scholarly journals Exploring atmospheric boundary layer characteristics in a severe SO<sub>2</sub> episode in the north-eastern Adriatic

2009 ◽  
Vol 9 (13) ◽  
pp. 4467-4483 ◽  
Author(s):  
M. T. Prtenjak ◽  
A. Jeričević ◽  
L. Kraljević ◽  
I. H. Bulić ◽  
T. Nitis ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Lower Troposphere ◽  
Temperature Inversion ◽  
Static Stability ◽  
Pollution Sources ◽  
Small Scale ◽  
Dynamical Structure ◽  
Atmospheric Conditions ◽  
Meteorological Model ◽  
Industrial Areas

Abstract. Stable atmospheric conditions are often connected with the occurrence of high pollution episodes especially in urban or industrial areas. In this work we investigate a severe SO2 episode observed on 3–5 February 2002 in a coastal industrial town of Rijeka, Croatia, where very high daily mean concentrations (up to 353.5 μg m−3) were measured. The episode occurred under high air pressure conditions, which were accompanied with a fog and low wind speeds. Three air quality models (50-km EMEP model, 10-km EMEP4HR model and 1-km CAMx model) were used to simulate SO2 concentrations fields and to evaluate the relative contribution of distant and local pollution sources to observed concentrations. Results suggest that the episode was caused predominately by local sources. Furthermore, using three-dimensional, higher-order turbulence closure mesoscale meteorological model (WRF), the wind regimes and thermo-dynamical structure of the lower troposphere above the greater Rijeka area (GRA) were examined in detail. Modelled atmospheric fields suggest several factors whose simultaneous acting was responsible for elevated SO2 concentrations. Established small scale wind directions supported the transport of air from nearby industrial areas with major pollution sources towards Rijeka. This transport was associated with strong, ground-based temperature inversion and correspondingly, very low mixing layer (at most up to about 140 m). Additionally, the surface winds in Rijeka were light or almost calm thus, preventing ventilation of polluted air. Finally, a vertical circulation cell formed between the mainland and a nearby island, supported the air subsidence and the increase of static stability.

scholarly journals Exploring atmospheric boundary layer characteristics in a severe SO<sub>2</sub> episode in the north-eastern Adriatic

2009 ◽  
Vol 9 (2) ◽  
pp. 6283-6324
Author(s):  
M. T. Prtenjak ◽  
A. Jeričević ◽  
T. Nitis ◽  
Z. B. Klaić
Keyword(s):  
Mixing Layer ◽  
Three Dimensional ◽  
Lower Troposphere ◽  
Temperature Inversion ◽  
Causative Factor ◽  
Dynamical Structure ◽  
Atmospheric Conditions ◽  
Industrial Areas ◽  
Wind Speeds ◽  
The North

Abstract. Stable atmospheric conditions are often connected with the occurrence of high pollutant episodes especially in urban or industrial areas. In this work we investigate a severe pollution SO2 episode observed on 3–5 February 2002 in a coastal industrial town of Rijeka, Croatia. The episode occurred under anticyclonic high pressure conditions during which a fog, low wind speeds and very high daily associated mean SO2 concentration of 353.5 μg m−3 were observed. First, the EMEP model was used to evaluate the long-range transport and its contribution to the local SO2 concentrations. The comparison between the EMEP modelled regional SO2 concentrations and measured ones in Rijeka showed that the episode was caused predominately by local sources. Furthermore, using three-dimensional, higher-order turbulence closure mesoscale models (WRF and MEMO), the wind regimes and thermo-dynamical structure of the lower troposphere above the greater Rijeka area were examined in detail. The obtained results suggest several factors responsible for elevated SO2 concentrations. The polluted air is transported towards Rijeka from nearby industrial areas where major pollution sources are located. This transport is associated with strong, ground-based temperature inversion and with a corresponding very low, mixing layer (below 140 m). Light winds or almost calm conditions in Rijeka town were another causative factor of the episode. Also, a vertical circulation cell formed between the mainland and a nearby island, causing the air subsidence and stability increase in the lowermost layer south of Rijeka.

scholarly journals Dynamic downscaling of the ERA-40 data using a mesoscale meteorological model

2011 ◽  
Vol 12 (1) ◽  
pp. 183 ◽  
Author(s):  
A. PAPADOPOULOS ◽  
G. KORRES ◽  
P. KATSAFADOS ◽  
D. BALLAS ◽  
L. PERIVOLIOTIS ◽  
...  
Keyword(s):  
Dynamical Downscaling ◽  
Weather Forecasting ◽  
Quantitative Estimation ◽  
Three Dimensional ◽  
Atmospheric Model ◽  
Hydrological Models ◽  
Atmospheric Conditions ◽  
Meteorological Model ◽  
Medium Range ◽  
Forecasting System

