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Background: The post-pandemic period, military conflicts, and geopolitical instability have all contributed to concerns regarding the world's sustainable and stable development, and small national economies are particularly vulnerable to these challenges. The five countries of the Western Balkan region (Republic of Serbia, Republic of North Macedonia, Bosnia and Herzegovina, Montenegro, and Albania) have established their national interests and formulated security policies in line with their strategic commitment to the green transition and integration into the European Union. The region has been grappling with a multitude of challenges for several decades, and further instability may be expected beyond 2022. This paper aims to analyze the impact of sustainable development politicization on the security policies of Western Balkan countries and identify critical challenges to the region's sustainable development. Main text: The main research findings suggest that the security strategy of the Western Balkan countries was distinct from their economic and energy development until the beginning of the twenty-first century. Sustainable development is a strategic commitment of the Western Balkan countries, but it necessitates intricate changes, particularly in energy and economy. However, the Western Balkan countries have been confronted with new challenges due to the intricate geopolitical developments that emerged after 2022. The following are particularly noteworthy: frequently conflicting regional initiatives, the usage of energy resources and essential minerals, and significant impacts on how individuals form their opinion on these matters. The factors mentioned above are distinct security threats that require the Western Balkan countries to pursue solutions. Conclusions: A politicized approach to sustainable development is a novel phenomenon that has to be incorporated into current security policy. Specifically, the present approach, which prioritizes the state's security, often conflicts with the emerging concept of individual security (which focuses on the stability of the economy and the environment). This situation adds a layer of complexity to the position of the Western Balkan countries. They have a limited capacity to impact geopolitical developments, and in order to make progress, maintain stability, and foster social peace, they must make concessions and cooperate with influential economies that frequently have conflicting geopolitical interests. [ABSTRACT FROM AUTHOR]

In recent years, with the continuous progress of Internet of things technology, the typical application of Internet of things has been gradually launched. The virtual reality platform of the Internet of things technology provides an effective means for the multi-path development of technology, and provides an important reference for the refinement of management mode. Virtual reality technology is the extension of network information. It sets up a virtual scene for people and realizes the integration between people and machines. As the most advanced information technology in the current situation, cloud computing technology and ubiquitous network contain innovative ideas. In the current era, CG image has entered into many fields, such as film, game, network, medical treatment, industry and so on, and quickly become the new focus of cultural industry. As an art form of art technology integration, CG image brings unprecedented development prospects for film and television art with its outstanding plasticity and simulacrity. In this paper, we use the ubiquitous Internet of things technology to build a CG virtual reality framework. The proposed model is validated under different database and the performance is tested with different information sources. [ABSTRACT FROM AUTHOR]

In the framework of the Multidisciplinary drifting Observatory for the Study of Arctic Climate Polarstern expedition, the Leibniz Institute for Tropospheric Research, Leipzig, Germany, operated the shipborne OCEANET-Atmosphere facility for cloud and aerosol observations throughout the whole year. OCEANET-Atmosphere comprises, amongst others, a multiwavelength Raman lidar, a microwave radiometer, and an optical disdrometer. A cloud radar was operated aboard Polarstern by the US Atmospheric Radiation Measurement program. These measurements were processed by applying the so-called Cloudnet methodology to derive cloud properties. To gain a comprehensive view of the clouds, lidar and cloud radar capabilities for low- and high-altitude observations were combined. Cloudnet offers a variety of products with a spatiotemporal resolution of 30 s and 30 m, such as the target classification, and liquid and ice microphysical properties. Additionally, a lidar-based low-level stratus retrieval was applied for cloud detection below the lowest range gate of the cloud radar. Based on the presented dataset, e.g., studies on cloud formation processes and their radiative impact, and model evaluation studies can be conducted. [ABSTRACT FROM AUTHOR]

