Simulated Drift Research Articles

How essential of the balance between large and small scale features to reproduce precipitation during a sudden sharp turn from drought to flood

Sudden turn from drought to flood (STDF) is a unique representation of intra-seasonal extreme events and occurs frequently. However, it is notoriously difficult to represent in climate simulations due to the accumulation of model errors. This study uses a regional climate model (RCM) with different initialization and nudging schemes to explore effective approaches for capturing a STDF event. Results show that the conventional continuous integration with single initialization cannot reproduce the STDF event, while nudging or re-initialization can. Furthermore, spectral nudging and re-initialization outperform the conventional continuous simulation in reproducing precipitation features, but grid nudging induces the largest biases for precipitation though it has the smallest biases for other meteorological elements. Scale separation analysis shows that the large-scale features of the conventional continuous simulation drift far from the actual fields and force erroneous small-scale features, whereas the nudging and re-initialization successfully prevent the model from drifting away from the forcing fields at large-scales. The different performance for simulating precipitation among spectral nudging, re-initialization and grid nudging can be attributed to that the former two methods generate their own small-scale information via the RCM, while grid nudging over-suppresses the small-scale information while retaining the large-scale features. The difference in small-scale features affects the simulation of different moisture fluxes and convergences, as well as clouds, and then results in diverse precipitation. These results illustrate that both the consistency with large-scale features and the local variability from small-scale features are both robust factors for reproducing precipitation features during extreme events using RCMs.

GROWTH ANALYSIS OF HYBRID Eucalyptus urograndis (E. grandis x E. urophylla) IN RESPONSE TO SIMULATED DRIFT OF AUXINIC HERBICIDES

ABSTRACT The aim of this study was to evaluate growth rates of E. urograndis under application of triclopyr and fluroxipyr+triclopyr herbicides. Was used a randomized block design with four replications in a factorial design (3x2x5), corresponding to herbicides (triclopyr and fluroxipyr+triclopyr), both with two doses (0.75 and 1.5% concentrations of 480 g and L-1 for triclopyr and 80+240 g and L-1 for fluroxipyr+triclopyr), plus one control (plants that did not receive herbicide application) and five evaluation dates at 15, 30, 45, 60 and 75 days after application (DAA). At 45 days after seedlings transplant, applications were performed with pressurized carbon dioxide backpack sprayer, equipped with beak tip (XR 110.02) with spray volume of 200 L ha-1 and constant pressure of 35 kgf/cm2. Were evaluated: leaf area (LA), specific leaf area (SLA), leaf area ratio (LAR), leaf weight ratio (LWR), absolute growth ratio (AGR), relative growth ratio (RGR) and net assimilatory ratio (NAR). The drift of triclopyr and fluroxipyr + triclopyr herbicide in the hybrid E. urograndis affect plant development in the beginning of the establishment. At 75 days after simulation drift of herbicides the plants showed characteristics of the symptoms of intoxication. It’s necessary to perform studies after 75 DAA to verify the complete recovery of the intoxication symptoms of E. urograndis hybrid plants resulting from the herbicide drift in the present study.

The dependence of energy dissipation on spatial resolution in a viscous-plastic sea-ice model

We present sea-ice kinetic energy budgets to quantify the relative importance of the various energy sinks in a viscous-plastic sea-ice model. To this end, we study two idealized model domains where energy dissipation associated with shear and axial (ridge/lead building) deformation can be analyzed independently. We find that when only shear deformation is present - either at the domain boundary induced by the no-slip boundary condition or within the model domain induced by gradients in the surface air stress - the energy dissipated through friction reduces in relative importance as the spatial resolution of the model is increased. In the limit where the spatial resolution tends to zero, the simulated sea ice drift tends to the analytical solution - giving us confidence in the numerical implementation of the governing differential equation. Increasing spatial resolution leads to a localization of deformation along the shear lines effectively increasing the area over which energy is input by the wind which is not compensated for by frictional shear dissipation. For instance at 40 km spatial resolution, 64% and 29% of the input power is dissipated through shear deformation and water drag respectively, while at 5 km spatial resolution 54% and 43% of the input power is dissipated by the respective processes. These values approach the respective values of 53% and 47% found analytically for this particular model configuration. The overall result is a 64% increase in the domain total sea-ice kinetic energy when the spatial resolution is increased from 40 km to 5 km due to the finer representation of shear lines. In convergence, the mean kinetic energy and potential energy do not depend meaningfully on the spatial resolution. In this case, the structure of the thickness and concentration fields effectively sets the velocity gradient near the boundary provided that the plastic deformation wave associated with the ridge building process is resolved.

