scholarly journals Surface Layer Turbulent Characteristics over the Complex Terrain of the Loess Plateau Semiarid Region

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zhida Zhang ◽  
Jiening Liang ◽  
Min Zhang ◽  
Qi Guo ◽  
Lei Zhang
Keyword(s):  
Surface Layer ◽  
Transfer Coefficient ◽  
Loess Plateau ◽  
Turbulence Intensity ◽  
Complex Terrain ◽  
Semiarid Region ◽  
The Loess Plateau ◽  
Mean Values ◽  
The Mean ◽  
Standard Deviations

Surface layer turbulence has an important influence on land-air interactions and pollutant dispersion, and studying the characteristics of surface layer turbulence in complex terrain can contribute to understanding land-air interactions, improving model surface layer parameterization, and enhancing pollution prediction capabilities. The surface layer turbulence observations from the Semi-Arid Climate and Environment Observatory (SACOL) of Lanzhou University in 2008 were processed in this study. High-quality turbulence parameters were calculated, the statistical and transfer characteristics of turbulence were analyzed, and the formation of turbulence was assessed in terms of dynamics and thermodynamics. The atmospheric stability in the semiarid region of the Loess Plateau is basically dominated by neutral/near-neutral and weakly unstable/weakly stable conditions; this pattern is significantly different from the preponderance of unstable and stable layers at other sites. The turbulence intensity differs significantly in both the horizontal and vertical directions and basically shows the relationship I u ≈ I v > I w . The mean values of I u and I v are 0.42 and 0.40, respectively, and the mean value of I w is 0.14, which is different from the general pattern of I u > I v > I w , indicating that the turbulence intensity at SACOL is characterized by a large lateral wind contribution. The dimensionless standard deviations of the nonneutral wind velocity components satisfy the “1/3rd law,” and the dimensionless standard deviations of u, v , and w components are 3.35, 2.98, and 1.26, respectively, in the semiarid Loess Plateau. These values are larger than those over flat terrain. The contribution of the shear term to the formation of turbulence is greater than that of the buoyancy term, and the mean annual values of the shear term and the buoyancy in the kinetic energy budget equation in SACOL are 47.94 × 10−4 m2·s−3 and 11.32 × 10−4 m2·s−3, respectively. The annual mean values of the momentum transfer coefficient C D and the heat transfer coefficient C H under near-neutral conditions are 8.54 × 10−3 and 2.52 × 10−3, respectively.

scholarly journals On the factors influencing surface-layer energy closure and their seasonal variability over the semi-arid Loess Plateau of Northwest China

2012 ◽  
Vol 16 (3) ◽  
pp. 893-910
Author(s):  
X. Xiao ◽  
H. C. Zuo ◽  
Q. D. Yang ◽  
S. J. Wang ◽  
L. J. Wang ◽  
...  
Keyword(s):  
Surface Layer ◽  
Energy Balance ◽  
Atmospheric Turbulence ◽  
Loess Plateau ◽  
Turbulence Intensity ◽  
Source Area ◽  
Northwest China ◽  
The Impact ◽  
Semi Arid

Abstract. The energy observed in the surface layer, when using eddy-covariance techniques to measure turbulent fluxes, is not balanced. Important progress has been made in recent years in identifying potential reasons for this lack of closure in the energy balance, but the problem is not yet resolved. In this paper, long-term data that include output of tower, radiation, surface turbulence flux and soil measurement collected from September 2006 to August 2010 in the Semi-Arid Climate Change and Environment Observatory, Lanzhou University, in the semi-arid Loess Plateau of Northwest China, were analysed, focusing on the seasonal characteristics of the surface energy and the factors that have impact on the energy balance closure (EBC). The analysis shows that (1) the long-term observations are successful; the interaction between the land and the atmosphere in semi-arid climates can be represented by the turbulent transport of energy. In addition, even though the residual is obvious, this suggests that the factors that impact the EBC are stable, and their seasonal variations are identical. The analysis also shows that (2) four factors have obvious impact on the EBC: the diverse schemes for surface soil heat flux, the flux contribution from the target source area, the low-frequency part of the turbulence spectra, and the strength of atmospheric turbulence motion. The impact of these four factors on the EBC are similar in all seasons. Lastly, the results indicate that (3) atmospheric turbulence intensity is a very important factor in terms of its impact on the EBC. The relative turbulence intensity, RIw, characterises the strength of atmospheric turbulence motion, and is found to exert a noticeable impact on the EBC; in all seasons, the EBC is increased when the relative turbulence intensity is enlarged.