Kelvin–Helmholtz billows (KHBs) within a rising turbulent layer during the transition period from stable to unstable stratification occurring in the morning hours in summertime at the interior of Antarctica (Dome C, Concordia station) are examined in this study. The wave pattern captured by high-resolution sodar echograms from November 2014–February 2015 exhibits regular braid-like structures, associated with Kelvin–Helmholtz shear instabilities. This phenomenon is observed in more than 70% of days in the selected period. Two main regimes of the morning evolution with KHBs are identified roughly, distinguished by the presence or absence of turbulence in the preceding night-time. The weather and turbulent conditions favouring the occurrence of these regimes are analyzed. Also, two distinct patterns of KHBs are identified: (i) quasi-periodical (with periods ≈ 8–15 min) trains containing 5–10 braids, (ii) about continuous series lasting 20–90 min containing 20–80 braids. A composite shape of KHBs is determined. The periodicity of these waves is estimated to be between 20 and 70 s, and their wavelength is estimated roughly to be 100–400 m. The vertical thickness of individual braids at the wave crests ranges between 5 and 25 m. The total depth of a rising turbulent layer containing these waves varies between 15 and 120 m, and the ratio of the wavelength to the depth of the wave layer varies from 3 to 12 with a mean value ≈ 8.2. The morphology of the turbulence structure in the ABL is studied as a function of both temperature and wind field characteristics retrieved from an instrumented 45-m tower and an ultrasonic anemometer-thermometer at 3.5 m. The observational results highlight the necessity of considering the interaction between convective and wave processes when occurring simultaneously. [ABSTRACT FROM AUTHOR]

In this paper, the trend of the surface sulfur dioxide (SO2) concentration over Serbia was analyzed from January 2010 to December 2020. In this analysis, the measured hourly SO2 concentrations from the SEPA (Serbian Environmental Protection Agency) automatic monitoring stations and one EMEP (European Monitoring and Evaluation Programme) station were used. We focused only on the stations with more than 70% of existing data, due to questionable accuracy of trend analysis for shorter time series dataset. On the annual time scale, 87.5% of all stations showed decreasing trends, while the significant trends were detected at 50% of those stations. On the seasonal time scale, the largest number of stations showed decreasing statistically significant or insignificant trends. The highest percentage of stations (62.5%) was characterized by significantly decreasing trends during DJF season, followed by 31.25% during SON season. [ABSTRACT FROM AUTHOR]

The forests of the boreal and mid-latitude zones of the Northern Hemisphere are the largest source of reactive volatile organic compounds (VOCs), which have an important impact on the processes occurring in the atmospheric boundary layer. However, the composition of biogenic emissions from them remains incompletely characterized, as evidenced by the significant excess OH radical concentrations predicted by models in comparison with those observed under the forest canopy. The missing OH sink in the models may be related to the fact that they do not take into account the emission of highly reactive VOCs by vegetation on the forest floor. In this work, we report the results of laboratory determinations of the composition of VOCs emitted by representatives of different groups of plants that form the living soil cover (LSC) in the forests of the boreal and mid-latitude zones: bryophytes, small shrubs, herbaceous plants, and ferns. In the chromatograms of volatile emissions of all 11 studied plant species, 254 compounds with carbon atoms ranging in number from two to 20 were registered. All plants were characterized by the emission of terpenes, accounting for 112 compounds, and the second largest group (35 substances) was formed by carbonyl compounds. Both groups of compounds are characterized by high reactivity and are easily included in the processes of gas-phase oxidation with the participation of radicals HO, NO3 and ozone. These data indicate the importance of a thorough study of the so far disregarded source of VOCs, that is, the LSC in forests. [ABSTRACT FROM AUTHOR]

The physical mechanisms determining the variability of the vertical profiles of electrical conductivity, space charge density, and electric field in the undisturbed midlatitude lower atmosphere are discussed. The influence of the global and local mesoscale processes on the variability of electrical conductivity and the main component of the atmospheric electric field is estimated. The sunrise effect is studied, estimates are obtained for the charge accumulation rate in the column of the lower atmosphere and the corresponding growth rate of the field strength close to the ground. It is shown that the increase in the average charge density is mainly due to the breakdown of the stable stratification of the atmospheric boundary layer and transformation of the vertical profile of electrical conductivity following the convective mixing of a radon and its daughter products. [ABSTRACT FROM AUTHOR]

