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The Battle of Salamis in 480 B.C. is one of the most important naval battles of all times. This work examines in detail the climatically prevailing weather conditions during the Persian invasion in Greece. We perform a climatological analysis of the wind regime in the narrow straits of Salamis, where this historic battle took place, based on available station measurements, reanalysis and modeling simulations (ERA5, WRF) spanning through the period of 1960&ndash, 2019. Our results are compared to ancient sources before and during the course of the conflict and can be summarized as follows: (i) Our climatological station measurements and model runs describing the prevailing winds in the area of interest are consistent with the eyewitness descriptions reported by ancient historians and (ii) The ancient Greeks and particularly Themistocles must have been aware of the local wind climatology since their strategic plan was carefully designed and implemented to take advantage of the diurnal wind variation. The combination of northwest wind during the night and early morning, converging with a south sea breeze after 10:00 A.M., formed a &ldquo, pincer&rdquo, that aided the Greeks at the beginning of the clash in the morning, while it brought turmoil to the Persian fleet and prevented them to escape to the open sea in the early afternoon hours.

Stratosphere-to-troposphere transport (STT) is an important natural source of tropospheric ozone, which can occasionally influence ground-level ozone concentrations relevant for air quality. Here, we analyse and evaluate the Copernicus Atmosphere Monitoring Service (CAMS) global and regional forecast systems during a deep STT event over Europe for the time period from 4 to 9 January 2017. The predominant synoptic condition is described by a deep upper level trough over eastern and central Europe, favouring the formation of tropopause folding events along the jet stream axis and therefore the intrusion of stratospheric ozone into the troposphere. Both global and regional CAMS forecast products reproduce the “hook-shaped” streamer of ozone-rich and dry air in the middle troposphere depicted from the observed satellite images of water vapour. The CAMS global model successfully reproduces the folding of the tropopause at various European sites, such as Trapani (Italy), where a deep folding down to 550 hPa is seen. The stratospheric ozone intrusions into the troposphere observed by WOUDC ozonesonde and IAGOS aircraft measurements are satisfactorily forecasted up to 3 days in advance by the CAMS global model in terms of both temporal and vertical features of ozone. The fractional gross error (FGE) of CAMS ozone day 1 forecast between 300 and 500 hPa is 0.13 over Prague, while over Frankfurt it is 0.04 and 0.19, highlighting the contribution of data assimilation, which in most cases improves the model performance. Finally, the meteorological and chemical forcing of CAMS global forecast system in the CAMS regional forecast systems is found to be beneficial for predicting the enhanced ozone concentrations in the middle troposphere during a deep STT event.

The annual and diurnal behavior of the temperature differences in urban areas is important to predict the possible impacts of the future land-use development on climate change and air pollution in heavily populated areas. The behavior of the temperature as well as wind spatio-temporal differences in turn is strongly interconnected with the turbulent and radiative fluxes variability. A 3-year dataset from three automated micrometeorological stations run by the Regional Agency for Environment Protection of Lazio and located in and around the city of Rome is used. The distribution of the urban heat island intensity for the whole period of measurements peaks at 1 °C, but higher values are frequently registered especially referring to differences with the coastal site also due to the sea-breeze cooling effects. The city is generally drier and characterized by winds of lower intensity reaching their maximum 1 h later with the respect to the sub-urban/coastal sites during the afternoon. The micrometeorological data are also analyzed to estimate some key parameter characteristic of the terrain, which represents the main forcing in the numerical models for UHI estimates, such as the albedo, aerodynamics and atmospheric turbulence parameters.

Modelling the effects of climate change on air quality over Central and Eastern Europe: concept, evaluation and projections Katarzyna Juda-Rezler, Magdalena Reizer, Peter Huszar, Bernd C. Kruger, Prodromos Zanis, Dimiter Syrakov, Eleni Katragkou, Wojciech Trapp, Dimitris Melas, Hristo Chervenkov, Ioannis Tegoulias, Tomas Halenka 1Faculty of Environmental Engineering, Warsaw University of Technology, 00-653 Warsaw, Poland 2Department of Meteorology and Environment Protection, Charles University, 180 00 Prague, Czech Republic 3Institute of Meteorology, University of Natural Resources and Life Sciences, 1190 Vienna, Austria 4Department of Meteorology and Climatology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 5Department of Air and Water Pollution, National Institute of Meteorology and Hydrology, 1784 Sofia, Bulgaria 6Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 7Air Protection Unit of Ekometria, 80-299 Gdansk, Poland 8National Institute of Meteorology and Hydrology, Branch Plovdiv, 4000 Plovdiv, Bulgaria

