Numerical simulation of particle transport in the boundary layer with implications for SARS-CoV-2 virions distribution in urban environments 

2021 ◽  
Author(s):  
Alexander Varentsov ◽  
Victor Stepanenko ◽  
Evgeny Mortikov
Keyword(s):  
Boundary Layer ◽  
Velocity Component ◽  
Particle Motion ◽  
Input Data ◽  
Field Experiments ◽  
Urban Environments ◽  
Biologically Active ◽  
Lagrangian Model ◽  
Pulsation Velocity ◽  
Time Step

<p>This paper presents the development and application of a numerical Lagrangian model of the transport of aerosol particles in the urban boundary layer of the atmosphere with a high spatial resolution. The development of the model is motivated by the limited measurement methods for observing aerosol concentrations in urban environments, both in terms of coverage density and in terms of accuracy and representativeness. The growing interest of the world community in the problems of monitoring air pollution in cities and the atmospheric distribution of biologically active aerosols also became a motivating factor.</p><p>The model uses the equation of motion to calculate the trajectory of a particle suspended in the air. It is based on Newton's second law and takes into account the forces of gravity, buoyancy and air resistance. The influence of stochastic turbulent eddies on the particle motion is taken into account in the model by using turbulent parameterizations. The effect of turbulence is important when describing the motion of particles in this model, since aerosols have a size much smaller than the grid step of the input data and can stay inside one cell for a long time, being under the influence of subgrid vortices. In this model, three parameterizations are implemented: a simple Gaussian model, a random displacement model, and a random walk model. In all three, the pulsation velocity component is a normally distributed random variable, but in the first two parameterizations it is generated at each time step of the Lagrangian model. In the last one, the interaction time of the particle with the turbulent vortex is introduced, during which the pulsation velocity component acting on the particle remains constant, characterizing the effect of a particular vortex. Additionally, a version of the model based on the Langevin equation has been implemented to more accurately account for the effect of turbulence on particle motion.</p><p>The developed numerical model is implemented in a program code in the C++ programming language and allows one to calculate individual trajectories of motion and concentrations of particles. Input data (wind speed components, turbulence characteristics and others) can be set analytically or imported from hydrodynamic models.</p><p>The model has been successfully tested and verified on several idealized analytical solutions – an equivalence is obtained in terms of the concentration field. Experiments have also been carried out to reproduce the transport of particles in a series of urban canyons, including particles with a finite half-life that simulate the COVID-19 virions (SARS-CoV-2). Based on the results of the calculations, the influence of stratification, particle size and lifetime on the transport of aerosols in a typical urban environment was estimated.</p><p>The work is partially supported by RFBR grants 18-05-60126 and 19-05-50110.</p>

scholarly journals Nutritional Value of Jerusalem Artichoke Tubers (Helianthus tuberosus L.) Grown in Organic System under Lithuanian and Polish Conditions

Agriculture ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 440
Author(s):  
Barbara Sawicka ◽  
Honorata Danilčenko ◽  
Elvyra Jariene ◽  
Dominika Skiba ◽  
Leszek Rachoń ◽  
...  
Keyword(s):  
Nutritional Value ◽  
Field Experiments ◽  
Geographic Location ◽  
Jerusalem Artichoke ◽  
Farming System ◽  
Biologically Active ◽  
Block Method ◽  
Organic System ◽  
Organic Farming System ◽  
True Protein

The aim of the study was to assess the nutritional value of H. tuberosus tubers grown in the organic farming system in Poland and Lithuania. The work was based on field experiments carried out in 2015–2017 in Parczew (Poland) and Akademija (Lithuania). The experiments were carried out using the randomized block method in four replications. Two cultivars of Jerusalem artichoke (JA) ‘Albik’ and ‘Rubik’ were tested. After the harvest of tubers, an assessment of their quality was carried out by standard methods. Due to the relocation of JA cultivation from Central and Eastern Europe to Northeast Europe, there were changes in the chemical composition of H. tuberosus tubers. The tubers from crops in Lithuania were characterized by a lower content of inulin, crude fiber and protein, ascorbic acid, total and endogenous amino acids than in Poland, but a higher content of true protein and macroelements. Edaphic factors determined, to a greater extent than genetic factors, the nutritional value of tubers. Assessment of the influence of varietal characteristics, meteorological conditions, and geographic location on the amount of biologically active compounds in JA will allow growers and consumers to choose the most suitable cultivars.

scholarly journals Testing the Effect of Hedge Height on Perceived Safety—A Landscape Design Intervention

