Study on Storm Surge Using Parametric Model with Geographical Characteristics

Recently, the intensities of natural disasters have increased significantly owing to climate change and various other environmental factors, causing unprecedented damage. Measures must be established to reduce damage from large-scale natural disasters caused by the rapidly changing environment. The Japanese government published a hazard map manual in 2015 and obligates the creation of a hazard map as a measure to reduce high-scale storm surges. This manual presents a typhoon model based on a parametric model that is used to create a hazard map. The Myers model assuming concentric circles, which is primarily used in East Asia, is disadvantageous as it cannot consider geographic characteristics. Therefore, a new parametric model is necessary to calculate wind and pressure fields, which change according to geographic characteristics. To improve this limitation of the Myers model, we calculated the wind and pressure fields considering geographical effects by combining the Holland model, which can consider the size of a developing typhoon, and the Mascon model, which changes by geographic characteristics. To determine the gradient coefficient of the Holland model, the coefficient that changes every moment was calculated using grid point value data. The result indicated excellent reproducibility of storm surge height according to the geographic characteristics.

Effects of Typhoon Paths on Storm Surge and Coastal Inundation in the Pearl River Estuary, China

A coastal inundation simulation system was developed for the coast of the Pearl River estuary (PRE), which consists of an assimilation typhoon model and the coupled ADCIRC (Advanced Circulation) + SWAN (Simulating Waves Nearshore) model. The assimilation typhoon model consists of the Holland model and the analysis products of satellite images. This is the first time an assimilation typhoon model has been implemented and tested for coastal inundation via case studies. The simulation results of the system agree well with the real measurements. Three observed typhoon paths (Hope, Nida, and Hato) were chosen to be the studied paths based on their positions relative to the PRE, China. By comparing the results of experiments with different forcing fields, we determined that the storm surge and the coastal inundation were mainly induced by wind forcing. By simulating coastal inundation for different typhoon center speeds, the Hato3 path most easily causes coastal inundation in the PRE. Moreover, the moving speed of the typhoon’s center significantly affects the coastal inundation in the PRE. The inundation becomes very serious as the movement of the typhoon center was slow down. This study provides a new reference for future predictions of coastal inundations.

An Efficient Method for Simulating Typhoon Waves Based on a Modified Holland Vortex Model

A combination of the WAVEWATCH III (WW3) model and a modified Holland vortex model is developed and studied in the present work. The Holland 2010 model is modified with two improvements: the first is a new scaling parameter, bs, that is formulated with information about the maximum wind speed (vms) and the typhoon’s forward movement velocity (vt); the second is the introduction of an asymmetric typhoon structure. In order to convert the wind speed, as reconstructed by the modified Holland model, from 1-min averaged wind inputs into 10-min averaged wind inputs to force the WW3 model, a gust factor (gf) is fitted in accordance with practical test cases. Validation against wave buoy data proves that the combination of the two models through the gust factor is robust for the estimation of typhoon waves. The proposed method can simulate typhoon waves efficiently based on easily accessible data sources.

A Probabilistic Approach to Tropical Cyclone Modelling

Tropical cyclones are highly variable and, in many areas of the world, are the main cause of extreme wind and associated waves, surge and current conditions. At a given location, cyclones that cause a significant impact are relatively rare but severe events, which means that the number of historical events for which data are available is often quite small. In addition, the effects, particularly surge, can be relatively localized and affected by the local bathymetry and topography. This causes considerable difficulty in making quantitative predictions of extreme events for design of offshore or coastal structures in areas affected by tropical cyclones. A new probabilistic method has been developed to increase the sample of tropical cyclones by producing 10,000 years of synthetic cyclone tracks with a range of paths, intensities and sizes based on Hall and Jewson [1] and Casson and Coles [2]. From this set of synthetic tracks, those tropical cyclones most likely to affect the site of interest are modelled using time-varying wind fields based on the Holland model [3] with surge, current and waves then modelled using the hydrodynamic model TELEMAC-2D coupled to the SWAN wave model. As it is impractical to model 10,000 years of tropical cyclones, a Gaussian process emulator is employed to relate the resultant conditions to parameters defining the cyclones, such as track position, heading, intensity and radius to maximum wind. The result is a synthesized 10,000 years of cyclone events from which design conditions for a range of return periods can be predicted with a greater degree of certainty than by extrapolating from historical events.

Wave–current interaction during Hudhud cyclone in the Bay of Bengal

The present work describes the interaction between waves and currents utilizing a coupled ADCIRC+SWAN model for the very severe cyclonic storm Hudhud, which made landfall at Visakhapatnam on the east coast of India in October 2014. Model-computed wave and surge heights were validated with measurements near the landfall point. The Holland model reproduced the maximum wind speed of ≈ 54 m s−1 with the minimum pressure of 950 hPa. The modelled maximum surge of 1.2 m matches with the maximum surge of 1.4 m measured off Visakhapatnam. The two-way coupling with SWAN showed that waves contributed ≈ 0.25 m to the total water level during the Hudhud event. At the landfall point near Visakhapatnam, the East India Coastal Current speed increased from 0.5 to 1.8 m s−1 for a short duration ( ≈ 6 h) with net flow towards the south, and thereafter reversed towards the north. An increase of ≈ 0.2 m in Hs was observed with the inclusion of model currents. It was also observed that when waves travelled perpendicular to the coast after crossing the shelf area, with current towards the southwest, wave heights were reduced due to wave–current interaction; however, an increase in wave height was observed on the left side of the track, when waves and currents opposed each other.

Wave-current interaction during Hudhud cyclone in the Bay of Bengal

The present work describes the interaction between waves and currents utilizing a coupled ADCIRC + SWAN model for the very severe cyclonic storm Hudhud which made landfall at Visakhapatnam on the east coast of India in October 2014. Model computed wave and surge heights were validated with measurements near the landfall point. The Holland model reproduced the maximum wind speed of ≈ 54 m/s with the minimum pressure of 950 hPa. The modelled maximum surge of 1.2 m matches with the maximum surge of 1.4 m measured off Visakhapatnam. The two-way coupling with SWAN showed that waves contributed ≈ 0.25 m to the total water level during the Hudhud event. At the landfall point near Visakhapatnam, the East India Coastal Current speed increased from 0.5 to 1.8 m/s for a short duration (≈ 6 h) with net flow towards south, and thereafter reversed towards north. An increase of ≈ 0.2 m in Hs was observed with the inclusion of model currents. It was also observed that when waves travelled normal to the coast after crossing the shelf area, with current towards southwest, wave heights were reduced due to wave-current interaction; however, an increase in wave height was observed on the left side of the track, when waves and currents opposed each other.

Assessment of the Holland Model for Silicon Phonon-Phonon Relaxation Times Using Lattice Dynamics Calculations

We assess the ability of the Holland model to accurately predict phonon-phonon relaxation times from bulk thermal conductivity values. Lattice dynamics calculations are used to obtain phonon-phonon relaxation times and thermal conductivities for temperatures ranging from 10 to 1000 K for Stillinger-Weber silicon. The Holland model is then fit to these thermal conductivities and used to predict relaxation times, which are compared to the relaxation times obtained by lattice dynamics calculations. We find that fitting the Holland model to both total and mode-dependent thermal conductivities does not result in accurate mode-dependent phonon-phonon relaxation times.