bluuebunny/crossref_metadata_2025 huggingface dataset:
Contribution to the Exploitation of Artificial Intelligence in the Domain of Maintenance Diagnosis
Authors: INEL Fouad
Published: February 2021

Increasing the performance of production units becomes a complex task from the technical point of view, especially when it comes to ensuring the availability and continuity of production systems where maintenance plays a fundamental role; it consists of checking and ensuring permanent monitoring of the installations of these systems. This operation requires continuous and high-level training of the operators, in order to overcome this limit, we call upon the field of artificial intelligence and expert systems. The basic idea of this work is the study of the contribution of expert systems in maintenance. It is a matter of synthesizing, from a bibliographic study, a logic to allow integrating the expert systems of diagnosis of breakdowns and dysfunctions in the maintenance of the systems of production; this last expert systems gives the better performance concerning the settling time and it’s always taken
Elliptic and Concentric-Elliptic Antenna Array Design using Grey Wolf Optimization
Authors: RECIOUI Abdelmadjid , Traikia Oussama , GRAINAT Youcef
Published: February 2021

In this work, Grey Wolf Optimization (GWO) is applied to the optimization of elliptical and concentric elliptical antenna arrays. The objective is to minimize the Sidelobe level and improve the directivity. GWO is a nature-inspired meta-heuristic algorithm inspired by the social hierarchy and hunting behavior of grey wolves. The obtained optimal values result in a good reduction of the sidelobe level for the elliptical and concentric elliptical antenna arrays with an enhancement in the directivity. This makes the designed arrays of practical use in the communication systems.
A Smart Metering Simulation in LABVIEW
Authors: RECIOUI Abdelmadjid , DJEMAI Hassiba , BOUCENNA Farah
Published: February 2021

The smart grid delivers electricity from producers to consumers using two-way digital technology and considers the involvement of the user. The implementation of smart grids should start at the consumer side using smart meters, control devices and a communication link. Smart metering is the bridge between smart buildings and smart grids. It is viewed as a crucial factor for an efficient functioning of the internal electricity market and a successful implementation of the renewable energy and security of supply. The replacement of the currently used electromechanical meters with smart digital meters along with domestic load controllers is identified for better energy conservation at the consumer side .These devices can be remotely read and are able to measure consumption multiple times per day which is beneficial for a good demand response, customer feedback and energy management. The purpose of the present paper is to illustrate how smart meters operate and how their implementation can improve the current grid
Power Quality Detection, Classification and Monitoring Using LABVIEW
Authors: DEKHANDJI Fatma Zohra , TALHAOUI Salim , ARKAB Youcef
Published: February 2021

In recent years, Power Quality becomes increasingly a major concern for both electric utilities and end users. Accordingly, the electrical engineering community has to deal with the analysis, diagnosis and solution of PQ issues using system approach rather than handling these issues as individual problems. This paper describes the analysis of PQ using advanced signal processing tools represented in Hilbert & Wavelet Transforms (HT-WT) and artificial intelligence tools represented in Artificial Neural Network & Support Vector Machine (ANN-SVM) for detection and classification of power quality disturbances respectively. These techniques were successfully simulated using LABVIEW software capabilities. The results of simulation indicate that the signal processing techniques are effective mechanisms to detect and classify power quality disturbances. At the end, the combination of WT as a tool of detection and features extraction with SVM as a classifier tool resulted as the best combination for PQ monitoring system.
New Approach to System Safety of human- multi-robot mobile system control with STPA and FTA
Authors: BENSACI Chaima , ZENNIR Youcef , POMORSKI Denis
Published: February 2021

Autonomous Mobile multi-robots are among the most complex systems in their control. Especially when those robots navigate in hazardous and dynamic environments such as chemical analysis laboratories which include dangerous and harmful products (poisonous, flammable, explosive ...). This study deals the safety problem in a robotic analysis laboratory and investigates the possibility to use those autonomous multi-robots in such environments with the presence of human workers without serious hazards. We used a systems-theoretic hazard analysis technique (STPA) in addition to fault tree analysis to identify the potential safety hazard scenarios, their causal factors and we conclude by a set of recommendations. Keywords: Hazard Analysis, STPA, FTA, Collaborative multi-mobile robots.
Traffic Urban Control Using an Intelligent PSO Algorithm Based on Integrated Approach
Authors: DIAF Radja , TOLBA Cherif , Nait Sidi Moh Ahmed
Published: February 2021

In this paper, we intend to contribute to the improvement of urban traffic mobility using a learning method of traffic lights controllers. We proposed a Particle Swarm Optimization (PSO) method in which the intelligent swarm acts as the cycle time of the traffic signal. The best swarm (solution found) meets the evaluation criteria selected to describe desired objectives. The main measures of traffic lights efficiency are to maximize flow-rate at which vehicles can cross a road junction and minimize the additional travel time of the driver called vehicle delay. Particle Swarm Optimizer was coupled with the traffic flow model based on Continuous Petri nets (PN). One potential advantage of CPN model is to provide insights regarding a behavior of the platoon of vehicles on the target road network. The result obtained from this study has tested with various scenarios related to intersections in different situations. The developed self-scheduling of the optimal signal timing ensures safety and continuous traffic flow, thus increasing the mobility and reducing fuel consumption and pollutant emissions.
New Design Method for Fractional Order Proportional Integral (FO-PI) Controller of 3x3 Multivariable Systems
Authors: LAIFA Sami , BOUDJEHEM Badreddine
Published: February 2021

