Storm Waves Research Articles

Bore Impact on Decks of Coastal Structures

Bore impact on horizontal fixed decks of coastal structures is studied by use of the Level I Green–Naghdi (GN) equations and the Navier–Stokes (NS) equations. The bore is generated by the breaking of a water reservoir, and may represent the propagation of a tsunami on land or broken storm waves. The bore-induced horizontal and vertical forces are determined and their variation with the bore and deck conditions is studied in this work. Various conditions of deck location with respect to the water level are considered, including cases with the deck under or above the still-water level. Two types of bore are considered, namely (i) a bore generated by a dam break, where the reservoir water depth is substantially larger than the downstream depth, and (ii) a bore generated by an initial mound of water, where the reservoir water depth is comparable to the downstream depth. It is shown that these mechanisms result in the formation of significantly different bore shapes. It is also shown that the relative height of the reservoir and the downstream water depth play a significant role in the bore generation and its impact on coastal structures. It is also found that the bore-induced forces vary almost linearly with the change in amplitude of the reservoir, while a change in the length of the reservoir has little effect on the loads. The horizontal force on submerged decks is shown to be independent of the submergence depth of the deck; this is due to the uniform velocity distribution over the water column of the bore. Results of the GN and NS models are compared with each other for submerged cases and the limitations, accuracy, and efficiency of these models in studying this problem are discussed. Results of the GN equations are in close agreement with the NS equations, making them a computationally efficient alternative for the study of this problem.

Cross‐Shore Distribution of the Wave‐Induced Circulation Over a Dissipative Beach Under Storm Wave Conditions

AbstractThis study explores the spatial distribution and the driving mechanisms of the wave‐induced cross‐shore flow within the shoreface and surf zone of a dissipative beach. Unpublished results from a field campaign carried out in early 2021 under storm wave conditions are presented and compared with the predictions from a state‐of‐the‐art phase‐averaged three‐dimensional circulation modeling system based on the vortex force formalism. Under storm wave conditions, the cross‐shore flow is dominated by a strong seaward‐directed current in the lower part of the water column. The largest current velocities of this return current are located in the surf zone, where the dissipation by depth‐induced breaking is most intense, but offshore‐directed velocities up to 0.25 m/s are observed as far as 4 km from the shoreline (≃12 m‐depth). Numerical experiments further highlight the key control exerted by non‐conservative wave forces and wave‐enhanced mixing on the cross‐shore flow across a transition zone, where depth‐induced breaking, whitecapping, and bottom friction all significantly contribute to the wave energy dissipation. Under storm conditions, this transition zone extended almost 6 km offshore and the cross‐shore Lagrangian circulation shows a strong seaward‐directed jet in the lower part of the water column, whose intensity progressively decreases offshore. In contrast, the surf zone edge appears clearly delimited under fair weather conditions and the seaward‐directed current is weakened by a near bottom shoreward‐directed current associated with wave bottom streaming in the shoaling region, such that the clockwise Lagrangian overturning circulation is constrained by an additional anti‐clockwise overturning cell at the surf zone edge.

Dynamics, Evolution, and Facies Preservation of a Microtidal Chenier Plain, Joal-Fadiouth (Senegal, West Africa)

Youm, C.I.; Morales, J.A.; Doumbouya, M.F.; Garcia-Villalba, E.; Sow, I.S., and Sow, E., 2023. Dynamics, evolution, and facies preservation of a microtidal chenier plain, Joal-Fadiouth (Senegal, West Africa). Journal of Coastal Research, 39(2), 257–265. Charlotte (North Carolina), ISSN 0749-0208. Cheniers are coarse sediment ridges formed above finer sediments deposited on a tidal flat, the origin and development of which have traditionally been attributed to storm waves. Joal-Fadiouth is a microtidal system located on the southern coast of Senegal (West Africa). This system presents a succession of sandy and shelly ridges displaying a facies architecture consistent with a chenier plain facies model. This study combines aerial orthophotographs and sediment cores to interpret the sedimentary dynamics and facies of the chenier plain under analysis. The genesis of the last active chenier is related to the arrival of sand from the frontal ebb-tidal delta. Breaching processes occurred in the ebb delta, inducing the abandonment of the frontal lobe by the ebb-tidal currents. Fair-weather waves rework the sand from the frontal lobe, causing a migration of the sand in a manner similar to the formation of a typical nearshore swash bar. In Joal-Fadiouth, these bars soar and migrate over a tidal flat through the action of normal waves during spring high tides. Relict cheniers present shelly gravel sediments coarser than those observed in active cheniers. Thus, the final stage of stabilization of cheniers was attributed to the action of more energetic storm waves. The cheniers that accumulate during the action of ordinary and continuous processes tend not to persist, and only the coarsest cheniers formed during high-energy events finally remain in the sedimentary record. In addition to discussing the preservation of active coastal forms, this work is of regional interest, given that so far there has been only one work on cheniers in West Africa since 1989.