We investigate the area-averaged sensible heat flux (QH) obtained with a scintillometer along a 3.1-km path length over the city centre of Łódź, Central Poland. The annual cycle of QH peaks in June but is lower by the middle of summer. In winter, due to a large amount of anthropogenic heat input, QH remains positive all day long, with positive night-time fluxes also found during months with frequent cold advection, e.g., June 2010. In the diurnal cycle of this flux, several features specific to urban areas are seen: the peak shifts 1-2 h after noon, the heat flux turns from positive to negative 1-2 h after sunset. In Łódź QH was observed during inflow from the north and north-west, i.e. from the city centre. As this area is mostly covered with impervious materials, most of the heat exchanged between the ground and the overlying air is in the form of sensible heat flux. Under the conditions of inflow from the east and south-east, the maximum heat flux is approximately 100Wm-2 lower than during the inflow from the city centre, since more vegetation exists to the east and south-east of the scintillometer path. Cold and warm advection are found to be a vital factor in the observed heat-flux variability in the centre of Łódź. [ABSTRACT FROM AUTHOR]

Due to the chaotic motion of charged particles carried by turbulent eddies, electrical quantities in the atmospheric boundary layer (ABL) have short-term variability superimposed on long-term variability caused by sources from regional to global scales. In this study the influence of radon exhalation rate, aerosol distribution and turbulent transport efficiency on the variability of fair-weather atmospheric electricity is investigated via Lagrangian stochastic modelling. For the mid-latitude lower atmosphere undisturbed by precipitation, electrified clouds, or thunderstorms, the model is capable of reproducing the diurnal variation in atmospheric electrical parameters detected by ground-based measurements. Based on the analysis of field observations and numerical simulation it is found that the development of the convective boundary layer, accompanied by an increase in turbulent kinetic energy, forms the vertical distribution of radon and its decaying short-lived daughters to be approximately coincident with the barometric law for several eddy turnover times. In the daytime ABL the vertical distribution of atmospheric electrical conductivity tends to be uniform except within the surface layer, due to convective mixing of radon and its radioactive decay products. At the same time, a decrease in the conductivity near the ground is usually observed. This effect leads to an enhanced ground-level atmospheric electric field compared to that normally observed in the nocturnal stably-stratified boundary layer. The simulation showed that the variability of atmospheric electric field in the ABL associated with internal origins is significant in comparison to the variability related to changes in global parameters. It is suggested that vertical profiles of electrical quantities can serve as informative parameters on ABL turbulent dynamics and can even more broadly characterize the state of the environment. [ABSTRACT FROM AUTHOR]

The performance of different detrending methods in removing the low-frequency contribution to the calculation of turbulent fluxes is investigated. The detrending methods are applied to the calculation of turbulent fluxes of different scalars (temperature, ultrafine particle number concentration, carbon dioxide and water vapour concentration), collected at two different measurement sites: one urban and one suburban. We test and compare the performance of filtering methodologies frequently used in real-time and automated procedures (mean removal, linear detrending, running mean, autoregressive filter) with the results obtained from a reference method, which is a spectral filter based on the Fourier decomposition of the time series. In general, the largest differences are found in the comparison between the reference and the mean-removal procedures. The linear detrending and running-mean procedures produce comparable results, and turbulent-flux estimations in better agreement with the reference procedure than those obtained with the mean-removal procedure. The best agreement between the running mean and the spectral filter is achieved with a time window of 15 min at both sites. For all the variables studied, average fluxes calculated using the autoregressive filter are increasingly overestimated for a time constant $$\tau $$ compared with that obtained using the spectral filter. The minimization of the difference between the two detrending methods is achieved with a time constant of 120 s, with similar behaviour observed at both sites. [ABSTRACT FROM AUTHOR]

