Electric charge in clouds at temperatures above 0° C

It is well-established that heavy rain can fall under certain conditions, from clouds whose temperatures are nowhere below the freezing point and where the Bergeron mechanism is pot applicable, and coalescence of droplets can provide the initial step in the growth of rain drops. It is, however, generally believed that lightning discharges occur in heavy cumulus or cumulonimbus clouds in which glaciations has begun to be apparent, and most of the theories so far advanced on the development of electric charges in the clouds assume the change of state to play a direct role in the electrification of the cloud.

Structure and electrical resistance of the passivating ZnSe layer on Ge

In this article, we have considered the p-i-n Ge photodetector with ZnSe passivating layer. Passivation layer needs to be protected photodetector from dust, rain drops and other external influences. However, this passivation layer can cause errors in photodetector image. When creating a passivating ZnSe layer on Ge, which is used in p-i-n Ge photodetectors, we found two additional phases GeSe and GeSe2 that do not contradict with their state diagram. The above phases can have an essential effect on performances of the passivating layer. Therefore, to study the electrical resistance of this layer, we prepared model samples of layers containing the GeSe and GeSe2 with the thickness 0.5…1.8 µm and area 1 cm2. To measure the electrical resistance of these layers, we used elastic contacts. The performed measurements have shown that Se layers on Ge have an intermediate resistance between that of ZnSe on Ge and pure Ge, and, therefore, the effect of additional phases practically does not worsen the passivating properties of the ZnSe layer on Ge.

IoT Based Smart Umbrella

Automatic sensor-based umbrella can be used during rainy, summer, snowfall and dense foggy seasons. It can be helpful not only to save the life of the cloth, street vegetables, fruits but in some situations also to save the human life. The idea is to design an umbrella that can be open and shut automatically with the help of NodeMCU programming. In present research work has come over with a smart rain sensing system that can detect the rain and opens up the umbrella’s link support. A raindrop sensing system is adding in this smart system, which gives a reading proportional to the amount of rain pouring on it. The smart system consists of a rack and pinion system, the rack is fixed to an umbrella such that when a sensor senses the exceeding value of rain drops, it gives a signal to the pinion attached to a motor. Then the motor starts rotating and the umbrella opens.

Device Substantiation for Generating Artificial Rain Drops by Pneumohydraulic Liquid Spraying

The authors studied the pneumohydraulic device indicators for spraying liquids for irrigation, nutrition and protection of agricultural plants, taking into account the principles of water and energy conservation, based on preliminary gas saturation of sprayed water and the use of a cavitation effect in the design of the aerator unit during ejection and supply of air under pressure. (Research purpose) To determine the technological parameters of a pneumohydraulic device for spraying liquids to obtain controlled dispersive artificial rain and substantiate the choice of its optimal technical parameters depending on the operating modes. (Materials and methods) The authors used an algorithm for calculating parameters in EXCEL or WPS spreadsheet processor and mathematical expressions. (Results and discussion) The authors theoretically determined the minimum and maximum calculated parameters of the constructive solution geometry for spraying the liquid phase: water nozzle, air nozzle channel, mixing cell, middle annular gap, outlet nozzle. They changed indicators of operating water pressure – 0.20; 0.25; 0.30 and 0.35 megapascals; air – 0.25 and 0.30 megapascals, provided the water flow rate from 0.002 to 0.010 liter per second and air – from 0.0005 to 0.0090 kilogram per second. With an increase in the water flow rate within the specified limits and the ejection coefficient from 0.5 to 0.9, a linear increase in the average annular gap diameter from 2 to 15 millimetres was revealed, as well as a nonlinear dependence of the increase in the sprayer mixing cell diameter from 5 to 20 millimetres. The authors showed the possibility of reducing the mixing cell diameter if the water pressure was increased from 0.25 to 0.35 megapascal's and the air pressure was from 0.20 to 0.30 megapascals. They obtained the parameters values for the designed and experimental samples development, which turned out to be significantly less than when operating in the air ejection mode: the outlet nozzle and the middle annular gap – by 16 percent, the air nozzle – by 23, the diameter of the mixing cell – by 50 percent or more. (Conclusions) The authors obtained calculated data to optimize technological parameters and design solutions, which would speed up the manufacture of designed and model samples of the device and its experimental testing for the generation of dispersive artificial rain drops.

