Rip current spacing

4 - Ocean remote sensing for spatiotemporal variability of wave energy density and littoral current velocity in the Southern Indian offshore

To understand many geophysical phenomena, including ocean circulation, tectonic plate movement, and the Earth’s interior, it is important to study the Earth’s gravity field. During the past three decades, satellites have measured the Earth’s static gravity. As a result, high-resolution global gravity field models have been available. This paper aims to examine the appropriateness of the satellite derived gravity field models for the offshore and coastal regions of Sri Lanka.While these eight gravity field models with ID 155-EIGEN-6S4 V2, 168-Tongji-Grace 02K, 171-GO-CONS-GCF2-TIM-R6, 174-ITSG-GRACE 2018S, 178-Tongji-GMMG2021S, 148-EIGN-6C4, 152-GECO, 167-SGG-UGM-1, and 177-SGG-UGM2 were used for the study. The mean difference value, standard deviation value, and Root Mean Square values modeled by each of the model between the observed gravity data and the BGI observed gravity data. The results indicated that 171-GO-CONS-GCF2-TIM-R6 and 177-SGG-UGM2 is the more suited model for the coastal and offshore region of Sri Lanka. The study used the SARAL-Altika satellite Altimetry data to investigate the relationship between Mean see surface height and observed gravity. No significant relationship between Mean sea surface height and marine gravity is indicated by. In addition, the influence of gravity model type on each of the LEO satellite orbit predictions was also studied. The findings of the research demonstrate that the optimal type of gravity model applied for LEO satellite orbit prediction depends on a short-term or long-term predictions. The models JGM3, EGM2008, and GL04C are more appropriate for short-term predictions, while the models JGM3, EGM96, and EIGEN2 are the best for long-term predictions. The gravity order and permanent tides also have to be taken into account for the orbital prediction.In conclusion, this research provides valuable insights into the suitability of various satellite-derived gravity field models for Sri Lanka's coastal and offshore regions. The findings also emphasize the need to consider the impact of gravity models on LEO satellite orbit prediction, particularly for new applications such as LEO navigation, which require real-time precise orbits.

Non-hydrostatic numerical modelling of nearshore wave transformation over shore-oblique sandbars

A class of identities relating Whittaker and Bessel functions

A theory of confluent hypergeometric functions is developed, based upon the methods described in the first three papers (I, II and III) of this series for replacing the divergent parts of asymptotic expansions by easily calculable series involving one or other of the four ‘ basic converging factors ’ which were investigated and tabulated in I. This theory is then illustrated by application to the special cases of exponential-type integrals, parabolic cylinder functions, modified Bessel functions, and ordinary Bessel functions.

Modeling reveals the shift in phytoplankton community structure in coastal ocean caused by the Three Gorges Dam.

Tropical cyclones (TC) often induce strong mixing in the upper ocean that generates a trail of cooler sea surface temperature (Twake) in their wakes. The Twake can affect TC intensity, so its prediction is important, especially in coastal regions where TCs can make landfall. Coastal Twakes are often more complex than those in the open ocean due to the influences of coastline geometry, highly variable water depth, continental runoff, and shelf processes. Using observational data since 2002, here we show a significantly stronger global mean Twake in coastal regions compared to offshore regions. Temperature stratification is the main driver of stronger coastal Twakes in the North Atlantic and east Pacific. In the northwest Pacific and north Indian Ocean, the differences between coastal and offshore Twakes are smaller due to compensation between TC forcings and ocean stratification. The north Indian Ocean is unique in the Northern Hemisphere because salinity stratification plays a major role on the spatial distribution of Twake. In the South Pacific Ocean, TC intensity and translation speed are crucial for explaining coastal–offshore Twake differences, while ocean stratification and mixed layer depth are more important for the coastal–offshore Twake differences in the south Indian Ocean. These findings suggest that coastal–offshore differences in ocean stratification need to be properly represented in models in order to capture changes in TC-induced ocean cooling as storms approach landfall. Significance Statement Landfalling tropical cyclones (TCs) often cause considerable damage in coastal regions with dense human populations. Understanding TC–ocean interaction and how it differs between coastal and offshore regions can help predict TC intensity prior to landfall. Sea surface cooling after TC passage is an important proxy for TC–ocean interaction. A global evaluation of coastal TC-induced cooling has not been conducted. Using data covering two decades, we show significantly stronger TC-induced surface cooling in coastal regions compared to offshore regions at the global scale and in all basins except the northwest Pacific and north Indian Ocean. The difference is driven mainly by upper-ocean conditions in the North Atlantic, east Pacific, and south Indian Ocean, and by TC characteristics in the South Pacific.