Bibliometric analysis was applied to identify global patterns and trends in the research of biogenic volatile organic compounds (BVOCs), which are important to atmospheric ozone formation and secondary organic aerosol formation. Yearly publications, mainstream subject categories and journals, leading countries and institutions, research emphases and trends were identified. Number of publications and times of citation were used as indicators to evaluate publication performances. A summary of the most frequently used keywords obtained from author keywords and KeyWords Plus provided clues for research emphases in different periods. A network of keywords was drawn to visualize the cross-relationship of keywords. Results indicated that annual output of the related scientific papers increased notably during 1991-2014. Atmospheric Sciences, Environmental Sciences & Ecology, Environmental Sciences & Engineering, and Chemistry were the main subject categories. Journal of Geophysical Research- Atmospheres was the most competitive journal in productivity and academic impact. The USA and the National Center for Atmospheric Research (NCAR) were, respectively, the leading country and leading institution in BVOC research. 'Emissions,' 'isoprene,' and 'model' were the leading research emphases in BVOC field in terms of word frequencies and centrality driven from the network structure. The three leading research hotspots cross-fields, emissions-isoprene, emissions-model, and isoprene-model showed substantial growth in scientific outputs during the study period. These trends were evidenced by the evolution of research contents in various studies. [ABSTRACT FROM AUTHOR]

In the period January-February 2014, observations were made at the Concordia station, Dome C, Antarctica to study atmospheric turbulence in the boundary layer using a high-resolution sodar. The turbulence structure was observed beginning from the lowest height of about 2 m, with a vertical resolution of less than 2 m. Typical patterns of the diurnal evolution of the spatio-temporal structure of turbulence detected by the sodar are analyzed. Here, we focus on the wavelike processes observed within the transition period from stable to unstable stratification occurring in the morning hours. Thanks to the high-resolution sodar measurements during the development of the convection near the surface, clear undulations were detected in the overlying turbulent layer for a significant part of the time. The wavelike pattern exhibits a regular braid structure, with undulations associated with internal gravity waves attributed to Kelvin-Helmholtz shear instability. The main spatial and temporal scales of the wavelike structures were determined, with predominant periodicity of the observed wavy patterns estimated to be 40-50 s. The horizontal scales roughly estimated using Taylor's frozen turbulence hypothesis are about 250-350 m. [ABSTRACT FROM AUTHOR]

Field observations of the atmospheric boundary layer were made over urban and suburban terrain in the Yangtze River Delta, China. A multiresolution decomposition was applied over three different types of terrain: flat homogeneous terrain, suburban terrain and urban terrain, with results indicating that, (1) the average scale contribution of u, v, w and $$T_{v}$$ had a similar variability with length scale for all these three sites respectively, and the dimensionless length scale corresponding to the maximum sensible heat flux contribution increased with the terrain complexity; (2) the length scale corresponding to the maximal average scale contribution for vertical wind velocity $$\lambda _w $$ was directly proportional to the roughness length $$z_{0}$$ in unstable conditions; and (3) the contributions of large-scale motions led to sensible heat fluxes determined with a large-aperture scintillomter being larger than those using the eddy-covariance method for the suburban case, whereas this phenomenon was not substantial for the urban case. [ABSTRACT FROM AUTHOR]

