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In this study, we propose a two-step strategy for tracking oil-spill trajectories. First, an X-band radar is established to monitor oil spills. Accordingly, we propose a radar image-processing technique for identifying the oil slicks from the nautical radar images. Second, we apply the SCHISM to determine the water surface elevations and currents at the event site and obtain the trajectories of the oil slicks using a Lagrangian particle-tracking method incorporated in the SCHISM. An oil-spill event caused by the container ship T. S. Taipei is used as a case study for testing the capability of the proposed oil-tracking strategy. The SCHISM simulation results for the fouled coastline obtained using the wind data from a nearby data buoy agree quite well with those obtained from field observations. However, the predicted fouled coastline based on the forecasted wind data is unsatisfactory. The reasons for the unsatisfactory prediction are discussed and revealed.

Coastal regions are threatened by natural processes, such as erosion driven by storm surge and the effect of jetties, as well as by human behavior. This study outlines a management framework based on an analysis of a case study dataset of long-term coastal change in southwestern Taiwan. Specifically, the coastal structure of Taiwan’s largest lagoon, Cigu, was analyzed over a 300-year-long period. A series of satellite-derived images between 1974 and 2015 were assessed. The dataset was integrated with a geographic information system (GIS). The results revealed that human activities, including the construction of hard structures along the coastline and along an upstream reservoir, altered the balance of sediment transmission and resulted in the retreat and erosion of barrier sandbars along the coast. A lagoon evolution model revealed that the Cigu Lagoon may disappear in the future. Furthermore, the coastline will continue to retreat because harbor dykes and offshore breakwaters stop sediment transportation to the downdrift. Soft erosion mitigation is suggested as an immediate approach. However, recovering the sediment budget from reservoirs and dykes could be a long-term solution. In principle, the best coastal environmental protection plan from the national involves delaying urbanization and preserving unexploited coastal wetlands.

The property of over the horizon (OTH) allows the HF surface (ground) wave radar system to be used in a variety of maritime applications. In terms of the location of Taiwan, ionospheric clutter which may limit the system performance occasionally appears in the radar spectrum, and this is another way to obtain the ionosphere features. As a kind of severe weathers, typhoon which is closely related to ionospheric disturbances may generate the powerful damage, this attracts our research interests. However, most ionospheric observation is difficult in continuous observation of typhoons. The aim of this study is to explore the change of ionospheric clutter patterns through the Range-Doppler (RD) spectra under the typhoon influence. In order to determine the morphologies of ionospheric clutters, the image processing algorithm was used for ionospheric signals identification and implemented to make comparison with corresponding typhoon records during the same period. Finally, the statistics of the spatial-temporal characteristics and clutter patterns of ionosphere before and after typhoon can be obtained. In this study, the ionospheric features were investigated by ionospheric clutters of the RD spectra. The results show that when the Typhoon Soulik approached Taiwan in 2013, the morphologies of ionospheric clutter were getting greatly different. The proportion of band-like ionospheric clutters under the effects increased greatly, which is highly likely connecting to the unstable ionosphere more unstable. Regarding the possible physical mechanism, the lower atmospheric disturbances created by typhoon were possibly transmitted to the ionosphere altitude in the format of acoustic gravity waves (AGWs) which may result in unstable ionosphere and plasma irregularities.

Because comfort on whale watching vessels is important to tourist satisfaction, this paper aims to identify its associated factors and establish a prediction model of comfort in the Taiwanese context. A survey of 1199 passengers was conducted over 41 voyages. Information on passenger characteristics, prior seasickness experiences, use of anti-seasickness tablets and self-assessed comfort were collected. Results indicate that gender, prior seasickness experiences and sea conditions were significantly associated with self-assessed comfort. A binary logit regression was employed to establish a prediction model of comfort with a correct classification rate of 76.6%. This model, serving as a recreation guide, preferably developed in the form of websites or Apps, facilitates visitors’ decision-making on whether to take trips or take precautions against potential discomfort. Future research was suggested on the robustness and refinement of the model and use of alternative scales in measuring comfort.

