Bore collapse and wave run-up on a sandy beach

Wave run-up on beaches and coastal structures is initiated and driven by collapsing incident bores, this process is often considered to define the seaward limit of the swash zone. It is hence a key feature in nearshore wave processes as extreme run-up can lead to structure overtopping and coastal inundation during storm conditions. In addition, the turbulent nature of incident bores and their collapse suspends and advects sediment, resulting in a highly morphologically dynamic swash zone. The cross shore bore collapse location varies from wave to wave and the process is very limited in both spatial and temporal extent, making direct measurement problematic. This paper presents high spatial-temporal resolution LiDAR field measurements of the evolving free-surface in the surf and swash zone which enable the bore collapse detection for 166 waves. These measurements are used to investigate the link between broken wave properties at bore collapse and wave run-up. Incident bores are identified at the seaward boundary of the LiDAR profiles and tracked through the inner surf and swash zones to the run-up limit. It is found that the vertical run-up height exceeds that which would be expected for a perfect conversion of potential to kinetic energy during bore collapse for 24% of the bores measured. By returning to an existing ballistic-type model to describe the run-up of individual waves, we show that wave run-up can be divided into three components: the bore collapse, terminal bore celerity and their non-linear interaction. For the present dataset, the contribution of the bore collapse and terminal bore celerity is 26% and 27% respectively, while non-linear interactions between the two dominates and account for 47% of the measured run-up. By including the terminal bore celerity, the ability to predict run-up is increased by 30% with the determination coefficient r increasing from 0.573 to 0.785. Likewise, the RMS-error for the wave run-up shows an approximately 10% reduction from 0.325 to 0.295 m

Bore collapse and wave run-up on a sandy beach

Wave run-up on beaches and coastal structures is initiated and driven by collapsing incident bores, this process is often considered to define the seaward limit of the swash zone. It is hence a key feature in nearshore wave processes as extreme run-up can lead to structure overtopping and coastal inundation during storm conditions. In addition, the turbulent nature of incident bores and their collapse suspends and advects sediment, resulting in a highly morphologically dynamic swash zone. The cross shore bore collapse location varies from wave to wave and the process is very limited in both spatial and temporal extent, making direct measurement problematic. This paper presents high spatial-temporal resolution LiDAR field measurements of the evolving free-surface in the surf and swash zone which enable the bore collapse detection for 166 waves. These measurements are used to investigate the link between broken wave properties at bore collapse and wave run-up. Incident bores are identified at the seaward boundary of the LiDAR profiles and tracked through the inner surf and swash zones to the run-up limit. It is found that the vertical run-up height exceeds that which would be expected for a perfect conversion of potential to kinetic energy during bore collapse for 24 % of the bores measured. By returning to an existing ballistic-type model to describe the run-up of individual waves, we show that wave run-up can be divided into three components: the bore collapse, terminal bore celerity and their non-linear interaction. For the present dataset, the contribution of the bore collapse and terminal bore celerity is 26 % and 27 % respectively, while non-linear interactions between the two dominates and account for 47% of the measured run-up. By including the terminal bore celerity, the ability to predict run-up is increased by 30 % with the determination coefficient r increasing from 0.573 to 0.785. Likewise, the RMS-error for the wave run-up shows an approximately 10 % reduction from 0.325 to 0.295 m.</p

DEVELOPMENT OF A GROUP OF MOBILE ROBOTS FOR CONDUCTING COMPREHENSIVE RESEARCH OF DANGEROUS WAVE CHARACTERISTICS IN COASTAL ZONES

New methods and approaches for carrying out comprehensive measurements of hazardous waves (tsunami, storm surges) and background wave climate with telemetrically related group of ground, surface and underwater based robots are discussed. The design and equipment list of the ground robot are considered. It includes three various types of movers, an add-on for the installation of devices on the mobile platform and the hardware part. Ground robot was tested in 2016 on the coast of Sakhalin Island, cape Svobodny. Based on test results there were made conclusions on the possibility of increasing mobility of the ground robot and expanding its use. Specially designed underwater robot collects data using a video inspection system and a hydrostatic wave recorder with a string sensor. It has the ability to adjust the position of the center of gravity to increase stability when driving on steep slopes of the seabed. The surface robot was designed for conducting detailed bathymetry measurements of investigated water areas by means of a multi-beam echo sounder. Underwater and surface-based robots were tested in July 2017 on Sakhalin Island. Both robotic systems were merged into the united local network. The results of their operation were obtained to verify the data from measuring systems of the ground robot. In 2018, it is planned to conduct a series of tests involving the three robots and merging them into a local network to manage and process data in real-time