Drift of 2,4-D and dicamba applied to soybean at vegetative and reproductive growth stage

ABSTRACT: The introduction of dicamba and 2,4-D-resistant soybean will increase the use of auxin herbicides for management of herbicide-resistant weeds, increasing risk of drift in non-target crops. The field experiment was conducted in 2016/17 to evaluate injury, growth, yield, germination and seeds vigor of soybean effects to simulated drift of 2,4-D and dicamba applied to soybean at the V3 and R2 growth stages. To simulate drift, 2,4-D was applied at 0; 5.16; 10.4; 20.8 e 41.5g ae ha-1 and dicamba at: 0; 3.7; 7.4; 14.9 e 29.8g ae ha-1. The injury of the dicamba is greater than 2,4-D, and the V5 stage is more susceptible to both herbicides. The greatest reductions in soybean yield follow the drift of dicamba in R2 and 2,4-D in V5. The physiological quality seeds of the soybean is reduced by dicamba and 2,4-D drift at both the V5 and R2 stages of the soybean. Soybean is highly sensitive to low rates of 2,4-D and dicamba at the vegetative or reproductive growth stages. Dicamba causes greater negative effects than 2,4-D on soybean. The low rate of 2,4-D and dicamba reduce germination and vigor seed on soybean offspring.

Walnut Response to Multiple Exposures to Simulated Drift of Bispyribac-Sodium

AbstractA field study was established to evaluate symptoms, growth, yield, and nut quality of walnut trees subjected to multiple exposures of simulated bispyribac-sodium drift. Nut yield the year following simulated drift treatment was also evaluated because tissue differentiation for future fruiting position occurs in the prior season. Bispyribac-sodium was applied four times, at weekly intervals, at 0.5% and 3% of the use rate in rice (45 g ai ha-1). Injury from the 0.5% rate exceeded 5% after three applications. In general, the severity of the symptoms peaked 14 d after last application (23% and 40% injury for 0.5% and 3% rate, respectively) and subsequently remained nearly constant over the duration of the study. Growth of shoots treated with the 0.5% rate was initially delayed during the treatment regime but recovered after treatments ended; however, walnut shoots exposed to the higher rate had fewer internodes than nontreated trees at the end of the season. No measurable reduction in walnut yield or average nut weight either in the year of exposure or in the subsequent year was observed. However, both rates negatively affected walnut kernel color in the year of exposure.

Response of Walnuts to Simulated Drift Rates of Bispyribac-Sodium, Bensulfuron-Methyl, and Propanil

AbstractA field study was established to study symptoms, growth and yield of 2-year-old walnut trees exposure to simulated drift of several herbicides commonly used in rice production. Bispyribac-sodium, bensulfuron-methyl, and propanil were applied at four rates representing 0.5%, 1%, 3% and 10% of the normal use rate in rice (45, 70, and 6725 g ai ha−1, for the three herbicides respectively). Symptoms started to appear approximately 7 days after application (DAT) and peaked 28 DAT. At that time, bispyribac-sodium caused greater injury at low drift rates (6% and 15% visual injury for 0.5% and 1% rate, respectively) compared to bensulfuron-methyl and propanil. Bispyribac-sodium also appeared to slow walnut shoot elongation compared to nontreated trees; however, no yield reductions were observed either in the year after drift exposure. The effect of bispyribac-sodium simulated drift on the yield and nut quality in the year of drift exposure was evaluated in a separate study on 3-year-old walnut trees. While no yield or nut quality reductions were observed, a linear correlation between rate of bispyribac-sodium and color, an important quality factor, was found: higher herbicide rates tended to be associated with darker kernel color. Bispyribac-sodium may damage nearby walnut orchards if drifted at significant amounts. However, it is unlikely that in a field situation bispyribac-sodium would drift at high enough levels to cause the symptoms observed from the 10% use rates in this study.

Reassessing Sea Ice Drift and Its Relationship to Long‐Term Arctic Sea Ice Loss in Coupled Climate Models

AbstractResults of an earlier study suggest that sea ice drift in climate models is unrealistic, and this has undermined confidence in model projections of “long‐term” (i.e., secular) Arctic sea ice loss. We revisit this by analyzing 22 models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5). It is shown that, when consistent temporal sampling is applied, sea ice drift speed in models and observations come into closer agreement than previously suggested. There is still considerable intermodel scatter in climatological drift speed, and we show that much of this likely relates to prescribed parameters in the sea ice models. Since 1979, observations show a long‐term positive trend of annual mean Arctic average sea ice drift speed resulting primarily from sea ice thinning, and most of the CMIP5 models qualitatively reproduce this. The simulated annual mean drift speed trends reflect strong cancellation between winter trends (which are positive in most models and in good agreement with observations) and summer trends (which are negative in most models and in poor agreement with observations). Positive Arctic average drift speed trends do not consistently coincide with positive trends of Fram Strait outflow. The simulated regional relationship between sea ice strength and drift speed changes dramatically as the Arctic transitions from full to partial ice cover, and this “sea ice extent effect” likely influences simulated summer drift speed trends. Altogether, these results highlight aspects in which models show encouraging agreement with observations, while pinpointing aspects in which models require improvement.