High-frequency surface wave radar is suitable for large-area detection of vessels. This study develops an automated identification procedure to improve an artificial technique for finding the local peak in Doppler spectra. For obtaining vessel information, an image processing method, namely the watershed segmentation, is integrated into the adaptive signal identification (ASI) algorithm, which has been developed by our research group, for rapid division of several local regions of spectra to extract ship returns. A comparison with automatic identification system (AIS) data proves the feasibility of the proposed method for automatically detecting vessel echoes.

High frequency (HF) radar can overcome the limits caused by the curvature of the earth when its electromagnetic wave operated over high conductivity sea water. The HF radar spectrum is critical for large-area current mapping because of mechanism of Bragg resonance. Taiwan is located in an equatorial ionization anomaly area, in which the ionosphere causes strong interference on HF radar bands that may limit system performance. The unwanted radar echoes, called ionospheric clutter, are of various types with time-variable and range-specific properties, which require different suppression techniques. Additionally, these radar echoes could yield ionospheric information as a by-product of an HF radar system function. It is therefore critical to understand the regional characteristics of these ionospheric clutter phenomena. In this study, we first identify the ionospheric clutter boundaries for the Doppler spectrum range. Then, the distribution pattern of the spectra for identified areas was analyzed to determine the characteristics of ionospheric clutter and the extent to which the ionospheric clutter affects the system. The identified echoes at these ranges are presumed mainly to come from the E-layer, which may influence the system performance in those areas. The results show there exist a similarity of distribution in spectral density and DOAs which ionospheric clutter occurs. Hence, through aforementioned analysis can help distinguish the regions in which ionospheric clutter occurs and provide an opportunity for noise suppression strategies.

Daily wind patterns and their relational associations with other metocean (oceanographic and meteorological) variables were algorithmically computed and extracted from a year-long wind and weather dataset, which was collected hourly from an ocean buoy located in the Penghu archipelago of Taiwan. The computational algorithm is called data cloud geometry (DCG). This DCG algorithm is a clustering-based nonparametric learning approach that was constructed and developed implicitly based on various entropy concepts. Regarding the bivariate aspect of wind speed and wind direction, the resulting multiscale clustering hierarchy revealed well-known wind characteristics of year-round pattern cycles pertaining to the particular geographic location of the buoy. A wind pattern due to a set of extreme weather days was also identified. Moreover, in terms of the relational aspect of wind and other weather variables, causal patterns were revealed through applying the DCG algorithm alternatively on the row and column axes of a data matrix by iteratively adapting distance measures to computed DCG tree structures. This adaptation technically constructed and integrated a multiscale, two-sample testing into the distance measure. These computed wind patterns and pattern-based causal relationships are useful for both general sailing and competition planning.

High-frequency (HF) ground wave radar's over-the-horizon property can effectively overcome the restraints posed by the curvature of the earth. HF radar transmits low-power radar waves and its detection distance is up to several hundred kilometers. However, radar in HF bands may be easily contaminated by noise, which has temporal and spatial variability, and ionospheric interference, limiting system performance. Therefore, understanding the regional properties of noise environmental is critical. This study investigates the spatial-temporal properties of noise in long-term radar data and then analyzes the relation between noise and ionospheric indices. A comparison of the time series of ionosphere and noise indices indicates a diurnal fluctuation property. These results through cross correlation show the consistency of SUAO and HABN HF radar sites and a dramatic change of correlation coefficients over time delay. Most of the strongest negative correlations at both radar sites were found with lead time of noise index about time delay between 2 to 4 h during test period.

In this paper, a new image processing technique is introduced for the analysis of consecutive ocean wave images by spatiotemporal continuous wavelet transform (STCWT) using the Morlet wavelet as the mother wavelet. This technique, which has been adapted to give a full time–frequency and spatiofrequency representation of ocean surface waves from remotely captured wave image sequences, provides more detailed information from wave-field measurements than the traditional Fourier transform (FT) method. A series of numerical simulations of wave image sequences was analyzed to justify the algorithm and to present quantitative theoretical results on the propagation of ocean waves for normal incidence, diffraction, reflection, and shoaling in coastal areas. The comparisons of these estimates to simulated conditions for several wave parameters show that the wavelet theory is applicable to the identification of wave spectra from inhomogeneous sea-surface image sequences.

