scholarly journals The Contributions to the Explosive Growth of PM<sub>2.5</sub> Mass due to Aerosols-Radiation Feedback and Further Decrease in Turbulent Diffusion during a Red-alert Heavy Haze in JING-JIN-JI in China

2018 ◽  
Author(s):  
Hong Wang ◽  
Xioaye Zhang ◽  
Yao Peng ◽  
Hongli Liu ◽  
Meng Zhang ◽  
...  
Keyword(s):  
Turbulent Diffusion ◽  
Model Errors ◽  
Turbulent Diffusion Coefficient ◽  
Chemical Tracers ◽  
Haze Pollution ◽  
Study Results ◽  
Pbl Scheme ◽  
Local Inversion ◽  
Reasonable Description ◽  
Radiation Feedback

Abstract. The explosive growth (EG) of PM2.5 mass usually resulted in PM2.5 extreme levels and severe haze pollution in east China and they were generally underestimated by current atmospheric chemical models. Based on the atmospheric chemical model GRPAES_CUACE, three experiments of background (EXP_bk), normal turbulent diffusion and aerosols feedback (EXP_td_af), and retaining 20 % of normal turbulent diffusion of chemical tracers of EXP_td_af (EXP_td20_af) are designed to study the contributions to the EG of PM2.5 due to aerosols-radiation feedback (AF) and further decrease in turbulent diffusion (DTD) focusing on a red-alert heavy haze in JING-JIN-JI of China. The study results showed that turbulent diffusion coefficient (DC) calculated by EXP_bk is about 60–70 m2/s on clear day and 30–35 m2/s on haze day. This difference of DC was not enough to discriminate the unstable atmosphere on clear day and extreme stable atmosphere during EG stage of PM2.5, and the inversion calculated by EXP_bk was obviously weaker than the actual atmosphere of sounding observation on haze day. This led to 40–51 % underestimation of PM2.5 EG by EXP_bk; AF reduced about 43–57 % of DC during EG stage of PM2.5, which strengthened the local inversion obviously on haze day and local inversion by EXP_td_af was much closer to the sounding observation than that by EXP_bk. This resulted in 20–25 % reduction of model errors of PM2.5 and it was as low as −16 to −11 %. However, the inversion by EXP_td_af was still weaker than the actual observation and AF could not solve all the problems of PM2.5 underestimation. Based on EXP_td_af, 80 % DTD of chemical tracers resulted in a near-zero turbulent diffusion named as turbulent intermittent atmosphere state in EXP_td20_af resulting in a further 14–20 % reduction of PM2.5 underestimation and the negative PM2.5 errors of was reduced to −11 to 2 % during the EG stage of PM2.5. The combined effects of AF and DTD solved over 79 % underestimation of PM2.5 EG in this case study. The results showed that the online calculation of aerosol-radiation feedback and a further improving arithmetic of PBL scheme focusing on extreme stable atmosphere stratification are indispensable for reasonable description of local turbulent intermittent and more accurate prediction of PM2.5 EG and high levels during the severe haze in Jing-Jin-Ji in China.

scholarly journals Contributions to the explosive growth of PM<sub>2.5</sub> mass due to aerosol–radiation feedback and decrease in turbulent diffusion during a red alert heavy haze in Beijing–Tianjin–Hebei, China

2018 ◽  
Vol 18 (23) ◽  
pp. 17717-17733 ◽  
Author(s):  
Hong Wang ◽  
Yue Peng ◽  
Xiaoye Zhang ◽  
Hongli Liu ◽  
Meng Zhang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Atmospheric Chemistry ◽  
Turbulent Diffusion ◽  
Growth Stage ◽  
Eastern China ◽  
Turbulent Diffusion Coefficient ◽  
Chemical Tracers ◽  
Haze Pollution ◽  
Local Inversion ◽  
Radiation Feedback