Spotting areas critical to storm waves and surge impacts on coasts with data scarcity: a case study in Santa Catarina, Brazil

The impacts of severe storms on the coastal zone, combined with rapid population growth in this area, have made coastal risk management an urgent need. However, integrated risk assessment can be a challenging task for many locations worldwide, as it normally requires the use of a large amount of data. The Coastal Risk Assessment Framework phase one (CRAF1) is a recently proposed analytical scheme based on empirical models and spatial analysis that combines different indicators to identify storm-induced hotspots. With a high degree of flexibility, the methodology was originally designed to be of broad use. Still, there is little information about the tool applicability in data scarcity conditions. In this study, we show that this approach can be applied, with some simplifications, on data-poor areas, allowing the identification of hotspots considering one or multiple hazards. Here, the coastal risk was assessed for erosion and coastal flooding events with return periods of 10 and 50 years on the Santa Catarina Central Coast. The study area is characterized by the occurrence of storm-induced impacts that historically cause disruption and damage to local communities. Although the components of risk have been assessed using various methods along this sector, to date, no integrated risk analysis has been presented in probabilistic terms. Predicted scenarios for the Santa Catarina Central Coast suggest that extreme episodes may cause several impacts, exposing urban settlements as well local road systems, especially in the municipalities of Tijucas and Florianópolis. The results show that the CRAF1 is an appropriate approach for a first-level risk analysis, even when implemented with poor data resolution, as it effectively points to some of the most vulnerable stretches detected in the study area.

Wave attenuation prediction of artificial coral reef using machine-learning integrated with hydraulic experiment

Various prevention methods have been proposed to resolve such coastal erosion problems, known as an important social issue in many countries. However, most of the methods designed and constructed involve gravity-type structures, causing various problems such as the obstruction of seawater circulation and changes in water quality and marine ecosystem. In this study, we propose an eco-friendly artificial coral reef structure that can control coastal erosion and help preserve the coastal environment. We investigated the wave height distribution and energy reduction characteristics through a two-dimensional hydraulic model experiment under various conditions, including different external force conditions (wave height, water depth, and wave period) and design conditions (dimensionless crown width and submergence ratio). Furthermore, we investigated the drift sand control and morphological characteristics of artificial coral reefs through a movable bed experiment. The results of the hydraulic experiment revealed that the dimensionless crown width and submergence ratio factors had a dominant effect on the wave height attenuation. In addition, the artificial coral reef structures outperformed broadly applied tetrapod structures in terms of coastline advancement and seabed protection under storm wave conditions. Moreover, to estimate the wave attenuation characteristics of artificial coral reefs, we introduced a prediction study of wave attenuation characteristics of artificial coral reefs to propose an explicit method composed of weights and biases using modified artificial neural network. We found that the method of calculating the wave dissipation coefficient calculated with the presented weight and bias matrix shows more accurate reliability than the calculation method based on the existing empirical formula.

Development of damage curves for buildings near La Rochelle during storm Xynthia based on insurance claims and hydrodynamic simulations

Abstract. The Delft3D hydrodynamic and wave model is used to hindcast the storm surge and waves that impacted La Rochelle, France, and the surrounding area (Aytré, Châtelaillon-Plage, Yves, Fouras, and Île de Ré) during storm Xynthia. These models are validated against tide and wave measurements. The models then estimate the footprint of flow depth, speed, unit discharge, flow momentum flux, significant wave height, wave energy flux, total water depth (flow depth plus wave height), and total (flow plus wave) force at the locations of damaged buildings for which insurance claims data are available. Correlation of the hydrodynamic and wave results with the claims data generates building damage functions. These damage functions are shown to be sensitive to the topography data used in the simulation, as well as the hydrodynamic or wave forcing parameter chosen for the correlation. The most robust damage functions result from highly accurate topographic data and are correlated with water depth or total (flow plus wave) force.