Numerical simulation of ionospheric convection with a global MHD simulation

A case study was conducted for simulated processes of magnetosphere-ionosphere (M-I) coupling process using a magnetohydrodynamic (MHD) simulation code developed by Tanaka (2010). We combined the MHD simulation and solar wind parameters derived from the ACE satellite, and compared the ionospheric E × B plasma drift obtained from the global MHD simulation and that obtained from the SuperDARN HF Radar Network. The simulated plasma drift was not always reproducible under a southward interplanetary magnetic field (IMF) condition. We believe that the M-I boundary conditions in the global MHD simulation includes insufficient factors for the M-I coupling process.

파랑 표류력을 고려한 선박의 파랑 중 선회성능 해석

This paper performs a numerical computation of ship maneuvering performance in waves. For this purpose, modular-type model (MMG (Mathematical Modeling Group) model) is adopted for maneuvering simulation and wave drift force is included in the equation of maneuvering motion. In order to compute wave drift force, two different seakeeping programs are used: AdFLOW based on Wave Green function method and SWAN based on Rankine panel method. When wave drift force is calculated using SWAN program, not only ship forward speed but also ship lateral speed are considered. By doing this, effects of lateral speed on wave drift force and maneuvering performance in waves are confirmed. The developed method is validated by comparing turning test results in regular waves with existing experimental data. Sensitivities of wave drift force on maneuvering performance are, also, checked.

Spring wheat response to simulated glyphosate drift

The nearly ubiquitous use of glyphosate‐resistant soybean, corn, sugar beet, and/or canola cultivars in the Northern Great Plains can result in off‐target movement to sensitive crops like spring wheat. The objective of this study was to measure the effect of simulated glyphosate drift at a concentration of 0.07 lb acid equivalent/acre on spring wheat crop injury, crop residue, and yield. Earn 0.5 CEUs in Integrated Pest Management by reading this article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/554.

Impact of rheology on probabilistic forecasts of sea ice trajectories: application for search and rescue operations in the Arctic

Abstract. We present a sensitivity analysis and discuss the probabilistic forecast capabilities of the novel sea ice model neXtSIM used in hindcast mode. The study pertains to the response of the model to the uncertainty on winds using probabilistic forecasts of ice trajectories. neXtSIM is a continuous Lagrangian numerical model that uses an elasto-brittle rheology to simulate the ice response to external forces. The sensitivity analysis is based on a Monte Carlo sampling of 12 members. The response of the model to the uncertainties is evaluated in terms of simulated ice drift distances from their initial positions, and from the mean position of the ensemble, over the mid-term forecast horizon of 10 days. The simulated ice drift is decomposed into advective and diffusive parts that are characterised separately both spatially and temporally and compared to what is obtained with a free-drift model, that is, when the ice rheology does not play any role in the modelled physics of the ice. The seasonal variability of the model sensitivity is presented and shows the role of the ice compactness and rheology in the ice drift response at both local and regional scales in the Arctic. Indeed, the ice drift simulated by neXtSIM in summer is close to the one obtained with the free-drift model, while the more compact and solid ice pack shows a significantly different mechanical and drift behaviour in winter. For the winter period analysed in this study, we also show that, in contrast to the free-drift model, neXtSIM reproduces the sea ice Lagrangian diffusion regimes as found from observed trajectories. The forecast capability of neXtSIM is also evaluated using a large set of real buoy's trajectories and compared to the capability of the free-drift model. We found that neXtSIM performs significantly better in simulating sea ice drift, both in terms of forecast error and as a tool to assist search and rescue operations, although the sources of uncertainties assumed for the present experiment are not sufficient for complete coverage of the observed IABP positions.

Molecular dynamics simulation of ion mobility in gases.