Abstract. The explosive growth of PM2.5 mass usually results in extreme PM2.5 levels and severe haze pollution in eastern China, and is generally underestimated by current atmospheric chemistry models. Based on one such model, GRAPES_CUACE, three sensitivity experiments – a “background” experiment (EXP1), an “online aerosol feedback” experiment (EXP2), and an “80 % decrease in the turbulent diffusion coefficient of chemical tracers” experiment, based on EXP2 (EXP3) – were designed to study the contributions of the aerosol–radiation feedback (AF) and the decrease in the turbulent diffusion coefficient to the explosive growth of PM2.5 during a “red alert” heavy haze event in China's Jing–Jin–Ji (Beijing–Tianjin–Hebei) region. The results showed that the turbulent diffusion coefficient calculated by EXP1 was about 60–70 m−2 s−1 on a clear day and 30–35 m−2 s−1 on a haze day. This difference in the diffusion coefficient was not enough to distinguish between the unstable atmosphere on the clear day and the extremely stable atmosphere during the PM2.5 explosive growth stage. Furthermore, the inversion calculated by EXP1 was obviously weaker than the actual inversion from sounding observations on the haze day. This led to a 40 %–51 % underestimation of PM2.5 by EXP1; the AF decreased the diffusion coefficient by about 43 %–57 % during the PM2.5 explosive growth stage, which obviously strengthened the local inversion. In addition, the local inversion indicated by EXP2 was much closer to the sounding observations than that indicated by EXP1. This resulted in a 20 %–25 % reduction of PM2.5 negative errors in the model, with errors as low as −16 % to −11 % in EXP2. However, the inversion produced by EXP2 was still weaker than the actual observations, and the AF alone could not completely explain the PM2.5 underestimation. Based on EXP2, the 80 % decrease in the turbulent diffusion coefficient of chemical tracers in EXP3 resulted in near-zero turbulent diffusion, referred to as a “turbulent intermittence” atmospheric state, which subsequently resulted in a further 14 %–20 % reduction of the PM2.5 underestimation; moreover, the negative PM2.5 errors were reduced to −11 % to 2 %. The combined effects of the AF and the decrease in the turbulent diffusion coefficient explained over 79 % of the underestimation of the explosive growth of PM2.5 in this study. The results show that online calculation of the AF is essential for the prediction of PM2.5 explosive growth and peaks during severe haze in China's Jing–Jin–Ji region. Furthermore, an improvement in the planetary boundary layer scheme with respect to extremely stable atmospheric stratification is essential for a reasonable description of local “turbulent intermittence” and a more accurate prediction of PM2.5 explosive growth during severe haze in this region of China.

Understanding core tungsten (W) transport and control in an improved high-performance fully non-inductive discharge on EAST

2021 ◽  
Author(s):  
Shengyu Shi ◽  
Jiale Chen ◽  
Clarisse Bourdelle ◽  
Xiang Jian ◽  
Tomas Odstrcil ◽  
...  
Keyword(s):  
Density Profile ◽  
Turbulent Diffusion ◽  
High Performance ◽  
Electron Cyclotron Resonance ◽  
Transport Coefficients ◽  
Linear Instability ◽  
Electron Cyclotron Resonance Heating ◽  
Plasma Parameters ◽  
Turbulent Diffusion Coefficient ◽  
Inductive Discharge

Abstract The behavior of heavy/high-Z impurity tungsten (W) in an improved high-performance fully non-inductive discharge on EAST with ITER-like divertor (ILD) is analyzed. It is found that W could be well controlled. The causes of no W accumulation are clarified by analyzing the background plasma parameters and modeling the W transport. It turns out that the electron temperature (T_e) and its gradient are usually high while the toroidal rotation and density peaking of the bulk plasma are small. In this condition, the modeled W turbulent diffusion coefficient is big enough to offset the total turbulent and neoclassical pinch, so that W density profile for zero particle flux will not be very peaked. Combining NEO and TGLF for the W transport coefficient and the impurity transport code STRAHL, not only the core W density profile is predicted but also the radiated information mainly produced by W in the experiment can be closely reconstructed. At last, the physics of controlling W accumulation by electron cyclotron resonance heating (ECRH) is illustrated considering the effects of changed T_e by ECRH on ionization balance and transport of W. It shows that the change of ionization and recombination balance by changed T_e is not enough to explain the experimental observation of W behavior, which should be attributed to the changed W transport. By comparing the W transport coefficients in two kinds of plasmas with different T_e profiles, it is shown that high T_e and its gradient play a key role to generate large turbulent diffusion through increasing the growth rate of linear instability so that W accumulation is prevented.