Coastal floods are a consistent threat to oceanfront countries, causing major human suffering and substantial economic losses. Climate change is exacerbating the problem. An early warning system is essential to mitigate the loss of life and property from coastal flooding. The purpose of this study is to develop a coastal flooding early warning system (CoFEWs) by integrating existing sea-state monitoring technology, numerical ocean forecasting models, historical database and experiences, as well as computer science. The proposed system has capability of offering data for the past, information for the present and future. The system was developed for the Taiwanese coast due to its frequent threat by typhoons. An operational system without any manual work is the basic requirement of the system. Integration of various data sources is the system kernel. Numerical ocean models play an important role within the system because they provide data for assessment of possible flooding. The regional wave model (SWAN) that nested with the large domain wave model (NWW III) is operationally set up for coastal wave forecasting, in addition to the storm surge predicted by a POM model. Data assimilation technology is incorporated for enhanced accuracy. A warning signal is presented when the storm water level that accumulated from astronomical tide, storm surge, and wave-induced run-up exceeds the alarm sea level. This warning system has been in practical use for coastal flooding damage mitigation in Taiwan for years. An example of the system operation during the Typhoon Haitung which struck Taiwan in 2005 is illustrated in this study.

Ocean remote sensing is a useful way to obtain ocean wave information. Due to possible inhomogeneities from remotely sensed images, the current work proposes issues concerning ocean wave image analysis using the two-dimensional continuous wavelet transforms 2-D CWTs to calculate local wave image spectra from inhomogeneous images. To optimize the algorithm of the 2-D CWT for wave image analysis, this work explores ideal parameter values for the wavelet function. The current study also analyses the limits of spatial image resolution and wave image size. After implementing the 2-D CWT on satellite and X-band radar images, this study presents local image spectra and ocean wave information from all the ocean images. These local image spectra reveal the phenomenon of wave refraction and wave nonlinearity nearshore. Compared to real wave spectra, the wavelet spectra present accurate results to describe local wave features in the spatial frequency domain.

In this study, a two-dimensional continuous wavelet transform is applied to quantify the non-homogeneity from remote-sensing wave images. Our study shows that the non-homogeneity index, which is proposed here, is capable of identifying the degree of non-homogeneity from the wave-field images. However, the influence from the edges of the wave-field image should be considered in analysis. The calculated results from the simulated wave fields and from the natural wave-field images reveal that the non-homogeneity index is influenced by the bathymetry inside the area of the ocean-wave image. It conforms to the character of the natural wave non-homogeneity. After discussing the wave characteristics from the wave-field image with a high non-homogeneity index, an inhomogeneous algorithm is recommended for obtaining accurate and reasonable wave results from the wave image.

The wavelet transform (WT) is now recognized as a useful, flexible, and efficient technique to analyze intermittent, non-stationary and inhomogeneous signals as well as images which are obtained from experimental or in situ measurements. In this study, the two-dimensional continuous wavelet transform (2-D CWT) was introduced to analyze the spatial image of waves. The numerical algorithm of 2-D CWT was developed and testified in simulated wave field of regular and random waves. Some more simulated wave fields of various wave conditions and sea bed slopes were then assumed to verify the analytical accuracy of this new technique. The comparisons of estimations to theoretical values for several wave parameters show that the 2-D CWT is capable of identifying the directional spectra and wave properties in shallow water.

The purpose of this study is to discuss the influence of signal nonlinearity upon X-band radar observations. A method for estimating the degree of nonlinearity by bispectral analysis was applied and discussed. We found that bispectral analyses from spatial radar backscatter series are similar to results obtained from water level time series. In addition, the average nonlinear degree from radar backscatter is related to wind speed. The accuracy of wave observations derived by consideration of the nonlinear effect from radar backscatter was also investigated. The estimated error in wave height from the radar data is also related to the degree of nonlinearity. In order to improve accuracy, the modulation transfer function method was applied in order to eliminate the influence of nonlinearity.

