To predict extreme weather events, we conducted high-resolution global atmosphere modeling and simulation using high-performance computing. Using a new-generation global weather/climate prediction model called MPAS (Model for Prediction Across Scales) with variable resolution, we tested strong scalability on the KISTI (Korea Institute of Science and Technology Information) supercomputer NURION. In addition to assessing computational performance, we simulated three typhoons that occurred in 2019 to analyze the forecast accuracy of MPAS. MPAS results were also applied to force an ADCIRC (The Advanced CIRCulation) + SWAN (Simulating Waves Nearshore) model to predict coastal flooding over southern Korea. The time-integration of MPAS showed excellent scalability up to 4096 cores of NURION KNL (KNight Landing) nodes, but a serious I/O bottleneck issue was still found after trying two additional I/O strategies (i.e., adjusting the stripe count and using a burst buffer). On the other hand, the forecast accuracy of MPAS showed very encouraging results for wind and pressure during typhoons. ADCIRC+SWAN also generated a good estimate of significant wave height for typhoon Mitag. The proposed variable-resolution MPAS model, under an efficient computational environment, could be utilized to predict and understand the highly nonlinear chaotic atmosphere and coastal flooding in typhoons.

The south coast of Korea is vulnerable to coastal disasters, such as storm surges, high waves, wave overtopping, and coastal flooding caused by typhoons. It is imperative to predict such disastrous events accurately in advance, which requires accurate meteorological forcing for coastal ocean modeling. In this study, to acquire accurate meteorological data as important forcing variables for the prediction of storm surges and waves, we examined the forecast performance and applicability of a next-generation global weather/climate prediction model, the Model for Prediction Across Scales (MPAS). We compared the modeled surface pressure and wind with observations on the south coast of Korea for three typhoons that damaged Korea in 2020—Bavi, Maysak, and Haishen—and investigated the accuracy of these observations with the MPAS prediction. Those meteorological forcing variables were then used in the tightly coupled tide-surge-wave model, Advanced CIRCulation (ADCIRC) and the Simulating Waves Nearshore (SWAN) for the simulation of a typhoon-induced storm surge and wave. We also performed the hindcast of the wave and storm surges using a parametric tropical cyclone model, the best-track-based Generalized Asymmetric Holland Model (GAHM) embedded in ADCIRC+SWAN, to better understand the forecast performance and applicability of MPAS. We compared the forecast results of the typhoon-induced wave and storm surges with their hindcast in terms of the time-series and statistical indices for both significant wave height and storm surge height and found that wave and storm surge prediction forced by MPAS forecast provides a comparable accuracy with the hindcast. Comparable results of MPAS forcing with that of hindcast using best track information are encouraging because ADCIRC+SWAN forced by MPAS forecast with an at most four-day lead time still provides a reasonable prediction of wave and storm surges.

Yuk, J.-H. and Joh, M., 2019. Prediction of typhoon-induced storm surge, waves and coastal inundation in the Suyeong River Area, South Korea: A case study during typhoon Chaba. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 156-160. Coconut Creek (Florida), ISSN 0749-0208.Typhoon-induced storm surge and high waves caused coastal inundation and resulting coastal damages in the south-eastern coast of South Korea (the Republic of Korea), especially in the Suyeong River Area (SRA), Busan during typhoon Chaba (201618) which occurred early in October 2016. This study developed a prediction system based on weather and tide-surge-wave models to guide countermeasures against coastal inundation. The weather prediction model is named K-MPAS (KISTI - Model for Prediction Across Scales), and was optimized by KISTI to more accurately predict typhoons in the Western Pacific Ocean. The tide-surge-wave model ADCIRC+SWAN, a widely-used model, is based on a flexible unstructured grid with a more detailed grid for the region of interest (SRA). As a case study, the meteorological condition, storm-surge, and waves due to typhoon Chaba were predicted using this prediction system, and are presented and discussed in terms of the typhoon track, surface pressure, wind, storm-surge, waves, and resultant coastal inundation in the SRA. The model results were in good agreement with observations, thus this prediction system can provide a reliable service for coastal disaster management.

Yuk, J.-H.; Park, J.H., and Joh, M., 2018. Modelling of Storm-induced Seawater Flooding in the Suyeong River Area, South Korea: A Case Study due to the Storm Surge and Waves during Typhoon Sanba. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 746–750. Coconut Creek (Florida), ISSN 0749-0208. The Suyeong River Area (SRA), located in Busan, a major city on the southeastern coast of South Korea, is frequently damaged by storm-induced seawater flooding. One of the main reasons for seawater flooding is the propagation of storm surges and wind waves through the Suyeong River in the SRA. In this study, a series of prediction systems of storm tides, surges, waves and resultant seawater flooding for the SRA based on unstructured meshes with a high resolution of approximately 10 m covering the entire flood plain and a HPC-based parallel tide-surge-wave model were developed. Meteorological forcing variables such as wind and air pressure calculated by the parametric tropical cyclone model based on typhoon information were used in the storm-surge and wave models. The modeled meteorological data were in good agreement with observations of both the wind and air pressure. The simulated surge heights and wave properties showed good agreement with the observations as well. Waves reached the mid-stream area of the SRA, likely affecting the duration of seawater flooding. The prediction system in this study can reasonably simulate tide-surge-wave and resultant seawater flooding (coastal inundation) during extreme conditions, e.g., storms in the SRA of Busan, South Korea.

Kim, K.O.; Yuk, J.-H.; Jung, K.T., and Choi, B.H., 2017. Swell propagation caused by typhoon passage to the Yellow and East China Seas. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 144–148. Coconut Creek (Florida), ISSN 0749-0208. Typhoons generate big swells frequently propagating over the East China Sea, the wide continental shelf sea with depth shallower than 200 m. The characteristic features of swell propagation into the Yellow and East China Seas caused by typhoon Herb in 1996 has been investigated applying a ray-tracing technique and a spectral wave model (SWAN) with an unstructured-mesh grid system. This study discusses the generation and propagation of the swells into the Yellow and East China Seas using the integration of ray trajectories and model-based simulated wave. Calculated and observed wave heights and periods at Gadeokdo, Korea are found to be in reas...