This paper presents a new design method of Fractional Order Proportional Integral Controller (FO-PI) for 3x3 multivariable system (three-input-three-output). The Optimal parameters of the FO-PI controllers are tuning by minimizing performance index criterion as objective function. The irrational transfer function of the fractional operator is performed by means of diffusive representation and allows to formulate the optimization problem as a function of fractional order. The simulation results show that the performance of the response obtained by diffusive approach -based FO-PI are better than whose obtained by the classical controllers.
Simulation and Analysis of a Petrochemical Process (Deethanizer Column- MLE field) using HYSYS Aspen Simulator
Authors: BELHOCINE Amel , BENDIB Riad , ZENNIR Youcef
Published: February 2021

Natural gas industry has a great strategic and economic importance; it becomes one of the most attractive business opportunities in the petroleum and petrochemical field. In order to produce high quality gas, many companies all over the world including Algeria create many plants for natural gas processing to clean raw natural gas, by using separation unites and other services to get a product that respect the commercial specifications. Natural gas fractions are separated by distillation column in our case is called deethanizer tower. In this work a dynamic simulation study of deethanizer column is developed and implemented in HYSYS simulator. Simulation results prove that the HYSYS is a powerful tool to simulate industrial processes such that the simulated results are close to the real ones.
Impacts of the black clay soil moisture on the corrosion and cathodic protection performance of the API X70 Pipeline
Authors: HENDI R. , SAIFI H. , BELMOKRE K. , OUADAH M.
Published: February 2021

The impact of the black clay soil moisture of Skikda (East of Algeria), on the corrosion cathodic protection performance of the API X70 pipeline was studied in this paper. To achieve this objective, first, electrochemical analysis has been carried out. Then, in order the show impact of the black clay soil moisture of Skikda on the cathodic protection of the API X70 Pipeline, the corrosion parameters of the API X70 steel pipeline obtained by electrochemical measurements such as Tafel slopes, corrosion current densities, and corrosion potentials were used as boundary conditions in the elaborated cathodic protection model. The obtained results show that the corrosion current I corr is directly proportional to the moisture content up to 50 wt. %, with a potential shift towards the more electronegative values. The cathodic protection perfermance has been well proven in black soil at 100 wt. % moisture contents.
Fractional order adaptive MRAC controller for an active suspension system
Authors: KHELAS SEIF EDDINE , LADACI SAMIR , BENSAFIA YASSINE
Published: February 2021

This paper investigates the use of fractional order operators in conventional model reference adaptive control (MRAC). A fractional adaptive controller is designed based on the use of a fractional-order parameter adjustment rule. Applied in numerical simulations for an active suspension system and compared with the conventional MRAC, it is shown that the performances of FOMRAC are superior to classical control schemes.
Synthesis of activated carbon sand their application in the synthesis of monometallic and bimetallic supported catalysts
Authors: BOUSBA DALILA , SOBHI CHAFIA , ZOUAOUI AMNA , BOUASLA SOUAD
Published: February 2021

Biomass-derived porous carbons are attractive materials for the synthesis of carbon-supported catalysts, carbonaceous catalysts are environmentally benign and could provide an important competitive advantage as compared to existing heterogeneous catalysts, however the surface properties of carbon materials and excellent physical and chemical properties are compatible with diverse catalysis reactions including organic transformations. Currently, activated carbons are one of well known carbonaceous materials for their catalytic properties and for use as support in heterogeneous catalysis. The supported catalysts have been successfully used in the chemical industries for a long time, in which carbon supported catalysts have allowed to a new chemical catalytic process, on the other hand Heterogeneous catalysis plays a key role in the manufacture of essential products in different fields. In this paper, we present a comparative study, between two main different methods for activated carbons (ACs) preparation namely, physical and chemical activations. Latter was prepared from agro-industrial biomass and used as a support to prepare monometallic (dry impregnation and excess impregnation) and bimetallic catalyst (successive impregnation and co impregnation).
RLS-based Identification of fractional order H n1,n2 system using the Singularity Function approximation
Authors: Ali Larnene Yamina , LADACI Samir , Belemeguenai Aissa
Published: February 2021

This paper presents a study of fractional order systems modeling and identification by recursive least squares (RLS) with forgetting factor estimation technique. The fractional order integrators are implemented using the Singularity Function approximation method. Parametric Identification of fractional order differential equations (FDE) is investigated when estimating system parameters by a linear model with respect to parameters, as well as non-integer orders from temporal data (H n1,n2 )-type model. A numerical simulation example illustrates the effectiveness of the proposed identification approach to ensure the convergence of the plant and model outputs even if a bias is persistent in parameters’ values.
Capacity Optimization of MIMO Systems Involving Conformal Antenna Arrays using a Search Group Algorithm
Authors: RECIOUI Abdelmadjid
Published: February 2021

