Toward a Methodology for Estimating Coastal Extreme Sea Levels From Satellite Altimetry

This work represents the first attempt to study the behavior of sea level extreme events nearshore using satellite altimetry data. A novel approach based on the application of a nonstationary extreme model to nontidal residual monthly maxima from remote data is presented. With the aim of countering the lack of accuracy, an extreme scale factor to correct satellite data is defined. The extreme scale factor depends on local morphology and its definition makes use of the information provided by 14 tide gauges along the North American East Coast. The methodology is validated using eight additional tide gauge records along the study region. Low differences on values associated to high return periods using satellite and tide gauge data input are found for all the validated locations. Besides, a regional study of the climate variability of extreme sea levels from satellite is also presented. The found climate patterns strongly agree with the historical climate variations from in situ data. Results show a great potential of this approach, especially at those locations where in situ information is not available.The work reported here was partially supported by the Spanish Government through the grant PORTIO (BIA2015-70644-R); project ECLISEA, part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by UC-IHC, HZG, BRGM, NCSRD, and CNRS and cofunding by the European Union (Grant 690462), and the US DOD Strategic Environmental Research and Development Program (SERDP Project RC-2644)

A Physics-based prognostics approach for Tidal Turbines

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordTidal Stream Turbines (TST) have the potential to become an important part of the sustainable energy mix. One of the main hurdles to commercialization is the reliability of the turbine components. Literature from the Offshore Wind sector has shown that the drive train and particularly the Pitch System (PS) are areas of frequent failures and downtime. The Tidal energy sector has much higher device reliability requirements than the wind industry because of the inaccessibility of the turbines. For Tidal energy to become commercially viable it is therefore crucial to make accurate reliability assessments to assist component design choices and to inform maintenance strategy. This paper presents a physics-based prognostics approach for the reliability assessment of Tidal Stream Turbines (TST) during operation. Measured tidal flow data is fed into a turbine hydrodynamic model to generate a synthetic loading regime which is then used in a Physics of Failure model to predict component Remaining Useful Life (RUL). The approach is demonstrated for the failure critical Pitch System (PS) bearing unit of a notional horizontal axis TST. It is anticipated that the approach developed here will enable device/project developers, technical consultants and third party certifiers to undertake robust reliability assessments both during turbine design and operational stages.ETIEngineering and Physical Sciences Research Council (EPSRC

Sixteen years of bathymetry and waves at San Diego beaches.

Sustained, quantitative observations of nearshore waves and sand levels are essential for testing beach evolution models, but comprehensive datasets are relatively rare. We document beach profiles and concurrent waves monitored at three southern California beaches during 2001-2016. The beaches include offshore reefs, lagoon mouths, hard substrates, and cobble and sandy (medium-grained) sediments. The data span two energetic El Niño winters and four beach nourishments. Quarterly surveys of 165 total cross-shore transects (all sites) at 100 m alongshore spacing were made from the backbeach to 8 m depth. Monthly surveys of the subaerial beach were obtained at alongshore-oriented transects. The resulting dataset consists of (1) raw sand elevation data, (2) gridded elevations, (3) interpolated elevation maps with error estimates, (4) beach widths, subaerial and total sand volumes, (5) locations of hard substrate and beach nourishments, (6) water levels from a NOAA tide gauge (7) wave conditions from a buoy-driven regional wave model, and (8) time periods and reaches with alongshore uniform bathymetry, suitable for testing 1-dimensional beach profile change models

Can Tidal Perturbations Associated with Sea Level Variations in the Western Pacific Ocean be used to Understand Future Effects of Tidal Evolution?

This study examines connections between mean sea level (MSL) variability and diurnal and semidiurnal tidal constituent variations at 17 open-ocean and 9 continental shelf tide gauges in the western tropical Pacific Ocean, a region showing anomalous rise in MSL over the last 20 years and strong interannual variability. Detrended MSL fluctuations are correlated with detrended tidal amplitude and phase fluctuations, defined as tidal anomaly trends (TATs), to quantify the response of tidal properties to MSL variation. About 20 significant amplitude and phase TATs are found for each of the two strongest tidal constituents, K1 (diurnal) and M2 (semidiurnal). Lesser constituents (O1 and S2) show trends at nearly half of all gauges. Fluctuations in MSL shift amplitudes and phases; both positive and negative responses occur. Changing overtides suggest TATs are influenced by changing shallow water friction over the equatorial Western Pacific and the eastern coast of Australia (especially near the Great Barrier Reef). There is a strong connection between semidiurnal TATs at stations around the Solomon Islands and changes in thermocline depth, overtide generation, and the El Niño Southern Oscillation (ENSO). TATs for O1, K1 and M2 are related to each other in a manner that suggests transfer of energy from M2 to the two diurnals via resonant triad interactions; these cause major tidal variability on sub-decadal time scales, especially for M2. The response of tides to MSL variability is not only spatially complex, it is frequency dependent; therefore, short-term responses may not predict long-term behavior