Macroorganisms fouled in marine anthropogenic litter (rafting) arround a tropical bay in the Southwest Atlantic

The presence of floating marine anthropogenic litter in marine environments increase the possibility of transportation of fouling organisms using these substrates as a vector, mainly for those species with close affinities to artificial substrates. The objectives were to qualitatively and quantitatively report anthropogenic litter and its associated fouling groups arround Ilha Grande Bay (IGB). Litter was collected, classified and examined for the presence of fouling organisms on beaches located at two different levels of wave exposure during rainy and dry seasons. The types of litter do not differ among beaches, and the highest density and cover of fouling were reported on exposed beaches due the currents, winds, and storm waves. Bryozoans, barnacles, polychaetes, and mollusks were the most frequent fouling groups observed in litter and represents a potential vector for the dispersion of species in the IGB and adjacent coastal areas.

Sedimentology and lithofacies of organic-rich Namurian Shale, Namur Synclinorium and Campine Basin (Belgium and S-Netherlands)

Organic-rich Namurian A mudstone is the main potential shale gas play in Belgium and neighboring countries. In order to reveal the regional depositional setting and its influence on lithofacies and origin of organic matter, this study investigates lithofacies, depositional processes and mechanisms controlling organic matter accumulation based on analysis of sedimentary structures, grain size, mineralogy, optical petrography, pyrite framboid diameter, total organic carbon and gamma log in five wells from Namurian A mudstone in Belgium and the southern part of the Netherlands. These mudstones, located in the Namur Synclinorium and Campine Basin, consist of an organic-rich mudstone succession that was deposited in the epicontinental basin within the Variscan foredeep within a moderate deep water environment below storm wave base in a distal shelf to basin floor setting under mainly euxinic and anoxic conditions with occasional dysoxic and oxic conditions. These sediments were deposited through various processes, including turbidity currents, debris flows, pelagic suspension settling with minor contribution of bottom currents, slumping processes and storm events. Lithofacies stacks generate repeated regressive and transgressive units. In the Campine Basin and the western Namur Synclinorium, 3 regressive units are characterized by basal lithofacies derived from pelagic suspension settling changing upward to lithofacies derived from mainly turbidity currents and debris flows while 2 transgressive units are characterized by basal lithofacies derived from mainly turbidity currents and debris flows changing up to lithofacies from pelagic suspension settling. In contrast in the eastern Namur Synclinorium which reflects a more proximal depositional setting, only 2 regressive units were identified. They are characterized by basal lithofacies derived from turbidity currents and debris flows changing upward to lithofacies from debris flows, bottom currents and slumping processes. 2 transgressive units were also identified. The first unit is characterized by basal breccia from karstification while in the second unit, lithofacies evolve from debris flows and slumping processes changing upward to lithofacies deposited from turbidity currents, debris flows and bottom currents. Overall, carbonate and silica dominated lithofacies from pelagic suspension settling with minor input from debris flows were deposited during high relative sea-level under euxinic to anoxic conditions. Quartz-rich lithofacies from debris flows and turbidity currents with minor input from pelagic suspension settling and bottom currents were deposited during intermediate relative sea-level under anoxic conditions. In contrast, clay, silt and carbonate-rich lithofacies from turbidity currents, debris flows, bottom currents, slumping processes and storm events were deposited during low relative sea-level under anoxic to dysoxic conditions with occasional oxic conditions near the basin margin. The highest total organic carbon observed in lithofacies from intermediate relative sea-level is caused by relative high primary marine productivity with dominant marine organic matter, low siliciclastic dilution and excellent preservation under anoxic conditions. Organic matter accumulation is low in lithofacies deposited during high and low relative sea-level. During high relative sea-level, it was controlled by clay mineral content, organic matter consumption and carbonate dilution, while during low relative sea-level, it was controlled by water redox conditions and siliciclastic dilution.