MIMO systems constitute a backbone of the fourth and fifth generations of wireless communication systems. The purpose of this paper is to introduce the involvement of conformal antenna arrays into MIMO systems. The Search Group Algorithm (SGA) is then used to further enhance the capacity of MIMO system employing conformal antenna arrays at both ends (Transmitter; Tx and Receiver; Rx). The results reveal that compared to the linear and 2D cases, conformal antenna arrays promise higher capacity values which motivates their employment in future MIMO communication systems.
Characterization of Aluminum-doped SnO2 thin films obtained by spray pyrolysis method
Authors: Sefardjella Hocine , Kabir Abdennour , Boudjema Bouzid , Benhaoua Athmen
Published: February 2021

Aluminum doped tin oxide SnO2: Al thin films were deposited on glass substrates using spray pyrolysis method. The deposited films are a polycrystalline with a tetragonal rutile structure. The variation of lattice parameters a and c decreases as a function of Al concentration due to ionic radius of (Sn=0.71Å) and (Al=0.51Å).Crystallites sizes varied between 29.25 and 32.80 nm. Al the samples have a transmission raised between 92 and 95% in the visible range. The optical band gap energy was found to vary in the range of 3.68 - 3.85eV. Electrical measurements revealed the increase of the electrical conductivity with Al content and show a maximum at 2% of the doping and then decreases due to decrease of the grain size. Following this study we can conclude that the Aluminum doped tin oxide developed by this technique can be used in gas sensors and photovoltaic cells.
Gestión estratégica de Instagram en los partidos españoles. El avance de la política espectáculo en el proceso independentista de Cataluña
Authors: López-Rabadán Pablo , Domenech-Fabregat Hugo
Published: February 2021

En los últimos años Instagram se ha de­sarrollado también como una innova­dora herramienta para la distribución de imágenes políticas. El objetivo de este trabajo es analizar la gestión estra­tégica que realizan los partidos en un contexto de crisis política. En concreto, se ha seleccionado como caso de estu­dio la fase más intensa del proceso in­dependentista en Cataluña. A partir de una propuesta metodológica propia, se han revisado nueve categorías de aná­lisis contenido asociadas a la especta­cularización de la política. Integran la muestra 291 imágenes publicadas por los 8 principales partidos del mapa polí­tico español. Los resultados muestran la normalización de su uso político, pero una gestión más regular y estratégica entre los partidos independentistas, y de mayor calidad técnica entre los con­trarios a la independencia. En el aspecto temático, el mensaje viene determinado por una orientación hacia temas profesionales, y un reparto del protagonismo entre líderes, cuadros del partido y la ciudadanía. Y, además, se detecta la aplicación inicial de recursos de base espectacular como la hibridación de es­pacios, la apelación emocional y la ex­perimentación con filtros y rótulos. Parties. The Advance of “Politics of Spectacle” in the Independence Process in CataloniaIn recent years, Instagram has also be­come an innovative tool for the distri­bution of political images. The objective of this article is to analyze the strategic management of the parties in a context of political crisis. Specifically, the most intense phase of the independence pro­cess in Catalonia has been selected as a case study. Based on our own methodo­logical proposal, nine categories of content analysis associated with the spectacularization of politics have been reviewed. The sample includes 291 images published by the 8 main par­ties of the Spanish political spectrum. The results show the normalization of its political use, but a more regular and strategic management among the pro-independence parties, and of greater technical quality among those opposed to independence. On a thematic level, the message is determined by an orien­tation towards professional issues, and a distribution of the leading role among leaders, party cadres and citizens. And, in addition, the initial application of spectacular-based resources such as space hybridization, emotional appeal and experimentation with filters and labels is detected. Palabras clave: comunicación política, medios sociales, Instagram, espectacularización, partidos políticos, España.Key words: political communication, social media, Instagram, spectacularization, political parties, Spain.
Media system dependency and change in risk perception during the COVID-19 pandemic
Authors: Muñiz Carlos
Published: February 2021

On February 27, 2020 the first case of COVID-19 contagion was detected in Mexico, and by the end of March phase 2 of the epidemic had been declared in the country when local transmission was detected. In a context of crisis and uncertainty like the one described, a risk perception tends to arise among the population that fears to be affected personally, to a large extent due to the influence exerted by the media by information they provide about the contingency, which derived from the media system dependency that occurs in the population. In order to determine the risk perception present in view of the COVID-19 pandemic, as well as the influence that media consumption had on the population’s attitude, an online analytical survey was carried out on 630 Mexican respondents. The results present a population with a relatively low risk perception, but with a moderate dependency when it comes to getting information about everything that has to do with the pandemic. In addition, it is possible to observe that this dependency tends to generate an increase, in an indirect manner, of the risk perception through the consumption of television, the digital press and Facebook.
Buffer Overflow Attack –Vulnerability in Heap
Authors: Kurariya Satyendra
Published: February 2021