A sophisticated downscaling procedure that was applied to reproduce high resolution historical records of the atmospheric conditions across the Mediterranean region is presented in this paper. This was accomplished by the dynamical downscaling of the European Center for Medium-Range Forecasts ERA-40 reanalyses with the aid of the atmospheric model of the POSEIDON weather forecasting system. The full three dimensional atmospheric fields with 6 hours of temporal resolution and the surface meteorological parameters at hourly intervals were produced for a 10-year period (1995-2004). The meteorological variables are readily available at 10 km resolution and may constitute the atmospheric forcing to drive wave, ocean hydrodynamic and hydrological models, as well as the baseline data for environmental impact assessment studies. A brief overview of the procedure and a quantitative estimation of the benefit of the new dynamical downscaling dataset are presented.

scholarly journals Large Scale Experimental Study of the Scour Protection Damage Around a Monopile Foundation Under Combined Wave and Current Conditions

2020 ◽  
Vol 8 (6) ◽  
pp. 417 ◽  
Author(s):  
Minghao Wu ◽  
Leen De Vos ◽  
Carlos Emilio Arboleda Chavez ◽  
Vasiliki Stratigaki ◽  
Tiago Fazeres-Ferradosa ◽  
...  
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Static Stability ◽  
Future Research ◽  
Small Scale ◽  
Flume Experiments ◽  
Wave Flume ◽  
Scale Models ◽  
Damage Data ◽  
Scour Protection

This paper presents a series of large-scale wave flume experiments on the scour protection damage around a monopile under combined waves and current conditions with model scales of 1:16.67 and 1:8.33. The main objective is to compare the damage data obtained from these large-scale models with existing monopile scour protection design approaches, which were proposed based on small scale wave flume experiments, and to study the applicability of the existing approaches. The static stability (onset of motion and bed shear stress) and the dynamic stability (three-dimensional damage numbers) of the scour protection are investigated. Both results show that the existing design approaches can be conservative when applied to large scale models, which highlights the need of further investigations on scale and model effects. In addition, this paper also analyses the scour protection damage depth. It is observed that damage depths of the scour protection layer under low Keulegan–Carpenter number (KC) conditions are smaller than predictions. The study provides valuable large scale experimental data for future research on the monopile scour protection design.

scholarly journals Climatological Description of Seasonal Variations in Lower-Tropospheric Temperature Inversion Layers over the Indochina Peninsula

2006 ◽  
Vol 19 (13) ◽  
pp. 3307-3319 ◽  
Author(s):  
Masato I. Nodzu ◽  
Shin-Ya Ogino ◽  
Yoshihiro Tachibana ◽  
Manabu D. Yamanaka
Keyword(s):  
Seasonal Variations ◽  
Potential Temperature ◽  
Lower Troposphere ◽  
Temperature Inversion ◽  
Static Stability ◽  
Boreal Winter ◽  
Type I ◽  
Tropospheric Temperature ◽  
Malay Peninsula ◽  
Indochina Peninsula

Abstract In this study operational rawinsonde data are used to investigate climatological features of seasonal variations in static stability in order to understand the behavior of temperature inversion layers, that is, extremely stable layers in the lower troposphere over the Indochina Peninsula region, at the southeastern edge of the Asian continent. Static stability was evaluated from the vertical gradient in potential temperature (Δθ/Δz). Stable (Δθ/Δz &gt; 10 K km−1) and unstable (Δθ/Δz &lt; 1 K km−1) layers frequently appear over the Indochina Peninsula region during boreal winter. Temporal and vertical variations in stability during the boreal winter can be categorized into three characteristic types, type I: the mean height of stable layers increases from 2 to 5 km from the dry to the rainy season over inland areas of the Indochina Peninsula and southern China; type II: similar to type I, with the additional occurrence of stable layers at a height of ∼1 km, mainly over coastal areas of the Indochina Peninsula; and type III: stable layers at a height of ∼2 km, mainly over the Malay Peninsula. We did not find any significant seasonal change in the vertical distribution of stable layers over the Malay Peninsula.

scholarly journals The Tropical Tropopause Inversion Layer

2016 ◽  
Author(s):  
Robin Pilch Kedzierski ◽  
Katja Matthes ◽  
Karl Bumke
Keyword(s):  
Vertical Structure ◽  
Inversion Layer ◽  
Temperature Inversion ◽  
Static Stability ◽  
Small Scale ◽  
Equatorial Waves ◽  
Fine Scale ◽  
Satellite Mission ◽  
Tropical Tropopause ◽  
The Tropics

