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The average PM10 daily levels over the urban area of Thessaloniki, Greece, usually exceed the air quality limits and therefore the improved PM chemical composition and air quality modeling results that will facilitate the design of the most appropriate mitigation measures (e.g., limitations in wood combustion for heating purposes) are essential. The air quality modeling system WRF-CAMx was applied over a 2 × 2 km2 horizontal resolution grid covering the greater area of Thessaloniki for the year 2015, when Greece was still confronting the consequences of the financial crisis. The output hourly surface concentrations of twelve PM species at three sites of different environmental type characterization in the city of Thessaloniki were temporally and spatially analyzed. Carbonaceous aerosols (organic and elemental) are the major contributor to total PM10 levels during winter representing a 35–40% share. During summer, mineral aerosols (excluding dust) distribute by up to 48% to total PM10 levels, being the major contributor attributed to road traffic. PM species, during winter, increase in the morning and in the afternoon mainly due to road transport and residential heating, respectively, in addition with the unfavorable meteorological conditions. An underestimation of the primary organic carbon aerosol levels during winter is identified. The application of the modeling system using a different speciation profile for the fine particles emissions from residential heating based on observational data instead of the CAMS emissions profile revealed an improvement in the simulated OC/EC values for which a 50% increase was identified compared to the base run.

This study aims to investigate, in microscale, the pollutant emissions due to road traffic under traffic-congested conditions at street level and the impacts on air quality of traffic emissions reduction scenarios by applying an Integrated Modelling Tool (IMT) for a main road axis in Thessaloniki, Greece. ΙΜΤ links a real-world traffic model, a dynamic emissions model and a Lagrangian dispersion model coupled with a boundary layer flow module. Pollutant emissions from cars at edges with traffic lights were + 30% higher than those estimated at other edges while NOx emissions were + 22% higher at the edges with bus stops. A comparison of the IMT and COPERT Street Level emissions results showed that the IMT emissions were higher than the COPERT Street Level emissions for roads with traffic lights or bus stops, characterized by high variability in vehicle speed per second due to stopping and accelerating. This resulted in up to 2 times higher NOx emissions. IMT was applied to assess the impact on the atmospheric environment of the redesign of the road axis promoting sustainable urban transportation. A reduction by − 20% of the cars and motorcycles traffic flows in combination with the increase by a factor of 2 of the frequency in the circulation of city buses replaced with battery electric vehicles will result in lower pollutant and CO2 emissions ranging from − 29 to − 41%. Reductions of about − 65% in the road traffic NOx maximum concentration levels were also estimated.

BACKGROUND AND AIM: In the LIFE ASTI project a forecasting system for estimating the urban heat island intensity (UHI) and defining high resolution heat health watch warning systems was developed i...

In this study the exposure levels from Quercus pollen in the greater area of Thessaloniki are estimated. The estimation is implemented with a modeling system, comprising the meteorological model WRF, the Natural Emissions Model (NEMO) for the calculation of the Quercus pollen emissions and the chemistry-transport model CAMx for the advection and the deposition of the pollen particles. The period of 2016 with the highest potential is selected, based on the available measurements for the area of interest. The modeling system is evaluated with meteorological and pollen measurements, as well on the expected exposure levels, indicating a satisfactory overall performance. The modeling system is finally utilized for the estimation of exposure levels in the greater area of Thessaloniki, showing that the city of is not going to experience significant number of days with high Quercus pollen concentrations, although other, smaller cities and towns might be affected.