We advise a paper which indicates a heap attack due to buffer over .Buffer overflow attack is the oldest and maximum pervasive attack technique. A buffer overflow takes place while a method or program attempts to put in writing more statistics to a set buffer, or duration block of reminiscence than the buffer is allotted to hold. Since buffers are layout to incorporate a defined quantity of records, the extra information can revoke statistics values in memory deal with which is adjacent to the destination buffer till and unless this system include enough bounds checking to flag or discard information while an excessive amount of is despatched to a reminiscence buffer. Buffer overflow attacks are classify into two categories: Heap and stack based attack .The time period heap outline pool of memory utilized in dynamic allocation for run time environment and the heap based totally attack define the flooded reminiscence space reserved for a software, but the problem arrives when appearing such an assault it make the situation critical
PENGARUH KOMPETENSI, KOMITMEN TERHADAP KEPUASAN KERJA DAN KINERJA PEGAWAI (STUDI PADA BADAN PELAYANAN PERIZINAN TERPADU KOTA MALANG)
Authors: Juwarsih Juwarsih
Published: February 2021

Tujuan dari penelitian ini adalah untuk mengatahui dan menganalisa pengaruh kompetensi terhadap kepuasan kerja, pengaruh komitmen terhadap kepuasan kerja, pengaruh kompetensi terhadap kinerja pegawai, pengaruh komitmen terhadap kinerja pegawai, serta pengaruh kepuasan terhadap kinerja pegawai pada Badan Pelayanan Perizinan Terpadu Kota Malang.Teknik analisa yang digunakan adalah Analisis Deskriptif Variable dan Analisis Structural Equation Modeling (SEM). Hasil penelitian ini menunjukan bahwa Kompetensi pegawai terhadap kepuasan kerja diperoleh nilai koefisien positif dan signifikan Komitmen Organisasional terhadap Kepuasan kerja diperoleh nilai koefisien positif signifikan, kompetensi pegawai terhadap kinerja pegawai diperoleh nilai koefisien positif dan, Komitmen Organisasional terhadap kinerja pegawai diperoleh nilai koefisien negatif tidak signifikan dan kepuasan kerja terhadap kinerja pegawai diperoleh nilai koefisien positif signifikan, sedangkan komitmen organisasional tidak memberikan pengaruh yang signifikan terhadap kinerja pegawai, Ini mengindikasikan bahwa pegawai memiliki komitmen yang rendah terhadap Badan Pelayanan Perizinan Terpadu Kota Malang, sehingga disarankan supaya pegawai dapat bekerja dengan penuh rasa tanggung jawab sesuai dengan tugas dan fungsinya, memiliki komitmen yang tinggi dan kinerjanya baik, maka hendaknya dibuat job description untuk Pegawai Negeri Sipil Non struktural.Tujuan dari penelitian ini adalah untuk mengatahui dan menganalisa pengaruh kompetensi terhadap kepuasan kerja, pengaruh komitmen terhadap kepuasan kerja, pengaruh kompetensi terhadap kinerja pegawai, pengaruh komitmen terhadap kinerja pegawai, serta pengaruh kepuasan terhadap kinerja pegawai pada Badan Pelayanan Perizinan Terpadu Kota Malang. Teknik analisa yang digunakan adalah Analisis Deskriptif Variable dan Analisis Structural Equation Modeling (SEM).Hasil penelitian ini menunjukan bahwa Kompetensi pegawai terhadap kepuasan kerja diperoleh nilai koefisien positif dan signifikan Komitmen Organisasional terhadap Kepuasan kerja diperoleh nilai koefisien positif signifikan, kompetensi pegawai terhadap kinerja pegawai diperoleh nilai koefisien positif dan, Komitmen Organisasional terhadap kinerja pegawai diperoleh nilai koefisien negatif tidak signifikan dan kepuasan kerja terhadap kinerja pegawai diperoleh nilai koefisien positif signifikan, sedangkan komitmen organisasional tidak memberikan pengaruh yang signifikan terhadap kinerja pegawai, Ini mengindikasikan bahwa pegawai memiliki komitmen yang rendah terhadap Badan Pelayanan Perizinan Terpadu Kota Malang, sehingga disarankan supaya pegawai dapat bekerja dengan penuh rasa tanggung jawab sesuai dengan tugas dan fungsinya, memiliki komitmen yang tinggi dan kinerjanya baik, maka hendaknya dibuat job description untuk Pegawai Negeri Sipil Non struktural.
PENGARUH KEGUNAAN PRODUK, KEMUDAHAN PENGGUNAAN PRODUK, DAN PERGAULAN SOSIAL TERHADAP MINAT MEREFERENSIKAN MELALUI NILAI PELANGGAN PADA PRODUK TELKOMSEL FLASH DI SURABAYA
Authors: Methasar Melanny , Kurniawan Gogi
Published: February 2021

