Abstract: 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.
Abstract: We investigated the short-term effects of particulate matter with aerodynamic diameter <10 μg/m(3) (PM(10)), sulfur dioxide (SO(2)), nitrogen dioxide (NO(2)) and ozone (O(3)) on pediatric asthma emergency admissions in Athens, Greece over the period 2001-2004. We explored effect modification patterns by season, sex, age and by the presence of desert dust transported mainly from the Sahara area. We used daily time-series data provided by the children's hospitals and the fixed monitoring stations. The associations were investigated using Poisson regression models controlling for seasonality, weather, influenza episodes, day of the week and holiday effects. A 10 μg/m(3) increase in PM(10) was associated with a 2.54% increase (95% confidence interval (CI): 0.06%, 5.08%) in the number of pediatric asthma hospital admissions, while the same increase in SO(2) was associated with a 5.98% (95% CI: 0.88%, 11.33%) increase. O(3) was associated with a statistically significant increase in asthma admissions among older children in the summer. Our findings provide limited evidence of an association between NO(2) exposure and asthma exacerbation. Statistically significant PM(10) effects were higher during winter and during desert dust days, while SO(2) effects occurred mainly during spring. Our study confirms previously reported PM(10) effects on emergency hospital admissions for pediatric asthma and further provides evidence of stronger effects during desert dust days. We additionally report severe effects of SO(2), even at today's low concentration levels.
Abstract: In this study, the mean rain intensity (mm/h) in Athens and Thessaloniki, Greece, is examined during the period 1930-2007. The daily meteorological data were acquired from the meteorological stations of the National Observatory of Athens (Thissio) and the University Campus of Thessaloniki. These stations have recorded the longest and reliable daily rain time series in Greece. The trends of the annual and seasonal mean, as well as the maximum rain intensity, are analyzed. On the one hand, all of the time series in Athens present higher figures of mean rain intensity during the period 1990-2007 compared to the period 1930-1990. On the other hand, regarding the time series in Thessaloniki, the mean rain intensity remains in lower level than the respective one in Athens without significant trend at the Confidence Level (CL) 95%. As far as the annual and seasonal maximum rain intensity is concerned, similar patterns appear. However, the summer maximum rain intensity in Thessaloniki remains at higher levels till 1970's. The atmospheric circulation patterns for the extreme rain intensities show intense negative anomalies centred over Greece and positive anomalies to the north, with centre over Scandinavia.
Abstract: The application of harmonic analysis to the annual variability of precipitation is the object of this study, so that the modes, which compose the annual variability, be elicited. For this purpose, monthly precipitation totals from 30 meteorological stations of the Hellenic National Meteorological Service (HNMS), for the period 1950-2000, were used. The initial target is to reduce the number of variables and to detect structure in the relationships between the variables. The most commonly used technique for this purpose is the application of Factor Analysis (FA) resulted in five main factors (sub-regions) with common precipitation characteristics, explaining 77% of the total variance. For each sub-region, a representative station is selected for the analyses, mainly, as the station within the sub-region with the highest factor loading. In the process, the Fourier Analysis is applied to the mean monthly precipitation, so that 2 harmonic components are derived, which explain more than 90% of the total variability of each station, and are due to different synoptic and thermodynamic processes associated with Greece's precipitation regime. Finally the calculation of the time of the maximum precipitation, for each harmonic component, gives the spatial distribution of the appearance of the maximum precipitation in the Greek region.
Abstract: Particulate matter with diameter less than 10 micrometers (PM10) that originates from anthropogenic activities and natural sources may settle in the bronchi and cause adverse effects possibly via oxidative stress in susceptible individuals, such as asthmatic children. This study aimed to investigate the effect of outdoor PM10 concentrations on childhood asthma admissions (CAA) in Athens, Greece.