A force field molecular dynamics method is developed to directly simulate ion drift in buffer gases driven by an electric field. The ion mobility and collision cross sections (CCSs) with relevance to ion mobility spectrometry can be obtained from the simulated drift velocity in high-density buffer gases (pressure ∼50 bars) and high electric fields (∼107 V/m). Compared to trajectory methods, the advantage of the molecular dynamics method is that it can simultaneously sample the internal dynamic motions of the ion and the ion-gas collisions. For ions with less than 100 atoms, the simulated collision cross section values can be converged to within ±1%-2% by running a 100 ns simulation for 5-19 h using one computer core. By using a set of element-based Lennard-Jones parameters that are not tuned for different atomic types in different molecules, the simulated collision cross sections for 15 small molecular ions (number of atoms ranging from 17 to 85, mass ranging from 74.1 to 609.4 g/mol) are consistent with experimental values: the mean unsigned error is 2.6 Å2 for He buffer gas and 4.4 Å2 for N2 buffer gas. The sensitivity of the simulated CCS values to random diffusion, drift velocity, electric field strength, temperature, and buffer gas density is examined.

Deuterium temperature, drift velocity, and density measurements in non-Maxwellian plasmas at ASDEX Upgrade

We measure the deuterium density, the parallel drift velocity, and parallel and perpendicular temperatures (, ) in non-Maxwellian plasmas at ASDEX Upgrade. This is done by taking moments of the ion velocity distribution function measured by tomographic inversion of five simultaneously acquired spectra of -light. Alternatively, we fit the spectra using a bi-Maxwellian distribution function. The measured kinetic temperatures ( keV, keV) reveal the anisotropy of the plasma and are substantially higher than the measured boron temperature (7 keV). The Maxwellian deuterium temperature computed with TRANSP (6 keV) is not uniquely measurable due to the fast ions. Nevertheless, simulated kinetic temperatures accounting for fast ions based on TRANSP ( keV, keV) are in excellent agreement with the measurements. Similarly, the Maxwellian deuterium drift velocity computed with TRANSP (300 km s−1) is not uniquely measurable, but the simulated kinetic drift velocity accounting for fast ions agrees with the measurements (400 km s−1) and is substantially larger than the measured boron drift velocity (270 km s−1). We further find that ion cyclotron resonance heating elevates and each by 2 keV without evidence for preferential heating in the spectra. Lastly, we derive an expression for the 1D projection of an arbitrarily drifting bi-Maxwellian onto a diagnostic line-of-sight.

Turbulence-Induced Anti-Stokes Flow and the Resulting Limitations of Large-Eddy Simulation

AbstractThis study shows that the presence of Stokes drift us in the turbulent upper ocean induces a near-surface Eulerian current that opposes the Stokes drift. This current is distinct from previously studied anti-Stokes currents because it does not rely on the presence of planetary rotation or mean lateral gradients. Instead, the anti-Stokes flow arises from an interaction between the Stokes drift and turbulence. The new anti-Stokes flow is antiparallel to us near the ocean surface, is parallel to us at depth, and integrates to zero over the depth of the boundary layer. The presence of Stokes drift in large-eddy simulations (LES) is shown to induce artificial energy production caused by a combination of the new anti-Stokes flow and LES numerics. As a result, care must be taken when designing and interpreting simulations of realistic wave forcing, particularly as rotation becomes weak and/or us becomes perpendicular to the surface wind stress. The mechanism of the artificial energy production is demonstrated for a generalized LES subgrid scheme.

Simulated drift of herbicides applied alone and in tank mix in grapevine

Simulated drift of herbicides applied alone and in tank mix in grapevine

Spring Wheat Response to Simulated Glyphosate Drift

Core Ideas Drift prior to stem elongation may go unnoticed, yet producers can expect yield reductions up to 15% Drift encountered during stem elongation and the appearance of the flag leaf will result in yield losses that can exceed 85%. Symptomology of drift that occurs during heading is very innocuous, as no stunting will be observed and yellowing of leaf tissue can easily be mistaken for symptoms of Septoria leaf blotch. Glyphosate is one of the most widely used nonselective herbicides. The nearly ubiquitous use of glyphosate‐resistant soybean [Glycine max (L.) Merr.], corn (Zea mays L.), sugar beet (Beta vulgaris L.), and/or canola (Brassica napus L.) cultivars in the Northern Great Plains can, unfortunately, result in off‐target movement to sensitive crops. Off‐target movement generally exposes a sensitive crop like spring wheat (Triticum aestivum L.) to rates ranging from 1 to 10% of the applied rate. The objective of this study was to measure the effect of simulated glyphosate drift at a concentration of 0.07 lb acid equivalent/acre on spring wheat crop injury, crop residue, and yield. At 28 d after treatment (DAT), crop injury varied from none to 67.5%. Across years, the application at Zadoks GS17 resulted in the most crop injury, with symptoms typical of glyphosate injury as the crop was severely stunted and yellow at 28 DAT, resulting in yield losses between 82 and 96% of the untreated control. Glyphosate residue could be detected at 7 DAT for all treatments, but the number of false negatives increased to over half at 21 DAT. No clear quantitative relationship could be discerned from the amount of glyphosate residue detected and the application timing.