scholarly journals Comparison of the Reactive Scalar Gradient Evolution between Homogeneous MILD Combustion and Premixed Turbulent Flames

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7677
Author(s):  
Hazem S.A.M. Awad ◽  
Khalil Abo-Amsha ◽  
Umair Ahmed ◽  
Nilanjan Chakraborty
Keyword(s):  
Strain Rate ◽  
Turbulence Intensity ◽  
Premixed Flames ◽  
Premixed Flame ◽  
Normal Strain ◽  
Mean Values ◽  
Mild Combustion ◽  
The Mean ◽  
Displacement Speed ◽  
Reactive Scalar

Moderate or intense low-oxygen dilution (MILD) combustion is a novel combustion technique that can simultaneously improve thermal efficiency and reduce emissions. This paper focuses on the differences in statistical behaviours of the surface density function (SDF = magnitude of the reaction progress variable gradient) between conventional premixed flames and exhaust gas recirculation (EGR) type homogeneous-mixture combustion under MILD conditions using direct numerical simulations (DNS) data. The mean values of the SDF in the MILD combustion cases were found to be significantly smaller than those in the corresponding premixed flame cases. Moreover, the mean behaviour of the SDF in response to the variations of turbulence intensity were compared between MILD and premixed flame cases, and the differences are explained in terms of the strain rates induced by fluid motion and the ones arising from flame displacement speed. It was found that the effects of dilatation rate were much weaker in the MILD combustion cases than in the premixed flame cases, and the reactive scalar gradient in MILD combustion cases preferentially aligns with the most compressive principal strain-rate eigendirection. By contrast, the reactive scalar gradient preferentially aligned with the most extensive principal strain-rate eigendirection within the flame in the premixed flame cases considered here, but the extent of this alignment weakened with increasing turbulence intensity. This gave rise to a predominantly positive mean value of normal strain rate in the premixed flames, whereas the mean normal strain rate remained negative, and its magnitude increased with increasing turbulence intensity in the MILD combustion cases. The mean value of the reaction component of displacement speed assumed non-negligible values in the MILD combustion cases for a broader range of reaction progress variable, compared with the conventional premixed flames. Moreover, the mean displacement speed increased from the unburned gas side to the burned gas side in the conventional premixed flames, whereas the mean displacement speed in MILD combustion cases decreased from the unburned gas side to the middle of the flame before increasing mildly towards the burned gas side. These differences in the mean displacement speed gave rise to significant differences in the mean behaviour of the normal strain rate induced by the flame propagation and effective strain rate, which explains the differences in the SDF evolution and its response to the variation of turbulence intensity between the conventional premixed flames and MILD combustion cases. The tangential fluid-dynamic strain rate assumed positive mean values, but it was overcome by negative mean values of curvature stretch rate to yield negative mean values of stretch rate for both the premixed flames and MILD combustion cases. This behaviour is explained in terms of the curvature dependence of displacement speed. These findings suggest that the curvature dependence of displacement speed and the scalar gradient alignment with local principal strain rate eigendirections need to be addressed for modelling EGR-type homogeneous-mixture MILD combustion.