2021 ◽  
Vol 13 (9) ◽  
pp. 5063
Author(s):  
Katinka H. Evensen ◽  
Helena Nordh ◽  
Ramzi Hassan ◽  
Aslak Fyhri
Keyword(s):  
Field Study ◽  
Field Experiments ◽  
Landscape Design ◽  
Urban Environments ◽  
Space Management ◽  
Perceived Safety ◽  
Urban Green Spaces ◽  
Outdoor Spaces ◽  
Surrounding Areas ◽  
The Impact

Access to safe, green urban environments is important for quality of life in cities. The objective of this study is to explore the impact of a safety-enhancing landscape design measure on visitors’ experiences in an urban park. Additionally, this paper combines the use of field and virtual reality (VR) experiments, contributing methodological insights into how to evaluate safety measures in green space management and research on perceived safety. In a field experiment (n = 266), we explored whether the height of a hedge along a pathway influenced perceived safety among users. The field study showed that cutting down the hedge improved the perceived prospect of the immediate surrounding areas for female users, which again made them feel safer in the park. We developed a VR experiment for an evening scenario in the same environment (n = 19) to supplement the field study and test the effect of the intervention further. The VR experiment also found a gender effect on perceived safety, with females reporting lower perceived safety, but no effect was shown for the height of the hedge. The results in this study show that environmental attributes such as perceived prospect and concealment should be considered in the design and management of urban green spaces. Additionally, this research demonstrates an approach to conducting field experiments to test the effects of actual design interventions and then further developing these experiments using VR technology. Further research on perceived safety in outdoor spaces is needed to make use of this combined method’s potential.

scholarly journals Simulation of Daily Mean Soil Temperatures for Agricultural Land Use Considering Limited Input Data

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 441
Author(s):  
Philipp Grabenweger ◽  
Branislava Lalic ◽  
Miroslav Trnka ◽  
Jan Balek ◽  
Erwin Murer ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Input Data ◽  
Agricultural Land ◽  
Soil Column ◽  
Soil Conditions ◽  
Snow Layer ◽  
Time Step ◽  
Soil Temperatures ◽  
Dimensional Simulation ◽  
Limited Input Data

A one-dimensional simulation model that simulates daily mean soil temperature on a daily time-step basis, named AGRISOTES (AGRIcultural SOil TEmperature Simulation), is described. It considers ground coverage by biomass or a snow layer and accounts for the freeze/thaw effect of soil water. The model is designed for use on agricultural land with limited (and mostly easily available) input data, for estimating soil temperature spatial patterns, for single sites (as a stand-alone version), or in context with agrometeorological and agronomic models. The calibration and validation of the model are carried out on measured soil temperatures in experimental fields and other measurement sites with various climates, agricultural land uses and soil conditions in Europe. The model validation shows good results, but they are determined strongly by the quality and representativeness of the measured or estimated input parameters to which the model is most sensitive, particularly soil cover dynamics (biomass and snow cover), soil pore volume, soil texture and water content over the soil column.

scholarly journals An innovative technical solution to the issue of conditioning forage grasses

2021 ◽  
Vol 901 (1) ◽  
pp. 012049
Author(s):  
S A Otroshko ◽  
A V Shevtsov ◽  
N D Sharikov
Keyword(s):  
Field Experiments ◽  
Vertical Axis ◽  
Biologically Active ◽  
Technical Solution ◽  
Forage Grasses ◽  
Forage Production ◽  
Meadow Fescue ◽  
Forage Crops ◽  
High Quality Protein ◽  
Working Bodies

Abstract Acceleration of wilting of forage grasses treated during mowing by the working bodies of dynamic conditioners installed on disc mowers is a prerequisite for improving the quality of forage, primarily in terms of the concentration of high-quality protein, vitamins and other biologically active substances, as well as energy. The main working body of modern conditioning devices is a horizontal shaft rotating at a speed of 18-29 m / s with hinged beaters of various configurations placed on its surface, which ensure grass dragging along the surface of corrugated decks, through combs, etc. [1]. Such devices significantly increase the weight of the mowers, which increases their cost by about 1/3, and the use of an additional drive of the conditioner shaft leads to operational difficulties. In this regard, the search for innovative technical solutions aimed at improving this situation is a very urgent task. The article describes the design and principle of operation of a rotary conditioner with a vertical axis of rotation developed in Federal Williams Research Center of Forage Production & Agroecology for the KR-2.1M mower of the “Agramak” company, the articulated beams of which are installed directly on its discs. The mower with an innovative conditioner was tested on a mixture of reed fescue with clover of the first cut and on tetraploid meadow fescue of the second. The yield of green mass, the composition of the herbage, its height and lodging, as well as the phase of development were determined in accordance with the guidelines for conducting field experiments with forage crops. The work of the mower was evaluated according to GOST 28722-90. The article presents data on the degree of damage to treated plants and the dynamics of the rate of their dehydration.