Self-consistency of electron-THF cross sections using electron swarm techniques.

The drift velocity and first Townsend ionization coefficient of electrons in gaseous tetrahydrofuran are measured over the range of reduced electric fields 4-1000 Td using a pulsed-Townsend technique. The measured drift velocities and Townsend ionization coefficients are subsequently used, in conjunction with a multi-term Boltzmann equation analysis, as a further discriminative assessment on the accuracy and completeness of a recently proposed set of electron-THF vapor cross sections. In addition, the sensitivity of the transport coefficients to uncertainties in the existing cross sections is presented. As a result of that analysis, a refinement of the momentum transfer cross section for electron-THF scattering is presented, along with modifications to the neutral dissociation and dissociative electron attachment cross sections. With these changes to the cross section database, we find relatively good self-consistency between the measured and simulated drift velocities and Townsend coefficients.

How to reduce long-term drift in present-day and deep-time simulations?

Climate models are often affected by long-term drift that is revealed by the evolution of global variables such as the ocean temperature or the surface air temperature. This spurious trend reduces the fidelity to initial conditions and has a great influence on the equilibrium climate after long simulation times. Useful insight on the nature of the climate drift can be obtained using two global metrics, i.e. the energy imbalance at the top of the atmosphere and at the ocean surface. The former is an indicator of the limitations within a given climate model, at the level of both numerical implementation and physical parameterisations, while the latter is an indicator of the goodness of the tuning procedure. Using the MIT general circulation model, we construct different configurations with various degree of complexity (i.e. different parameterisations for the bulk cloud albedo, inclusion or not of friction heating, different bathymetry configurations) to which we apply the same tuning procedure in order to obtain control runs for fixed external forcing where the climate drift is minimised. We find that the interplay between tuning procedure and different configurations of the same climate model provides crucial information on the stability of the control runs and on the goodness of a given parameterisation. This approach is particularly relevant for constructing good-quality control runs of the geological past where huge uncertainties are found in both initial and boundary conditions. We will focus on robust results that can be generally applied to other climate models.

SUNFLOWER PLANT RESPONSE TO SIMULATED DRIFT OF GLYPHOSATE AND TRINEXAPAC-ETHYL

ABSTRACT Chemical ripeners are frequently used on sugarcane crops in order to increase profitability. However, the drift of these products to neighbouring fields can expose susceptible non-target plants, such as sunflower, to these agents causing indirect impacts on growth and development. Therefore, this study aimed to assess the toxicity characterize possible changes in the growth of sunflower plants exposed to simulated drift of the ripeners glyphosate and trinexapac-ethyl. For each ripener, the following doses were used: glyphosate (0 (control), 3.6, 7.2, 14.4, 28.8 and 86.4 g a.e ha-1) and trinexapac-ethyl (0, 3.12, 6.25, 12.50, 25 and 75 g a.i ha-1). The effects of these products on plant height, number of leaves, leaf area, stem diameter and dry matter (leaves, stem, flower, root, shoot and total) were evaluated. We also conducted a visual analysis of symptoms of phytotoxicity after exposure. The effects of the ripeners on sunflower plants varied depending on the type of agent used and the dose. Plants treated with glyphosate showed altered growth patterns, indicating high sensitivity of these plants to the herbicide. With increasing doses, glyphosate drift promoted lower growth and development of sunflower plants and negatively affected productivity. Nevertheless, trinexapac-ethyl drift, in the evaluated doses, did not affect sunflower plants.

A CMOS compatible micro-Pirani vacuum sensor based on mutual heat transfer with 5-decade operating range and 0.3 Pa detection limit

A Pirani vacuum sensor based on mutual heating between a heater and a distinct temperature probe, separated by a 5μm air gap, is proposed. The sensor is fabricated by applying a simple post-processing procedure to chips designed and fabricated using the BCD6s process (Bipolar-CMOS-DMOS) of STMicroelectronics. The sensor layout has been optimized to exploit the layers of the original process in order to enhance the sensor performance. The sensors exhibit a resolution better than 0.4Pa from nearly 0.3Pa to 1kPa and better than 50Pa from 1kPa to 100kPa. The sensor response at the lower extreme of the pressure interval is marked by an offset voltage, which is three orders of magnitude smaller than the full-scale value. Finite Element Method simulations suggest that the offset is due to pressure-independent heat transfer due to radiation and conduction through the substrate. The simulated equivalent offset drift is 50MPa/K.