The short–term prediction of near surface ozone levels is very important due to the negative impacts of ozone on human health, climate and vegetation. The objective of this paper is to develop and test an analytical model that could be applied to predict next day's maximum ozone concentration for the first time in Tirana, Albania, where ozone's monitoring has been recently started. The relationship of the daily maximum hourly ozone values with meteorological variables, including near surface air temperature and relative humidity and with air pollution variables like the persistency of ozone levels and its seasonal variation is examined. The data analysis reveals that the pollution persistency and the near surface air temperature are the factors that mainly affect the peak ozone levels. Multiple linear regression analysis has been performed to establish the relationship between the above mentioned parameters and peak ozone concentration. The agreement between observed and predicted daily maximum hourly ozone values is very good, with a correlation coefficient (R) of 0.87. The model slightly under–predicts the ozone concentration while no significant mispredictions are observed. Additionally, the model’s ability to predict the exceedances of a specific ozone limit value is examined. The model successfully predicts the exceedances of 105 μg m −3 , a value that corresponds to the 75 th percentile, in the 86% of the cases applied.

This paper provides a comprehensive overview of the actual knowledge on the atmospheric pollution sources, transport, transformation and levels in the East Mediterranean. It focuses both on the background atmosphere and on the similarities and differences between the urban areas that exhibited important urbanization the past years: the two megacities Istanbul, Cairo and the Athens extended area. Ground-based observations are combined with satellite data and atmospheric modeling. The overall evaluation pointed out that long and regional range transport of natural and anthropogenic pollution sources have about similar importance with local sources for the background air pollution levels in the area.

During the summer of 2007 several Greek regions suffered periods of extreme heat, with midday temperatures of over 40 degrees C on several consecutive days. High temperatures were also recorded on the east coast of central Greece, where a complex sea breeze circulation system frequently develops. The more intense events occurred at the end of June and July. The highest temperatures were observed on 26 June and 25 July, while the sea breeze developed only on 25 July. Meteorological data collected at two sites-a coastal urban location and an inland suburban site that is not reached by the sea breeze flow-as well as pollution data collected at the urban site, were analysed in order to investigate the relationship between sea breeze development and the prevailing environmental conditions during these two heat wave events. The analysis revealed that sea breeze development affects temperature and pollution levels at the shoreline significantly, causing a decrease of approximately 4 degrees C from the maximum temperature value and an increase of approximately 30% in peak PM10 levels. Additionally, several stress indices were calculated in order to assess heat comfort conditions at the two sites. It was found that nocturnal comfort levels are determined mainly by the urban heat island effect, the intensity of which reaches up to 8 degrees C, while the applied indices do not demonstrate any significant daytime thermal stress relief due to sea breeze development.

[1] The Photochemical Activity and Ultraviolet Radiation (PAUR) II project (a continuation of an earlier PAUR I project) had the purpose of studying the interrelationships between changes in total ozone, tropospheric aerosols, UV radiation and photochemical activity. As part of PAUR II project, a campaign took place in Greece and Italy during May–June 1999, with the participation of 15 European and 3 American research institutions. A variety of radiation and gaseous and aerosol atmospheric composition and optical characteristics measurements were made during the campaign. Radiative transfer models and three-dimensional (3-D) regional chemistry transport models (CTM) were applied and compared to the available data set of PAUR II. The present overview paper gives an introduction to the project and to the meteorological and environmental conditions that prevailed and outlines some results that are extensively described in the subsequent papers which form this special section. The modulation of the UVB field in the presence of different types of aerosols, its transmittance and role in the photochemistry of the particular eastern Mediterranean environment is overviewed. Using a 3-D CTM, it is shown that even a 50% reduction in Greek anthropogenic emissions has only a small effect in reducing the ozone levels over the eastern Mediterranean in summer. The environmental conditions, which prevailed during the PAUR I and PAUR II campaigns, offered cases of background conditions over the Aegean Sea as well as conditions with Saharan dust episodes and extremes in total ozone.

The NOPEX two concentrated field efforts (CFEs) (June 1994 and April–July 1995) provide high quality data sets for the Boreal environment. The analysis of these data with traditional meteorological and hydrological approaches allow estimations of fluxes of latent and sensible heat, but these flux estimates are not directly comparable due to differences in temporal and spatial scales. The challenge here has been to overcome these difficulties so that the different estimates can be critically compared and evaluated in a systematical way. Five different approaches for the estimation of the regional flux of sensible and/or latent heat over the NOPEX area have been evaluated: (1) Direct aggregation — mixed layer evolution method, (2) Weighted averages of (a) aircraft measurements in the boundary layer and of (b) mast measurements, (3) Numerical models (a) ECOMAG — a distributed hydrological model and (b) MIUU — a mesoscale meteorological model. In general, good agreement was found between the regional estimates of the sensible heat flux, based on the mixed layer evolution method and land use weighted mast measurements. The aircraft measurements were found to be systematically smaller than the land use weighted mast estimates. For the latent heat flux good agreement was found between the regional latent heat flux derived from airplane measurements, land use weighted mast estimates, and the two mesoscale numerical models.