A Parameterization of Sticking Efficiency for Collisions of Snow and Graupel with Ice Crystals: Theory and Comparison with Observations*

Abstract A new parameterization of sticking efficiency for aggregation of ice crystals onto snow and graupel is presented. This parameter plays a crucial role for the formation of ice precipitation and for electrification processes. The parameterization is intended to be used in atmospheric models simulating the aggregation of ice particles in glaciated clouds. It should improve the ability to forecast snow. Based on experimental results and general considerations of collision processes, dependencies of the sticking efficiency on temperature, surface area, and collision kinetic energy of impacting particles are derived. The parameters have been estimated from some laboratory observations by simulating the experiments and minimizing the squares of the errors of the prediction of observed quantities. The predictions from the new scheme are compared with other available laboratory and field observations. The comparisons show that the parameterization is able to reproduce the thermal behavior of sticking efficiency, observed in published laboratory studies, with a peak around −15°C corresponding to dendritic vapor growth of ice. Finally, a new theory of sticking efficiency is proposed. It explains the empirically derived parameterization in terms of a probability distribution of the work that would be required to separate two contacting particles colliding in all possible ways among many otherwise identical collisions of the same pair with a given initial collision kinetic energy. For each collision, if this work done would exceed the initial collision kinetic energy, then there is no separation after impact. The probability of that occurring equals the sticking efficiency.

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Kinetic energy-conserving hyperdiffusion can improve low resolution atmospheric models

Journal of Advances in Modeling Earth Systems ◽

10.1002/2015ms000480 ◽

2015 ◽

Vol 7 (3) ◽

pp. 1117-1135 ◽

Cited By ~ 6

Author(s):

Pablo Zurita-Gotor ◽

Isaac M. Held ◽

Malte F. Jansen

Keyword(s):

Kinetic Energy ◽

Atmospheric Models ◽

Low Resolution ◽

Energy Conserving

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Pesticide mixture toxicity to algae in agricultural streams – Field observations and laboratory studies with in situ samples and reconstituted water

Ecotoxicology and Environmental Safety ◽

10.1016/j.ecoenv.2021.112153 ◽

2021 ◽

Vol 215 ◽

pp. 112153

Author(s):

Jenny Rydh Stenström ◽

Jenny Kreuger ◽

Willem Goedkoop

Keyword(s):

Mixture Toxicity ◽

Field Observations ◽

Laboratory Studies ◽

Pesticide Mixture ◽

Agricultural Streams

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Tracker-assisted modelling: simultaneous validation of the conservation law of energy and the work-energy theorem

Physics Education ◽

10.1088/1361-6552/ac36a9 ◽

2021 ◽

Vol 57 (1) ◽

pp. 015012

Author(s):

Unofre B Pili ◽

Renante R Violanda

Keyword(s):

Kinetic Energy ◽

Potential Energy ◽

Gravitational Potential ◽

Conservation Law ◽

Gravitational Potential Energy ◽

Time Data ◽

Home Based ◽

Basic Physics ◽

Free Falling ◽

Work Done

Abstract The video of a free-falling object was analysed in Tracker in order to extract the position and time data. On the basis of these data, the velocity, gravitational potential energy, kinetic energy, and the work done by gravity were obtained. These led to a rather simultaneous validation of the conservation law of energy and the work–energy theorem. The superimposed plots of the kinetic energy, gravitational potential energy, and the total energy as respective functions of time and position demonstrate energy conservation quite well. The same results were observed from the plots of the potential energy against the kinetic energy. On the other hand, the work–energy theorem has emerged from the plot of the total work-done against the change in kinetic energy. Because of the accessibility of the setup, the current work is seen as suitable for a home-based activity, during these times of the pandemic in particular in which online learning has remained to be the format in some countries. With the guidance of a teacher, online or face-to-face, students in their junior or senior high school—as well as for those who are enrolled in basic physics in college—will be able to benefit from this work.