The Impact of Typhoon Intensity on Wave Height and Storm Surge in the Northern East China Sea: A Comparative Case Study of Typhoon Muifa and Typhoon Lekima

A comparative study was conducted on typhoon intensity factors affecting the marine environment using two representative cases: Typhoon Lekima, which made landfall at Shandong Peninsula, the Northern East China Sea, and Typhoon Muifa, which did not. Using the ADCIRC and SWAN models, we developed a coupled numerical model and applied it to simulate the storm surge and destructive waves caused by typhoons. Three typhoon parameters—maximum wind speed, radius of maximum wind speed, and translation speed—were investigated through sensitivity experiments. The storm surge during the typhoon that made landfall showed a positive correlation with the distance of the typhoon’s center. The maximum significant wave height and storm surge had near-linear growth with a maximum wind speed but decreased with the growth rate of the radius of maximum wind. A rapid typhoon translation speed from 47 km/h to 60 km/h could cause a storm surge resonance phenomenon at the northern coast of the East China Sea.

Coastal ecosystem engineers and their impact on sediment dynamics: Eelgrass–bivalve interactions under wave exposure

AbstractHabitat forming ecosystem engineers play critical roles in structuring coastal seascapes. Many ecosystem engineers, such as seagrasses and epifaunal bivalves, are known to have positive effects on sediment stability and increase coastal protection and ecosystem resilience. Others, such as bioturbating infaunal bivalves, may instead destabilize sediment. However, despite the common co‐occurrence of seagrasses and bivalves in coastal seascapes, little is known of their combined effects on sediment dynamics. Here, we used wave flumes to compare sediment dynamics in monospecific and multispecific treatments of eelgrass, Zostera marina, and associated bivalves (infaunal Limecola balthica, infaunal Cerastoderma edule, epifaunal Magellana gigas) under a range of wave exposures. Eelgrass reduced bedload erosion rates by 25–50%, with digital elevation models indicating that eelgrass affected the sediment micro‐bathymetry by decreasing surface roughness and ripple sizes. Effects of bivalves on sediment mobilization were species‐specific; L. balthica reduced erosion by 25%, C. edule increased erosion by 40%, while M. gigas had little effect. Importantly, eelgrass modified the impacts of bivalves: the destabilizing effects of C. edule vanished in the presence of eelgrass, while we found positive additive effects of eelgrass and L. balthica on sediment stabilization and potential for mutual anchoring. Such interspecific interactions are likely relevant for habitat patch emergence and resilience to extreme wave conditions. In light of future climate scenarios where increasing storm frequency and wave exposure threaten coastal ecosystems, our results add a mechanistic understanding of sediment dynamics and interactions between ecosystem engineers, with relevance for management and conservation.

Numerical Simulation of Storm Waves during Typhoon Maysak and Haishen in the Korean Peninsula

In this study, we simulated storm waves induced by typhoon Maysak and Haishen in the Korean peninsula by using the third-generation numerical wave model SWAN(Simulating WAves Nearshore). We used the sea-surface wind data of KMA(Korea Meteorological Agency)’s operational meteorological model RDAPS(Regional Data Assimilation Prediction System), and JMA(Japan Meteorological Agency)’s weather forecast model JMA-MSM(Meso-Scale Model) as input forcing of the numerical wave model. In addition, the wind field of the tropical cyclone was established with JTWC(Joint Typhoon Warning Center)’s best track data for the storm wave simulation. We used two different source term options, which consider other physics of energy generation by wind and dissipation by whitecapping. Validation of the simulation result was conducted over statistical analysis with the observation data from KMA and KHOA(Korea Hydrographic and Oceanographic Agency)’s buoys. As a result, the whole scenario tended to overestimate significant wave height. The simulation result by using RDAPS as input forcing outperformed the result by using JMA-MSM. It denoted that the performance of a wave model depends on the accuracy of input forcing wind. The wind field by JTWC’s best track data was not suitable compared with the meteorological numerical model. ST6 simulated the wave height higher than Komen’s source term. However, Komen's source term simulated storm waves better than ST6 in this study, and further researches under various conditions are required to evaluate ST6 for the storm waves simulation. In the simulation of wave period parameters, it was hard to estimate the accuracy of the model, and other approaches are necessary for the evaluation.