Spatial and temporal variability and long-term trends in skew surges globally

Storm surges and the resulting extreme high sea levels are among the most dangerous natural disasters and are responsible for widespread social, economic and environmental consequences. Using a set of 220 tide gauges, this paper investigates the temporal variations in storm surges around the world and the spatial coherence of its variability. We compare results derived from two parameters used to represent storm surge: skew surge and the more traditional, non-tidal residual. We determine the extent of tide-surge interaction, at each study site, and find statistically significant (95% confidence) levels of tide-surge interaction at 59% of sites based on tidal level and 81% of sites based on tidal-phase. The tide-surge interaction was strongest in regions of shallow bathymetry such as the North Sea, north Australia and the Malay Peninsula. At most sites the trends in the skew surge time series were similar to those of non-tidal residuals, but where there were large differences in trends, the sites tended to have a large tidal range. Only 13% of sites had a statistically significant trend in skew surge, and of these approximately equal numbers were positive and negative. However, for trends in the non-tidal residual there were significantly more negative trends. We identified 8 regions where there were strong positive correlations in skew surge variability between sites, which meant that a regional index could be created to represent these groups of sites. Despite strong correlations between some regional skew surge indices, none were significant at the 95% level, however, at the 80% level there was significant positive correlation between the north-west Atlantic—south and the North Sea. Correlations between the regional skew surge indices and climate indices only became significant at the 80% level, where Ni?o 4 was positively correlated with the Gulf of Mexico skew surge index and negatively correlated with the east Australia skew surge index. The inclusion of autocorrelation in the calculation of correlation greatly reduced their significance, especially in the short time-series used for the regional skew surge indices. Skew surge improved the representation of storm surge magnitudes, and therefore allows a more accurate detection of changes on secular and inter-annual time scales

Nearshore vertical distribution of barnacle cyprids: temporal patterns and hydrographic variability

Most benthic organisms living in the intertidal zone have planktonic larvae that reside temporarily in the water column before settling in their adult habitats. Larvae aggregate in offshore larval pools, and transport horizontally and vertically in the water to remain in the nearshore and during their pelagic life. While some horizontal transport of larvae can be attributed to advection, behavioral responses, like vertical swimming and buoyancy control, allow larvae to position themselves at depths where flow direction can be exploited. Thus, knowledge on how vertical larval distribution relates to physical processes can be fundamental to better understand larval transport. These larvae must then return to shore to successfully metamorphose and complete their life cycle. Recent work at our study site in Bird Rock (La Jolla), California, USA suggests that late-stage barnacle larvae (cyprids) accumulate at a mid-depth in a shallow (4m) station when offshore waters are stratified. However, it remains unknown how the water column structure (e.g., temperature) varies at this site, and the consequences to the vertical distribution and abundance of larvae. This study conducted repeated hourly larval collections at 1m-depth intervals at a 4m-deep station ~300m from shore. Sampling was conducted over 5, 24-hour cruises during the summers of 2017 and 2018. Larval vertical distributions were characterized and compared to hydrographic (thermal stratification, thermocline depth) and hydrodynamic (currents) variables collected at three stations (4m, 5m and 8m depths). Vertical distribution patterns of barnacle cyprids showed that they remained closer to the bottom during the day and migrated slightly shallower at night, despite varied physical conditions between cruises. Additionally, our results showed that higher thermal stratification allowed the thermocline to penetrate closer to shore, and more larvae to accumulate at 4m-deep. This study supports previous work suggesting that thermal stratification is a key factor in nearshore accumulation and suggests that larval behavior can be better exercised when thermal stratification is high, all of which have important implications on barnacle settlement and recruitment to the intertidal

From Cells to Coastlines: How Can We Use Physiology to Forecast the Impacts of Climate Change?

The interdisciplinary fields of conservation physiology, macrophysiology, and mechanistic ecological forecasting have recently emerged as means of integrating detailed physiological responses to the broader questions of ecological and evolutionary responses to global climate change. Bridging the gap between large-scale records of weather and climate (as measured by remote sensing platforms, buoys and ground-based weather stations) and the physical world as experienced by organisms (niche-level measurements) requires a mechanistic understanding of how ‘environmental signals’ (parameters such as air, surface and water temperature, food availability, water flow) are translated into signals at the scale of the organism or cell (e.g. body temperature, food capture, hydrodynamic force, aerobic capacity). Predicting the impacts of how changing environments affect populations and ecosystems further mandates an understanding of how organisms ‘filter’ these signals via their physiological response (e.g. whether they respond to high or low frequencies, whether there is a time lag in response, etc.) and must be placed within the context of adult movement and the dispersal of larvae and gametes. Recent studies have shown that patterns of physiological stress in nature are far more complex in space and time than previously assumed and challenge the long-held paradigm that patterns of biogeographic distribution can be based on simple environmental gradients. An integrative, systems-based approach can provide an understanding of the roles of environmental and physiological variability in driving ecological responses and can offer considerable insight and predictive capacity to researchers, resource managers and policy makers involved in planning for the current and future effects of climate change

Eficácia de medidas de similaridade para a classificação de séries temporais associadas ao comportamento fenológico de plantas

