Publications by Year: 2012

Nastos, P.T. & Matzarakis, A. The effect of air temperature and human thermal indices on mortality in Athens, Greece. Theoretical and Applied Climatology 108, 591 - 599 (2012). WebsiteAbstract
This paper investigates whether there is any association between the daily mortality for the wider region of Athens, Greece and the thermal conditions, for the 10-year period 1992-2001. The daily mortality datasets were acquired from the Hellenic Statistical Service and the daily meteorological datasets, concerning daily maximum and minimum air temperature, from the Hellinikon/Athens meteorological station, established at the headquarters of the Greek Meteorological Service. Besides, the daily values of the thermal indices Physiologically Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) were evaluated in order to interpret the grade of physiological stress. The first step was the application of Pearson's χ 2 test to the compiled contingency tables, resulting in that the probability of independence is zero (p = 0. 000); namely, mortality is in close relation to the air temperature and PET/UTCI. Furthermore, the findings extracted by the generalized linear models showed that, statistically significant relationships (p < 0. 01) between air temperature, PET, UTCI and mortality exist on the same day. More concretely, on one hand during the cold period (October-March), a 10°C decrease in daily maximum air temperature, minimum air temperature, temperature range, PET and UTCI is related with an increase 13%, 15%, 2%, 7% and 6% of the probability having a death, respectively. On the other hand, during the warm period (April-September), a 10°C increase in daily maximum air temperature, minimum air temperature, temperature range, PET and UTCI is related with an increase 3%, 1%, 10%, 3% and 5% of the probability having a death, respectively. Taking into consideration the time lag effect of the examined parameters on mortality, it was found that significant effects of 3-day lag during the cold period appears against 1-day lag during the warm period. In spite of the general aspect that cold conditions seem to be favourable factors for daily mortality, the air temperature and PET/UTCI exceedances over specific thresholds depending on the distribution reveal that, very hot conditions are risk factors for the daily mortality. © 2011 Springer-Verlag.
Moustris, K.P., et al. Seven-days-ahead forecasting of childhood asthma admissions using artificial neural networks in Athens, Greece. International Journal of Environmental Health Research 22, 93 - 104 (2012). WebsiteAbstract
Artificial Neural Network (ANN) models were developed and applied in order to predict the total weekly number of Childhood Asthma Admission (CAA) at the greater Athens area (GAA) in Greece. Hourly meteorological data from the National Observatory of Athens and ambient air pollution data from seven different areas within the GAA for the period 2001-2004 were used. Asthma admissions for the same period were obtained from hospital registries of the three main Children's Hospitals of Athens. Three different ANN models were developed and trained in order to forecast the CAA for the subgroups of 0-4, 5-14-year olds, and for the whole study population. The results of this work have shown that ANNs could give an adequate forecast of the total weekly number of CAA in relation to the bioclimatic and air pollution conditions. The forecasted numbers are in very good agreement with the observed real total weekly numbers of CAA. © 2012 Taylor & Francis.
Kaskaoutis, D.G., et al. Transport pathways of Sahara dust over Athens, Greece as detected by MODIS and TOMS. Geomatics, Natural Hazards and Risk 3, 35 - 54 (2012). WebsiteAbstract
This study analyses the Saharan dust (SD) events over Athens during 2000-2005 using daily Moderate Resolution Imaging Spectroradiometer (MODIS) and Total Ozone Mapping Spectrometer (TOMS) satellite data. The dust events were identified using the MODIS daily observations over Greece and the dates with detectable dust plumes were collected. The aerosol optical depth (AOD 550) and fine-mode (FM) values from Terra-MODIS and Aerosol Index (AI) values from TOMS were obtained over Athens for the dusty days focusing on analysing the seasonality, intensity, transport pathways and mechanisms of dust. Seventy-nine dusty days were identified corresponding to SD events with duration from 1 to 4 consecutive days; the majority of SD events occur in April-May and July, with less during winter. The dust frequency presents large seasonal and intra-annual variation, with a maximum of 20 dust events in 2002 and a minimum of 7 in 2003. The use of TOMS-AI seems to be adequate for the characterization of dust over Athens despite the fact that 35% of the dusty days do not correspond to high AI values. The dust events are more intense during spring, mostly associated with dust transport from near surface to mid troposphere (vertical transport mechanism), while dust events detected only within the boundary layer have the lowest AOD values. On the other hand, the dust events in summer are of larger duration due to stable weather conditions and absence of precipitation and transportation at elevated heights. © 2012 Taylor and Francis Group, LLC.