Keberhasilan peluncuran produk baru ditentukan oleh tanggapan atau reaksi konsumen selama mereka menggunakan produk. Pada tahap ini konsumen mempunyai pengalaman secara langsung interaksi produk dan memberikan penilaian terhadapnya, serta mengembangkan sikap suka atau tidak suka terhadap produk. Salah satu penilaian yang dilakukan konsumen terhadap produk, adalah berdasarkan kegunaan produk tersebut bagi dirinya.Kegunaan produk merupakan derajat kepercayaan konsumen bahwa dalam penggunaan produk atau jasa tertentu akan membawa peningkatan terhadap kinerja pekerjaannya. Bila konsumen merasa bahwa suatu produk berguna bagi dirinya, maka minat pakai konsumen terhadap produk tersebut akan besar. Prinsip yang mengatakan bahwa apapun yang diperbuat oleh produsen akan laku di pasar sudah tidak relevan lagi di masa kini. Oleh karena itu, produsen harus menyesuaikan produk dan jasanya dengan apa yang diinginkan oleh konsumen. Telkomsel selaku provider dari Telkomsel Flash harus merumuskan strategi pemasaran yang tepat sebagai dasar untuk keunggulan bersaing mengingat tingginya minat mereferensikan akan membawa dampak yang positif terhadap keberhasilan produk di pasar.Penelitian ini mempunyai tujuan untuk : Menganalisis pengaruh persepsi nilai pelanggan terhadap minat mereferensikan konsumen terhadap produk Telkomsel Flash; Menganalisis pengaruh persepsi terhadap kegunaan produk terhadap persepsi nilai pelanggan produk Telkomsel Flash; Menganalisis pengaruh persepsi terhadap kemudahan penggunaan produk terhadap persepsi nilai pelanggan produk Telkomsel Flash; Menganalisis pengaruh dari pergaulan sosial terhadap pemakaian produk terhadap persepsi nilai pelanggan Telkomsel Flash.Dari pengolahan, pengujian dan pembahasan hasil penelitian yang berkaitan dengan permasalahan, maka simpulan dan saran yang dapat diambil yang ada hubungannya dengan penelitian adalah sebagai berikut : Pengujian hipotesis pertama menunjukkan adanya hubungan pengaruh yang positif antara nilai pelanggan dengan minat mereferensikan.Pengujian hipotesis kedua menunjukkan adanya hubungan pengaruh yang positif antara konstruk kegunaan produk dan nilai pelanggan. Pengujian hipotesis ketiga menunjukkan hubungan pengaruh yang positif antar konstruk kemudahan penggunaan produk dan nilai pelanggan.Pengujian hipotesis keempat menunjukkan hubungan pengaruh yang positif antar konstruk pengaruh pergaulan sosial dan nilai pelanggan, yang berarti bila pelanggan merasakan bahwa produk dapat menunjang pergaulan sosialnya, maka pelanggan akan merasa produk itu memberikan manfaat bagi dirinya dan bernilai bagi dirinya
Development of Critical Reading Modules With a Reflective Approach in Grade VIII of Junior High School
Authors: Usman Usman , Nurhaliza Siti
Published: February 2021

Research purpose to: (1) determine the level of need for the critical reading module of exposition text with reflective learning in grade VIII of junior high school; (2) produce a critical reading module for exposition text with reflective learning in grade VIII of junior high school that students can use to learn; (3) test the feasibility of the critical reading module of exposition text with reflective learning in grade VIII of junior high school. This research is a research and development designed with R2D2 (Recursive, Reflective Design and Development Model). The data in this study are qualitative and quantitative data from expert and practitioner tests. Qualitative data are sourced from comments, criticisms, and suggestions from expert and practitioner ratings of the module. Quantitative data is sourced from expert and practitioner assessments of module components. The data analysis technique of this research is qualitative data analysis and quantitative data analysis. This research and development resulted in the product of the Critical Text Exposition Reading Module with a ReflectiveApproach in Grade VIII of Junior High School which was assessed by experts and practitioners. The results of expert and practitioner assessments of the module indicate that the assessment in the category is very feasible. The critical reading module of exposition text with a reflective approach was declared very feasible to improve critical reading skills as well as providing knowledge about exposition text to students of grade VIII junior high school.
Unexpected enhancement of ozone exposure and health risks during National Day in China
Authors: Wang Peng , Shen Juanyong , Xia Men , Sun Shida , Zhang Yanli , Zhang Hongliang , Wang Xinming
Published: February 2021

Abstract. China is confronting increasing ozone (O3) pollution that worsens air quality and public health. Extremely O3 pollution occurs more frequently under special events and unfavorable meteorological conditions. Here we observed significantly elevated maximum daily 8-h average (MDA8) O3 (up to 98 ppb) during the Chinese National Day Holidays (CNDH) in 2018 throughout China, with a prominent rise by up to 120 % compared to the previous week. The air quality model shows that increased precursor emissions and regional transport are major contributors to the elevation. In the Pearl River Delta region, the regional transport contributed up to 30 ppb O3 during the CNDH. Simultaneously, aggravated health risk occurs due to high O3, inducing 33 % additional deaths throughout China. Moreover, in tourist cities such as Sanya, daily mortality even increases by up to 303 %. This is the first comprehensive study to investigate O3 pollution during CNDH at national level, aiming to arouse more focuses on the O3 holiday impact from the public.
GUV long-term measurements of total ozone column and effective
cloud transmittance at three Norwegian sites
Authors: Svendby Tove M. , Johnsen Bjørn , Kylling Arve , Dahlback Arne , Bernhard Germar H. , Hansen Georg H. , Petkov Boyan , Vitale Vito
Published: February 2021