Abstract: In this paper we examined whether the recorded precipitation changes cause erosion in Naxos Island, Greece using precipitation indices derived from daily precipitation totals, during the period 1955-2007, in order to develop an erosion risk model. Although the mean annual precipitation appear to be low (similar to 360.0 mm), the erosion processes of the area are very intense, because of the intensive character of precipitation, the high slope relief, the differential lithology and the absence of important land cover The results of the analysis showed that the climatic changes in precipitation and the changes in land cover and land use are the main drivers for the erosion. This is why the 2nd (1971-1985) and 3rd (1986-2007) studied sub-periods may be called of high erosion risk, and especially the second one mainly because of the increased frequency of extreme precipitation events.
Abstract: The goal of this work is the analysis of air quality levels in the area of Volos, a city of average size on the eastern seaboard of Central Greece. For this purpose, concentration measurements of sulfur dioxide, nitrogen oxide, and nitrogen dioxide, for a 4-year period (2001-2004) are analyzed. Air pollution data were obtained by a monitoring station, fully automated, which was established by the Hellenic Ministry of the Environment, Physical Planning, and Public Works, in order to measure air pollution levels in Volos, a medium-sized city, which faces the effects of industrialization. The main conclusions from the statistical analysis of the 4-year measurements of hourly SO(2), NO(2), and NO concentrations in the city of Volos, showed that the mean seasonal variation of the examined air pollutant concentration presents a minimum during the warm period of the year and a maximum during the cold period. Although the local geomorphology and meteorology encourage particularly the accumulation of air pollutants, the analysis shows that the SO(2) and NO(2) concentration levels remain lower than corresponding thresholds for human health protection set by the European Union, in this urban measuring site, during the examined period. The application of harmonic analysis revealed the difference between the annual variation of the SO(2) and NO(x) concentrations. Regarding NO(x), the variation is mainly due to the first harmonic term (anthropogenic factor), while the SO(2) variation is interpreted by the two harmonic terms, which represent the anthropogenic and meteorological factors, respectively.
Abstract: Ship-borne sunphotometer measurements obtained in the Arabian Sea (AS) in the pre-monsoon season (18 April-10 May 2006) during a cruise campaign (ICARB) have been used to retrieve the Aerosol Optical Depth (AOD; tau) and the Angstrom wavelength exponent (alpha). The continents surrounding the AS produce natural and anthropogenic aerosols that have distinctive influences on alpha and its spectral distribution. The alpha values were estimated by means of the least-squares method over the spectral bands 340-1020 nm and 340-870 nm. The spectral distribution of AOD in logarithmic co-ordinates could be fit using a 2nd order polynomial with higher accuracy in the wavelength band 340-1020 nm than in the 340-870 nm band. A polynomial fit analytically parameterizes the observed wavelength dependencies of AOD with least errors in spectral variation of alpha and yields accurate estimates of the coefficients (a(1) and a(2)). The coarse-mode (positive curvature in the ln tau(lambda) vs. ln lambda) aerosols are mainly depicted in the Northern part of the AS closely associated with the nearby arid areas while fine-mode aerosols are mainly observed over the far and coastal AS regions. In the study period the mean AOD at 500 nm is 0.25 +/- 0.11 and the alpha(340-1020) is 0.90 +/- 0.19. The alpha(340-870) exhibits similar values (0.92 +/- 0.18), while significant differences revealed for the constant terms of the polynomial fit (a(1) and a(2)) proportionally to the wavelength band used for their determination. Observed day-to-day variability in the aerosol load and optical properties are direct consequence of the local winds and air-mass trajectories along with the position of the ship.
Abstract: Extreme precipitation events have significant environmental consequences because they may cause considerable damages to urban as well as rural areas. The aim of this work is to construct a threshold model which will describe the exceedances over a threshold for the daily precipitation totals over Athens, Greece. The data used are daily precipitation totals recorded at the National Observatory of Athens, for a 115-year period (1891-2005). The generalized Pareto distribution is considered as the proper distribution for the study of the exceedances. The threshold of u=15.8 mm (10% upper limit) is used for the construction of the optimal return level function.