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Exploring probability distribution functions best-fitting the kinetic energy of coarse particles at above threshold flow conditions

10.5194/egusphere-egu21-1820 ◽

2021 ◽

Author(s):

Hamed Farhadi ◽

Manousos Valyrakis

Keyword(s):

Probability Distribution ◽

Kinetic Energy ◽

Test Section ◽

Particle Transport ◽

River Flow ◽

Distribution Functions ◽

Transport Processes ◽

Flow Conditions ◽

Probability Distribution Functions ◽

Transport Regime

Applying an instrumented particle [1-3], the probability density functions of kinetic energy of a coarse particle (at different solid densities) mobilised over a range of above threshold flow conditions&#160;conditions corresponding to the intermittent transport regime, were explored. The experiments were conducted in the Water Engineering Lab at the University of Glasgow on a tilting recirculating flume with 800 (length) &#215; 90 (width) cm dimension. Twelve different flow conditions corresponding to intermittent transport regime for the range of particle densities examined herein, have been implemented in this research. Ensuring fully developed flow conditions, the start of the test section was located at 3.2 meters upstream of the flume outlet. The bed surface of the flume is flat and made up of well-packed glass beads of 16.2 mm diameter, offering a uniform roughness over which the instrumented particle is transported. MEMS sensors are embedded within the instrumented particle with 3-axis gyroscope and 3-axis accelerometer. At the beginning of each experimental run, instrumented particle is placed at the upstream of the test section, fully exposed to the free stream flow. Its motion is recorded with top and side cameras to enable a deeper understanding of particle transport processes. Using results from sets of instrumented particle transport experiments with varying flow rates and particle densities, the probability distribution functions (PDFs) of the instrumented particles kinetic energy, were generated. The best-fitted PDFs were selected by applying the Kolmogorov-Smirnov test and the results were discussed considering the light of the recent literature of the particle velocity distributions.[1] Valyrakis, M.; Alexakis, A. Development of a &#8220;smart-pebble&#8221; for tracking sediment transport. In Proceedings of the International Conference on Fluvial Hydraulics (River Flow 2016), St. Louis, MO, USA, 12&#8211;15 July 2016.[2] Al-Obaidi, K., Xu, Y. & Valyrakis, M. 2020, The Design and Calibration of Instrumented Particles for Assessing Water Infrastructure Hazards, Journal of Sensors and Actuator Networks, vol. 9, no. 3, 36.[3] Al-Obaidi, K. & Valyrakis, M. 2020, Asensory instrumented particle for environmental monitoring applications: development and calibration, IEEE sensors journal (accepted).

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A new species of Hypatima Hübner (Lepidoptera: Gelechiidae) injurious to mango trees in East Africa

Bulletin of Entomological Research ◽

10.1017/s0007485300018411 ◽

1989 ◽

Vol 79 (3) ◽

pp. 411-420 ◽

Cited By ~ 1

Author(s):

K. Sattler ◽

A. B. Stride

Keyword(s):

Life History ◽

New Species ◽

East Africa ◽

Female Genitalia ◽

Field Observations ◽

Laboratory Studies ◽

Male And Female ◽

Extensive Field ◽

A New Species

AbstractHypatima mangiferae Sattler sp. n. is described from Kenya, where its larva is injurious to commercial mango trees. A description of its life-history, based on extensive field observations and laboratory studies, is also provided. The moth, its male and female genitalia and the damage caused by the larva are illustrated.

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The theory of the chain fountain revisited

Journal of Physics Conference Series ◽

10.1088/1742-6596/2090/1/012166 ◽

2021 ◽

Vol 2090 (1) ◽

pp. 012166

Author(s):

Dragos-Victor Anghel

Keyword(s):

Energy Transfer ◽

Kinetic Energy ◽

Significant Role ◽

Mechanical Work ◽

Scientific Consensus ◽

Energy And Momentum ◽

Work Done

Abstract We analyze the chain fountain effect-the chain siphoning when falling from a container onto the floor. We argue that the main reason for this effect is the inertia of the chain, whereas the momentum received by the beads of the chain from the bottom of the container (typically called “kicks”) plays no significant role. The inertia of the chain leads to an effect similar to pulling the chain over a pulley placed up in the air, above the container. In another model (the so called “scientific consensus”), it was assumed that up to half of the mechanical work done by the tension in the chain may be wasted when transformed into kinetic energy during the pickup process. This prevented the chain to rise unless the energy transfer in the pickup process is improved by the “kicks” from the bottom of the container. Here we show that the “kicks” are unnecessary and both, energy and momentum are conserved-as they should be, in the absence of dissipation-if one properly considers the tension and the movement of the chain. By doing so, we conclude that the velocity acquired by the chain is high enough to produce the fountain effect. Simple experiments validate our model and certain configurations produce the highest chain fountain, although “kicks” are impossible.

