Wave-Induced Distribution of Microplastic in the Surf Zone

In this study, the wave-induced distribution of 13 microplastic (MP) samples of different size, shape, and density was investigated in a wave flume with a sandy mobile beach bed profile. The particle parameter were chosen based on an occurrence probability investigated from the field. MP abundances were analyzed in cross-shore and vertical direction of the test area after over 40,000 regular waves. It was found, that MP particles accumulated in more shallow waters with increasing size and density. Particles with high density (ρs>1.25 g/cm3) have been partly confined into deeper layers of the sloping beach during the formation of the bed profile. Particles with a density lower than that of water used in the experiments floated constantly in the surf zone or deposited on the beach caused by wave run-up. A correlation was found between the settling velocity of the MP particles and the flow velocity at the accumulation point and a power function equation developed. The obtained results were critically discussed with findings from the field and further laboratory studies.

Infrared limb sounding of cirrus clouds: state of knowledge, recent progress, and future prospects

<p>Cirrus clouds are the highest altitude clouds in the troposphere and play an important role in the climate system. They can either have a cooling or heating effect in radiation balance around of the planet, depending on which altitude and temperature they appear. Despite the importance of this type of clouds for the radiation budget there are still big gaps of knowledge regarding their micro and macro physical properties (e.g. particle sizes, ice water content, occurrence and coverage at the upper troposphere and lower stratosphere), especially for optically very thin cirrus in the tropopause region, which are difficult to detect even for active lidar measurements. <span>Due to the long path length through the atmosphere and good vertical resolution passive infrared limb measurements are especially well suited to observe this type of clouds. The presentation will highlight the current status in infrared limb sounding and corresponding particle parameter retrievals with respect to recent and future space and airborne sensors (e.g. CRISTA, MIPAS, </span><span>and IR limb-imaging instruments</span><span>). </span></p>

Mechanics of bed particle saltation in turbulent wall-shear flow

In this paper, we explore the mechanics of bed particle saltation in turbulent wall-shear flow, analysing the forces on a particle to perform saltation. The hydrodynamic drag encompasses the form drag and turbulent drag. The hydrodynamic lift comprises the Saffman lift, Magnus lift and turbulent lift. The subtle role of the Basset force in governing the particle trajectory is accounted for in the analysis. The bedload flux, emanating from the mathematical analysis of bed particle saltation, is determined. The results reveal that for the particle parameter range 20–100, the transport stage function equalling unity corroborates the threshold of bed particle saltation, where the saltation height and length are 1.3 and 9 times the particle size. For a given transport stage function, the relative saltation height and length decrease with an increase in particle parameter. For the particle parameter range 20–100, the relative saltation height and length increase with an increase in transport stage function, reaching their peaks, and then, they decrease. For a given particle parameter, the peak and mean particle densimetric Froude numbers increase as the transport stage function increases. The bedload flux curves for particle parameters 26 and 63 produce the upper and lower bound curves, respectively.

Limiting Velocities of Primary, Obscure and Normal Particles: Self-Annihilating Obscure Particle as an Example of Dark Matter Particle

From recently established bicubic equation, three particle limiting velocities are derived, primary, c1,obscure, c2 and normal, c3,that in principle may belong to a single particle. The values of limiting velocities are governed by the congruent particle parameter, z = 3\sqrt3mv2=2E, with m; v and E being, respectively, particle mass, velocity and energy, generally satisfying 1 &lt;= z &lt;= 1, and here just 0 &lt;= z &lt;= 1.<br />While c3 is practically the same in value as v, c1 and c2 can depart from v as z changes from 1 to 0, since c1, c2 and c3; are, in forms, explicitly different from each other, which offers the chance to look at possible new forms of matter, such as dark matter. For instance, one finds that c3 could be slightly different from c, the velocity of light, for the 2010 Crab Nebula Flare PeV electron energy region and for the OPERA 17 GeV muon neutrino velocity experiments, while at the same time, although not measurable in these experiments, calculated c1 and jc2j, are numerically about 105 times larger than c3.<br />There is a belief that an exemplary particle of small velocity, v = 10-3c ,and small energy, E = 1eV , but as yet of not known mass, should belong to the dark matter class. Once knowing z the value of the mass is fixed with 3\sqrt3m(z)v2 = 2Ez ,and its maximum value m(1) is at z = 1, m(1) = 2E=(v23\sqrt3):This mass value defines the test particle, with which one calulates primary, obscure and normal particle rest energies at z = 1: Snce at z = 1 theory predicts c21(1) = (3=2) v2;c22<br />(1) = 3v2; c23 (1) = (3=2) v2, the rest energies are m(1) c21(1) = m(1) c23(1) = 0:58eV and m(1)(c22(1))= 1:15eV. The primary and normal particles, with positive kinetic energies self-creation process increase their energies from 0:58eV to desired1eV: The obscure particle, with negative kinetic energy self-annihilation process decreases its energy of 1:15eV to desired 1eV. This makes the obscure (imaginary c2) particle as a good candidate for a dark matter particle,since as it is believed that a trapped dark matter particle with self-annihilation properties helps keeping the equilibrium between capture and annihilation rates in the sun.