Search

In this study, we assess the homogeneity of aerosol optical depth (AOD) between two sun photometer networks, the Global Atmosphere Watch-Precision Filter Radiometer (GAW-PFR) and the European SKYNET radiometers network (ESR), at the common wavelengths of their main instruments (500 and 870 nm). The main focus of this work is to evaluate the effect of the improved Langley plot calibration method (ILP) used by SKYNET and to investigate the factors affecting its performance. We used data from three intercomparison campaigns that took place during 2017–2021. Each campaign was organized at two locations (mountainous rural – Davos, Switzerland; urban – Rome, Italy). Our analysis shows that differences in AOD due to post-processing and instrument differences are minor. The main factor leading to AOD differences is the calibration method. We found a systematic underestimation of AOD in ESR compared to in GAW-PFR due to underestimation of the calibration constant calculated with the ILP method compared to the calibration transfers using the PFR as a reference. The calibration and AOD differences are smaller in Davos, where the traceability criteria are satisfied at 870 nm and where the median differences are below 0.01 at 500 nm. In Rome, the AOD median differences at 500 nm were in the 0.015–0.034 range. We conducted a sensitivity study, which shows that part of the difference can potentially be explained by errors in the assumed surface albedo and instrument solid-view angle provided as inputs to the ILP code (based on Skyrad pack 4.2). Our findings suggest that the ILP method is mainly sensitive to the measured sky radiance. The underestimation in calibration is probably caused by an error in the retrieved scattering AOD (sc-AOD) through the sky radiance inversion. Using an alternative retrieval method (Skyrad MRI pack version 2) to derive sc-AOD and to recalibrate the instruments with the ILP method, we found no significant differences between the retrieved sc-AOD and no systematic increase in the ILP-derived calibration constant when using the MRI pack for sc-AOD inversion instead of the Skyrad 4.2. The potential error may be a result of the model assumptions used for the sky radiance simulations. In conclusion, the on-site calibration of sun photometers has several advantages, including the fact that instrument shipments and data gaps can be avoided. However, it has also the disadvantages of a larger uncertainty and significant systematic differences compared to the traditional Langley calibration performed under low- and constant-AOD conditions at high-altitude sites. The larger uncertainty of the ILP method can be attributed to the required modelling and input parameters.

To retrieve columnar intensive aerosol properties from sun–sky photometers, both irradiance and radiance calibration factors are needed. For the irradiance the solar calibration constant, V0, which denotes the instrument counts for a direct normal solar flux extrapolated to the top of the atmosphere, must be determined. The solid view angle, SVA, is a measure of the field of view of the instrument, and it is important for obtaining the radiance from sky diffuse irradiance measurements. Each of the three sun-photometer networks considered in the present study (SKYNET, AERONET, WMO GAW) adopts different protocols of calibration, and we evaluate the performance of the on-site calibration procedures, applicable to every kind of sun–sky photometer but tested in this analysis only on SKYNET Prede POM01 instruments, during intercomparison campaigns and laboratory calibrations held in the framework of the Metrology for Aerosol Optical Properties (MAPP) European Metrology Programme for Innovation and Research (EMPIR) project. The on-site calibration, performed as frequently as possible (ideally monthly) to monitor changes in the device conditions, allows operators to track and evaluate the calibration status on a continuous basis, considerably reducing the data gaps incurred by the periodic shipments for performing centralized calibrations. The performance of the on-site calibration procedures for V0 was very good at sites with low turbidity, showing agreement with a reference calibration between 0.5 % and 1.5 % depending on wavelengths. In the urban area, the agreement decreases between 1.7 % and 2.5 %. For the SVA the difference varied from a minimum of 0.03 % to a maximum of 3.46 %.