scholarly journals A comprehensive assessment of land surface-atmosphere interactions in a WRF/Urban modeling system for Indianapolis, IN

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Daniel P. Sarmiento ◽  
Kenneth J. Davis ◽  
Aijun Deng ◽  
Thomas Lauvaux ◽  
Alan Brewer ◽  
...  
Keyword(s):  
Land Surface ◽  
Model Comparison ◽  
Urban Canopy ◽  
Heat Fluxes ◽  
Meteorological Variables ◽  
Model Errors ◽  
Urban Land Cover ◽  
Model Configuration ◽  
Pbl Scheme ◽  
Physics Ensemble

As part of the Indianapolis Flux (INFLUX) experiment, the accuracy and biases of simulated meteorological fields were assessed for the city of Indianapolis, IN. The INFLUX project allows for a unique opportunity to conduct an extensive observation-to-model comparison in order to assess model errors for the following meteorological variables: latent heat and sensible heat fluxes, air temperature near the surface and in the planetary boundary layer (PBL), wind speed and direction, and PBL height. In order to test the sensitivity of meteorological simulations to different model packages, a set of simulations was performed by implementing different PBL schemes, urban canopy models (UCMs), and a model subroutine that was created in order to reduce an inherent model overestimation of urban land cover. It was found that accurately representing the amount of urban cover in the simulations reduced the biases in most cases during the summertime (SUMMER) simulations. The simulations that used the BEP urban canopy model and the Bougeault & Lacarrere (BouLac) PBL scheme had the smallest biases in the wintertime (WINTER) simulations for most meteorological variables, with the exception being wind direction. The model configuration chosen had a larger impact on model errors during the WINTER simulations, whereas the differences between most of the model configurations during the SUMMER simulations were not statistically significant. By learning the behaviors of different PBL schemes and urban canopy models, researchers can start to understand the expected biases in certain model configurations for their own simulations and have a hypothesis as to the potential errors and biases that might occur when using a multi-physics ensemble based modeling approach.

scholarly journals Modeling inflatable fabric with undevelopable surfaces by motion folding method

2019 ◽  
Vol 14 ◽  
pp. 155892501988640
Author(s):  
Xiao-Shun Zhao ◽  
He Jia ◽  
Zhihong Sun ◽  
Li Yu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Numerical Study ◽  
Technical Problem ◽  
Three Dimensional ◽  
Element Model ◽  
Model Errors ◽  
Folding Model ◽  
Study Results ◽  
The Stability

At present, most space inflatable structures are composed of flexible inflatable fabrics with complex undevelopable surfaces. It is difficult to establish a multi-dimensional folding model for this type of structure. To solve this key technical problem, the motion folding method is proposed in this study. First, a finite element model with an original three-dimensional surface was flattened with a fluid structure interaction algorithm. Second, the flattened surface was folded based on the prescribed motion of the node groups, and the final folding model was obtained. The fold modeling process of this methodology was consistent with the actual folding processes. Because the mapping relationship between the original finite element model and the final folding model was unchanged, the initial stress was used to modify the model errors during folding process of motion folding method. The folding model of an inflatable aerodynamic decelerator, which could not be established using existing folding methods, was established by using motion folding method. The folding model of the inflatable aerodynamic decelerator showed that the motion folding method could achieve multi-dimensional folding and a high spatial compression rate. The stability and regularity of the inflatable aerodynamic decelerator numerical inflation process and the consistency of the inflated and design shapes indicated the reliability, applicability, and feasibility of the motion folding method. The study results could provide a reference for modeling complex inflatable fabrics and promote the numerical study of inflatable fabrics.