Abstract: Measurements of positive and negative small atmospheric ion concentrations have been made regularly since 1968 at the National Observatory of Athens (NOA). In this paper the 17-year period 1968-1984 is summarized. The diurnal and annual variations are examined, and Fourier analysis is also used for the study of the diurnal variation. The concentrations of small ions follow a double diurnal course. The maxima occur near 3-5 h and 13-16 h local time (LT=GMT+2 h). The minima are observed at 6-8 h and 21-23 h. The annual course of small ions presents maximum concentration values around the summer season. The mean of the small ion concentration (SIC) for the 17-year period (1968-1984) is n(+)=188.8 ions/cm(3) for positive ions and n(-) = 151.1 ions/cm(3) for negative ions. Their ratio is equal to 1.25. The year-to-year variation of SIC for the examined period shows a negative trend. The results from multiple regression analysis show that wind speed and SIC are positively correlated, while relative humidity, smoke and sulphur dioxide are negatively correlated. (C) 2008 Elsevier B.V. All rights reserved.
Abstract: In this study, the distribution patterns of physical (sand%, loam%, clay%, pH and organic matter%) and chemical (calcium carbonate (CaCo3), sodium (Na+), magnesium (Mg+2), phosphorus (P), boron (B), iron (Fe), manganese (Mn) and zinc (Zn)) parameters of soil commonly assayed in analytical chemistry laboratories, are reported. Three representative areas (lowland (LL), semi-mountainous (SM), and coastal (Q) and 170 sample sites were selected, 5 10 soil samples were collected and analyzed for a 3-years period (2002-2004), in the prefecture of Larissa, Thessaly, central Greece. In each studied site, the kind of cultivation is also reported. Soils in LL area of the prefecture of Larissa were found to be rich in organic matter, Mg, B, but poor in Fe, Mn and Zn, when compared to the other two sites. The studied SM area of Larissa's prefecture constituted from clayey soils showed big concentrations of Mg, Zn, high value of clay and low value of sand, when compared to the other two studied areas. The studied C area is characterized by the sandy soils near the coastal areas of the prefecture of Larissa. In each studied area, the parameters are principally separated into two main clusters, each of them divided additionally into sub-clusters with slight differences. Six latent factors explain 78.1%, 74.3%, and 74.6% of the total variance of the LL-site, SM-site, and C-site, respectively, which is an indication for the factor analysis model adequacy.
Abstract: The objective of this study is to find out the spatial and temporal variability of the dry and wet spells in Greece, during the period 1958-2007. The meteorological data with respect to daily precipitation totals were acquired from 27 meteorological stations of the Hellenic National Meteorological Service, which are uniformly distributed over the country. The dry spells concern consecutive dry days (CDD); the largest number of consecutive days with daily precipitation amount less than I mm, within a year. The wet spells concern consecutive wet days (CWD); the largest number of consecutive days with daily precipitation amount more than or equal to 1 mm, within a year, as defined by the Expert Team on Climate Change Detection and Indices (ETCCDI), jointly sponsored by the Commission for Climatology (CCl) of the World Meteorological Organization's (WMO) World Climate Data and Monitoring Programme (WCDMP), the Climate Variability and Predictability (CLIVAR) Programme of the World Climate Research Programme (WCRP) and the joint WMO-IOC Technical Commission for Oceanography and Marine Meteorology (JCOMM). As results from the analysis, the spatial distributions of the mean annual CDD and the mean annual CWD along with their trends, within the examined period, are presented. The findings indicate that CDD obtain maxima in the Cyclades Islands and the southeastern Aegean Sea, while minima are found in the northwestern Greece. On the contrary, the longest CWD are observed in western Greece and western part of Crete Island and the shortest in the eastern continental Greece and in the majority of the Aegean Sea. On an annual basis, the temporal variability of CWD shows statistically significant (confidence level of 95%) negative trends, mainly in the western region of Greece, while insignificant positive trends for CDD appear almost all over the country with emphasis in the southeastern region. Finally, in order to interpret the drier and wetter periods within the examined period, the 850 hPa and the 500 hPa geopotential height (m) composites of the anomalies from 1958-1996 climatological normal (clino), are analysed using the National Centers for Environmental Prediction (NCEP) reanalysis data. (C) 2009 Elsevier B.V. All rights reserved.