Where are rainfall drops falling in a turbulent wind field ?

<p>Weather radars measure rainfall in altitude whereas hydro-meteorologists are mainly interested in rainfall at ground level. During their fall, drops are advected by the wind which affects the location of the measured field. In this study, we investigate the fall of rain drops in a turbulent wind field between an height of 1500m and the ground.</p><p>The equation governing a rain drop motion relates the acceleration to the forces of gravity and buoyancy along with the drag force. The latter depends non-linearly on the instantaneous relative velocity between the drop and the local wind; which yields to complex behaviour. In this work, the drag force is expressed in a standard way with the help of a drag coefficient, which is itself determined according to a Reynolds number. Corrections accounting for the oblateness of drops greater than 1-2 mm are implemented. Such corrections are validated through comparison of retrieved “terminal fall velocity” (i.e. without wind) with commonly used relationships in the literature.</p><p>An explicit numerical scheme is implemented to solve this equation for 3+1D turbulent wind field, and hence analyse the temporal evolution of the velocities and trajectories of rain drops during their fall. Two types of wind inputs are used : (i) Four months of 100 Hz 3D sonic anemometers data. (ii) Numerical simulations of space-time varying wind carried out with the help of Universal Multifractals which are a framework that has been widely used to characterize and simulate geophysical fields extremely variable over a wide range of scales such as wind.</p><p>The behaviour of drop velocities is then characterized through temporal multifractal analysis. It notably enables to highlight a scale, depending on the drop size, below which turbulent eddies have a limited impact on their motion. Finally the dispersion on the ground of drops all starting at the same location is quantified and consequences on rainfall remote sensing with radars discussed.</p><p> </p><p>Authors acknowledge the RW-Turb project (supported by the French National Research Agency - ANR-19-CE05-0022), for partial financial support.</p><p> </p>

A laboratory and model investigation of secondary ice production during to supercooled drop collisions with ice surfaces

<p>This work presents new laboratory data investigating collisions between supercooled drops and ice particles as a source of secondary ice particles in natural clouds. Furthermore we present numerical model simulations to put the laboratory measurements into context.</p><p>Secondary ice particles form during the breakup of freezing drops due to so-called “spherical freezing” (or Mode 1), where an ice shell forms around the freezing drop. This process has been studied and observed for drops in free-fall in laboratory experiments since the 1960s, and also more recently by Lauber et al. (2018) with a high-speed camera. Aircraft field measurements (Lawson et al. 2015) and lab data (Kolomeychuk et al. 1975) suggest that such a process is dependent on the size of drops, with larger drops being more effective at producing secondary ice.  Collision induced break-up of rain drops has been well studied with pioneering investigations in the mid-1980s, and numerous modelling studies showing that it is responsible for observed trimodal rain drop size distributions in the atmosphere, which can be well approximated by an exponential distribution.</p><p> </p><p>In mixed-phase clouds we know that rain-drops can collide with more massive ice particles. This, depending on the type of collision, may lead to the break-up of the supercooled drop (e.g. as hinted by Latham and Warwicker, 1980), potentially stimulating secondary ice formation (Phillips et al. 2018 - non-spherical, Mode 2).  There is a dearth of laboratory data investigating this mechanism.  This mechanism is the focus of the presentation.</p><p>Here we present the results of recent experiments where we make use of the University of Manchester (UoM) cold room facility. The UoM cold room facility consists of 3 stacked cold rooms that can be cooled to temperatures below -55 degC. A new facility has been built to study secondary ice production via Mode 2 fragmentation. We generate supercooled drops at the top of the cold rooms and allow them to interact with different ice surfaces near the bottom. This interaction is filmed with a new camera setup.</p><p>Our latest results will be presented at the conference.</p><p>References</p><p>Kolomeychuk, R. J., D. C. McKay, and J. V. Iribarne. 1975. “The Fragmentation and Electrification of Freezing Drops.” <em>Journal of the Atmospheric Sciences</em> 32 (5): 974–79. https://doi.org/10.1175/1520-0469(1975)032<0974>2.0.CO;2.</p><p>Latham, J., and R. Warwicker. 1980. “Charge Transfer Accompanying the Splashing of Supercooled Raindrops on Hailstones.” Quarterly Journal of the Royal Meteorological Society 106 (449): 559–68. https://doi.org/10.1002/qj.49710644912.</p><p>Lauber, Annika, Alexei Kiselev, Thomas Pander, Patricia Handmann, and Thomas Leisner. 2018. “Secondary Ice Formation during Freezing of Levitated Droplets.” Journal of the Atmospheric Sciences 75 (8): 2815–26. https://doi.org/10.1175/JAS-D-18-0052.1.</p><p>Lawson, R. Paul, Sarah Woods, and Hugh Morrison. 2015. “The Microphysics of Ice and Precipitation Development in Tropical Cumulus Clouds.” Journal of the Atmospheric Sciences 72 (6): 2429–45. https://doi.org/10.1175/JAS-D-14-0274.1.</p><p> </p><p> </p>