scholarly journals On the relationship between acetone and carbon monoxide in air masses of different origin

2003 ◽  
Vol 3 (1) ◽  
pp. 1017-1049
Author(s):  
M. de Reus ◽  
H. Fischer ◽  
F. Arnold ◽  
J. de Gouw ◽  
R. Holzinger ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Carbon Monoxide ◽  
Field Experiments ◽  
Marine Boundary Layer ◽  
Biogenic Emissions ◽  
Model Calculations ◽  
Single Observation ◽  
Tropical Regions ◽  
Air Masses ◽  
Clean Air

Abstract. Carbon monoxide and acetone measurements are presented for five aircraft measurement campaigns at mid-latitudes, polar and tropical regions in the northern hemisphere. Throughout all campaigns, free tropospheric air masses, which were influenced by anthropogenic emissions, showed a similar linear relation between CO and acetone, with a slope of 21–25 pptv acetone/ppbv CO. Measurements in the anthropogenically influenced marine boundary layer revealed a slope of 13–16 pptv acetone/ppbv CO. The different slopes observed in the marine boundary layer and the free troposphere indicate that acetone is emitted by the ocean in relatively clean air masses and taken up by the ocean in polluted air masses. In the lowermost stratosphere, a good correlation between CO and acetone was observed as well, however, with a much smaller slope (~5 pptv acetone/ppbv CO) compared to the troposphere. This is caused by the longer photochemical lifetime of CO compared to acetone in the lower stratosphere, due to the increasing photolytic loss of acetone and the decreasing OH concentration with altitude. No significant correlation between CO and acetone was observed over the tropical rain forest due to the large direct and indirect biogenic emissions of acetone. The common slopes of the linear acetone-CO relation in various layers of the atmosphere, during five field experiments, makes them useful for model calculations. Often a single observation of the CO-acetone correlation, determined from stratospheric measurements, has been used in box model applications. This study shows that different slopes have to be considered for marine boundary layer, free tropospheric and stratospheric air masses, and that the CO-acetone relation cannot be used for air masses which are strongly influenced by biogenic emissions.

scholarly journals Summertime observations of elevated levels of ultrafine particles in the high Arctic marine boundary layer

2017 ◽  
Vol 17 (8) ◽  
pp. 5515-5535 ◽  
Author(s):  
Julia Burkart ◽  
Megan D. Willis ◽  
Heiko Bozem ◽  
Jennie L. Thomas ◽  
Kathy Law ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ultrafine Particles ◽  
Marine Boundary Layer ◽  
Ultrafine Particle ◽  
High Arctic ◽  
Particle Formation ◽  
Open Ocean ◽  
Biologically Active ◽  
The Arctic ◽  
Depositional Processes

Abstract. Motivated by increasing levels of open ocean in the Arctic summer and the lack of prior altitude-resolved studies, extensive aerosol measurements were made during 11 flights of the NETCARE July 2014 airborne campaign from Resolute Bay, Nunavut. Flights included vertical profiles (60 to 3000 m above ground level) over open ocean, fast ice, and boundary layer clouds and fogs. A general conclusion, from observations of particle numbers between 5 and 20 nm in diameter (N5 − 20), is that ultrafine particle formation occurs readily in the Canadian high Arctic marine boundary layer, especially just above ocean and clouds, reaching values of a few thousand particles cm−3. By contrast, ultrafine particle concentrations are much lower in the free troposphere. Elevated levels of larger particles (for example, from 20 to 40 nm in size, N20 − 40) are sometimes associated with high N5 − 20, especially over low clouds, suggestive of aerosol growth. The number densities of particles greater than 40 nm in diameter (N >  40) are relatively depleted at the lowest altitudes, indicative of depositional processes that will lower the condensation sink and promote new particle formation. The number of cloud condensation nuclei (CCN; measured at 0.6 % supersaturation) are positively correlated with the numbers of small particles (down to roughly 30 nm), indicating that some fraction of these newly formed particles are capable of being involved in cloud activation. Given that the summertime marine Arctic is a biologically active region, it is important to better establish the links between emissions from the ocean and the formation and growth of ultrafine particles within this rapidly changing environment.

scholarly journals Calculating the turbulent fluxes in the atmospheric surface layer with neural networks