This work aims to assess differences in the aerosol optical depth (AOD) trend estimations when using high-quality AOD measurements from two different instruments with different technical characteristics and operational (e.g. measurement frequency), calibration and processing protocols. The different types of sun photometers are the CIMEL that is part of AERONET (AErosol RObotic NETwork) and a precision filter radiometer (PFR) that is part of the Global Atmosphere Watch Precision Filter Radiometer network. The analysis operated for two wavelengths (500 and 501 and 870 and 862 nm for CIMEL–PFR) in Davos, Switzerland, for the period 2007–2019. For the synchronous AOD measurements, more than 95 % of the CIMEL–PFR AOD differences are within the WMO-accepted limits, showing very good measurement agreement and homogeneity in calibration and post-correction procedures. AOD trends per decade in AOD for Davos for the 13-year period of analysis were approximately −0.017 and −0.007 per decade for 501 and 862 nm (PFR), while the CIMEL–PFR trend differences have been found 0.0005 and 0.0003, respectively. The linear trend difference for 870 and 862 nm is larger than the linear fit standard error. When calculating monthly AODs using all PFR data (higher instrument frequency) and comparing them with the PFR measurements that are synchronous with CIMEL, the trend differences are smaller than the standard error. Linear trend differences of the CIMEL and PFR time series presented here are not within the calculated trend uncertainties (based on measurement uncertainty) for 870 and 862 nm. On the contrary, PFR trends, when comparing high- and low-measurement-frequency datasets are within such an uncertainty estimation for both wavelengths. Finally, for time-varying trends all trend differences are well within the calculated trend uncertainties.

In this study we focus on the retrieval of aerosol and trace gas vertical profiles from multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations for the first time over Thessaloniki, Greece. We use two independent inversion algorithms for the profile retrievals: the Mexican MAX-DOAS Fit (MMF) and the Mainz Profile Algorithm (MAPA). The former is based on the optimal estimation method (OEM), while the latter follows a parameterization approach. We evaluate the performance of MMF and MAPA, and we validate their retrieved products with ancillary data measured by other co-located reference instruments. The trace gas differential slant column densities (dSCDs), simulated by the forward models, are in good agreement, except for HCHO, where larger scatter is observed due to the increased spectral noise of the measurements in the UV. We find an excellent agreement between the tropospheric column densities of NO2 retrieved by MMF and MAPA (slope=1.009, Pearson's correlation coefficient R=0.982) and a good correlation for the case of HCHO (R=0.927). For aerosols, we find better agreement for the aerosol optical depths (AODs) in the visible (i.e., at 477 nm) compared to the UV (at 360 nm), and we show that the agreement strongly depends on the O4 scaling factor that is used in the analysis. The agreement for NO2 and HCHO near-surface concentrations is similar to the comparison of the integrated columns with slightly decreased correlation coefficients. The seasonal mean vertical profiles that are retrieved by MMF and MAPA are intercompared, and the seasonal variation in all species along with possible sources is discussed. The AODs retrieved by the MAX-DOAS are validated by comparing them with AOD values measured by a CIMEL sun photometer and a Brewer spectrophotometer. Four different flagging schemes were applied to the data in order to evaluate their performance. Qualitatively, a generally good agreement is observed for both wavelengths, but we find a systematic bias from the CIMEL sun photometer and Brewer spectrophotometer measurements, due to the limited sensitivity of the MAX-DOAS in retrieving information at higher altitudes, especially in the UV. An in-depth validation of the aerosol vertical profiles retrieved by the MAX-DOAS is not possible since only in very few cases is the true aerosol profile known during the period of study. However, we examine four cases, where the MAX-DOAS provided a generally good estimation of the shape of the profiles retrieved by a co-located multi-wavelength lidar system. The NO2 near-surface concentrations are validated against in situ observations, and the comparison of both MMF and MAPA revealed good agreement with correlation coefficients of R=0.78 and R=0.73, respectively. Finally, the effect of the O4 scaling factor is investigated by intercomparing the integrated columns retrieved by the two algorithms and also by comparing the AODs derived by MAPA for different values of the scaling factor with AODs measured by the CIMEL sun photometer and the Brewer spectrophotometer.