Determination of qualitative indicators of the work of the wide sprinkling machine

The aim of the research is to select the diameters of the nozzles of the deflector nozzles and to determine the quality indicators of the operation of a new wide-grip sprinkler of circular action, developed at the Federal State Budgetary Scientific Institution «RosNIIPM». The selection of the diameters of the nozzles of the deflector nozzles was carried out from the conditions of passing three different flows through the DM water pipeline: 15, 30 and 60 l/s. The scheme of their arrangement – rain-forming devices have different flow rates and diameters of nozzles at the same distance between them along the DM water-conducting pipeline. The analysis of the results obtained showed small deviations in the actual flow rate of the deflector nozzles through the water pipeline (cf. deflector nozzles with calculated nozzle diameters. Investigations of irrigation uniformity were carried out, as a result of which the following results were obtained: effective irrigation coefficient – 0.67–0.78; the coefficient of insufficient irrigation is 0.10–0.12, the coefficient of excessive irrigation is 0.12–0.15. At the same time, a decrease in the uniformity of irrigation is associated with an increase in wind speed and thereby an increase in the drift of artificial rain drops, the worst condition for the use of a WDM is a wind speed of more than 5 m/s, and therefore it is recommended to use this DM in the morning and evening, characterized by a more reduced wind load.

Research characteristics of deflector attacks of circle type

The aim of the research is to analyze the characteristics of experimental circular-type deflector nozzles installed as rain-forming devices on a new wide-grip circular sprinkler machine developed at the Federal State Budget Scientific Institution «RosNIIPM» obtained during laboratory field trials. In this case, circular-type baffle nozzles with nozzle diameters, mm, were used: 2, 4, 6, 8, 10, 12, 14. The maximum irrigation radius of a circulartype baffle nozzle (for various nozzle diameters) at a maximum pressure equal to 0.3 MPa lies in the range of 2.6–11.5 m. Processing of the experimental data made it possible to obtain the dependences of the irrigation radius of circular-type deflector nozzles on the head and nozzle diameter and average droplet diameter on nozzle and head flow rate, which will allow the selection of the necessary circular-type deflector nozzles at the installation height of 2.7 m Thus, the developed nozzles provide a uniform distribution of irrigation water over the irrigation area, and the average diameter of rain drops can be attributed to the fine-structured one, which ensures the fulfillment of agrotechnical requirements.