156. The composition of milk and whey, with special reference to the partition of calcium and phosphorus

1937 ◽  
Vol 8 (2) ◽  
pp. 173-194 ◽  
Author(s):  
E. R. Ling
Keyword(s):  
Special Reference ◽  
Cold Storage ◽  
Analytical Data ◽  
Special Treatment ◽  
Mean Values ◽  
Rennet Coagulation ◽  
The Mean ◽  
Calcium And Phosphorus ◽  
Standard Deviations

1. The means and standard deviations of analytical data obtained from fifty-four samples of mixed milk (alternate a.m. and p.m.) and whey from the College herd of Dairy Shorthorns are presented in Table I. The samples were taken at intervals during the period late September 1935 to November 1936.2. While no outstanding differences in composition are evident between morning and evening samples, the time of rennet coagulation was appreciably greater with the evening's samples. Evidence is presented to show that the longer time of cold storage of these samples must be regarded as a contributory cause of this effect.3. In the discussion of the mean values, special treatment has been given to the partition of calcium and phosphorus between the four phases, soluble and insoluble, organic and inorganic. The caseinogen values are examined in the light of current theories.

scholarly journals Radiosity Approach for the Shortwave Surface Radiation Balance in Complex Terrain

2009 ◽  
Vol 66 (9) ◽  
pp. 2900-2912 ◽  
Author(s):  
Nora Helbig ◽  
Henning Löwe ◽  
Michael Lehning
Keyword(s):  
Complex Terrain ◽  
Gaussian Approximation ◽  
Three Dimensional ◽  
Gaussian Random Fields ◽  
Surface Radiation ◽  
Radiation Balance ◽  
Length Scales ◽  
Mean Values ◽  
Terrain Effects ◽  
The Mean

Abstract The influence of topography on the radiation balance in complex terrain has so far been investigated either with very simple or very sophisticated approaches that are limited, respectively, by an uncontrolled spatial representation of radiative fluxes or heavy computational efforts. To bridge this gap in complexity, this paper proposes the radiosity approach, well known in computer graphics, to study anisotropic reflections of radiation in complex terrain. To this end the radiosity equation is rederived in the context of three-dimensional radiative transfer. The discretized equation is solved by means of an adapted version of progressive refinement iteration. To systematically study terrain effects, the geometrical disorder provided by the topography is considered in its simplest approximation by Gaussian random fields. These model topographies capture the most important length scales of complex terrain, namely a typical elevation and a typical valley width via the variance and the correlation length of the field, respectively. The mean reflected radiation is computed as a function of these length scales and sun elevation, thereby explicitly addressing finite system sizes and grid resolutions. A comparison with an isotropic parameterization of terrain reflections reveals that mean values are similar whereas spatial distributions vary remarkably. It is also shown that the mean reflected radiation in real topography is reasonably well characterized by the Gaussian approximation. As a final application of the method, the effective albedo of a topography is shown to vary with sun elevation and domain-averaged albedo, leading to albedo differences up to 0.025.

scholarly journals Exploring the knowledge of social media platforms among higher education institute students’ of Rangpur, Bangladesh

2020 ◽  
pp. 1-5 ◽  
Author(s):  
Md. Tabiur Rahman Prodhan ◽  
Md. Nazrul Islam ◽  
Md. Sajjat Hossain
Keyword(s):  
Higher Education ◽  
Social Media ◽  
Mean Values ◽  
Wide Range ◽  
Dependent Variables ◽  
Social Media Platforms ◽  
The Mean ◽  
R Value ◽  
Standard Deviations