INSIGHTS FROM FOSSIL FISH TAPHONOMY INTO THE DEPOSITIONAL ENVIRONMENT OF THE LOWER MILWAUKEE FORMATION (BERTHELET MEMBER, LATEST MIDDLE DEVONIAN)

ABSTRACT The fossiliferous, argillaceous dolostone of the latest Middle Devonian (Givetian) Milwaukee Formation contains abundant disarticulated fish skeletal elements. This study refines depositional environment reconstruction of the Milwaukee Formation through taphonomic analysis of this fish assemblage. Robust skeletal elements of placoderm grinding teeth, fin spines, and armored plating dominate the assemblage. Specimens display variation in taphonomic attributes including color, luster, corrasion (chemical corrosion and/or physical abrasion), presence of pyrite and phosphate permineralization, and epibionts. Rare occurrences of teeth belonging to osteichthyan fish are also taphonomically variable. Associated invertebrates are diverse and include abundant cephalopod internal molds and pyritized brachiopods often randomly oriented in shell hashes. In sum, these observations suggest deposition on a marine shelf between normal and storm wave base. During low-energy background periods, fish plates exposed on the seafloor would undergo initial disarticulation, epibiont attachment, and color- and luster-altering corrasion and phosphatization. Buried skeletal elements were ‘protected' from epibiont attachment and corrasion, but occasional low oxygen conditions in the substrate led to early diagenetic pyrite permineralization. Periodic high-energy storm events were responsible for complete disarticulation as well as reworking and reexposure of buried skeletal elements (and burial of others), resulting in a time-averaged assemblage with a wide range of taphonomic attributes. Robust placoderm skeletal elements were best suited to survive fossilization in this setting and therefore the placoderm-dominated fossil assemblage appears to be an artifact of taphonomic processes and energy of the depositional environment.

Effects of beach width variability on recreational function: A case study of NE Brazil

Beaches have historically been recognized as one of the main spaces for leisure and recreation for residents and tourists worldwide. They are maintained by the combined action of waves, tides, currents, and winds that directly affect their composition, shape, and size. Subject to morphological variations on a short-term scale (hours and days) as a result of the action of storm waves or extraordinary tidal events, the geomorphic and sedimentary characteristics of the beach are important for determining recreational function. Considering that the beach profile changes seasonally owing to the conditions of sea agitation and sand supply, some uses may not adapt to these variations. Thus, there must be a minimum beach width for recreational functions to be developed. The method used to measure beach width is an important parameter to study erosion and accretion on beaches around the world. However, the detection of long-term changes in beach width is challenging because it is necessary to have observational data on the beach morphological change. In this study, we evaluated the relationship between the variability of the width of the emerged beach and its effects on recreational function in a stretch of Tabuba beach, Caucaia, Ceará.

Coastal Erosion Vulnerability in Mainland China Based on Fuzzy Evaluation of Cloud Models

Global climate change-induced sea-level rise and storm wave intensification, along with the large population densities and high-intensity human development activities in coastal areas, have caused serious burden and damage to China’s coasts, led to the rapid growth of artificial shorelines development, and formed a “new Great Wall” of reinforced concrete against the laws of nature. After the last ice age, transgression formed the different features of China’s coast. Depending on the types of geological and landform features, coasts are divided into 36 evaluation units, and 10 indicators are selected from natural aspects (including tectonics, geomorphology, sediment, and storms) and aspects of social economy (population, GDP, Gross Domestic Product), and cloud model theory is used to build a coastal erosion vulnerability evaluation index system in China. The results show that high grade (V), high-middle grade (IV), middle grade (III), low-middle grade (II), and low grade (I) coastal erosion vulnerability degrees account for 5.56, 13.89, 41.67, 33.33, and 5.56% of the Chinese coastlines, respectively. The coastal erosion vulnerability of the subsidence zone is significantly higher than that of the uplift zone. Reverse cloud model and analytic hierarchy process calculation show that the main factors that control coastal erosion vulnerability since the transgression after the last ice age are geological structure, topography and lithological features, and in recent years, the decrease in sea sediment loads and increase in reclamation engineering. Mainland China must live with the basic situation of coastal erosion, and this study shows that the index system and method of cloud modeling are suitable for the evaluation of the coastal erosion vulnerability of the Chinese mainland. This study provides a scientific basis for the adaptive management of coastal erosion, coastal disaster assessment and the overall planning of land and sea.