Abstract. Measurements of total ozone column and effective cloud transmittance have been performed since 1995 at the three Norwegian sites Oslo/Kjeller, Andøya/Tromsø and in Ny-Ålesund (Svalbard). These sites are a subset of 9 stations included in the Norwegian UV monitoring network, which uses GUV multi-filter instruments and is operated by DSA and NILU. The network includes unique data sets of high time-resolution measurements that can be used for a for broad range of atmospheric and biological exposure studies. Comparison of the 25-year records of GUV (global sky) total ozone measurements with Brewer direct sun measurements show that the GUVs provide valuable supplements to the more standardized ground-based instruments. The GUVs can fill in missing data and extend the measuring season at sites with reduced staff and/or characterized by harsh environmental conditions, such as Ny-Ålesund. Also, a harmonized GUV can easily be moved to more remote/unmanned locations and provide independent total ozone column datasets. The GUV in Ny-Ålesund captured well the Arctic ozone hole in March/April 2020, whereas the GUV in Oslo recorded a mini ozone hole in December 2019 with total ozone values below 200 DU. For all the three Norwegian stations there is a slight increase in total ozone from 1995 until today. Measurements of GUV effective cloud transmittance in Ny-Ålesund indicate that there has been a significant change in albedo during the past 25 years, most likely resulting from increased temperatures and Arctic ice melt in the area surrounding Svalbard.
Non-linear response of PM2.5 to changes in NOx and NH3 emissions in the Po basin (Italy): consequences for air quality plans
Authors: Thunis Philippe , Clappier Alain , Beekmann Matthias , Putaud Jean Philippe , Cuvelier Cornelis , Madrazo Jessie , de Meij Alexander
Published: February 2021

Abstract. Air pollution is one of the main causes of damages to human health in Europe with an estimate of about 380 000 premature deaths per year in the EU28, as the result of exposure to fine particulate matter (PM2.5) only. In this work, we focus on one specific region in Europe, the Po basin, a region where chemical regimes are the most complex, showing important non-linear processes, especially those related to interactions between NOx and NH3. We analyse the sensitivities of PM2.5 to NOx and NH3 emissions by means of a set of EMEP simulations performed with different levels of emission reductions, from 25 % up to a total switch-off of those emissions. Both single and combined precursor reduction scenarios are applied to determine the most efficient emission reduction strategies and quantify the interactions between NOx and NH3 emission reductions. The results confirmed the peculiarity of secondary PM2.5 formation in the Po basin, characterised by contrasting chemical regimes within distances of few (hundreds of) kilometres, as well as strong non-linear responses to emission reductions during wintertime. One of the striking results is the increase of the PM2.5 concentration levels when NOx emission reductions are applied in NOx-rich areas, such as the surroundings of Bergamo. The increased oxidative capacity of the atmosphere is the cause of the increase of PM2.5 induced by a reduction in NOx emission. This process can have contributed to the absence of significant PM2.5 concentration decrease during the COVID-19 lockdowns in many European cities. It is important to account for this process when designing air quality plans, since it could well lead to transitionary increases in PM2.5 at some locations in winter as NOx emission reduction measures are gradually implemented. While PM2.5 responses to NOx and NH3 emission reduction show large variations seasonally and spatially, these responses remain close to linear, i.e. proportional to the emission reduction levels, at least up to −50 % because secondary aerosol formation chemical regimes are not modified by those relatively moderate ranges.
Wildfire smoke-plume rise: a simple energy balance parameterization
Authors: Moisseeva Nadya , Stull Roland
Published: February 2021

Abstract. The buoyant rise and the resultant vertical distribution of wildfire smoke in the atmosphere have a strong influence on downwind pollutant concentrations at the surface. The amount of smoke injected vs. height is a key input into chemical transport models and smoke modelling frameworks. Due to scarcity of model evaluation data as well as the inherent complexity of wildfire plume dynamics, smoke injection height predictions have large uncertainties. In this work we use the coupled fire–atmosphere model WRF-SFIRE configured in large-eddy simulation (LES) mode to develop a synthetic plume dataset. Using this numerical data, we demonstrate that crosswind integrated smoke injection height for a fire of arbitrary shape and intensity can be modelled with a simple energy balance. We introduce two forms of updraft velocity scales that exhibit a linear dimensionless relationship with the plume vertical penetration distance through daytime convective boundary layers. Lastly, we use LES and prescribed burn data to constrain and evaluate the model. Our results suggest that the proposed simple parameterization of mean plume rise as a function of vertical velocity scale offers reasonable accuracy (30 m errors) at little computational cost.
Very long-period oscillations in the atmosphere (0–110 km)
Authors: Offermann Dirk , Kalicinsky Christoph , Koppmann Ralf , Wintel Johannes
Published: February 2021