Detailed measurements of water levels, and tide and wave-induced currents were undertaken to examine physical processes and their relationship with morphology in the Cocos (Keeling) Islands, a medium sized atoll in the Indian Ocean. Results indicate that the atoll structure controls both lagoon circulation and the spatial pattern of energy distribution. Lagoon circulation is tide dominated (currents 16–31 cms-1) with flushing (2–5 days) of the lagoon occurring through the deep leeward passages. Wave- and tide-driven unidirectional flows through shallow passages (26–65 cms-1) are important mechanisms of ocean to lagoon water exchange and contribute up to 24% of the lagoon neap tide prism. Reef flats are dominated by wave energy (maximum velocity 140 cms-1, east) with measurements of the attenuation of wave energy between reef flats and shallow lagoon (80–90%) conforming to measurements from fringing and barrier reefs. Spectral analysis shows that the characteristics of wave energy vary on different sectors of the atoll, with gravity wave energy dominating the east, and infragravity wave energy dominating the southern reef flat and passages. Wave setup at the reef crest is considered to be responsible for an identified 0.1 m higher water level in the southern as opposed to eastern and northern atoll, which promotes higher reef flat growth. Transmission of gravity waves across reef flats requires threshold water depths of 0.65 (east) and 0.70 m (south). The higher southern reef is an effective filter of gravity wave energy for most tidal elevations. Differences in the type and magnitude of physical processes within the atoll are discussed with relation to geomorphic development on Cocos.

Kang, Y.K. and An, S.H., 2018. Development of New Coastal Erosion Countermeasure Using Wave Energy Control Method. 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. 1516–1520. Coconut Creek (Florida), ISSN 0749-0208.Coastal erosion has become a social issue around the world, including Korea. A Considerable number of coastal erosions have occurred along the East Sea in Korea, primarily caused by port and harbor developments. Countermeasures have generally utilized wave breaks with wide–low–crest submerged breakwater (so-called artificial reefs), which are coastal constructions emulating the wave absorbing effect of natural reefs with good wave–protection performance. However, these result in secondary damages such as scouring near openings and erosion towards the rear because of strong currents generated by wave setups. This study suggests a new countermeasure for coastal erosion by controlling wave energy differentiated by incident wave, i.e., wave direction control method (WDCM) to prevent the critical coastal erosion expected from a massive harbor expansion project planned along the east coast of Korea. The WDCM attempts to balance disparities in wave energy caused by harbor expansion to restrain imbalanced wave energies that result in imbalanced littoral drift. To accomplish this purpose, low crest structures are obliquely deployed at 250–300 m from the coastline to manipulate the wave energy by modulating incident wave direction. This new deployment method avoids excessive interference with the incident waves, and prevents resilience by leaving cross-shore sediment transport unhindered. In order to determine the effectiveness of the proposed WDCM, numerical computations were conducted evaluating its performance regarding coastal erosion prevention.