Linear mixing model applied to coarse resolution satellite data

A linear mixing model typically applied to high resolution data such as Airborne Visible/Infrared Imaging Spectrometer, Thematic Mapper, and Multispectral Scanner System is applied to the NOAA Advanced Very High Resolution Radiometer coarse resolution satellite data. The reflective portion extracted from the middle IR channel 3 (3.55 - 3.93 microns) is used with channels 1 (0.58 - 0.68 microns) and 2 (0.725 - 1.1 microns) to run the Constrained Least Squares model to generate fraction images for an area in the west central region of Brazil. The derived fraction images are compared with an unsupervised classification and the fraction images derived from Landsat TM data acquired in the same day. In addition, the relationship betweeen these fraction images and the well known NDVI images are presented. The results show the great potential of the unmixing techniques for applying to coarse resolution data for global studies

The Application of Tomographic Reconstruction Techniques to Ill-Conditioned Inverse Problems in Atmospheric Science and Biomedical Imaging

A methodology is presented for creating tomographic reconstructions from various projection data, and the relevance of the results to applications in atmospheric science and biomedical imaging is analyzed. The fundamental differences between transform and iterative methods are described and the properties of the imaging configurations are addressed. The presented results are particularly suited for highly ill-conditioned inverse problems in which the imaging data are restricted as a result of poor angular coverage, limited detector arrays, or insufficient access to an imaging region. The class of reconstruction algorithms commonly used in sparse tomography, the algebraic reconstruction techniques, is presented, analyzed, and compared. These algorithms are iterative in nature and their accuracy depends significantly on the initialization of the algorithm, the so-called initial guess. A considerable amount of research was conducted into novel initialization techniques as a means of improving the accuracy. The main body of this paper is comprised of three smaller papers, which describe the application of the presented methods to atmospheric and medical imaging modalities. The first paper details the measurement of mesospheric airglow emissions at two camera sites operated by Utah State University. Reconstructions of vertical airglow emission profiles are presented, including three-dimensional models of the layer formed using a novel fanning technique. The second paper describes the application of the method to the imaging of polar mesospheric clouds (PMCs) by NASA’s Aeronomy of Ice in the Mesosphere (AIM) satellite. The contrasting elements of straight-line and diffusive tomography are also discussed in the context of ill-conditioned imaging problems. A number of developing modalities in medical tomography use near-infrared light, which interacts strongly with biological tissue and results in significant optical scattering. In order to perform tomography on the diffused signal, simulations must be incorporated into the algorithm, which describe the sporadic photon migration. The third paper presents a novel Monte Carlo technique derived from the optical scattering solution for spheroidal particles designed to mimic mitochondria and deformed cell nuclei. Simulated results of optical diffusion are presented. The potential for improving existing imaging modalities through continual development of sparse tomography and optical scattering methods is discussed

Flow-3D CFD model of bifurcated open channel flow: setup and validation

Bifurcation is a morphological feature present in most of fluvial systems; where a river splits into two channels, each bearing a portion of the flow and sediments. Extensive theoretical studies of river bifurcations were performed to understand the nature of flow patterns at such diversions. Nevertheless, the complexity of the flow structure in the bifurcated channel has resulted in various constraints on physical experimentation, so computational modelling is required to investigate the phenomenon. The advantages of computational modelling compared with experimental research (e.g. simple variable control, reduced cost, optimize design condition etc.) are widely known. The great advancement of computer technologies and the exponential increase in power, memory storage and affordability of high-speed machines in the early 20th century led to evolution and wide application of numerical fluid flow simulations, generally referred to as Computational Fluid Dynamics {CFD). In this study, the open-channel flume with a lateral channel established by Momplot et al (2017) is modelled in Flow-3D. The original investigation on divided flow of equal widths as simulated in ANSYS Fluent and validated with velocity measurements

Goddard Visiting Scientist Program for the Space and Earth Sciences Directorate

Progress reports of the Visiting Scientist Program covering the period from 1 Jul. - 30 Sep. 1992 are included. Topics covered include space science and earth science. Other topics covered include cosmic rays, magnetic clouds, solar wind, satellite data, high resolution radiometer, and microwave scattering