The relative contribution of the main mechanisms that control indoor air quality in residential flats was examined. Indoor and outdoor concentration measurements of different type pollutants (black carbon, SO 2, O 3, NO, NO 2,) were monitored in three naturally ventilated residential flats in Athens, Greece. At each apartment, experiments were conducted during the cold as well as during the warm period of the year. The controlling parameters of transport and deposition mechanisms were calculated from the experimental data. Deposition rates of the same pollutant differ according to the site (different construction characteristics) and to the measuring period for the same site (variations in relative humidity and differences in furnishing). Differences in the black carbon deposition rates were attributed to different black carbon size distributions. The highest deposition rates were observed for O 3 in the residential flats with the older construction and the highest humidity levels. The calculated parameters as well as the measured outdoor concentrations were used as input data of a one-compartment indoor air quality model, and the indoor concentrations, the production, and loss rates of the different pollutants were calculated. The model calculated concentrations are in good agreement with the measured values. Model simulations revealed that the mechanism that mainly affected the change rate of indoor black carbon concentrations was the transport from the outdoor environment, while the removal due to deposition was insignificant. During model simulations, it was also established that that the change rate of SO 2 concentrations was governed by the interaction between the transport and the deposition mechanisms while NO X concentrations were mainly controlled through photochemical reactions and the transport from outdoors. © 2009 Springer Science+Business Media B.V.

The sensitivity of regional air quality modeling simulations to boundary conditions over Greece is investigated, for various synoptic conditions. For this purpose, a global to mesoscale model-chain is developed and applied, coupling the individual models’ simulations. The global chemical transport model GEOS-CHEM, applied in a one-way nested procedure, is used to drive the regional UAM-V chemical dispersion model with time-varying lateral and top boundary conditions. The results of the coupling procedure are compared with the MINOS campaign measurements at Finokalia (Southern Greece) during the period from 1 to 16 August 2001 which is mainly characterized by an interchange of two synoptic types, High-Low and Long Wave trough. The comparison between the simulation results and the measurements reveals that the coupling procedure captures satisfactorily the range of observed CO concentrations at the southern part of Greece. The most severe deviations are observed under strongly variable atmospheric circulation, when no distinct synoptic circulation is allowed to be established in the area. Regarding O3, the highest, though underestimated, surface concentrations are simulated under Long Wave trough conditions due to the influence of the ozone inflow predicted by GEOS-CHEM at the western boundary of the innermost domain and/or under enhanced NOy emissions arriving at Finokalia from urban and ships plumes. © 2009 Elsevier Ltd. All rights reserved.

The objective of this study is to investigate the impact of the eastern Mediterranean teleconnection pattern (EMP) on the present and future climate of the eastern Mediterranean during winter. For the present climate, daily precipitation and maximum and minimum surface temperature station data are employed for the period of 1958-2003. For the future climate, datasets of the same parameters are derived from the Hadley Centre Regional Climatic Model (HadRM3P) for the period of 2070-2100, using two Intergovernmental Panel on Climate Change (IPCC) emission scenarios for the evolvement of the future atmospheric concentrations of greenhouse gases. The investigation of the impact was based on the regularized canonical correlation analysis (RCCA), while qualitative estimations were performed for each phase of the pattern. It was found that the pattern indeed affects the mean winter patterns of temperature, precipitation, and their extreme events with inverse impacts between the two phases. More specifically, a positive phase of EMP is associated with a decrease in temperatures and an increase in precipitation, while the opposite occurs during the negative phase of EMP. In the future, the present impact according to each phase persists and intensifies in most of the cases. However, results are quite different between the two scenarios, because of the different estimated future shift of the EMP poles. © 2009 American Meteorological Society.

In this study, an assessment of indoor air quality (IAQ) and thermal comfort in the Athens Traffic Control Tower (ATCT) offices of Hellinicon building complex, which is mechanically ventilated, is presented. Measurements of PM 10, PM 2.5, TVOCs and CO 2 concentrations were performed during three experimental cycles, while the Thom Discomfort Index was calculated to describe the employees’ feeling of discomfort. The aim of the first cycle was to identify the IAQ status, the second to investigate the effectiveness of certain measures taken, and the third to continuously monitor and control IAQ. During the first two cycles, daily spot measurements of TVOCs and CO 2 were performed at various indoor locations and at the respective outdoor air intake positions, in addition with mean 24-h spot measurements of indoor PM 10 and PM 2.5. Results revealed that pollution levels vary according to the occupancy and the kind of activity. Following that, an automated system (IMAS) was designed and employed to continuously monitor indoor and outdoor CO 2, TVOCs, temperature and relative humidity. The ultimate scope was to control the IAQ and offer acceptable comfort conditions to the employees, whose work is of special nature and extremely demanding. Intervention scenarios were formulated and applied to the system to improve indoor conditions, when and where necessary. Regarding the third cycle, 1-year measurements collected from the system to examine its effectiveness. While it was shown that discomfort may be attributed to co-existence of unsatisfactory thermal comfort conditions and IAQ, usually the sole predominant factor of discomfort feeling is thermal comfort. © Springer Science+Business Media B.V. 2008.