The abundance of the eastern Taiwan Strait (ETS) population of the Chinese white dolphin (Sousa chinensis) has been estimated to be less than 100 individuals. It is categorized as critically endangered in the IUCN Red List of Threatened Species. Thus, immediate measures of conservation should be taken to protect it from extinction. Currently, the Taiwanese government plans to designate its habitat as a Major Wildlife Habitat (MWH), a type of marine protected area (MPA) for conservation of wildlife species. Although the designation allows continuing the current exploitation, however, it may cause conflicts among multiple stakeholders with competing interests. The study is to explore the attitude and opinions among the stakeholders in order to better manage the MPA. This study employs a semi-structured interview and a questionnaire survey of local fishers. Results from interviews indicated that the subsistence of fishers remains a major problem. It was found that stakeholders have different perceptions of the fishers’ attitude towards conservation and also thought that the fishery-related law enforcement could be difficult. Quantitative survey showed that fishers are generally positive towards the conservation of the Chinese white dolphin but are less willing to participate in the planning process. Most fishers considered temporary fishing closure as feasible for conservation. The results of this study provide recommendations for future efforts towards the goal of better conservation for this endangered species.

The purpose of this study is to describe the characteristics of occurrence of coastal freak waves and to investigate their statistical and spectral structures. According to Ochi's definition of fre...

This article introduces operational ocean monitoring technologies for the purpose of coastal flooding warning in Taiwan. The in-situ sea state data and field images are linked to the coastal monitoring network of Taiwan. This network provides real-time meteorological and oceanographic information, which is not only for the climate change study but also for the hazard mitigation purposes as well. The whole network has been operated for more than 10 years in Taiwan. It plays an important role on the decision making for the mitigation of coastal flooding.

Coastal wetlands are important resources. Many developed countries have actively promoted coastal wetlands ecotourism in order for the public to understand the importance of coastal wetlands. The key to the successful promotion of coastal wetlands ecotourism lies in finding out their appeal. In order to achieve this research purpose, this paper is divided into several stages. First, through literature review and expert interviews, coastal wetlands ecotourism related appeal candidate factors were collected. Then, through the Fuzzy Delphi Method, the important factors were filtered. Finally, through the Fuzzy Analytic Hierarchy Process, the relative weights of the related factors were estimated, and a hierarchical structure also can be established to evaluate appeal on coastal wetlands ecotourism.

The current work develops a procedure for carrying out the theories of continuous wavelet transform and inverse wavelet transform to derive sea surface level from acceleration records. Wave signals were applied to verify the practicability of the wavelet algorithm. It is revealed the accuracy of sea surface elevation is influenced by the margins of wave signals, noise in the low frequency band, and the mother wavelet function. After discussing cases of regular and irregular wave signals, this investigation confirms the method for deriving sea surface elevation from the acceleration signal using the wavelet transform.

Twelve data buoys are being operated at Taiwanese Waters in East Asia Pacific Ocean. Typhoon-induced sea-states are the main targets of measurements. In this study, ocean waves generated by typhoons from 1997 to 2008 are analyzed. Preliminary results show that the trends of increasing scale of maximum wave heights and the duration of severe sea-states during typhoons are found. In addition, extreme large wave was also recorded. All the identities show the changing of wave climate. This may bring large impacts for the coast as well as for ocean, is an un-pretermitted issue.

The parameters in numerical wave models need to be calibrated be fore a model can be applied to a specific region. In this study, we selected the 8 most important parameters from the source term of the WAVEWATCH III model and subjected them to sensitivity analysis to evaluate the sensitivity of the WAVEWATCH III model to the selected parameters to determine how many of these parameters should be considered for further discussion, and to justify the significance priority of each parameter. After ranking each parameter by sensitivity and assessing their cumulative impact, we adopted the ARS method to search for the optimal values of those parameters to which the WAVEWATCH III model is most sensitive by comparing modeling results with ob served data at two data buoys off the coast of north eastern Taiwan; the goal being to find optimal parameter values for improved modeling of wave development. The procedure adopting optimal parameters in wave simulations did improve the accuracy of the WAVEWATCH III model in comparison to default runs based on field observations at two buoys.