kain and Fritsch 1993), respectively. The Betts–Miller (Betts and Miller 1993) scheme is the most popular for tropical systems, and the Grell scheme is routinely run near 10-km grid spacings. Davis and Low-Nam (2001) reported that physical 123 Nat Hazards (2009) 51:151–162 155 schemes are very sensitive to regional and synoptic situations. The selected physics schemes were applied to the MM5 and WRF model, and the results were then compared with the output from the COAMPS model.