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Estimating Surface Attachment Kinetic and Growth Transition Influences on Vapor-Grown Ice Crystals

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-19-0303.1 ◽

2020 ◽

Vol 77 (7) ◽

pp. 2393-2410

Author(s):

Gwenore F. Pokrifka ◽

Alfred M. Moyle ◽

Lavender Elle Hanson ◽

Jerry Y. Harrington

Keyword(s):

Diffusion Chamber ◽

Ice Crystals ◽

Growth Theory ◽

Growth Data ◽

Surface Attachment ◽

Mass Growth ◽

Vapor Growth ◽

Deposition Coefficient ◽

Direct Use ◽

Large Decline

AbstractThere are few measurements of the vapor growth of small ice crystals at temperatures below −30°C. Presented here are mass-growth measurements of heterogeneously and homogeneously frozen ice particles grown within an electrodynamic levitation diffusion chamber at temperatures between −44° and −30°C and supersaturations si between 3% and 29%. These growth data are analyzed with two methods devised to estimate the deposition coefficient α without the direct use of si. Measurements of si are typically uncertain, which has called past estimates of α into question. We find that the deposition coefficient ranges from 0.002 to unity and is scattered with temperature, as shown in prior measurements. The data collectively also show a relationship between α and si, with α rising (falling) with increasing si for homogeneously (heterogeneously) frozen ice. Analysis of the normalized mass growth rates reveals that heterogeneously frozen crystals grow near the maximum rate at low si, but show increasingly inhibited (low α) growth at high si. Additionally, 7 of the 17 homogeneously frozen crystals cannot be modeled with faceted growth theory or constant α. These cases require the growth mode to transition from efficient to inefficient in time, leading to a large decline in α. Such transitions may be, in part, responsible for the inconsistency in prior measurements of α.

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Turbulence Adjustment and Scaling in an Offshore Convective Internal Boundary Layer: A CASPER Case Study

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-19-0189.1 ◽

2020 ◽

Vol 77 (5) ◽

pp. 1661-1681

Author(s):

Qingfang Jiang ◽

Qing Wang ◽

Shouping Wang ◽

Saša Gaberšek

Keyword(s):

Boundary Layer ◽

Surface Layer ◽

Kinetic Energy ◽

Wind Shear ◽

Vertical Wind Shear ◽

Internal Boundary Layer ◽

Turbulence Kinetic Energy ◽

Internal Boundary ◽

Field Observations ◽

The Mean

Abstract The characteristics of a convective internal boundary layer (CIBL) documented offshore during the East Coast phase of the Coupled Air–Sea Processes and Electromagnetic Ducting Research (CASPER-EAST) field campaign has been examined using field observations, a coupled mesoscale model (i.e., Navy’s COAMPS) simulation, and a couple of surface-layer-resolving large-eddy simulations (LESs). The Lagrangian modeling approach has been adopted with the LES domain being advected from a cool and rough land surface to a warmer and smoother sea surface by the mean offshore winds in the CIBL. The surface fluxes from the LES control run are in reasonable agreement with field observations, and the general CIBL characteristics are consistent with previous studies. According to the LESs, in the nearshore adjustment zone (i.e., fetch < 8 km), the low-level winds and surface friction velocity increase rapidly, and the mean wind profile and vertical velocity skewness in the surface layer deviate substantially from the Monin–Obukhov similarity theory (MOST) scaling. Farther offshore, the nondimensional vertical wind shear and scalar gradients and higher-order moments are consistent with the MOST scaling. An elevated turbulent layer is present immediately below the CIBL top, associated with the vertical wind shear across the CIBL top inversion. Episodic shear instability events occur with a time scale between 10 and 30 min, leading to the formation of elevated maxima in turbulence kinetic energy and momentum fluxes. During these events, the turbulence kinetic energy production exceeds the dissipation, suggesting that the CIBL remains in nonequilibrium.

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