Abstract: Relativistic electrons (with energies >150 keV) which originate in the outer radiation belt and detected by the Russian 'Meteor' series of satellites have been correlated with the atmospheric total ozone data compiled by almost 90 stations located around the world within the latitude zone 40 degrees-70 degrees N. In more than 60% of the stations examined we have detected a clear decrease of the ozone 3-5 days after the electron flux excess. A numerical model has been applied to approximate this effect based oil relativistic electron initiated nitric oxides creation in the upper mesosphere with subsequent atmospheric transport (both vertical and horizontal) towards the upper stratosphere. A first attempt of local and temporal prediction of ozone depletion because of energetic electrons impact in the middle atmosphere has been illustrated. (C) 2008 COSPAR. Published by Elsevier Ltd. All rights reserved.
Abstract: A discrimination of the different aerosol types over the Arabian Sea (AS) during the Integrated Campaign for Aerosols, Gases and Radiation Budget (ICARB-06) is made using values of aerosol optical depth (AOD) at 500 nm (AOD(500)) and Angstrom exponent (alpha) in the spectral band 340-1020 nm (alpha(340-1020)). For this purpose, appropriate thresholds for AOD(500) and alpha(340-1020) are applied. It is shown that a single aerosol type in a given location over the AS can exist only under specific conditions while the presence of mixed aerosols is the usual situation. Analysis indicates that the dominant aerosol types change significantly in the different regions (coastal, middle, and far) of AS. Thus the urban/industrial aerosols are mainly observed in coastal AS, the desert dust particles occur in the middle and northern AS, while clear maritime conditions mainly occur in far AS. Spectral AOD and Angstrom exponent data were analyzed to obtain information about the adequacy of the simple use of the Angstrom exponent and spectral variation of a for characterizing the aerosols. Using the least squares method, a is calculated in the spectral interval 340-1020 nm along with the coefficients a(1) and a(2) of the second-order polynomial fit to the plotted logarithm of AOD versus the logarithm of wavelength. The results show that the spectral curvature can effectively be used as a tool for their discrimination, since the fine mode aerosols exhibit negative curvature, while the coarse mode particles exhibit positive curvature. The correlation between the coefficients a(1) and a(2) with the Angstrom exponent, and the atmospheric turbidity, is further investigated.
Abstract: Precipitating electrons from the radiation belts with energies greater than from 150 keV to 5 MeV have been correlated with ozone data of a large number of stations located within 40-70 degrees N. Energetic electrons have been collected by the low altitude polar Russian satellite METEOR while ozone data have been compiled from almost ninety (90) stations located all over the world within the latitude zone 40-70 degrees N. In more than 60% of the stations examined, we detect a clear decrease of the ozone variation during and after the occurrence of all electron flux excess, which recovers within 3-5 days. The more northern is a station located, the deeper is the ozone decrease. Moreover, clear evidence that the solar cycle affects ozone destruction through energetic electron events is presented. The preliminary results of the present work stimulate a future attempt for a simple ozone destruction mechanism formulation, which could describe atomic nitrogen ionization by energetic electrons, which in the following merge to atomic oxygen and produce nitrogen oxides. Finally, nitrogen oxides destruct ozone creating characteristic decreases on the normal ozone variation. (C) 2008 COSPAR. Published by Elsevier Ltd. All rights reserved.