Middle East Area and especially the central part is a dust dominated domain and therefore estimation of natural dust emissions is critical. Aim of this study is to assess the sensitivity of state-of-the art dust modules, utilized in multiple modelling schemes, and especially of their three main components; namely the horizontal mass flux, the drag partition and the sandblasting efficiency. To accomplish this, several simulations with the Natural Emission MOdel (NEMO), driven by the Weather Research and Forecasting (WRF) model, were made for the period April–June 2015 focusing in the central Middle East (CME). First, the meteorological model was evaluated over the study period, as well as during a Shamal event, showing a satisfactory performance on wind speed which is the most important meteorological variable inserted in the dust modules. Second, dust emissions were found to be a few tenths of μg/m2s on average, while the daily amount exceeds 1000 mg/m2day. Over the studied period, the fluxes range from 15 to 750 g/m2. The total emissions in CME were estimated with the NEMO's basic configuration at 139 Tg. The most active areas are associated with clay content ranging between 17 and 25%, highlighting the importance of soil texture on the definition of the dust sources. During a Shamal event in the second half of June 2015, the mean dust emission fluxes reached up to several hundreds of μg/m2s, contributing 21 Tg in CME. Few such events could cover a large portion of the dust emissions. Finally, concerning the sensitivity of the total emissions, the drag partition scheme has the largest effect, followed by sandblasting efficiency and horizontal mass flux. The total dust emissions budget, among the 16 simulations was found to be in the range of 21–139 Tg, with the choice of the drag partition scheme to be mandatory for the narrowing of the total emissions in CME.

In this study a high resolution modeling system is developed to simulate Quercus pollen concentrations in the greater area of Thessaloniki, Greece, under an a priori oak phenological season. The modeling system consists of three models in series, the Weather Research and Forecasting (WRF) meteorological model, the natural emissions model NEMO for Quercus pollen emissions and the chemistry-transport model CAMx. The modeling system is evaluated with daily meteorological and pollen measurements during the phenological season of 2016 of Quercus taxa. The modeling system's performance is satisfactory on both meteorology and Quercus pollen concentrations, although for the latter the relative uncertainty is slightly above the 50% criterion usually applied in air quality modeling. Additional analysis was performed on three parameters related to pollen emissions, namely the assigned pollen production, the spread of the phenology and the assigned diameter. The analysis shows that the greatest impact on Quercus pollen concentrations, on both near the sources as well at remote areas, is the assigned pollen production, followed by the spread and the assigned diameter.

Post-processing techniques can provide significant improvement in the forecast skill of air quality models. In this study, the implementation of an analog-based technique to Comprehensive Air Quality Model with Extensions (CAMx) coupled with Weather Research and Forecasting (WRF) model results is examined. WRF-CAMx runs with a 2-km horizontal grid increment over Greece for one month of every season of the year 2012 (i.e., January, April, July and October). The analog ensemble (AnEn) technique attempts to improve the accuracy of ozone and particulate matter forecasts by using a method that searches for analogs in past forecasts. An optimization process that minimizes Root Mean Square Error (RMSE) metric has been used to find the best AnEn configuration. The corrected forecasts are computed with two approaches, i.e., AnEn ‘mean’ and AnEn ‘bias correction’ (AnEn-bias) approach. The methods are tested with observations from 23 surface stations for ozone, 16 stations for PM10 and 3 stations for PM2.5 for an 11-day period for each month. The results which are very similar for both techniques show an improvement of the forecast skill of all pollutants. The corrected forecasts have smaller RMSE and higher Correlation Coefficient (R). A reduction of 40 and 70% for AnEn RMSE values is found for ozone and particulate matter, respectively. For AnEn R, an improvement of 11% for ozone, 46% for PM10 and 26% for PM2.5 is estimated. These techniques are also successful in drastically reducing the mean bias of raw forecasts to close to zero.