Abstract. Multi-annual oscillations have been observed in measured atmospheric data.
These oscillations are also present in general circulation models. This is
the case even if the model boundary conditions with respect to solar cycle,
sea surface temperature, and trace gas variability are kept constant. The
present analysis contains temperature oscillations with periods from below 5 up to more than 200 years in an altitude range from the Earth's surface to the
lower thermosphere (110 km). The periods are quite robust as they are found
to be the same in different model calculations and in atmospheric
measurements. The oscillations show vertical profiles with special
structures of amplitudes and phases. They form layers of high or low
amplitudes that are a few dozen kilometres wide. Within the layers the data are
correlated. Adjacent layers are anticorrelated. A vertical displacement
mechanism is indicated with displacement heights of a few 100 m.
Vertical profiles of amplitudes and phases of the various oscillation
periods as well as their displacement heights are surprisingly similar. The
oscillations are related to the thermal and dynamical structure of the
middle atmosphere. These results are from latitudes and longitudes in central
Europe.
Generalized canonical transform method for radio occultation sounding with improved retrieval in the presence of horizontal gradients
Authors: Gorbunov Michael , Kirchengast Gottfried , Lauritsen Kent B.
Published: February 2021

Abstract. By now, a series of advanced wave optical approaches to the processing of radio occultation (RO) observations are widely used. In particular, the canonical transform (CT) method and its further developments need to be mentioned. The latter include the full spectrum inversion (FSI) method, the geometric optical phase matching (PM) method, and the general approach based on the Fourier integral operators (FIOs), also referred to as the CT type 2 (CT2) method. The general idea of these methods is the application of a canonical transform that changes the coordinates in the phase space from time and Doppler frequency to impact parameter and bending angle. For the spherically symmetric atmosphere, the impact parameter, being invariant for each ray, is a unique coordinate of the ray manifold. Therefore, the derivative of the phase of the wave field in the transformed space is directly linked to the bending angle as a single-valued function of the impact parameter. However, in the presence of horizontal gradients, this approach may not work. Here we introduce a further generalization of the CT methods in order to reduce the errors due to horizontal gradients. We describe, in particular, the modified CT2 method, denoted CT2A, which complements the former with one more affine transform: a new coordinate that is a linear combination of the impact parameter and bending angle. The linear combination coefficient is a tunable parameter. We derive the explicit formulas for the CT2A and develop the updated numerical algorithm. For testing the method, we performed statistical analyses based on RO retrievals from data acquired by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) and collocated analysis profiles of the European Centre for Medium-Range Weather Forecasts (ECMWF). We demonstrate that it is possible to find a reasonably optimal value of the new tunable CT2A parameter that minimizes the root mean square difference between the RO retrieved and the ECMWF refractivity in the lower troposphere and allows the practical realization of the improved capability to cope with horizontal gradients and serve as the basis of a new quality control procedure.
What millimeter-wavelength radar reflectivity reveals about snowfall: an information-centric analysis
Authors: Wood Norman B. , L'Ecuyer Tristan S.
Published: February 2021

Abstract. The ability of single-frequency, millimeter-wavelength radar reflectivity
observations to provide useful constraints for retrieval of snow particle
size distribution (PSD) parameters, snowfall rates, and snowfall accumulations
is examined. An optimal estimation snowfall retrieval that allows
analyses of retrieval uncertainties and information content is applied
to observations of near-surface W-band reflectivities from multiple
snowfall events during the 2006–2007 winter season in southern Ontario.
Retrieved instantaneous snowfall rates generally have uncertainties
greater than 100 %, but single-event and seasonal snow accumulations
from the retrieval results match well with collocated
measurements of accumulations. Absolute fractional differences are
mainly below 30 % for individual events that have more substantial
accumulations and, for the season, 12.6 %. Uncertainties in retrieved
snowfall rates are driven mainly by uncertainties in the retrieved
PSD parameters, followed by uncertainties in particle model parameters
and, to a lesser extent, the uncertainties in the fall-speed model. Uncertainties attributable to assuming an exponential distribution
are negligible. The results indicate that improvements to PSD and
particle model a priori constraints provide the most impactful path
forward for reducing uncertainties in retrieved snowfall rates. Information
content analyses reveal that PSD slope is well-constrained by the
retrieval. Given the sensitivity of PSD slope to microphysical transformations,
the results show that such retrievals, when applied to radar reflectivity
profiles, could provide information about microphysical transformations
in the snowing column. The PSD intercept is less well-constrained by the retrieval. While applied to near-surface radar observations
in this study, the retrieval is applicable as well to radar observations
aloft, such as those provided by profiling ground-based, airborne,
and satellite-borne radars under lighter snowfall conditions when
attenuation and multiple scattering can be neglected.
Non-target analysis using gas chromatography with time-of-flight mass spectrometry: application to time series of fourth generation synthetic halocarbons at Taunus Observatory (Germany)
Authors: Lefrancois Fides , Jesswein Markus , Thoma Markus , Engel Andreas , Stanley Kieran , Schuck Tanja
Published: February 2021