Abstract: A long-term (2000-2005) data set of aerosol optical properties obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) is analyzed focusing on the Greater Athens Area in the Eastern Mediterranean region. The MODIS aerosol optical depth standard product (AOD at 550 nm) and its respective ratio attributed to fine-mode particles (FM) are employed to evaluate the inter-annual and seasonal variability of the aerosol properties over Athens. Based on AOD(550) and FM values three specific aerosol types are discriminated corresponding to different aerosol load and optical properties. The aerosol types considered correspond to urban/industrial aerosols, coarse-mode particles and clean maritime conditions. This study focuses on the seasonal and year-to-year fluctuation of the number of occurrences as well as the AOD(550) and FM values of each aerosol type. The coarse-mode particles are observed mainly in the summer, while spring is the most favorable season for the occurrence of urban/industrial aerosols. On the other hand, clean maritime conditions occur mainly in the winter. The AOD(550) values for the coarse-mode particles are higher in spring, while the urban/industrial and clean maritime aerosols exhibit slightly higher values in the summer. The seasonal distribution of the aerosol properties is related to anthropogenic and dust emissions in the spring/summer period, but is modified by atmospheric dispersion and precipitation in late autumn/winter. The main conclusion of the study is that the coarse-mode particles exhibit much stronger inter-annual and seasonal variability compared to the urban/industrial aerosols. Finally, three cases corresponding to each aerosol type are analyzed with the aid of synoptic weather maps, air mass trajectories and MODIS data. (C) 2007 Elsevier Inc. All rights reserved.
Abstract: The aim of this study was to determine whether there is any association between weather variability and asthma admissions among children in Athens, Greece. Medical data were obtained from hospital registries of the three main Children's Hospitals in Athens during the 1978-2000 period; children were classified into two age groups: 0-4 and 5-14 years. The application of Generalized Linear Models with Poisson distribution revealed a significant relationship among asthma hospitalizations and the investigated parameters, especially for the children aged 0-4 years. Our findings showed that Hospital admissions for childhood asthma in Athens, Greece, is negatively correlated with discomfort index, air temperature and absolute humidity whereas there is a positive correlation with cooling power, relative humidity and wind speed.
Abstract: Tropical days (TD) are defined as the days with a maximum air temperature greater than 30.0 degrees C. It is clear that the study of TD includes also the absolute maximum temperatures, which are of great interest for the description of a region's climate. These days are considered as very hot, and they particularly are of great importance not only for bioclimatology and applied sciences, but also for the individuals who are sensitive in the heat-stress. The regime of the TD in Greece is the focus of this study. The aim is to demonstrate their changes from decade to decade, for the time period 1960-2000. For this study, the Annual Number of Tropical Days (ANTD) recorded by each of the 26 meteorological stations of National Meteorological Service, which are uniformly distributed in the Hellenic peninsula, was calculated and analysed. In terms of quantifying the conditions in a humanbiometeorological manner, the thermal index Physiological Equivalent Temperature (PET) and the consecutive days for Athens have been included in this study. The trends of the TD for each station were analysed through the Mann-Kendall technique, while the spatial distribution per decade reveals the regions with change (increase or decrease) in the ANTD during the examined period. Two characteristic periods of change for the ANTD appear in the majority of the meteorological stations in Greece. The first period (1955-1976) is determined by a negative trend, which is statistically significant (c.l. 95%), for adequate stations. In the period between 1976 and 2000, the increase in the ANTD and the maximum temperature exceed the corresponding maximum that appeared in the beginning of the 1950s for several of the examined meteorological stations. The human-biometeorological analysis shows that the consecutive days of PET > 35 degrees C have had a positive trend in the last two decades of the last century.
Abstract: The aim of this study was to examine the effects of the daily minimum air temperature and human-biometeorological variables, as well as their day-to-day changes, on sleep disturbances (SD) in the inhabitants of Athens, Greece. The SD dataset used for the analysis included the daily records of the psychiatric emergency unit of the Athens University Medical School for the years 1989 (with mild thermal load) and 1994 (with heavy thermal load). The meteorological variables for the estimation of the thermal indices were recorded by the meteorological station of Hellenikon, which is located at the headquarters of the Hellenic National Weather Service. The mean radiant temperature (T-mrt) and the thermal indices predicted mean vote (PMV), physiologically equivalent temperature (PET) and standard effective temperature (SET*) have been analyzed. The first step was to assess the SD frequencies as a function of the meteorological and human-biometeorological variables on the basis of 10-day intervals to determine the influence of the examined variables on SD. The daily SD records were included as Poisson random variables in the applied Generalized Linear Models (GLM). The extracted results suggested that a considerable increase in SD existed in 1994 compared to 1989. This was due to the many consecutive days with heavy thermal load (PET>35 degrees C and T-min>23 degrees C) in 1994 compared to the lack of such days in 1989. Furthermore, statistically significant (p<0.01) positive relationships were found between minimum air temperature, all thermal indices and SD.
