Parametric Typhoon Model Research Articles

Strategy for the Prediction of Typhoon Wind and Storm Surge Height Using the Parametric Typhoon Model: Case Study for Hinnamnor in 2022

The parametric typhoon model is a powerful typhoon prediction and reproduction tool with advantages in accuracy, and computational speed. To simulate typhoons’ horizontal features, the longitude and latitude of the typhoon center, central pressure, radius of maximum wind speed (Rmax), and background states (such as surface air pressure and wind speed) are required. When a typhoon approaches or is predicted to affect Korea, the Korea Meteorological Agency (KMA) notifies the above-mentioned parameters, except for the Rmax and background state. The contribution of background wind and pressure is not very significant; however, Rmax is essential for calculating typhoon winds. Therefore, the optimized Rmax for the typhoons over the past five years was estimated at each time step compared with the in situ wind observation record. After that, a fifth-order polynomial fitting was performed between the estimated Rmax and the radius of strong wind (RSW; >15 m/s) provided by the KMA. Finally, the Rmax was calculated from the RSW via the empirical equation, and the horizontal fields of typhoon Hinnamnor (2211) were reproduced using a parametric model. Furthermore, the ocean storm surge height was adequately simulated in the surge model.

Uncertainty of storm surge forecast using integrated atmospheric and storm surge model: a case study on Typhoon Haishen 2020

ABSTRACT Hindcast experiments and pseudo-forecast experiments considering Typhoon Haishen (2020) were conducted using an atmospheric (WRF)-storm surge (GeoClaw) coupled model and a storm surge model with a parametric typhoon model. A series of simulations of the coupled model were used to quantify the error sources of the typhoon track and intensity in the forecast errors of storm surges. The results revealed that the typhoon track forecast had a larger error source for the storm surge forecast for the maximum surge height than the typhoon intensity. Furthermore, the parametric Holland typhoon model used in practice has an overestimation trend compared to the coupled model, and the parametric Holland typhoon model using WRF output was able to forecast the storm surge height near the typhoon (western Kyushu area) and its peak occurrence time accurately. However, the forecast accuracy tended to decrease as the distance from the typhoon to the target location increased. The pseudo-ensemble simulation of the storm surge forecast using forecast error information was conducted considering the uncertainty of the typhoon track forecast. The 20 ensemble forecast simulations revealed that the perturbed typhoon track simulation can increase the possibility of capturing the peak time of the storm surge.

Investigating typhoon-induced storm surge and waves in the coast of Taiwan using an integrally-coupled tide-surge-wave model

The coupled tide-surge and wave model was established for the coast of Taiwan and applied to simulate the storm surge during typhoon events. To prove the capability and availability of the coupled model, the model was calibrated and validated with measured water levels, atmospheric pressures, wind speeds, wave heights, and wave periods at different gauge stations under different historical typhoon events. Based on the statistical metrics including the mean absolute error, root mean square error, and skill, the simulated tide-surge, wave height, and wave period using coupled tide-surge-wave model reasonably reproduced the observational data. The parametric typhoon model provided reasonably simulated results compared to the observed atmospheric pressure and wind speed. The validated model was then utilized to explore the impact of waves on the storm surge and the influences of typhoon track, wind stress, and atmospheric pressure on the surge height around the Taiwan coast. The results showed that comparing the simulated water levels using the tide-surge-wave model and the tide-surge model, the averaged differences at Taipei Tamsui, Taichung Harbor, Kaohsiung Harbor, and Hualien Harbor are 0.24 m, 0.23 m, 0.22 m, and 0.22 m, respectively. The wave setup contributes between 6% and 35% to the total storm surge on Taiwan's coast. Furthermore, the typhoon track significantly affects the location of low pressure and the wind direction, subsequently causing the increase/decrease in surge height. The intensity of wind stress and the atmospheric pressure play crucial roles in affecting the water level and dominating the surge height along the coast of Taiwan.

Wind Field Reconstruction and Analysis of Super Typhoon Mangkhut (1822)

Liu, X.; Wang, Q.; Liu, C.; He, C.; Wang, S.; Hou, P.; Zhu, X., and Wu, Z., 2020. Wind field reconstruction and analysis of super typhoon Mangkhut (1822). In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 151–157. Coconut Creek (Florida), ISSN 0749-0208.This paper reports the research conducted on wind field reconstruction for super typhoon Mangkhut (1822), which occurred in 2018/09. The performances of two common methods, i.e., the parametric typhoon model and CCMP reanalysis data, for the hindcasting of typhoon wind fields are examined, and an improved method is then proposed, which avoids the radius effect in the traditional superposition method. The proposed method relies on a combination of CCMP reanalysis data and parametric wind field results and directly evaluates the maximum wind speed. Moreover, the central difference method is employed to smooth the transitional area. This method notably improves the hindcasting of typhoon wind fields, and its capability is calibrated by field data from buoy platforms in the Pearl River Estuary. Finally, certain typical parameters, such as the wind field, wind speed and wind stress curl, during super typhoon Mangkhut are determined and analyzed.