Abstract. Production and use of many synthetic halogenated trace gases are regulated internationally because of their contribution to stratospheric ozone depletion or to climate change. In many applications they have been replaced by shorter-lived compounds which have become measurable in the atmosphere as emissions increased. Non-target monitoring of trace gases rather than targeted measurements of well-known substances is needed to keep up with such changes in the atmospheric composition. We regularly deploy gas chromatography (GC) coupled to time-of-flight mass spectrometry (TOF-MS) for analysis of flask air samples and in situ measurements at the Taunus Observatory, a site in central Germany. TOF-MS record data over a continuous mass range enable a retrospective analysis of the data set, which can thus be considered a type of digital air archive. This archive can be made use of if new substances come into use and their mass spectrometric fingerprint is identified. However, quantifying new replacement halocarbons can be challenging, as mole fractions are generally low, requiring high measurement precision and low detection limits. In addition, calibration can be demanding, as calibration gases may not contain sufficiently high amounts of newly used substances or the amounts in the calibration gas have not been quantified. This paper presents an indirect data evaluation approach for TOF-MS data, where the calibration is linked to another compound which could be quantified in the calibration gas. We also present an approach to evaluate the quality of the indirect calibration method and to select periods of stable instrument performance and well suited reference compounds. The method is applied to three short-lived synthetic halocarbons: HFO-1234-yf, HFO-1234ze(E), and HCFO-1233zd(E). They represent replacements for longer-lived HFCs and exhibit increasing mole fractions in the atmosphere. The indirectly calibrated results are compared to directly calibrated measurements using data from TOF-MS canister sample analysis and TOF-MS in situ measurements, which are available for some periods of our data set. The application of the indirect calibration method on several test cases can result into accuracies around 13 % to 20 %. For H(C)FOs accuracies up to 25 % are achieved. The indirectly calculated mole fractions of the investigated H(C)FOs at Taunus Observatory range between measured mole fractions at urban Dübendorf and Jungfraujoch stations in Switzerland.
Technical note: A universal method for measuring the thickness of microscopic calcite crystals, based on bidirectional circular polarization
Authors: Beaufort Luc , Gally Yves , Suchéras-Marx Baptiste , Ferrand Patrick , Duboisset Julien
Published: February 2021

Abstract. Coccoliths are major contributors to the particulate inorganic carbon in the
ocean that is a key part of the carbon cycle. The coccoliths are a few micrometres
in length and weigh a few picogrammes. Their birefringence characteristics in
polarized optical microscopy have been used to estimate their mass. This
method is rapid and precise because camera sensors produce excellent
measurements of light. However, the current method is limited because it
requires a precise and replicable set-up and calibration of the light in the
optical equipment. More precisely, the light intensity, the diaphragm
opening, the position of the condenser and the exposure time of the camera
have to be strictly identical during the calibration and the analysis of
calcite crystal. Here we present a new method that is universal in the sense
that the thickness estimations are independent from a calibration but
result from a simple equation. It can be used with different cameras and
microscope brands. Moreover, the light intensity used in the microscope does
not have to be strictly and precisely controlled. This method permits the
measurement of crystal thickness up to 1.7 µm. It is based on the use of one
left circular polarizer and one right circular polarizer with a
monochromatic light source using the following equation: d=λπΔnarctanILRILL, where d is the thickness, λ the wavelength of the light used,
Δn the birefringence, and ILR and ILL the light intensity
measured with a right and a left circular polarizer. Because of the
alternative and rotational motion of the quarter-wave plate of the circular
polarizer, we coined the name of this method “bidirectional circular
polarization” (BCP).
A limited effect of sub-tropical typhoons on phytoplankton dynamics
Authors: Chai Fei , Wang Yuntao , Xing Xiaogang , Yan Yunwei , Xue Huijie , Wells Mark , Boss Emmanuel
Published: February 2021

Abstract. Typhoons are assumed to stimulate primary ocean production through the upward mixing of nutrients into the ocean surface. This assumption is based
largely on observations of increased surface chlorophyll concentrations following the passage of typhoons. This surface chlorophyll enhancement,
occasionally detected by satellites, is often undetected due to intense cloud coverage. Daily data from a BGC-Argo profiling float revealed the
upper-ocean response to Typhoon Trami in the northwest Pacific Ocean. Temperature and chlorophyll changed rapidly, with a significant drop in sea
surface temperature and a surge in surface chlorophyll associated with strong vertical mixing, which was only partially captured by satellite
observations. However, no net increase in vertically integrated chlorophyll was observed during Typhoon Trami or in its wake. In contrast to the
prevailing dogma, the result shows that typhoons likely have a limited effect on net primary ocean production. Observed surface chlorophyll
enhancements during and immediately following typhoons in tropical and subtropical waters are more likely to be associated with surface entrainment
of deep chlorophyll maxima. Moreover, the findings demonstrate that remote sensing data alone can overestimate the impact of storms on primary
production in all oceans. Full understanding of the impact of storms on upper-ocean productivity can only be achieved with ocean-observing robots
dedicated to high-resolution temporal sampling in the path of storms.