Abstract. The Tropical Tropopause Layer (TTL) acts as a "transition" layer between the troposphere and the stratosphere over several kilometers, where air has both tropospheric and stratospheric properties. Within this region, a fine-scale feature is located: the Tropopause Inversion Layer (TIL), which consists of a sharp temperature inversion at the tropopause and a corresponding increase in static stability above. The high static stability values reached within the TIL theoretically affect the dispersion relations of atmospheric waves like Rossby or Inertia-Gravity waves and hamper stratosphere-troposphere exchange (STE). Therefore, the TIL receives increasing attention from the scientific community, mainly in the extratropics so far. Our goal is to give a detailed picture of the properties, variability and forcings of the tropical TIL, with special emphasis on small-scale equatorial waves and the QBO. We use high-resolution temperature profiles from the COSMIC satellite mission, i.e. ~2000 measurements per day globally, between 2007 and 2013, to derive TIL properties and to study the fine-scale structures of static stability in the tropics. The meteorological situation at near tropopause level is described by the 100hPa divergence fields, and the vertical structure of the QBO is provided by the equatorial winds at all levels, both from the ERA-Interim reanalysis. We describe a new feature of the equatorial static stability profile: a secondary stability maximum below the zero wind line within the easterly QBO wind regime at about at 20–25 km altitude, which is forced by the descending westerly QBO phase and gives a double-TIL-like structure. In the lowermost stratosphere, the TIL is stronger with westerly winds. We provide the first evidence of a relationship between the tropical TIL strength and near-tropopause divergence, with stronger (weaker) TIL with near-tropopause divergent (convergent) flow, a relationship similar to the TIL strength with relative vorticity in the extratropics. To elucidate possible enhancing mechanisms of the tropical TIL, we quantify the dynamical forcing of the different equatorial waves on the vertical structure of static stability in the tropics. All waves show maximum cooling at the thermal tropopause, a warming effect above, and a net TIL enhancement close to the tropopause. The main drivers are Kelvin, inertia-gravity and Rossby waves. We suggest that a similar wave forcing will exist at mid and polar latitudes from the extratropical wave modes.

Extrusion-Based 3D Printing for Pharmaceuticals: Contemporary Research and Applications

2019 ◽  
Vol 24 (42) ◽  
pp. 4991-5008 ◽  
Author(s):  
Mohammed S. Algahtani ◽  
Abdul Aleem Mohammed ◽  
Javed Ahmad
Keyword(s):  
Cosmetic Surgery ◽  
Fused Deposition Modeling ◽  
Personalised Medicine ◽  
Organ Transplant ◽  
Three Dimensional ◽  
Dosage Forms ◽  
Release Profile ◽  
Small Scale ◽  
Drug Release Profile ◽  
Fused Deposition

Three-dimensional printing (3DP) has a significant impact on organ transplant, cosmetic surgery, surgical planning, prosthetics and other medical fields. Recently, 3 DP attracted the attention as a promising method for the production of small-scale drug production. The knowledge expansion about the population differences in metabolism and genetics grows the need for personalised medicine substantially. In personalised medicine, the patient receives a tailored dose and the release profile is based on his pharmacokinetics data. 3 DP is expected to be one of the leading solutions for the personalisation of the drug dispensing. This technology can fabricate a drug-device with complicated geometries and fillings to obtain the needed drug release profile. The extrusionbased 3 DP is the most explored method for investigating the feasibility of the technology to produce a novel dosage form with properties that are difficult to achieve using the conventional industrial methods. Extrusionbased 3 DP is divided into two techniques, the semi-solid extrusion (SSE) and the fused deposition modeling (FDM). This review aims to explain the extrusion principles behind the two techniques and discuss their capabilities to fabricate novel dosage forms. The advantages and limitations observed through the application of SSE and FDM for fabrication of drug dosage forms were discussed in this review. Further exploration and development are required to implement this technology in the healthcare frontline for more effective and personalised treatment.

scholarly journals Quantification of Measurement and Model Effects in Monopile Foundation Scour Protection Experiments

2021 ◽  
Vol 9 (6) ◽  
pp. 585
Author(s):  
Minghao Wu ◽  
Leen De Vos ◽  
Carlos Emilio Arboleda Chavez ◽  
Vasiliki Stratigaki ◽  
Maximilian Streicher ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Flow Field ◽  
Three Dimensional ◽  
Small Scale ◽  
Maximum Wave Height ◽  
Chaotic Flow ◽  
The Mean ◽  
Scour Protection ◽  
Damage Number ◽  
Measurement Effects

The present work introduces an analysis of the measurement and model effects that exist in monopile scour protection experiments with repeated small scale tests. The damage erosion is calculated using the three dimensional global damage number S3D and subarea damage number S3D,i. Results show that the standard deviation of the global damage number σ(S3D)=0.257 and is approximately 20% of the mean S3D, and the standard deviation of the subarea damage number σ(S3D,i)=0.42 which can be up to 33% of the mean S3D. The irreproducible maximum wave height, chaotic flow field and non-repeatable armour layer construction are regarded as the main reasons for the occurrence of strong model effects. The measurement effects are limited to σ(S3D)=0.039 and σ(S3D,i)=0.083, which are minor compared to the model effects.