Optical studies on the turbulent motion of solid particles in a pipe flow

1991 ◽  
Vol 231 ◽  
pp. 665-688 ◽  
Author(s):  
James B. Young ◽  
Thomas J. Hanratty
Keyword(s):  
Diffusion Coefficient ◽  
Particle Velocity ◽  
Turbulent Diffusion ◽  
Slip Velocity ◽  
Rate Of Change ◽  
Solid Particles ◽  
Mean Square ◽  
Turbulent Diffusion Coefficient ◽  
Fluid Turbulence ◽  
The Mean

An extension of an axial viewing optical technique (first used by Lee, Adrian & Hanratty) is described which allows the determination of the turbulence characteristics of solid particles being transported by water in a pipe. Measurements are presented of the mean radial velocity, the mean rate of change radial velocity, the mean-square of the radial and circumferential fluctuations, the Eulerian turbulent diffusion coefficient, and the Lagrangian turbulent diffusion coefficient. A particular focus is to explore the influence of slip velocity for particles which have small time constants. It is found that with increasing slip velocity the magnitude of the turbulent velocity fluctuations remains unchanged but that the turbulent diffusivity decreases. The measurements of the average rate of change of particle velocity are consistent with the notion that particles move from regions of high fluid turbulence to regions of low fluid turbulence. Measurements of the root-mean-square of the fluctuations of the rate of change of particle velocity allow an estimation of the average magnitude of the particle slip in a highly turbulent flow, which needs to be known to analyse the motion of particles not experiencing a Stokes drag.

scholarly journals Evolution of the sun with mixing by hydrodynamic instabilities

1984 ◽  
Vol 105 ◽  
pp. 523-524
Author(s):  
Wai-Yuen Law ◽  
E. Knobloch ◽  
H.C. Spruit
Keyword(s):  
Diffusion Coefficient ◽  
Turbulent Diffusion ◽  
The Sun ◽  
Hydrodynamic Instabilities ◽  
Constant Multiple ◽  
Turbulent Diffusion Coefficient

Following Schatzman and Maeder (1981) we compute the evolution of the sun with partial mixing by hydrodynamic instabilities. Instead of simply assuming a turbulent diffusion coefficient which is a constant multiple of the viscosity, we incorporate some of the properties of hydrodynamic instabilities. This puts limits on the amount of diffusion that can be obtained, and makes it dependent on time and position in the star.

scholarly journals The role of magnetic fields for planetary formation

2008 ◽  
Vol 4 (S259) ◽  
pp. 249-258 ◽  
Author(s):  
Anders Johansen
Keyword(s):  
Magnetic Fields ◽  
Turbulent Diffusion ◽  
Planet Formation ◽  
High Pressures ◽  
Mixing Time ◽  
Zonal Flow ◽  
Coherence Time ◽  
Maxwell Stress ◽  
Turbulent Diffusion Coefficient

AbstractThe role of magnetic fields for the formation of planets is reviewed. Protoplanetary disc turbulence driven by the magnetorotational instability has a huge influence on the early stages of planet formation. Small dust grains are transported both vertically and radially in the disc by turbulent diffusion, counteracting sedimentation to the mid-plane and transporting crystalline material from the hot inner disc to the outer parts. The conclusion from recent efforts to measure the turbulent diffusion coefficient of magnetorotational turbulence is that turbulent diffusion of small particles is much stronger than naively thought. Larger particles – pebbles, rocks and boulders – get trapped in long-lived high pressure regions that arise spontaneously at large scales in the turbulent flow. These gas high pressures, in geostrophic balance with a sub-Keplerian/super-Keplerian zonal flow envelope, are excited by radial fluctuations in the Maxwell stress. The coherence time of the Maxwell stress is only a few orbits, where as the correlation time of the pressure bumps is comparable to the turbulent mixing time-scale, many tens or orbits on scales much greater than one scale height. The particle overdensities contract under the combined gravity of all the particles and condense into gravitationally bound clusters of rocks and boulders. These planetesimals have masses comparable to the dwarf planet Ceres. I conclude with thoughts on future priorities in the field of planet formation in turbulent discs.

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