The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor (S5P) satellite was launched on 13 October 2017 to provide the atmospheric composition for atmosphere and climate research. The S5P is a Sun-synchronous polar-orbiting satellite providing global daily coverage. The TROPOMI swath is 2600 km wide, and the ground resolution for most data products is 7.2×3.5 km2 (5.6×3.5 km2 since 6 August 2019) at nadir. The Finnish Meteorological Institute (FMI) is responsible for the development of the TROPOMI UV algorithm and the processing of the TROPOMI surface ultraviolet (UV) radiation product which includes 36 UV parameters in total. Ground-based data from 25 sites located in arctic, subarctic, temperate, equatorial and Antarctic areas were used for validation of the TROPOMI overpass irradiance at 305, 310, 324 and 380 nm, overpass erythemally weighted dose rate/UV index, and erythemally weighted daily dose for the period from 1 January 2018 to 31 August 2019. The validation results showed that for most sites 60 %–80 % of TROPOMI data was within ±20 % of ground-based data for snow-free surface conditions. The median relative differences to ground-based measurements of TROPOMI snow-free surface daily doses were within ±10 % and ±5 % at two-thirds and at half of the sites, respectively. At several sites more than 90 % of cloud-free TROPOMI data was within ±20 % of ground-based measurements. Generally median relative differences between TROPOMI data and ground-based measurements were a little biased towards negative values (i.e. satellite data < ground-based measurement), but at high latitudes where non-homogeneous topography and albedo or snow conditions occurred, the negative bias was exceptionally high: from −30 % to −65 %. Positive biases of 10 %–15 % were also found for mountainous sites due to challenging topography. The TROPOMI surface UV radiation product includes quality flags to detect increased uncertainties in the data due to heterogeneous surface albedo and rough terrain, which can be used to filter the data retrieved under challenging conditions.

In this work, we analyze the spontaneous emission dynamics of a V-type quantum emitter near a graphene nanodisk based on the combination of electromagnetic and quantum dynamical calculations. The presence of the graphene nanodisk gives strong anisotropy to the Purcell factors of the quantum emitter, leading to interference effects in spontaneous emission appearing as coupling between the emitter’s upper levels. This effect is further enhanced by the strong light–matter interaction of the quantum emitter with the modified electromagnetic mode continuum, which induces non-Markovian spontaneous emission dynamics. We have studied the population dynamics of the quantum emitter at a specific distance from the center of the graphene nanodisk for various free-space decay widths and different quantum emitter’s initial conditions and have shown weak coupling results appearing with Markovian decay dynamics, obtained for quantum emitters with small free-space decay widths, and population dynamics that exhibits distinctly non-Markovian features, such as prominent decaying Rabi oscillations in the population evolution of the quantum emitter’s excited states and energy exchange between them during the overall population decay into the photonic mode continuum for largest free-space decay widths. Also, for the largest value of the free-space decay width, we obtain significant population trapping effects in the excited states of the quantum emitter. Furthermore, we find that the population dynamics for specific light–matter interaction strength conditions between the quantum emitter and the graphene nanodisk depend distinctively on the initial state of the quantum emitter, whether it is a single state or a superposition state.

One of the issues in Natural Language Processing (NLP) and Artificial Intelligence (AI) is language representation and modeling, aiming to manage its structure and find solutions to linguistic issues. With the pursuit of the most efficient capture of knowledge about the Modern Greek language and, given the scientifically certified usability of the ontological structuring of data in the field of the semantic web and cognitive computing, a new ontology of the Modern Greek language at the level of structure and vocabulary is presented in this paper, using the Protégé platform. With the specific logical and structured form of knowledge representation to express, this research processes and exploits in an easy and useful way the distributed semantics of linguistic information.

This paper introduces a classification model that detects and classifies argumentative behaviors between two individuals by utilizing a machine learning application, based on the MediaPipe Holistic model. The approach involves the distinction between two different classes based on the behavior of two individuals, argumentative and non-argumentative behaviors, corresponding to verbal argumentative behavior. By using a dataset extracted from video frames of hand gestures, body stance and facial expression, and by using their corresponding landmarks, three different classification models were trained and evaluated. The results indicate that Random Forest Classifier outperformed the other two by classifying argumentative behaviors with 68.07% accuracy and non-argumentative behaviors with 94.18% accuracy, correspondingly. Thus, there is future scope for advancing this classification model to a prediction model, with the aim of predicting aggressive behavior in patients suffering with dementia before their onset.