The influence of infragravity waves on the safety of coastal defences: a case study of the Dutch Wadden Sea

Abstract. Many coastlines around the world are protected by dikes with shallow foreshores (e.g. salt marshes and mudflats) that attenuate storm waves and are expected to reduce the likelihood and volume of waves overtopping the dikes behind them. However, most of the studies to date that assessed their effectiveness have excluded the influence of infragravity (IG) waves, which often dominate in shallow water. Here, we propose a modular and adaptable framework to estimate the probability of coastal dike failure by overtopping waves (Pf). The influence of IG waves on overtopping is included using an empirical approach, which is first validated against observations made during two recent storms (2015 and 2017). The framework is then applied to compare the Pf values of the dikes along the Dutch Wadden Sea coast with and without the influence of IG waves. Findings show that including IG waves results in 1.1 to 1.6 times higher Pf values, suggesting that safety is overestimated when they are neglected. This increase is attributed to the influence of the IG waves on the design wave period and, to a lesser extent, the wave height at the dike toe. The spatial variation in this effect, observed for the case considered, highlights its dependence on local conditions – with IG waves showing greater influence at locations with larger offshore waves, such as those behind tidal inlets, and shallower water depths. Finally, the change in Pf due to the IG waves varied significantly depending on the empirical wave overtopping model selected, emphasizing the importance of tools developed specifically for shallow foreshore environments.

Numerical estimation of maximum possible sizes of paleo-earthquakes and tsunamis from storm-derived boulders

Estimating the magnitudes of potential large earthquakes and associated tsunami hazards along a subduction zone is important for risk evaluation. Coastal boulder deposits can serve as valuable geological indicators in intertidal zones with high wave velocity, even though finer sediments are generally washed away. This report presents a new method to constrain the maximum possible sizes of paleo-earthquakes and tsunamis using boulders of storm wave origin as a constraint in numerical simulations. The fundamental assumption is that presently observed storm-derived boulders have not moved a great distance by past tsunami waves. This illustrative case study uses the sizes and spatial distributions of storm wave boulders on the reef at Kudaka Island, Okinawa Prefecture, which faces the Ryukyu Trench. In all, 47 tsunami scenarios with different locations and fault parameters were assumed. Results show that tsunami waves with a maximum water level of 2.2 m and maximum flow speed of 1.5 m/s at a beach of Kudaka Island did not strike the island. Under this condition, earthquakes of Mw≥8.3 are unlikely to have occurred in the central Ryukyu Trench if one obeys an empirical scaling law for subduction earthquakes or ≥2 m of maximum possible slip near the trench if the fault size is fixed as 100 km × 50 km. Those tsunami and earthquake sizes could not have been generated during this period if one assumes that the reef of Kudaka Island and emplacement of storm boulders began more than 3500 years ago. This finding implies that the seismogenic mechanism of the Ryukyu Trench and the risk of a giant earthquake differ from those of other trenches such as the Japan Trench and the Chilean Trench, where giant earthquakes of Mw≥9.0 have occurred repeatedly during the past. The proposed method would enable researchers to estimate the maximum possible sizes of the paleo-earthquakes and tsunami waves in any region, even in regions with a vague or unknown history of past events because of a lack of sandy tsunami deposits or seismic records.

Гидрометеорологические опасные природные явления Северного Каспия в зимний период на фоне климатических изменений

Hydrometeorological hazards of the Northern Caspian during the winter periods 1950–2020—due to climatic changes were investigated. Hydrometeorological hazards for the period 1950–2020 are considered: severe winter periods, early ice freeze-up, storm waves, wind surge, as well as cumulative hydrometeorological hazards—combinations of storm waves and surge. Geographic information system (GIS) “Ice regime of the southern seas of Russia” is the information basis for the study of the ice regime of the Caspian Sea. Storm activity in the Caspian Sea were reconstructed using SWAN spectral wave model. Based on the cumulative freezing-degree days winters were divided by severity—mild, moderate and severe. During the study period, moderate types of winters prevail (59.4 %), and the number of severe and mild winters is the same and amounts to 14 pcs. (20.3 %) of each type. Due to climate change, the number of mild winters is increasing, and the number of severe ones is decreasing. Since 1985, 3 severe winters (2002/03, 2007/08, 2011/12) have been recorded. As a result, the ice cover area decreased by ∼7–10 %, and the duration of the ice season at the observation point Peshnoy was reduced by 5 days. 157 situations of combinations of storm surge and storm waves are identified: 140 are cases of potential situations of cumulative phenomena of a combination of storm and surge phenomena with a speed of 15 m/s or more of winds of effective directions. The largest number of cases of cumulative dangerous hydrometeorological hazards with a wind speed of more than 15 m/s is observed in March. After the 2000s there was an increase in the number of cases and duration of dangerous hydrometeorological hazards in November and March. A direct relationship between the number of cases of cumulative dangerous hydrometeorological hazards and the severity of winters has not been found.