Orientadores: Luiz Camolesi Júnior, Ricardo da Silva TorresDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de TecnologiaResumo: Fenologia é o estudo de fenômenos naturais periódicos e sua relação com o clima. Nos últimos anos, tem se apresentado relevante como o indicador mais simples e confiável dos efeitos das mudanças climáticas em plantas e animais. É nesse contexto que se destaca o e-phenology, um projeto multidisciplinar envolvendo pesquisas na área de computação e fenologia. Suas principais características são: o uso de novas tecnologias de monitoramento ambiental, o fornecimento de modelos, métodos e algoritmos para apoiar o gerenciamento, a integração e a análise remota de dados de fenologia, além da criação de um protocolo para um programa de monitoramento de fenologia. Do ponto de vista da computação, as pesquisas científicas buscam modelos, ferramentas e técnicas baseadas em processamento de imagem, extraindo e indexando características de imagens associadas a diferentes tipos de vegetação, além de se concentrar no gerenciamento e mineração de dados e no processamento de séries temporais. Diante desse cenário, esse trabalho especificamente, tem como objetivo investigar a eficácia de medidas de similaridade para a classificação de séries temporais sobre fenômenos fenológicos caracterizados por vetores de características extraídos de imagens de vegetação. Os cálculos foram realizados considerando regiões de imagens de vegetação e foram considerados diferentes critérios de avaliação: espécies de planta, hora do dia e canais de cor. Os resultados obtidos oferecem algumas possibilidades de análise, porém na visão geral, a medida de distância Edit Distance with Real Penalty (ERP) apresentou o índice de acerto mais alto com 29,90%. Adicionalmente, resultados obtidos mostram que as primeiras horas do dia e no final da tarde, provavelmente devido à luminosidade, apresentam os índices de acerto mais altos para todas as visões de análiseAbstract: Phenology is the study of periodic natural phenomena and their relationship to climate. In recent years, it has gained importance as the more simple and reliable indicator of effects of climate changes on plants and animals. In this context, we emphasizes the e-phenology, a multidisciplinary research project in computer science and phenology. Its main characteristics are: The use of new technologies for environmental monitoring, providing models, methods and algorithms to support management, integration and remote analysis of data on phenology, and the creation a protocol for a program to monitoring phenology. From the computer science point of view, the e-phenology project has been dedicated to creating models, tools and techniques based on image processing algorithms, extracting and indexing image features associated with different types of vegetation, and implementing data mining algorithms for processing time series. This project has as main goal to investigate the effectiveness of similarity measures for the classification of time series associated with phenological phenomena characterized by feature vectors extracted from images. Conducted experiments considered different regions containing individuals of different species and considering different criteria such as: plant species, time of day and color channels. Obtained results show that the Edit Distance with Real Penalty (ERP) distance measure yields the highest accuracy. Additionally, the analyzes show that in the early morning and late afternoon, probably due to light conditions, it can be observed the highest accuracy rates for all views analysisMestradoTecnologia e InovaçãoMestre em Tecnologi

Where the river meets the sea : an initial investigation into the Riverine tidal freshwater zone

Riverine tidal freshwater zones (RTFZs) are transitional environments between terrestrial and coastal waters that have freshwater chemistry and tidal physics, and are neither river nor estuary. The residence time dynamics of RTFZs have not yet been discussed in the literature, but may ultimately control the timing and magnitude of freshwater and nutrient coastal discharges. Furthermore, climate change threatens to alter the nexus between the terrestrial hydrologic cycle and the coastal tidal environment where the RTFZ resides. This dissertation provides the foundation for investigations into RTFZs and their subsequent residence times. An initial residence time analysis of 15 tidal river reaches along the south Texas Gulf Coast introduces tidal river reaches into the lentic/lotic nomenclature. This residence time analysis also quantifies the vernacular of lentic (reservoir-like) and lotic (riverine) systems via the Freshwater Continuum Classification (FCC). The FCC framework also incorporates temporal hydrologic variability, which is typically absent from other lentic/lotic classifications. Further analysis on one of these systems (Aransas River, TX, USA) revealed an RTFZ. The analysis empirically observed RTFZ responses to precipitation and tide, while providing the RTFZ definition. The RTFZ is defined by three longitudinal points of interest: λ₁ – upstream limit of brackish water, downstream limit of freshwater, and downstream boundary of RTFZ; λ₂ – upstream limit of bidirectional tidal velocities; λ₃ – upstream limit of tidal stage fluctuations and of the RTFZ. The RTFZ was typically (median) 59.9 km long and typically (median) began 11.84 km upstream (15.43 km/11.16 km, max/min) of the river mouth. From field data collected during RTFZ isolation, a tidal rating curve was created to model tidal discharge. The tidal rating curve expanded on traditional non-tidal gauging methods by incorporating stage-rate-of-change observations into the typical stage to discharge relationship. The method was performed on several sites along the Mission and Aransas Rivers, TX, USA, and twelve USGS tidal gauging stations, and resulted in strong agreement between estimated and observed discharge (i.e., r² > 0.70). With the tidal discharge estimations and RTFZ observations, future investigations should focus on RTFZ residence times and their impacts on estuarine ecology.Geological Science