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Forecasting and characterizing fire weather conditions over a region days in advance is of great importance for developing early warning systems and supporting effective wildfire management. Furthermore, it is important for increasing awareness and preparedness of all the involved entities, including both the public and practitioners. In addition, considering climate projections over the Mediterranean, which indicate an environment more conducive to wildfire activity, the need for timely forecasting of extreme fire weather days becomes increasingly urgent. In this work we present an application of the newly developed fire weather forecasting framework that employs the concept of critical fire weather patterns on the 2018 Mati wildfire. Within our fire weather forecasting framework, we assign the large-scale circulation pattern to one of the predefined critical fire weather patterns of Greece which are associated with different levels of fire danger based on the dominating fire weather conditions and expected fire behavior. For the purpose of this study, we use historical forecast data to assess the predictability of the synoptic-scale fire weather conditions using the critical fire weather patterns, and we discuss the main advantages of the presented forecasting framework. This fire weather forecasting framework is applied operationally by the METEO Unit of the National Observatory of Athens within the frame of the "FLAME" project since the 2022 fire season in Greece. [ABSTRACT FROM AUTHOR]

Greece in the period July-August 2021 was affected by two heat waves characterized by very high temperatures. The result was the occurrence of fires in various regions of the country, with Attica being one of the most affected regions of Greece. The atmospheric burden was very high, and the smoke covered the Attica sky at times, affecting the sunshine and by extension the incoming solar radiation. In this study, we examine whether the reduction in solar UV radiation synergistically with the increase in atmospheric particulate pollution was related to the spread of COVID-19 in Attica in the summer of 2021. [ABSTRACT FROM AUTHOR]

Climate change raises concerns over the sustainability of the outdoor thermal environment and its impacts on societies. This study aims to examine the thermal conditions in Athens metropolitan area, Greece. Hourly data from 15 stations of the Automatic Weather Station Network of the National Observatory of Athens (2010-2021) were used to estimate the Net Effective Temperature (NET) and the Universal Thermal Climate Index (UTCI). The NET and UTCI were higher within the Athens basin (NET: mean ± sd = 15.3 ± 7.1 °C; UTCI: mean ± sd = 18.9 ± 10.4 °C) than in the surrounding area (NET: mean ± sd = 11.2 ± 9.3 °C; UTCI: mean ± sd = 13.4 ± 13.4 °C; p < 0.001). The highest numbers of hours with unfavorable warm conditions were found in Faliro (28.6%, NET; 27.7%, UTCI), Neos Kosmos (28.6%, NET; 27.4%, UTCI) and Patissia (28.6%, NET; 27.2%, UTCI). With respect to unfavorable cool conditions, the highest number was in Spata (65.1%, NET; 28.4%, UTCI). [ABSTRACT FROM AUTHOR]

At highly populated areas, such as the Greater Athens Area in Greece, the air quality differs significantly from one municipality to another, being highly affected by the local anthropogenic sources (traffic, residential heating, navigation) and consequent emissions. Thus, the existence of a dense network of low-cost air quality sensors provides evidence of seasonal patterns on particulate concentrations within the urban zone. In the present study, hourly PM2.5 concentrations recorded using low-cost sensors at six municipalities in the Greater Athens Area (Vrilissia, Psychiko, Peristeri, Rentis, Agia Varvara, Palaio Faliro) with different characteristics (population density, pollutant sources, surrounding land use) were collected for the year 2022. The highest mean seasonal values were recorded in the western and southern suburbs (Peristeri, Rentis and Palaio Faliro) during the cold period (winter of the year 2022). Mean concentrations decreased significantly in spring; the mean concentrations were 31.3 µg/m³ and 18.5 µg/m³ in Vrilissia in winter and spring, respectively (year: 2022). [ABSTRACT FROM AUTHOR]

Ozone is formed in the lower layers of the atmosphere mainly by gases emitted by anthropogenic activities in combination with solar radiation. In the present study, the short-term health impacts of ozone (O3) on people living in the Greater Athens Area in Greece are analyzed for the period 2001-2018 by estimating the cardiorespiratory deaths with the AirQ+ model. Ozone measurements (8-h mean values) for two areas with different characteristics (Thrakomakedones and Athinas) were used provided by the National Air Pollution Monitoring Network. Data processing showed that environmental conditions and geographical characteristics influence O3 variation and the risk of cardiorespiratory deaths. The statistical analysis of O3 measurements revealed that at the southwestern suburb of Thrakomakedones the mean annual concentrations range from 74 to 96 µgr/m³, much higher than in the Athens center (40-56 µgr/m³, station: Athinas). The O3 concentration threshold was exceeded in Thrakomakedones approximately 90 times per year, while in the Athinas monitoring station, it was exceeded only 25 times. According to the AirQ+ software package, the percentage of deaths due to O3 exposure ranges from 6% in Thrakomakedones to 7.5% in the Athinas station. [ABSTRACT FROM AUTHOR]

Based on ground-based measurements, the impact on air pollution over the Greater Athens Area (GAA) due to the two public lockdown periods (first lockdown period: 23 March 2020 until 3 May 2020; second lockdown period: 7 November 2020 until 2 May 2021) in the GAA implemented to stop the spread of the COVID-19 is analyzed. The findings demonstrated that vehicular traffic is the main culprit of air pollution in the GAA, while secondary factors for the air pollution over the GAA are considered heating systems and the weather, while the 'ozone paradox' was noticed, too. [ABSTRACT FROM AUTHOR]

In the present study, the microclimatic conditions of two courtyards in the city of Athens are evaluated based on filed monitoring data and data predicted by artificial neural network models (ANNs). The study focuses on the development and application of ANNs in order to estimate air temperature and relative humidity values in complex urban forms such as courtyards from a standard meteorological station, using air temperature and relative humidity as the only inputs. The results are then evaluated to identify the prognostic ability of the developed ANNs models, showing a remarkable predictive ability. [ABSTRACT FROM AUTHOR]

Air pollution is a global environmental issue that primarily affects the health of city residents. The purpose of this study was to comprehensively assess air pollution levels in the center of Athens and compare them with those in the peri urban Mt. Hymettus Aesthetic Forest. To achieve this, two low-cost sensors, namely, the "PurpleAir PA-II-SD," were combined with the employed methodology. The first sensor was stationed at a fixed central point in the Mt. Hymettus Aesthetic Forest, whereas the second one captured measurements along a specific route among six points in the historic center of Athens during the summer of 2021. The pollutants measured included PM10, PM2.5, and PM1, as well as temperature and humidity. The research findings indicated that all pollutant values were significantly higher in the center of Athens, particularly in terms of PM2.5, which exceeded the permissible limits set by the European Commission. Furthermore, notable variations in temperature were observed in both areas. [ABSTRACT FROM AUTHOR]

Air quality simulations were performed for the Greater Athens Area in very high spatial resolution using the modeling system WRF-CAMx. Sensitivity runs were performed using the SOAP and VBS schemes for organic gas-aerosol partitioning and oxidation. In January 2019, OA-VBS decreased compared to OA-SOAP because of POA reduction. In July 2019, the OA-VBS increased with respect to OA-SOAP as a result of the increase in SOA levels exceeding the decrease in POA ones. The comparison of the WRF-CAMx results against PM10, PM2.5, and OC surface measurements provides the first indications for improved CAMx performance with the VBS scheme. [ABSTRACT FROM AUTHOR]