Nummulites assemblages, biofabrics and sedimentary structures: The anatomy and depositional model of an extended Eocene (Bartonian) nummulitic accumulation from the Transylvanian Basin (NW Romania)

Extensive high-resolution palaeontological, stratigraphic and sedimentological data offer a new and comprehensive view of the genesis and evolution of the most extended Eocene nummulitic accumulation in the northern Neotethyan realm. The preserved Bartonian (SBZ 17) Nummulites assemblages consist of large, granulate Nummulites perforatus and/or small, radiate Nummulites beaumonti . The assemblages differ in taxonomic content and/or in the relative abundance of test type (A- versus B-forms): Assemblage 1 is dominated by N. beaumonti A-forms, N. perforatus A-forms are sporadic, while B-forms are rare or missing; Assemblage 2 consists of N. perforatus A- and B-forms; and Assemblage 3 consists essentially of N. perforatus A- and B-forms with only rare N. beaumonti A- and B-forms. These assemblages are interpreted as autochthonous and autochthonous to para-autochthonous, deposited on a low-angle inner shelf. Their distribution in space and time reflects the interplay between the palaeoenvironment and the ability of N. perforatus and N. beaumonti to colonize new habitats. Thus the genesis and development of the studied nummulitic accumulations mirrors the ecological preferences of the two Nummulites species, the relative sea-level, the sediment supply and possibly the climate history. The shelf around the storm wave base was first colonized by N. beaumonti and rare N. perforatus, then the mass nummulitic accumulation was formed by the accumulation of N. perforatus tests between the storm wave base and the fair weather wave base. The accumulation of abundant N. perforatus and rare N. beaumonti around the fair weather wave base occurred in the last phase. • Detailed description of a unique Eocene nummulitic accumulation. • Distribution of the assemblages are related to the relative sea-level changes. • Composition of the Nummulites assemblages are linked to the ecological preferences. • Development of the nummulitic accumulation is the result of biotic and abiotic factors.

Radar sensing of the sea surface using small spacecraft

The possibility of using a constellation of small spacecraft as receiving satellites, when “highlighting” the sea surface from existing (navigational, communication) or specially created spacecraft—to form a wide-area (about 1 000 km) radar survey zone at a given resolution (about 10 m)—is under consideration. Such a constellation could provide operational monitoring of fast-moving atmospheric cyclones, measuring directly the parameters of storm waves (altitude and orbital velocity)—which would replace the existing constellation of microwave scatterometers, providing operational monitoring of the World Ocean surface in the 3 H (H—altitude of the satellite’s orbit) field of view with a resolution of about 10 km—but with calibration of the received images by wind speed and direction, which leads to huge errors when trying to introduce altitude calibration in the Small spacecraft have many advantages over large satellites. For example, they are relatively inexpensive to build, take minimal time from design to launch, are easily modified to solve a specific problem, and create less radio interference. The approach under consideration consists in redistribution of tasks to be solved between the constellation of satellites in orbit. High orbiting navigation satellites, for example, can be used as transmitter carriers (of the illumination of the surface) that use the necessary broadband signal with acceptable periodicity. Receivers of reflected signals are placed on board small spacecraft, and at formation of wide-band radar image of sea surface with necessary resolution ∼10 m (that only on order exceeds acceptable on small spacecraft size of receiving antennas)—in flight direction is necessary to use synthesized aperture of receiving antenna. This work has the character of “staged” research.

Strong Perpendicular Velocity-space Diffusion in Proton Beams Observed by Parker Solar Probe

Abstract The SWEAP instrument suite on Parker Solar Probe (PSP) has detected numerous proton beams associated with coherent, circularly polarized, ion-scale waves observed by PSP’s FIELDS instrument suite. Measurements during PSP Encounters 4−8 revealed pronounced complex shapes in the proton velocity distribution functions (VDFs), in which the tip of the beam undergoes strong perpendicular diffusion, resulting in VDF level contours that resemble a “hammerhead.” We refer to these proton beams, with their attendant “hammerhead” features, as the ion strahl. We present an example of these observations occurring simultaneously with a 7 hr ion-scale wave storm and show results from a preliminary attempt at quantifying the occurrence of ion-strahl broadening through three-component ion VDF fitting. We also provide a possible explanation of the ion perpendicular scattering based on quasilinear theory and the resonant scattering of beam ions by parallel-propagating, right circularly polarized, fast magnetosonic/whistler waves.