2018 ◽  
Author(s):  
Lukas Hubert Leufen ◽  
Gerd Schädler
Keyword(s):  
Land Surface ◽  
Field Experiments ◽  
Climate Models ◽  
Similarity Theory ◽  
Turbulent Fluxes ◽  
Global Climate Models ◽  
Surface Model ◽  
Time Step ◽  
One Dimensional ◽  
Stability Functions

Abstract. The turbulent fluxes of momentum, heat and water vapour link the Earth's surface with the atmosphere. The correct modelling of the flux interactions between these two systems with very different time scales is therefore vital for climate (resp. Earth system) models. Conventionally, these fluxes are modelled using Monin–Obukhov similarity theory (MOST) with stability functions derived from a small number of field experiments; this results in a range of formulations of these functions and thus also in the flux calculations; furthermore, the underlying equations are non-linear and have to be solved iteratively at each time step of the model. For these reasons, we tried here a different approach, namely using an artificial neural network (ANN) to calculate the fluxes resp. the scaling quantities u* and θ*, thus avoiding explicit formulas for the stability functions. The network was trained and validated with multi-year datasets from seven grassland, forest and wetland sites worldwide using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) quasi-Newton backpropagation algorithm and six-fold cross validation. Extensive sensitivity tests showed that an ANN with six input variables and one hidden layer gave results comparable to (and in some cases even slightly better than) the standard method. Similar satisfying results were obtained when the ANN routine was implemented in a one-dimensional stand alone land surface model (LSM), opening the way to implementation in three-dimensional climate models. In case of the one-dimensional LSM, no CPU time was saved when using the ANN version, since the small time step of the standard version required only one iteration in most cases. This could be different in models with longer time steps, e.g. global climate models.

scholarly journals Transport of short-lived halocarbons to the stratosphere over the Pacific Ocean

2020 ◽  
Vol 20 (2) ◽  
pp. 1163-1181
Author(s):  
Michal T. Filus ◽  
Elliot L. Atlas ◽  
Maria A. Navarro ◽  
Elena Meneguz ◽  
David Thomson ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Lower Stratosphere ◽  
Atmospheric Transport ◽  
Convective Transport ◽  
Transport Processes ◽  
Lagrangian Model ◽  
Convection Scheme ◽  
Model Calculations ◽  
Upper Troposphere ◽  
Tropical Troposphere

Abstract. The effectiveness of transport of short-lived halocarbons to the upper troposphere and lower stratosphere remains an important uncertainty in quantifying the supply of ozone-depleting substances to the stratosphere. In early 2014, a major field campaign in Guam in the western Pacific, involving UK and US research aircraft, sampled the tropical troposphere and lower stratosphere. The resulting measurements of CH3I, CHBr3 and CH2Br2 are compared here with calculations from a Lagrangian model. This methodology benefits from an updated convection scheme that improves simulation of the effect of deep convective motions on particle distribution within the tropical troposphere. We find that the observed CH3I, CHBr3 and CH2Br2 mixing ratios in the tropical tropopause layer (TTL) are consistent with those in the boundary layer when the new convection scheme is used to account for convective transport. More specifically, comparisons between modelled estimates and observations of short-lived CH3I indicate that the updated convection scheme is realistic up to the lower TTL but is less good at reproducing the small number of extreme convective events in the upper TTL. This study consolidates our understanding of the transport of short-lived halocarbons to the upper troposphere and lower stratosphere by using improved model calculations to confirm consistency between observations in the boundary layer, observations in the TTL and atmospheric transport processes. Our results support recent estimates of the contribution of short-lived bromocarbons to the stratospheric bromine budget.

scholarly journals Turbulence fluxes and variances measured with a sonic anemometer mounted on a tethered balloon

2016 ◽  
Vol 9 (9) ◽  
pp. 4375-4386 ◽  
Author(s):  
Guylaine Canut ◽  
Fleur Couvreux ◽  
Marie Lothon ◽  
Dominique Legain ◽  
Bruno Piguet ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Frequency ◽  
Field Experiments ◽  
Sonic Anemometer ◽  
Motion Sensor ◽  
Tethered Balloon ◽  
Inertial Motion ◽  
Convective Boundary ◽  
Momentum Fluxes ◽  
Field Campaigns

Abstract. This study presents the first deployment in field campaigns of a balloon-borne turbulence probe, developed with a sonic anemometer and an inertial motion sensor suspended below a tethered balloon. This system measures temperature and horizontal and vertical wind at high frequency and allows the estimation of heat and momentum fluxes as well as turbulent kinetic energy in the lower part of the boundary layer. The system was validated during three field experiments with different convective boundary-layer conditions, based on turbulent measurements from instrumented towers and aircraft.

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