Social media (SM) is one of the best indicators of the technological era. Nowadays people are witnessing the rapid increase of SM in almost every field of our lives from education to politics, society, and economics. It attracts all ages of people. Especially students show an intense interest in social media. The purpose of the study was to know the most preferred SM and the using pattern knowledgeability of respondents regarding various social media platforms (SMPs). A questionnaire-based survey was conducted over 100 students (60 males and 40 females) who were selected randomly from two largest universities in Rangpur, northern part of Bangladesh, studying in undergraduate and postgraduate programs in 2019 between ages 18 and 26. 95% of the respondents used different social media platforms where the top preferred social media platforms are Facebook (88%), YouTube (81%), and IMO (45%). The mean values of the respondents' using pattern knowledgeability level were between 4.46 and 1.88, with standard deviations ranging from 1.10 to 1.83. Most of the respondents have enough using pattern knowledgeability of being a user of Facebook with a wide range of mean scores in both the variables. Respondents have less using pattern knowledgeability of being a user of Viber with a tight range of mean scores in both the variables. All the dependent variables (features), except one (r-value 0.253), showed positive and significant correlations with the usage period where both the features of Twitter have the highest positive significance (r-value 0.945, 0.941 respectively). These scores were significant at p<0.05 level of probability.

scholarly journals Soil Moisture Estimation and Its Influencing Factors Based on Temporal Stability on a Semiarid Sloped Forestland

2021 ◽  
Vol 9 ◽  
Author(s):  
Mingzhu Xu ◽  
Guoce Xu ◽  
Yuting Cheng ◽  
Zhiqiang Min ◽  
Peng Li ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Temporal Stability ◽  
Relative Difference ◽  
Root Density ◽  
Sand Content ◽  
The Loess Plateau ◽  
Factors Affecting ◽  
Dry Seasons ◽  
The Mean ◽  
Main Factors

Soil water content (SWC) plays a crucial role in the hydrological cycle and ecological restoration in arid and semi-arid areas. Studying the temporal stability of SWC spatial distribution is a requirement for the dynamic monitoring of SWC and the optimization of water resource management. The SWC in a Pinus tabulaeformis Carr. forest on the slope of the Loess Plateau of China were analyzed in five soil layers (0–100 cm with an interval of 20 cm) in the rainy and dry seasons from July 2014 to November 2017. The mean SWC was estimated and the main factors affecting the temporal stability of the SWC were further analyzed. Results showed that the SWC had strong temporal stability during the two seasons for several consecutive years. The temporal stability of SWC and the number of representative locations varied with season and depth. The elevation, soil total phosphorus (STP), clay, silt, or sand content of the representative locations approached the corresponding mean value of the study area. A single representative location accurately represented the mean SWC for the five depths in the rainy and dry seasons (RMSE &lt;2%; rainy season: 0.81 &lt; R2 &lt; 0.94; dry season: 0.63 &lt; R2 &lt; 0.83; p &lt; 0.01). The mean relative difference (MRD) and the relative difference standard deviation (SDRD) changed with the seasons and were significantly correlated with elevation, root density, and sand and silt content in two seasons (p &lt; 0.05). Elevation, root density, and sand content were the main factors influencing the change of SWC temporal stability in different seasons. The results provide scientific guidance to monitor SWC by using a small number of locations and enrich our understanding of the factors affecting the temporal stability of SWC in the rainy and dry seasons of the Loess Plateau of China.

scholarly journals Factors Affecting Weight Gain in Nelore Calves from Birth to Weaning in the Bolivian Tropic

2021 ◽  
Vol 10 (4) ◽  
pp. 33
Author(s):  
Ikeda Atsuko ◽  
Montellano-Paco Arturo ◽  
Barbona Ivana ◽  
Marini Roberto Pablo
Keyword(s):  
Average Daily Gain ◽  
Live Weight ◽  
Santa Cruz ◽  
Male And Female ◽  
Mean Values ◽  
Factors Affecting ◽  
Individual Weight ◽  
The Mean ◽  
Standard Deviations ◽  
Daily Gain