Numerical Simulation of Large Wave Heights from Super Typhoon Nepartak (2016) in the Eastern Waters of Taiwan

Super Typhoon Nepartak (2016) was used for this case study because it is the most intense typhoon that made landfall in Taiwan in the past decade. Winds extracted from the Climate Forecast System version 2 (CFSV2) and ERA5 datasets and merged with a parametric typhoon model using two hybrid techniques served as the meteorological conditions for driving a coupled wave-circulation model. The computed significant wave heights were compared with the observations recorded at three wave buoys in the eastern waters of Taiwan. Model performance in terms of significant wave height was also investigated by employing the CFSV2 winds under varying spatial and temporal resolutions. The results of the numerical experiments reveal that the simulated storm wave heights tended to decrease significantly due to the lower spatial resolution of the hourly winds from the CFSV2 dataset; however, the variations in the storm wave height simulations were less sensitive to the temporal resolution of the wind field. Introducing the combination of the CFSV2 and the parametric typhoon winds greatly improved the storm wave simulations, and similar phenomena can be found in the exploitation of the ERA5 dataset blended into the parametric wind field. The overall performance of the hybrid winds derived from ERA5 was better than that from the CFSV2, especially in the outer region of Super Typhoon Nepartak (2016).

Quantifying the contribution of nonlinear interactions to storm tide simulations during a super typhoon event

Wind field data from the National Centers for Environmental Prediction Climate Forecast System Version 2 (CFSV2), the European Centre for Medium-Range Weather Forecasts ERA-Interim and ERA5 and the ERA5 blended into the parametric typhoon model (ERA5H) from September 1 to 30, 2016, were adopted to drive a fully coupled circulation-wave model. The best performance of the maximum storm tide and significant wave height (SWH) and mean wave period simulation for typhoon events was found by applying the ERA5H. The contributions of nonlinear interactions to the storm tide induced by Super Typhoon Meranti in 2016 were quantified using seven scenario simulations. The results indicated that the wave setup had the most significant nonlinear interaction with the storm tide, which was up to 0.97 m both with and without tidal effects. The wave-tide interaction was relatively minor for the total water level and contributed only ± 0.1 m to the storm tide. Significant differences in the tide-surge interactions were detected with and without wave effects, as these interactions provided approximately 0.06–0.08 m and ± 0.02 m of the storm tide, respectively. The spatial distributions of the maximum SWH for typhoon events were similar when coupled and decoupled models were employed. In this paper, it is concluded that storm surge miscalculation can be avoided if wave setups are included when predicting typhoon-generated storm tides.

Hybrid methods combining atmospheric reanalysis data and a parametric typhoon model to hindcast storm surges in Tokyo Bay

Reanalysis data and a parametric typhoon model formula are often used to prepare wind and pressure fields for storm surge hindcasting. However, their optimum selection and usage have not been well established. To enhance the accuracy of wind and pressure fields, two hybrid methods were proposed by applying a parametric typhoon model of Mitsuta–Fujii’s formula, which is determined from the typhoon center to a certain radius of Rb, and then switching to the reanalysis data of ERA-Interim in the outer region through the interpolated transition bandwidth of Wb. In hybrid model I, Rb and Wb were fixed because the time-varying radius of the maximum wind speed was determined by the typhoon formula. In hybrid model II, these parameters were determined to minimize the mean difference between the reanalysis data and the fields obtained by typhoon formula in the transition band at each time step of the typhoon track. The hindcasting of eight significant typhoon events approaching Tokyo Bay was performed. This validated the proposed methods in comparison with the observed storm surge anomalies. Both models performed satisfactorily. Hybrid model II was found to be superior in terms of the balance of accuracy and preparation cost.