Abstract: The determination of the chemical composition of rainfall related to tile origin of the air masses, in two urban sites in Greece during the year 2006. is investigated in this study. Two model automatic rain samplers were installed, the first in the city of Larissa, Thessaly, central Greece and the second in Heraklio. Attica, a northern suburb of Athens. The concentrations (ppm) of the major cations (H+, Na+, K+, Ca2+, NH4+ and Mg2+) and major anions (NO3-, NO2-, HCO3-, and SO42-), as well as total hardness (ppm CaCO3) pH and electric conductivity in 25 degrees C (mu S/cm) for 27 rainfall samples -11 samples in Larissa and 16 samples in Heraklio (Athens)- were determined. In Larissa. the figures of pH range from 5.13 to 6.13 while in Heraklio (Athens), the pH within the range 5.62 to 7.88 indicates a shift of the rainfalls towards alkalinity. The electric conductivity in Larissa ranges from 16.30 mu S/ cm to 110.60 mu S/cm and in Heraklio (Athens) from 7.00 mu S/ cm to 15 1.00 mu S/cm. The analysis showed that Ca2+ and Mg2+ appear the highest concentrations out of the examined cations. while HCO3- and SO42- present the highest concentrations within the anions. Moreover, in order to find out the origin of the air masses, the air mass back trajectories were calculated using the HYSPLIT 4 model of Air Resources Laboratory of NOAA for two different levels: 1500 and 3000 m (a.m.s.l.).
Abstract: The aim of this study was to determine whether there is any association between weather variability and asthma admissions among children in Athens, Greece. Medical data were obtained from hospital registries of the three main Children's Hospitals in Athens during the 1978-2000 period; children were classified into two age groups: 0-4 and 5-14 years. The application of Generalized Linear Models with Poisson distribution revealed a significant relationship among asthma hospitalizations and the investigated parameters, especially for the children aged 0-4 years. Our findings showed that Hospital admissions for childhood asthma in Athens, Greece, is negatively correlated with discomfort index, air temperature and absolute humidity whereas there is a positive correlation with cooling power, relative humidity and wind speed.
Abstract: In the present study an assessment of the influence of the ambient air pollution on the incidence of the Childhood Asthma Admissions (CAA) is attempted by using cross spectrum analysis. The medical data concern the hospital registries of the three main Children's Hospitals of Athens for the 14-year period, 1987-2000. The air pollution data used in this study were mean monthly concentrations of CO, Black Smoke (BS), NOx, SO2, and O-3, averaged over all the available stations, for each air pollutant, in the network of the Greek Ministry of the Environment, Physical Planning and Public Works (GMEPPPW) for the aforementioned 14-year period. The performed analysis revealed that a pronounced seasonal variation of asthma exacerbation among Athenian children does exist, rising during the cold damp period in pre-schoolers and peaking around May in the schoolchildren. We found that asthma admissions are associated with ambient air pollution at different frequencies. Asthma exacerbation among the first age group (0-4 years) is strongly depended on winter air pollution whereas older children (5-14 years) appear to be more vulnerable to the exposure of primary air pollutants mainly during late spring. Our findings strengthen the aspect that weather conditions such as sea breeze, mainly happen at the late spring or early summer in association with air pollution episodes could affect childhood asthma exacerbation.