This study aims towards an accurate regional dust modeling system in the central Middle East area (CME), through the implementation of the state-of-art dust parameterizations. The modeling system consists of the natural emission model NEMO, the meteorological model WRF and the chemistry transport model CAMx. An extensive evaluation of 16 different configurations has been realized, incorporating all the combinations of the components utilized in the state-of-art dust modeling approaches, namely the drag partition, the sandblasting efficiency, the horizontal mass flux, as well two commonly used soil particle size distributions. Daily mean PM10 measurements in Doha, as well the satellite AOD products of MODIS have been used for the quantitative and the qualitative assessment of the simulations. Noteworthy, each of these assessments did not yield to the exact same ranking of the configurations (e.g. best five) but they assisted on identifying clear patterns. For example, a consistent overestimation of the daily mean PM10, when the MacKinnon's drag partition scheme is utilized, was found. On the other hand, the assessments led to best three performing configurations, with common components the Raupach's drag partition scheme and Alfaro and Gomes sandblasting efficiency. Although their overall performance is good, several issues were found i.e. on individual dust events and a mean underestimation during the studied period, ranging from −49 to −75 μg/m3. One cause of this underestimation could be the aerodynamic entrainment, a mechanism usually neglected from the dust modeling approaches. Another cause could be missed regional and/or local sources or underestimation of their emission rates.

A modeling system that consists of the meteorological model WRF and the photochemical model CAMx has been applied in very high horizontal resolution (2 km) in order to assess the air quality in Greece. An updated, high resolution emission inventory was compiled for all the main anthropogenic pollutants (CO, NOx, SO2, NMVOCs, PM10, PM2.5) while emissions from natural sources (dust, sea salt and biogenic NMVOCs) were calculated using the Natural Emissions MOdel (NEMO). Toxic particulates, such as As, Cd, Pb, Ni and benzo-(a)-pyrene, were simulated as inert pollutants. Simulations were performed for one month of every season of the year 2012, namely for the months of January, April, July and October. The comparison of simulated pollutant levels and those measured at the stations of the National Monitoring Network of the Air Quality revealed a satisfactory performance of the photochemical model. Following the EU legislation for the protection of human health and vegetation, the exceedances of the air quality limits were calculated for every grid cell over Greece.

ECMWF-Copernicus Atmospheric Monitoring Service (CAMS) interim reanalysis (CAMSiRA) provides global atmospheric composition fields at a horizontal resolution of ~80 km and 60 hybrid sigma-pressure levels from the surface up to 0.1 hPa which can be further used to serve as boundary conditions for regional air quality models over Europe and world-wide. Here we present an evaluation of near surface ozone reanalysis for the period 2003–2013 based on measurements at rural locations from the European Monitoring and Evaluation Program (EMEP) and the European Air Quality Database (AirBase). The CAMS interim reanalysis is also compared to a control run in order to assess the impact of assimilation on near surface ozone. The evaluation results are discussed in terms of the physical processes (transport and deposition) and the chemical processes (photochemical production and destruction) that control near surface ozone variability.

The impact of cruise and passenger ship emissions on air quality and human health risk in the greater Thessaloniki area has been studied for the present and future time. The study focuses on the pollutants regulated by the EU legislation. Simulations have been performed using the CALPUFF dispersion model for 2013, in order to estimate the pollutant surface concentrations due to passenger ship traffic. Additionally, projections for the year 2025 have been made, accounting also for emission mitigation measures including the use of LNG as ship fuel and the implementation of Cold ironing technology. Ship emissions have been estimated using the movement methodology of the EMEP/EEA. Population exposure maps have been prepared on the basis of the simulated surface concentrations, providing an overview of the affected areas and population. For both the present time and the future trend projection the NO2 is of major concern, with the hourly concentrations exceeding the air-quality limit. When the LNG scenario is adopted, future NO2 concentrations are expected to be reduced over the urban area by more than 40 %, while the exposure of the population will be significantly reduced.

The choice of the parameterization scheme, the input parameters and the spatial resolution are options that can provide significantly different modelling results for the processes of desert dust production and transport. This work will discuss the level of coherence between a regional and a global modelling system with regards to the simulation of desert dust production and transport in N-Africa. The limited-area model SKIRON/Dust and the atmospheric chemistry general circulation model EMAC (ECHAM5/MESSy2 Atmospheric Chemistry) have been applied using a common physically-based dust emission scheme. The differences between the two modelling systems and the comparison with the observations will be analysed and discussed, as well as the plans for future work in their offline coupling.