scholarly journals Experimental and Numerical Investigation about Small Clearance Journal Bearings under Static Load Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Fabrizio Stefani ◽  
Paolo Silvestri
Keyword(s):  
Three Dimensional ◽  
Journal Bearings ◽  
Radial Clearance ◽  
Small Scale ◽  
Test Rig ◽  
Small Clearance ◽  
Dimensional Simulation ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading ◽  
Good Agreement

The aim of the present research is to characterize both experimentally and numerically journal bearings with low radial clearances for rotors in small-scale applications (e.g., microgas turbines); their diameter is in the order of ten millimetres, leading to very small dimensional clearances when the typical relative ones (order of 1/1000) are employed; investigating this particular class of journal bearings under static and dynamic loading conditions represents something unexplored. To this goal, a suitable test rig was designed and the performance of its bearings was investigated under steady load. For the sake of comparison, numerical simulations of the lubrication were also performed by means of a simplified model. The original test rig adopted is a commercial rotor kit (RK), but substantial modifications were carried out in order to allow significant measurements. Indeed, the relative radial clearance of RK4 RK bearings is about 2/100, while it is around 1/1000 in industrial bearings. Therefore, the same original RK bearings are employed in this new test rig, but a new shaft was designed to reduce their original clearance. The new custom shaft allows to study bearing behaviour for different clearances, since it is equipped with interchangeable journals. Experimental data obtained by this test rig are then compared with further results of more sophisticated simulations. They were carried out by means of an in-house developed finite element (FEM) code, suitable for thermoelasto-hydrodynamic (TEHD) analysis of journal bearings both in static and dynamic conditions. In this paper, bearing static performances are studied to assess the reliability of the experimental journal location predictions by comparing them with the ones coming from already validated numerical codes. Such comparisons are presented both for large and small clearance bearings of original and modified RKs, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance 8/1000), as expected. In comparison with two-dimensional lubrication analysis, three-dimensional simulation improves prediction of journal location and correlation with experimental results.

scholarly journals Nonlinear effects of locally heterogeneous hydraulic conductivity fields on regional stream–aquifer exchanges

2015 ◽  
Vol 19 (11) ◽  
pp. 4531-4545 ◽  
Author(s):  
J. Zhu ◽  
C. L. Winter ◽  
Z. Wang
Keyword(s):  
Groundwater Flow ◽  
Effective Conductivity ◽  
Model Simulation ◽  
Three Dimensional ◽  
Small Scale ◽  
Heihe River ◽  
Effective Parameters ◽  
Aquifer Systems ◽  
Basin Scale ◽  
Local Grid

Abstract. Computational experiments are performed to evaluate the effects of locally heterogeneous conductivity fields on regional exchanges of water between stream and aquifer systems in the Middle Heihe River basin (MHRB) of northwestern China. The effects are found to be nonlinear in the sense that simulated discharges from aquifers to streams are systematically lower than discharges produced by a base model parameterized with relatively coarse effective conductivity. A similar, but weaker, effect is observed for stream leakage. The study is organized around three hypotheses: (H1) small-scale spatial variations of conductivity significantly affect regional exchanges of water between streams and aquifers in river basins, (H2) aggregating small-scale heterogeneities into regional effective parameters systematically biases estimates of stream–aquifer exchanges, and (H3) the biases result from slow paths in groundwater flow that emerge due to small-scale heterogeneities. The hypotheses are evaluated by comparing stream–aquifer fluxes produced by the base model to fluxes simulated using realizations of the MHRB characterized by local (grid-scale) heterogeneity. Levels of local heterogeneity are manipulated as control variables by adjusting coefficients of variation. All models are implemented using the MODFLOW (Modular Three-dimensional Finite-difference Groundwater Flow Model) simulation environment, and the PEST (parameter estimation) tool is used to calibrate effective conductivities defined over 16 zones within the MHRB. The effective parameters are also used as expected values to develop lognormally distributed conductivity (K) fields on local grid scales. Stream–aquifer exchanges are simulated with K fields at both scales and then compared. Results show that the effects of small-scale heterogeneities significantly influence exchanges with simulations based on local-scale heterogeneities always producing discharges that are less than those produced by the base model. Although aquifer heterogeneities are uncorrelated at local scales, they appear to induce coherent slow paths in groundwater fluxes that in turn reduce aquifer–stream exchanges. Since surface water–groundwater exchanges are critical hydrologic processes in basin-scale water budgets, these results also have implications for water resources management.

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