Critselis, E., et al. Time Trends in Pediatric Hospitalizations for Varicella Infection Are Associated with Climatic Changes: A 22-Year Retrospective Study in a Tertiary Greek Referral Center. PLoS ONE 7, (2012). WebsiteAbstract
Background/Aims: The transmission rate of air-borne infectious diseases may vary secondary to climate conditions. The study assessed time trends in the seasonality of hospitalized varicella cases in a temperate region in relation to climatic parameters prior to the implementation of universal varicella immunization. Methods: A retrospective descriptive study was conducted among all pediatric and adolescent varicella patients (n = 2366) hospitalized at the "Aghia Sophia" Children's Hospital during 1982-2003 in Athens, Greece. Date of infection was computed based on hospital admission date. Seasonal and monthly trends in the epidemiology of varicella infection were assessed with time series analysis (ARIMA modeling procedure). The correlation between the frequency of varicella patients and the meteorological parameters was examined by the application of Generalized Linear Models with Gamma distribution. Results: During 1982-2003, the occurrence of hospitalized varicella cases increased during summer (p = 0.025) and decreased during autumn (p = 0.021), and particularly in September (p = 0.003). The frequency of hospitalized varicella cases was inversely associated with air temperature (p<0.001). In contrast, the occurrence of hospitalized varicella cases was positively associated with wind speed (p = 0.009). Conclusions: Pediatric hospitalizations for varicella infection rates have increased during summer and decreased during autumn in the examined temperate region. Time trends in hospitalized varicella cases are associated with climatic variables. © 2012 Critselis et al.
Vouterakos, P.A., et al. Forecasting the discomfort levels within the greater Athens area, Greece using artificial neural networks and multiple criteria analysis. Theoretical and Applied Climatology 110, 329 - 343 (2012). WebsiteAbstract
In this work, artificial neural networks (ANNs) were developed and applied in order to forecast the discomfort levels due to the combination of high temperature and air humidity, during the hot season of the year, in eight different regions within the Greater Athens area (GAA), Greece. For the selection of the best type and architecture of ANNs-forecasting models, the multiple criteria analysis (MCA) technique was applied. Three different types of ANNs were developed and tested with the MCA method. Concretely, the multilayer perceptron, the generalized feed forward networks (GFFN), and the time-lag recurrent networks were developed and tested. Results showed that the best ANNs type performance was achieved by using the GFFN model for the prediction of discomfort levels due to high temperature and air humidity within GAA. For the evaluation of the constructed ANNs, appropriate statistical indices were used. The analysis proved that the forecasting ability of the developed ANNs models is very satisfactory at a significant statistical level of p < 0. 01. © 2012 Springer-Verlag.
Moustris, K.P., Nastos, P.T., Larissi, I.K. & Paliatsos, A.G. Application of multiple linear regression models and artificial neural networks on the surface ozone forecast in the greater Athens Area, Greece. Advances in Meteorology 2012, (2012). WebsiteAbstract
An attempt is made to forecast the daily maximum surface ozone concentration for the next 24 hours, within the greater Athens area (GAA). For this purpose, we applied Multiple Linear Regression (MLR) models against a forecasting model based on Artificial Neural Network (ANN) approach. The availability of basic meteorological parameters is of great importance in order to forecast the ozone's concentration levels. Modelling was based on recorded meteorological and air pollution data from thirteen monitoring sites within the GAA (network of the Hellenic Ministry of the Environment, Energy and Climate Change) over five years from 2001 to 2005. The evaluation of the performance of the constructed models, using appropriate statistical indices, shows clearly that in every aspect, the prognostic model by far is the ANN model. This suggests that the ANN model can be used to issue warnings for the general population and mainly sensitive groups. © 2012 K. P. Moustris et al.
Nastos, P.T. Meteorological patterns associated with intense saharan dust outbreaks over greece in winter. Advances in Meteorology 2012, (2012). WebsiteAbstract
The Mediterranean Basin and southern Europe are often affected by Saharan dust outbreaks, which influence the aerosol load and properties, air quality standards, visibility and human health. The present work examines, mainly of the meteorological point of view, three intense dust outbreaks occurred over Greece with duration of one or two days, on 4 and 6 February and 5-6 March 2009. The synoptic analysis on the dusty days showed the presence of low-pressure systems in the west coasts of Europe and the north Tyrrhenian Sea, respectively, associated with a trough reaching the north African coast. The result of these conditions was the strong surface and mid troposphere winds that carried significant amounts of dust over Greece. During the dusty days extensive cloud cover associated with the dust plume occurred over Greece. The air-mass trajectories showed a clear Saharan origin in all atmospheric levels, while the satellite (MODIS Terra/Aqua) observations as well as the model (DREAM) predictions verified the intense dust outbreaks over eastern Mediterranean and Greece. The ground based particulate matter concentrations in Athens were excessively increased on the dusty days (PM 150-560 g/m3), while significant dry and wet deposition occurred as forecasted by DREAM model. © 2012 P. T. Nastos.
