In the present study, the spatial and temporal variability of the Aridity Index (AI) in the Mediterranean region during the 30-year period 1971–2000 is analyzed. The analysis is performed on a decadal timescale. Subsequently, the projected change in the AI in the periods 2031–2060 (near future) and 2071–2100 (far future) under the RCP4.5 and RCP8.5 emission scenarios in comparison with 1971–2000 (reference period) is presented. The input of the calculations are simulation results supplied by the CORDEX EU project. In total, an ensemble of 20 combinations of global climate models (GCMs) and regional climate models (RCMs) are used. The calculation of the AI is based on potential evapotranspiration, which, in turn, is calculated according to the classic method of Thornthwaite. Our results show that drier conditions are to be expected in the future along a wide zone in southern Europe, including Spain, Italy, Bulgaria, Greece and Turkey, as well as in Northern Africa, particularly under the RCP8.5 scenario and towards the end of the century.

The city of Athens has faced air pollution problems over the last few decades due to the high population density associated with an intense emission load constrained by the local topography causing poor ventilation. In addition, the high levels of solar irradiation, in combination with emissions of nitrogen oxides and hydrocarbons, have led to the formation of photochemical pollutants, especially ozone. In this study, the evolution of the seasonal variation of primary and secondary photochemical urban air pollution in Athens was examined for the 2001–2021 period. For this purpose, the monthly NO_x (NO+NO₂), ozone, and O_x (O₃+NO₂) averages for the Athens air pollution monitoring stations of Geoponiki, Liossia, Ag. Paraskevi, and Thrakomakedones in the selected periods of 2001–2004, 2010–2013, 2016–2019, and 2020–2021 were plotted. In addition, summer diurnal NO_x, ozone, and O_x variations were examined. There was a clear reduction in NO_x levels at all four examined stations, especially at the urban background site of Geoponiki, as well as at the most polluted peripheral site of Liossia, following a reduction in urban emissions, mainly from car traffic during the examined period. The ozone and O_x curves did not show the same patterns due to the complicated nature of local ozone photochemical production, in combination with the rural surface ozone background, which was particularly high over the area.

Solar Ultraviolet (UV) radiation plays a key role in many chemical and biological processes, and affects significantly human health. Excessive UV exposure may lead to adverse health effects, including sunburns, skin cancer, and cataracts, whereas moderate exposure is beneficial, e.g., by supporting vitamin D production and promoting mental well-being, among other benefits. UV radiation interacts with various atmospheric components before reaching the Earth’s surface. Photons with shorter wavelengths are absorbed at higher atmospheric layers by oxygen and tropospheric ozone, and practically only UV-A and a small part of the UV-B irradiance reach the troposphere. In the troposphere, UV is scattered by air molecules and is further attenuated by aerosols and clouds. Interactions between UV radiation and aerosols are not yet completely understood, and their parameterization constitutes a major uncertainty factor in models and satellite retrieval algorithms. Understanding these interactions is thus essential for accurately assessing UV exposure using modeled UV irradiance.Τhe purpose of this study is to evaluate satellite- and reanalysis-based retrievals of the effective dose for the cutaneous vitamin D synthesis using ground-based measurements over Athens and Thessaloniki, Greece. We evaluate data that are derived (1) using the methodology described in Fragkos et al., (2024, https://doi.org/10.3390/rs16111878), based on CAMS information in combination with satellite data from OMI and MSG, and (2) the UV climatology of which is also based on data from various sensors analyzing air quality. Ground-based spectral solar UV irradiance measurements performed with a MKIV single monochromator Brewer spectrophotometer in Athens, and a MKIII double monochromator Brewer spectrophotometer in Thessaloniki are used to validate the Satellite-based retrievals. AOD measurements from co-located CIMEL sun-photometers, part of the AERONET network are used to assess the effect of aerosols. The evaluation has been performed for the period 2004 - 2024. Further analysis yielded positive trends in the effective dose for vitamin D production in the last two decades, mainly due the decreasing trends in aerosols.

The densely populated city of Athens has been facing air pollution problems over the past few decades due to the high population density associated with an intense emission load constrained by the local topography causing poor ventilation. In this study, the evolution of the interannual and seasonal variation in primary and secondary gaseous as well as particulate urban air pollution in Athens was examined for the 2001–2023 period and for the following pollution parameters: SO₂, CO, NO₂, NO_x (NO + NO₂), O₃, O_x (O₃ + NO₂), PM₁₀, and PM_2.5. For this purpose, the annual and monthly averages from the Athens air pollution monitoring stations of Peireas (SO₂, CO, NO₂, NO_x), Patission (SO₂, CO, NO₂, NO_x), Aristotelous (PM₁₀, PM_2.5), Lykovrissi (PM₁₀, PM_2.5, O₃, O_x), and Liossia (O₃, O_x) in the selected periods of 2001–2004 and 2020–2023 were examined. There was a clear reduction in most air pollution parameters at all stations during the period examined, relative to the average values. The ozone and O_x values, presenting a high interannual variability, remained generally unchanged. The smallest reductions are observed for NO₂ and NO_X (about −10% to −20%), while the highest reductions are observed for SO₂, CO, and PM₁₀ (about −50% to −60%). The change in pollutant concentrations for every month of the year between the 2001–2004 and 2020–2023 time periods is also examined, and the observed seasonal differences are discussed.