Weather maps refer to meteorological data that characterize the atmospheric circulation in a region. The classification of weather maps into categories becomes an important task for understanding regional climate. Towards this goal, manual and semiautomatic techniques have been used, requiring manpower and supervision. In this paper, we propose a machine vision based method for the classification of weather maps into distinct classes. The chain code descriptor is applied to extract the feature of isobaric lines and we introduce the Double-Side Chain Code (DSCC) histogram for feature representation. Handling DSCC histograms as multidimensional vectors, the A:-nearest neighbors (k- NN) algorithm classifies the objects to an appropriate number of classes, based on closest training set in the feature space. This method provides an automated and more ’objective’ classification scheme, applying straightforward to the input weather map’s image. © 2009 IEEE.

During the peak of an extensive heat wave episode on 23-25 July 2007, simultaneous thermophysiological measurements were made in two non-acclimated healthy adults of different sex in a suburban area of Greater Athens, Greece. Based on experimental measurements of mean skin temperature and metabolic heat production, heat fluxes to and from the human body were calculated, and the biometeorological index heat load (HL) produced was determined according to the heat balance equation. Comparing experimental values with those derived from theoretical estimates revealed a great heat stress for both individuals, especially the male, while theoretical values underestimated heat stress. The study also revealed that thermophysiological factors, such as mean skin temperature and metabolic heat production, play an important role in determining heat fluxes patterns in the heat balance equation. The theoretical values of mean skin temperature as derived from an empirical equation may not be appropriate to describe the changes that take place in a non-acclimated individual. Furthermore, the changes in metabolic heat production were significant even for standard activity. © 2008 ISB.

This study explores the influence of air gaseous pollutants-aerosols and solar zenith angle (SZA) on the spectral diffuse-to-direct beam Edλ/Ebλ irradiances ratio. It does so using ground-based spectroradiometric measurements taken over the Athens atmosphere during May 1995. It was found that the spectral Edλ/Ebλ ratio decreases rapidly with increasing wavelength and regression curves of the form EEdλ/Ebλ = aλ-b fitted the experimental data. These curves are strongly modified by aerosols-air pollutants, aerosol optical properties, and SZA. The log-log plot of Edλ/Ebλ versus λ reveals a significant departure from linearity, which is likely to be associated with aerosol physical properties and SZA effects. The effect of atmospheric turbidity, as expressed through the aerosol optical at 500 nm and SZA on the spectral Edλ/ Ebλ ratio, is investigated in detail for two discernible atmospheric conditions observed in the urban Athens atmosphere. The first case includes different atmospheric turbidity levels under the same SZA, while the second corresponds to different SZA values under the same turbidity levels. It was found that the correlation between Edλ/Ebλ and spectral aerosol optical depth can be a useful tool in determining the aerosol optical properties and aerosol types composition. © Springer-Verlag 2009.

Air pollution episodes in urban coastal areas follow certain pre-determined patterns, being associated with certain local meteorological conditions and emission of primary pollutants. In this study, the synoptic and local scale atmospheric circulation that prevails during air pollution episodes in a coastal major city in Greece, Thessaloniki, is examined for a period of 15 years (1989-2004). The study signifies the importance of studying air pollution meteorological patterns between coastal areas with different terrain characteristics. For Thessaloniki, it was found that the episodes occur mainly during the cold period of the year, while four types of synoptic scale circulation were recognized (I, II, III, IV) and five patterns of the local scale circulation (A1, A2, B1, B2 and B3). The highest percentage of episodes is associated with the presence of an anticyclone over the northern Greece (types I and IV), being characterized by weak or very weak surface pressure gradient intensity, according to the position and extension of the anticyclone. Moreover, a temperature increase of at least 1°C during the previous 3 days is required in the lower troposphere. Consistent with the synoptic conditions, the development of the sea breeze plays a crucial role in the occurrence of the episodes, even in the cold period of the year, when the sea breeze can still develop with smaller frequency and intensity. Finally, it was found that a small number of episodes is related with the advection of polluted air masses from the industrial area in the northwest of the city and from the Eordaia area in the west, which is the largest lignite producing area of Balkans. © Springer-Verlag 2008.