Moustris, K.P., Proias, G.T., Larissi, I.K., Nastos, P.T. & Paliatsos, A.G. Bioclimatic and air quality conditions in the greater Athens area, Greece, during the warm period of the year: Trends, variability and persistence. Fresenius Environmental Bulletin 21, 2368 - 2374 (2012). WebsiteAbstract
The aim of this work is to study the bioclimatic conditions as well as the air quality for three different regions of the greater Athens area (GAA), during the warm period of the year for the time period 2001-2005. Furthermore, the thermal discomfort and the air pollution persistence within 24 hours were studied. Finally, both the variability and the trend of the bioclimatic and air quality conditions during the examined period were studied. In order to determine the human thermal comfort-discomfort levels, a widely used biometeorological index, the Cooling Power Index, and microclimatic data (air temperature and wind speed) were used. On the other hand, data concerning the air pollutant concentrations surface ozone (O 3) and particulate matter with aerodynamic diameter less than 10μm (PM 10) measured over this area were used for the determination of the air quality levels. The performed analysis indicates throughout the examined area degradation of the air quality and intensive thermal discomfort episodes. More specifically, during the warm period of the year a relatively high frequency of days, in the city center of Athens showing thermal discomfort and air quality degradation, simultaneously, is observed. On the contrary, on the suburban GAA's monitoring sites a reduction of the frequency of days with thermal discomfort is observed while the number of days with air pollution exacerbations is relatively high. In any case, during the examined period the environmental conditions due to bioclimatic and air quality parameters seem to be rather degraded. © by PSP.
Proias, G.T., Moustris, K.P., Larissi, I.K., Nastos, P.T. & Paliatsos, A.G. Ambient PM10 concentrations and the impact of wind at an urban site in central Greece. Fresenius Environmental Bulletin 21, 1935 - 1941 (2012). WebsiteAbstract
The goal of this work is the analysis of particulate matter with aerodynamic diameter less than 10 μm (PM10) recorded in the urban area of Volos, a medium-sized Greek coastal city on the eastern seaboard of Central Greece. For this purpose, concentration measurements of PM10, for a seven-year period (2001-2007) are analyzed. Air pollution data were obtained by a monitoring station, fully automated, that was established by the Hellenic Ministry of the Environment, Energy and Climatic Change, in order to measure air pollution levels in Volos. The extracted findings showed that the mean diurnal variation of the examined air pollutant concentrations within the cold and the warm period of the year show a double peak structure with respect to morning and evening hours. Additionally, the intra annual variation of PM10 concentrations shows a double peak pattern. The dominant peak is observed in February and the secondary peak in May/June. Besides, the role of wind seems to be significant as the PM10 exceedances are strongly associated with predominant wind directions. © by PSP 2012.
Kaskaoutis, D.G., Nastos, P.T., Kosmopoulos, P.G. & Kambezidis, H.D. Characterising the long-range transport mechanisms of different aerosol types over Athens, Greece during 2000-2005. International Journal of Climatology 32, 1249 - 1270 (2012). WebsiteAbstract
This study analyses the weather conditions, the main pathways and transport mechanisms favouring the presence of specific aerosol types over Athens, Greece. On the basis of the aerosol optical depth at 550 nm (AOD 550) and fine mode (FM) values from a Terra-MODIS dataset in the period 2000-2005, three main aerosol types are identified (urban/industrial, UI; clean maritime, CM; and desert dust, DD), each one corresponding to different optical characteristics and source regions. The UI aerosols are associated with polluted air masses from Europe, the CM aerosols with clean Atlantic air masses and the DD aerosols with air masses from North African arid regions carrying significant amount of dust in certain cases. The comparison of the three aerosol types with the air masses from their favourable sector constitutes a first 'quick-validation' of the identification scheme. Thus, the incidence of transport from Europe explain 81% of the variability in the observed UI type, while the 73% of the Atlantic air masses correspond to the CM type; the 50% of the African air masses can be considered as DD aerosols over Athens. The mean synoptic meteorological patterns, favouring the presence of each aerosol type, are also investigated. Further analysing the air-mass trajectories at three altitudes, the transport mechanisms of the aerosol types are identified. The results clearly show that the UI aerosols are mainly transported within the boundary layer, while the CM conditions are associated with Atlantic air masses at higher altitudes. Moreover, the DD aerosols are transported either in the upper atmosphere or in the whole atmospheric column. This is among the first studies conducted over Athens aiming at investigating the weather conditions, pathways and transport mechanisms that favour the presence of aerosols of different characteristics. © 2011 Royal Meteorological Society.