Abstract: The study of particulate matter with diameter less than 1 mu m (PM1) in Athens' atmosphere and their impacts on human health is the goal of this study. PM1 concentrations were recorded by three detectors (light scattering method) at six vital points in high traffic peak roads, during the period 1/10/2006-30/9/2007. The collected PM1 samples concern the same hour of the day, in absence of wind. The spatial distributions of the PM1 concentrations for the warm (April to September) and the cold (October to March) period of the year were achieved by the use of Kriging method. Further to, in order to find out the impacts of PM1 concentrations on health, we analyzed daily admissions for nonfatal arrhythmias to emergency units of the Social Security Institute and a Regional Hospital of Athens. Results demonstrate a significant relationship of PM1 with sinus arrhythmias, which confirms the assumption that PM1 represent one of the main hazards in cardio respiratory syndromes in the most polluted cities of Europe, which confront high traffic problems, due to the enormous number of exhausts emissions.
Abstract: Objective - Genetic polymorphisms in the gene for endothelial nitric oxide synthase have been considered as potential risk factors for the development of coronary artery disease in some populations. Methods - We studied two polymorphisms of the NOS3 gene, the VNTR in intron 4 (4VNTR) and the Glu298Asp polymorphism in exon 7, in relation to the existence of premature coronary artery disease and the occurrence of myocardial infarction. A total number of 370 individuals of the Greek population was examined by PCR-RFLP method. The patient group consisted of 209 subjects, aged less than 58 years presenting symptomatic coronary artery disease, documented by coronary angiography. Results - The frequencies for bb, ab and aa genotypes of 4VNTR polymorphism were 0.67, 0.29, 0.04, respectively, for the patient group and 0.73, 0.24, 0.03 for the control group. The frequencies for GG (Glu/Glu), GT (Glu/Asp),TT (Asp/Asp) of the Glu298Asp polymorphism were 0.52, 0.41, 0.07, respectively, in patients compared to 0.47, 0.46, 0.07, in control subjects. Statistical analysis indicated that there are no significant differences in the frequencies of the genotypes between patients and control subjects for both polymorphisms. The combined analysis of the two polymorphisms indicated no synergistic effect of the a and T alleles on coronary artery disease. Conclusions - We have found no evidence for association between the a allele of the 4VNTR polymorphism, or the T allele of Glu298Asp polymorphism and the risk for premature coronary artery disease or occurrence of myocardial infarction. Furthermore, no synergistic contribution of these polymorphisms to the development of premature coronary artery disease has been observed.
Abstract: Springtime constitutes the most favorable period for Sahara dust outbreaks and transport over Eastern Mediterranean. This study investigates the aerosol properties during April 2005 using remote-sensing and ground-based measurements. Three dust events with high aerosol optical depth (AOD) values have been observed during the measuring period, with duration of two days, i.e. 11-12,16-17 and 25-26 April 2005. In this paper we mainly focus on the intense dust event of 16-17 April 2005, when a thick dust layer transported from Libya affected the whole Greek territory. Very high AOD values obtained from Aqua-MODIS sensor were observed over Greece (mean 2.42 +/- 1.25) on 17 April, while the respective mean April value was 0.31 +/- 0.09. The AOD at 550 nm (AOD(550)) Values over Crete were even larger, reaching similar to 4.0. As a consequence, the PM10 concentrations over Athens dramatically increased reaching up to 200 mu g m(-3). On the other hand, the fine-mode fraction values obtained from Terra-MODIS showed a substantial decrease in the whole Greek area on 17 April with values below 0.2 in the Southern regions. The intense dust layer showed a complex behavior concerning its spatial and temporal evolution and allowed us to study the changes in the optical properties of the desert dust particles along their transport routes due to the mixing processes with other aerosol types. The results from different measurements (ground-based and remote-sensing) did not contradict each other and, therefore, are adequate for monitoring of dust load over the Eastern Mediterranean. (C) 2008 Elsevier Ltd. All rights reserved.