Aiming at the breeding environment where the construction of marine pastures requires low wind and waves, a floating breakwater (FB) with a Savonius type (referred to as S type) runner with wave absorption and energy reduction function is studied for wave absorption and energy reduction in aquaculture sea areas. The wave-absorbing and energy-reducing performance of the floating breakwater is studied by the method of combining numerical simulation and experiment. Using Star-CCM+ numerical simulation software, based on linear wave theory and energy conservation law, using overlapping grid technology, calling DFBI model, second-order time discretization, a three-dimensional flow field model of the floating breakwater was established and numerically simulated. At the same time, a floating breakwater physical test system was developed for experimental verification, the transmission wave and the conversion power consumption of the S-shaped runner under different wave heights and different periods were measured, and the results Please carefully check the accuracy of names and affiliations. of numerical simulation and physical experiments were comprehensively evaluated. The research results show that the floating breakwater based on the S-shaped runner has the functions of reducing the wave height and reducing the wave energy, which have guiding significance for practical engineering.

Measurements of waves, water levels, currents, and winds at a nearshore site on the east coast of the United States coincided with the passage of Hurricane Gloria in September 1985. These measurements are described and compared to numerical model results of winds, waves, and wave induced setup and longshore current at the site. The model hindcasts reproduce the measured wind and wave height at three locations and the wave setup and longshore current at five gages close to shore. The wave setup component is found to be a relatively small percentage (approximately 10 percent) of the total mean water level anomaly due to the storm nearshore. This is attributed to an upper limit on wave energy nearshore, controlled by the depth, which in turn results in limitation on the gradient of wave energy and hence, wave setup and wave induced longshore current.

Sea-air CO2 exchanges, pCO2 drivers and phytoplankton communities in the southwestern South Atlantic Ocean during spring

In this work, theoretical development of void fraction effect over wave energy dissipation and wave setup in a surf zone is made. The formulation incorporates simple energy dissipation model, energy balance equation, and momentum balance equation in air-water mixture fields. The important quantities, such as the energy flux, the radiation stress, the energy dissipation, and the wave setup, are computed and the role of the individual terms in the governing equations is discussed. Void fraction effect in the estimated energy flux in energy balance equation shows to be less dominating over the others. Finally, the void fraction effects for wave height and wave setup are calculated, which demonstrates a good agreement with the experimental results.

We have produced an eddy-resolving local ensemble transform Kalman filter (LETKF)-based ocean research analysis (LORA) for the western North Pacific (WNP) and Maritime Continent (MC) regions (LORA-WNP and LORA-MC, respectively). This paper describes the system configuration and validation comparisons with Japan Coastal Ocean Predictability Experiment 2M (JCOPE2M) reanalysis and Archiving, Validation, and Interpretation of Satellite Oceanographic Data (AVISO) observational datasets. The results show that the surface horizontal velocity in the LORA-WNP is closer to independent drifter buoy observations in the mid-latitude region, especially along the Kuroshio Extension (KE), and is less close in the subtropical region than the JCOPE2M, although the AVISO is the closest over the whole domain. The sea surface temperatures (SSTs) in the LORA-WNP correspond better to assimilated satellite observations than the JCOPE2M over most of the domain except for coastal regions. The results using an independent buoy south of the KE indicate that better fit of temperature in the LORA-WNP may be limited to the upper 300 m depth, probably because of the prescribed vertical localization cutoff length of 370 m. In the MC region, the surface velocity in the LORA-MC is closer to the independent drifter buoys in the equatorial coastal region and is less close in the offshore region than the AVISO. The SSTs in the LORA-MC correspond better to the assimilated satellite observations in the offshore region than the nearshore region. Therefore, the LORA-WNP and LORA-MC have sufficient accuracy for geoscience research applications as well as for fisheries, marine transport, and environment consultants.

Motivated by recent results by Nadarajah, Srivastava and Gupta (2007) in which the authors introduced a new formula for CDF FK of the McKay Bessel function distribution containing the modified Bessel function we aim to present new formulae for FK, especially for certain values of parameters for which their formula fails to be calculated by in-built numerical routines. Also, several computational series formulae are obtained for the CDF of McKay Bessel distribution which contains modified Bessel function one is given in terms of the Horn confluent hypergeometric function and the others by Kampé de Fériet function Marcum Q-function and modified Bessel functions Horn confluent hypergeometric function and finally in terms of incomplete Gamma function γ and Exton’s double hypergeometric X–function.