We compare the structure parameter of the refractive index, $$C_{nn}$$ , measured simultaneously with two large-aperture scintillometers: the WagLAS (Wageningen University, Wageningen, the Netherlands) and the BLS900 (Scintec, Rottenburg, Germany). A 3.5-year dataset shows a bias in $$C_{nn}$$ of about 17 % between the instruments. Analysis of these data reveals firstly that the logarithmic amplifiers in the WagLAS exhibit a strong dependence on temperature, resulting in an overestimation of $$C_{nn}$$ of up to 35 % for temperatures $$<$$ 0 $$^{\circ }\hbox {C}$$ . Secondly, high-pass filtering of the WagLAS and BLS900 intensity data artificially reduces $$C_{nn}$$ for crosswinds $$<$$ 2 $$\hbox {m\,s}^{-1}$$ (error $$\le $$ 25 and $$\le $$ 5 % respectively). Thirdly, the BLS900 increasingly underestimates $$C_{nn}$$ (up to 10-15 %) with increasing signal saturation. We demonstrate that Scintec's data processing relies too heavily on the assumption that the intensity data obey a log-normal distribution, which they do not in the case of saturation. Fourthly, both instruments ignore the dissipation range of the refractive-index spectrum, which leads to an overestimation of $$C_{nn}$$ of up to 30 % for friction velocity $$<$$ 0.2 $$\hbox {m\, s}^{-1}$$ . Implications of these findings are discussed and placed into perspective for other scintillometer users. Furthermore, we present a tool for revealing saturation and other violations of Rytov theory for any given scintillometer type, including microwave scintillometers. [ABSTRACT FROM AUTHOR]

Small-scale turbulent fluctuations of temperature are known to affect the propagation of both electromagnetic and acoustic waves. Within the inertial-subrange scale, where the turbulence is locally homogeneous and isotropic, these temperature perturbations can be described, in a statistical sense, using the structure-function parameter for temperature, $$C_{T}^2$$ . Here we investigate different methods of evaluating $$C_{T}^2$$ , using data from a numerical large-eddy simulation together with atmospheric observations collected by an unmanned aerial system and a sodar. An example case using data from a late afternoon unmanned aerial system flight on April 24 2013 and corresponding large-eddy simulation data is presented and discussed. [ABSTRACT FROM AUTHOR]

Field observations of the atmospheric boundary layer were made over urban and suburban areas in the Yangtze River Delta, China. Sensible heat fluxes were obtained by eddy-covariance (EC) systems and large-aperture scintillometers (LASs). The results indicated that (1) the sensible heat flux obtained by LAS $$(H_\mathrm{LAS})$$ was less noisy and slightly larger than that obtained by EC $$(H_\mathrm{EC})$$ over both urban and suburban surfaces; (2) the values of $$H_\mathrm{LAS} /H_\mathrm{EC} $$ were higher when the correlation coefficient of vertical wind speed and temperature ( $$r_{wT}$$ ) was smaller. Lower values of $$r_{wT}$$ were due to low-frequency trends. The urban values of $$H_\mathrm{LAS} /H_\mathrm{EC}$$ were smaller than suburban values at low $$r_{wT} $$ values; (3) the sensible heat flux determined by LAS was improved by use of the Monin-Obukhov similarity theory of the temperature structure parameter $$(\phi _{\mathrm{CT}})$$ over urban and suburban areas, and the improvement is more significant over urban surface areas. [ABSTRACT FROM AUTHOR]

The global distribution of the contrail coverage is computed for several scenarios of aviation in the years 2015 and 2050 and compared to1992 using meteorological analysis data representative of present temperature and humidity conditions and assuming 0.5% cover in a reference region 30 deg. W-30 deg. E, 35 deg. N-75 deg. N covering partsof western Europe and the North Atlantic. The mean contrail coverageof the Earth is computed to increase by a factor of about three compared to 1992 and to reach 0.25% in 2015. For three different scenarios of aviation and for constant climatic conditions, the global mean contrail coverage reaches values between 0.26% and 0.75% for 2050. Contrail coverage increases more strongly than total fuel burn mainly because of more traffic in the upper troposphere and because of more efficient engines with cooler exhaust. The overall efficiency of propulsion is expected to grow from about 0.3 in the fleet average of 1992,to 0.4 in 2015, and to 0.5 in 2050. The expansion of air traffic makes Canada, Alaska, the North Pacific route from North America to Japan and most of the Asian continent new regions where contrails are expected to cover more than 0.5% on average. [ABSTRACT FROM AUTHOR]