Coastal cliff ground motions and response to extreme storm waves

Coastal cliff erosion from storm waves is observed worldwide, but the processes are notoriously difficult to measure during extreme storm wave conditions when most erosion normally occurs, limiting our understanding of cliff processes. Over January–February 2014, during the largest Atlantic storms in at least 60 years with deepwater significant wave heights of 6–8 m, cliff-top ground motions showed vertical ground displacements in excess of 50–100 µm; an order of magnitude larger than observations made previously. Repeat terrestrial laser scanner surveys over a 2 week period encompassing the extreme storms gave a cliff face volume loss of 2 orders of magnitude larger than the long-term erosion rate. The results imply that erosion of coastal cliffs exposed to extreme storm waves is highly episodic and that long-term rates of cliff erosion will depend on the frequency and severity of extreme storm wave impacts

Storm Tide and Wave Simulations and Assessment II

Storm tides, surges, and waves associated with typhoons/tropical cyclones/hurricanes are the most severe threats to coastal zones, nearshore waters, and navigational safety. Therefore, predicting typhoon/tropical cyclone/hurricane-induced storm tides, surges, waves, and coastal erosion is essential for reducing the loss of human life and property and mitigating coastal disasters. There is still a growing demand for novel techniques that could be adopted to resolve the complex physical processes of storm tides, surges, waves, and coastal erosion, even if many studies on the hindcasting/prediction/forecasting of typhoon-driven storm tides, surges, waves, and also morphology evolution have been carried out through numerical models in the last decade. This Special Issue intends to collect the latest studies on storm tide, surge, and wave modeling and analysis utilizing dynamic and statistical models and artificial intelligence approaches to improve our simulating and analytic capabilities and our understanding of storm tides, surges, and waves. Five high-quality papers have been accepted for publication in this Special Issue; these papers cover the application and development of many high-end techniques for storm tides, surges, waves, and on-site investigation of coastal erosion and accretion

Abnormal storm waves in the winter East/Japan Sea: generation process and hindcasting using an atmosphere-wind wave modelling system

Abnormal storm waves cause coastal disasters along the coasts of Korean Peninsula and Japan in the East/Japan Sea (EJS) in winter, arising due to developed low pressures during the East Asia winter monsoon. The generation of these abnormal storm waves during rough sea states were studied and hindcast using an atmosphere-wave coupled modelling system. Wind waves and swell due to developed low pressures were found to be the main components of abnormal storm waves. The meteorological conditions that generate these waves are classified into three patterns based on past literature that describes historical events as well as on numerical modelling. In hindcasting the abnormal storm waves, a bogussing scheme originally designed to simulate a tropical storm in a mesoscale meteorological model was introduced into the modelling system to enhance the resolution of developed low pressures. The modelling results with a bogussing scheme showed improvements in terms of resolved low pressure, surface wind field, and wave characteristics obtained with the wind field as an input

Further constraints on electron acceleration in solar noise storms

We reexamine the energetics of nonthermal electron acceleration in solar noise storms. A new result is obtained for the minimum nonthermal electron number density required to produce a Langmuir wave population of sufficient intensity to power the noise storm emission. We combine this constraint with the stochastic electron acceleration formalism developed by Subramanian & Becker (2005) to derive a rigorous estimate for the efficiency of the overall noise storm emission process, beginning with nonthermal electron acceleration and culminating in the observed radiation. We also calculate separate efficiencies for the electron acceleration -- Langmuir wave generation stage and the Langmuir wave -- noise storm production stage. In addition, we obtain a new theoretical estimate for the energy density of the Langmuir waves in noise storm continuum sources.Comment: Accepted for publication in Solar Physic

Boussinesq modelling of tsunami and storm wave impact

Many coastal protection structures in the UK have been designed for storm surges with appropriate return periods, but their performance during tsunami-type waves is uncertain. A shallow water and Boussinesq model is well suited to the investigation of both near-shore storm waves and tsunami waves. This paper makes use of the model to compare the effect on coastal structures of solitary waves and storm waves. Wave run-up parameters for both types of wave are generated and shown to be in good agreement with experimental data. The equations behind the model were derived assuming a small bed slope and therefore are not suitable for modelling waves interacting with vertical and near-vertical structures. However, the introduction of a reverse momentum term, to take account of a jet of water typical of a breaking wave impacting against a structure, allows wave overtopping volumes to be well predicted, although it had a minor effect on the forces acting on the structure. Comparisons with experimental data, for both solitary waves and storm waves, are presented. Using this model, the difference between the impact, in terms of wave forces and wave overtopping, of tsunami waves and storm waves for a given structure is investigated. </jats:p

The aurora as a source of planetary-scale waves in the middle atmosphere

Photographs of global-scale auroral forms taken by scanning radiometers onboard U.S. Air Force weather satellites in 1972 show that auroral bands exhibit well-organized wave motion with typical zonal wave number of 5 or so. The scale size of these waves is in agreement with that of well-organized neutral wind fields measured by the 1967-50B satellite in the 150- to 220-km region during the geomagnetic storm of May 27, 1967. The horizontal scale size revealed by these observations is in agreement with that of high-altitude traveling ionospheric disturbances. It is conjectured that the geomagnetic storm is a source of planetary and synoptic scale neutral atmospheric waves in the middle atmosphere. The possible existence of a source of waves of the proper scale size to trigger instabilities in middle atmospheric circulation systems may be significant in the study of lower atmospheric response to geomagnetic activity

The effect of latent heat release on synoptic-to-planetary wave interactions and its implication for satellite observations: Theoretical modeling

Simple models are being developed to simulate interaction of planetary and synoptic-scale waves incorporating the effects of large-scale topography; eddy heat and momentum fluxes (or nonlinear dynamics); radiative heating/cooling; and latent heat release (precipitation) in synoptic-scale waves. The importance of latent heat release is determined in oceanic storm tracks for temporal variability and time-mean behavior of planetary waves. The model results were compared with available observations of planetary and synoptic-scale wave variability and time-mean circulation. The usefulness of monitoring precipitation in oceanic storm tracks by satellite observing systems was ascertained. The modeling effort includes two different low-order quasi-geostrophic models-time-dependent version and climatological mean version. The modeling also includes a low-order primitive equation model. A time-dependent, multi-level version will be used to validate the two-level Q-G models and examine effects of spherical geometry