Retrospective data corresponding to the period between 2002 and 2018 were used, belonging to the Cooperativa Agropecuaria Integral San Juan de Yapacan&iacute;, Santa Cruz, Bolivia. Data corresponding to 663 male and female calves born to primiparous and multiparous cows were used. The calves had 13 individual weight controls. The calves had 13 individual weight controls. Variables used: Date of birth, Calf live weight at birth in kg, Calf live weight at weaning in kg, Average daily gain in kg, Live weight of cow in kg, Number of calving of cows. The mean values and standard deviations of the weights at birth were 35.1 &plusmn; 4.6 kg for males and 32.3 &plusmn; 4.7 kg for females, at 240 days (weaning) the weight of the males was 229 &plusmn; 35.8 kg and for females 206 &plusmn; 31.5 kg. The mean values and standard deviations of the weight increases were 0.807 &plusmn; 0.14 kg for males and 1.0 &plusmn; 0.13 kg for females. The selected model with the regressor variables: Year, Sex of the calf, Number of calving and Live Weight at Birth, all significant (p &le;0.001). No interaction was significant to be considered in the model (p&ge;0.05). The live weight at birth, the sex, the years and the number of deliveries of the mothers showed in this work and for the animals analyzed to be the factors affecting the increase in live weight in the rearing stage (from birth to weaning) in Nelore calves in the Bolivian tropics.

Attribution analysis of runoff decline in a semiarid region of the Loess Plateau, China

2016 ◽  
Vol 131 (1-2) ◽  
pp. 845-855 ◽  
Author(s):  
Binquan Li ◽  
Zhongmin Liang ◽  
Jianyun Zhang ◽  
Guoqing Wang ◽  
Weimin Zhao ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Semiarid Region ◽  
The Loess Plateau ◽  
Attribution Analysis

scholarly journals Improved Runoff Simulations for a Highly Varying Soil Depth and Complex Terrain Watershed in the Loess Plateau with the Community Land Model

2021 ◽  
Author(s):  
Jiming Jin ◽  
Lei Wang ◽  
Jie Yang ◽  
Bingcheng Si ◽  
Guo-Yue Niu
Keyword(s):  
Loess Plateau ◽  
Complex Terrain ◽  
Soil Depth ◽  
Loess Soil ◽  
Soil Evaporation ◽  
Hydrological Processes ◽  
River Channels ◽  
The Loess Plateau ◽  
Deep Soil ◽  
Community Land Model

Abstract. This study aimed to improve runoff simulations and explore deep soil hydrological processes for a watershed in the center of the Loess Plateau (LP), China. This watershed, the Wuding River Basin (WRB), has very complex topography, with soil depths ranging from 0 to 197 m. The hydrological model used for our simulations was the Community Land Model (CLM) version 5 developed by the National Center for Atmospheric Research. Actual soil depths and river channels were incorporated into CLM to realistically represent the physical features of the WRB. Through sensitivity tests, CLM with 150 soil layers produced the most reasonable results and was adopted for this study. Our results showed that CLM with actual soil depths significantly suppressed unrealistic variations of the simulated sub-surface runoff when compared to the default simulations with a fixed soil depth of 8 m. In addition, CLM with higher-resolution soil layering slightly improved runoff simulations, but generated simulations with much smoother vertical water flows that were consistent with the uniform distribution of soil textures in our study watershed. The runoff simulations were further improved by the addition of river channels to CLM, where the seasonal variability of the simulated runoff was reasonably captured. Moreover, the magnitude of the simulated runoff remarkably decreased with increased soil evaporation by lowering the soil water content threshold, which triggers surface resistance. The lowered threshold was consistent with the loess soil, which has a high sand component. Such soils often generate stronger soil evaporation than soils dominated by clay. Finally, with the above changes in CLM, the simulated total runoff matched very closely with observations. When compared with those for the default runoff simulations, the correlation coefficient, root-mean-square error, and Nash Sutcliffe coefficient for the improved simulations changed dramatically from 0.02, 10.37 mm, and −12.34 to 0.62, 1.8 mm, and 0.61. The results in this study provide strong physical insight for further investigation of hydrological processes in complex terrain with deep soils.

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