Wind forcing effect on hindcasting of typhoon-driven extreme waves

Large waves generated by typhoons can pose a serious threat to human life and property in the coastal areas of Taiwan. We hypothesize that an accurate hindcast of typhoon-generated significant wave heights (SWHs) is highly dependent on an accurate typhoon wind field. This paper evaluated the performance of SWH modeling for typhoons on the northeastern coast of Taiwan using different wind fields and a fully coupled tide-surge-wave model. Wind products from the Climate Forecast System Reanalysis (CFSR), ERA-Interim (ERA), and Cross-Calibrated Multi-Platform V2 (CCMPV2) were blended into the parametric typhoon models (hybrid wind models) to serve as the main forcing in the fully coupled model. The results of model-data comparison for SWHs reveal that the hindcasts only using the CFSR, ERA and CCMPV2 own the excellent skill indexes ranging from 0.92 to 0.94. The use of hybrid wind models indicated a consistent improvement in SWH hindcasting, and the CCMPV2 combined with the parametric typhoon model has the best overall performance. However, the extremely large typhoon-induced SWHs (exceeding 11 m) can only be well-matched when the CFSR merged with the parametric typhoon model was imposed on the fully coupled model.

Hazard Assessment of Typhoon-Driven Storm Waves in the Nearshore Waters of Taiwan

In Taiwan, the coastal hazard from typhoon-induced storm waves poses a greater threat to human life and infrastructure than storm surges. Therefore, there has been increased interest in assessing the storm wave hazard levels for the nearshore waters of Taiwan. This study hindcasted the significant wave heights (SWHs) of 124 historical typhoon events from 1978 to 2017 using a fully coupled model and hybrid wind fields (a combination of the parametric typhoon model and reanalysis products). The maximum SWHs of each typhoon category were extracted to create individual storm wave hazard maps for the sea areas of the coastal zones (SACZs) in Taiwan. Each map was classified into five hazard levels (I to V) and used to generate a comprehensive storm wave hazard map. The results demonstrate that the northern and eastern nearshore waters of Taiwan are threatened by a hazard level IV (SWHs ranging from 9.0 to 12.0 m) over a SACZ of 510.0 km2 and a hazard level V (SWHs exceeding 12.0 m) over a SACZ of 2152.3 km2. The SACZs threatened by hazard levels I (SWHs less than 3.0 m), II (SWHs ranging from 3.0 to 6.0 m), and III (SWHs ranging from 6.0–9.0 m) are of 1045.2 km2, 1793.9 km2, and 616.1 km2, respectively, and are located in the western waters of Taiwan.

Numerical estimation of extreme waves and surges over the northwest Pacific Ocean

A coupled modelling framework, consisting of the FVCOM circulation model and FVCOM-SWAVE wave model, was used to numerically estimate extreme waves and surges over the northwest Pacific Ocean. The ECMWF ERA-Interim atmospheric reanalysis data with modification by a parametric typhoon model were used as surface forcing to simulate waves and surges for a 35-year period. The extreme waves and surges with a 100-year return period were then estimated with the Gumbel distribution. The results showed that the extreme wave heights generally decreased northward and shoreward, varying from 23 m in deepwater areas to less than 7 m in nearshore areas. The extreme wave heights in the east and southeast directions were found to be larger than those in other directions; and the extreme waves in summer and autumn were found to be larger than those in other seasons. The extreme surge levels were relatively large in the radial sandy ridge area of the Jiangsu coast, Hangzhou Bay and north of the Qiongzhou Strait. This study demonstrated an effective approach to improve the representation of typhoon in the numerical estimation of extreme events. The results provide insights into the temporal and spatial distributions of extreme waves and surges over the northwest Pacific Ocean.

台風1330号によるフィリピン中部の高潮・波浪特性

This study estimated the storm surge and wave distributions of Typhoon Haiyan in Central Philippines by using a 2D parametric typhoon model, a one-layer long-wave-based fluid model, and SWAN. The simulation led at Tacloban that the storm surge waveform began with a trough due to north wind at the front of the typhoon and subsequently showed a quick rise up to 4m due to the suction-induced crest and the drift by south wind while the maximum significant wave height was about 2m. The spatial resolution can be critical in wave generation simulations for the typhoon with a very low central pressure and a small radius of maximum wind speed. The simulation with T1330-base model typhoons in Visayas showed that the storm surge can exceed 3m not only around Tacloban and Estancia.

ESTIMATION OF HIGH WAVES ON THE WESTERN SETO INLAND SEA DURING TYPHOONS 9119 AND 9918

Wave hindcasting with use of a shallow water model is conducted in order to estimate wave conditions on the Western Seto Inland Sea during Typhoons 9119 and 9918, which gave rise to severe damages to the coastal areas. Space-time variation of winds over the area calculated by either a space interpolation of wind data measured at coastal stations surrounding the sea area or a parametric typhoon model is given as input condition. Comparison between hindcast and measurement for time variation of wave height and period at coastal stations around the area reveals that hindcast waves under interpolated wind fields yield closer agreement with measured waves over those under typhoon model winds. Also, a detailed discussion is made for spatial distribution of the maximum wave height.