Nowadays, the business area cannot be sustainable and efficient without the presence of the Supply Chain. However, Supply Chain Management is by no means an easy task. Experts, in their effort to achieve the most efficient Supply Chain Management, have turned their attention to the management of knowledge related to supply chains. Thus, they model the concepts and the semantic relationships between them in Supply Chain Networks and create conceptual models and ontologies. In this paper, a survey of the existing ontologies in this field is carried out, with the aim of creating a new ontology of the Supply Chain that will unify its structural elements and lead to the integration of all supply systems. For this purpose, 22 ontological models from different supply systems, from over 90 sources, have been collected, briefly presented and commented on. These models, although being an intersection in the effort to model business operations and delineate a good basis for businesses to engage in Logistics processes, they lack an adequate formulation of appropriate semantics and terminology to describe all the different functions of the Supply Chain. Consequently, this lack inevitably leads to incompatible interpretations and uses of the knowledge that results from intercompany transactions.

This study develops a toolkit of sustainability indicators to analyze the economic, environmental, and social performance of various pasture-based production systems rearing Karagkouniko sheep (both specialized and mixed), and compares it with the intensive Lacaune production system in the same region. The analysis showed that despite the lower milk productivity, the group of specialized livestock Karagkouniko farms was more profitable compared to the Lacaune (35% higher net profit) production system, mainly due to savings in purchased feedstuff (64% lower expenses). This implies that grazing—if properly managed—can indeed enhance the profitability of farms. The group of mixed Karagkouniko farms—cultivating crops for both feedstuff and markets—was the least profitable group (−144.76 per ewe) as well as the least efficient in terms of use of energy (EUR 4.66 of output per EUR 1 of energy cost) and agrochemical inputs (537.2 kg of fertilizers and 3.3 liters of pesticides per ha). This suggests that strong organizational skills are required to effectively manage both crop and livestock production. Trade-offs were also observed between the sustainability dimensions. To address these trade-offs and ensure a transition to more sustainable agriculture, a comprehensive framework should be developed, integrating a mix of socioeconomic and agro-environmental schemes. [ABSTRACT FROM AUTHOR]

Police attendance in mental health contexts is often traumatic for the person in crisis, their family and first responders. Existing literature on police involvement in mental health responses tends to focus on police perspectives. Scholarship exploring lived experience perspectives is limited, yet is crucial for informing programmes, policies and reforms. We present findings from one of the first projects co-produced with people with lived experiences of being apprehended by police under mental health legislation. Interviews were conducted with twenty participants who had experience(s) of police apprehension across Australia. Findings highlight the social disadvantage experienced by participants prior to being apprehended and that use of force (such as tasering, pepper spraying and restraining in locked police vans) was common and over-used. Our study identified that police apprehension has lasting and wide-ranging impacts, leading to loss of employment, trauma, property damage, negative self-perceptions, discrimination, and fear of future police responses. Some participants were also apprehended by police while experiencing family violence and were misidentified as perpetrators. We argue police use of force mirrors the use of force within mental health services, with participants not experiencing a clear separation between police and mental health responses. The article shares participants' ideas for change, including response models based on human rights, police non-attendance and peer-led initiatives. Our findings suggest the need for investment in alternatives to police responses and further research involving lived experience perspectives to inform out understanding of mental health crisis responses. [ABSTRACT FROM AUTHOR]

One of the issues in Natural Language Processing (NLP) and Artificial Intelligence (AI) is language representation and modeling, aiming to manage its structure and find solutions to linguistic issues. With the pursuit of the most efficient capture of knowledge about the Modern Greek language and, given the scientifically certified usability of the ontological structuring of data in the field of the semantic web and cognitive computing, a new ontology of the Modern Greek language at the level of structure and vocabulary is presented in this paper, using the Protégé platform. With the specific logical and structured form of knowledge representation to express, this research processes and exploits in an easy and useful way the distributed semantics of linguistic information. [ABSTRACT FROM AUTHOR]