Abstract: In this study, the variability and trends of the mean annual and seasonal surface air temperature in Greek peninsula are examined. The climatic data used, concern mean monthly values of air temperature of 20 meteorological stations of the Hellenic Meteorological Service, for the period 1951-2000. The air temperature time series for each station are analyzed, so that the variability and trends be described. Regarding the annual time series, a cooling trend is observed since the early 1960's till the middle of the decade of 1970, when the trend reverses to heating till nowadays. It is remarkable that the today air temperature levels do not exceed the levels of the middle of the century. During the winter, it is crystal clear that a cooling trend exists from the middle of the decade of 1950 to the end of the decade of 1980, especially in the south region of the country. Afterwards an increasing trend is obvious till nowadays. The pattern in spring appears a slight heating trend in the northern region of Greece and a cooling trend in the south. The summer time series are similar to the annual ones, so the contribution of summer to annual variability is unquestionable. Generally speaking, the air temperature in autumn follows the same distribution in time. In the process, the Factor Analysis is applied on the mean annual and seasonal air temperature and thereafter the regions, within the air temperature covariates, are defined. Finally, the application of spectral analysis to annual and seasonal air temperature is regarded necessary so that the periodicities are derived.
Abstract: The paper studies changes in daily precipitation records at the National Observatory, Athens, during the period 1891-2004. This is the longest available time series of precipitation for Greece. The results show that both the shape and scale parameter of a fitted two parameter gamma distribution for the last two decades do show a significant difference of these parameters, when compared to any previous period from the 1890s through the 1970s. Also important changes are observed in daily precipitation totals exceeding various thresholds such as 10, 20, 30 and 50 mm. More specifically, a negative trend in the number of wet days (remarkable after 1968) and a positive trend in extreme daily precipitation are evident. The changes of heavy and extreme precipitation events in this part of SE Europe have significant environmental consequences which cause considerable damage and loss of life.
Abstract: A long-term (2000-2005) monitoring of aerosol data from the moderate resolution imaging spectroradiometer (MODIS) is analyzed focusing on the Greater Athens Area (GAA) in the Eastern Mediterranean region. The MODIS aerosol optical depth standard product (AOD at 550 nm) and its respective ratio attributed to fine-mode (FM) particles are employed to evaluate the seasonal variability of the aerosol properties over Athens. The climatological trend of both parameters in the period 2000-2005 is nearly absent, while remarkable year-to-year variability can be observed. The seasonal analysis reveals a significant AOD variability over Athens, with minimum values in winter (AOD(550) similar to 0.2), and maximum in summer (AOD(550)similar to 0.45). Regarding the FM fraction, maximum values are present in spring and minimum in summer, thus revealing the dominance of FM and coarse-mode particles, respectively. For the whole data set, a method is implemented to distinguish the main aerosol types (urban/industrial (hereafter UI), clean maritime (hereafter CM type) and desert dust (hereafter DD) over Athens, based on both AOD and FM values. Because of the mixing processes in the atmosphere the majority of the cases (46.6%) belong to a mixed (hereafter MT) aerosol type. The U aerosols are more frequent in spring (41.2%) and less in winter (9.1 %), while the coarse particles, probably DD, more frequent in summer (35.8%) and less in winter (3.5%). In contrast, the clean atmospheric conditions are more frequent in winter (23.9%), when the mixing processes are also well established (63.5%). For each aerosol type, the mean AOD(550) and FM values are also computed. Their seasonal variability exhibits a clear summer maximum for UI, CM and MT aerosols, while the DD exhibits maximum in spring. As regards the FM values of the different aerosol types they exhibit a rather constant variation with small fluctuations from season to season. (c) 2007 Elsevier Ltd. All rights reserved.
Abstract: The goal of this study is to determine the chemical composition of rain, in the wider region of Athens, Greece for the time period 1st September 2001 to 31st August 2002. Two model automatic rain samplers were installed in the Meteorological Station of Laboratory of Climatology (latitude: 37 degrees 58' N, longitude: 23 degrees 47' E) inside the Athens University Campus and in a site at Heraklio Attica, a northern suburb of Athens ( latitude: 38 degrees 03' N, longitude: 23 degrees 45' E). The concentrations ( mu eq l(-1)) of the major cations (H+, Na+, K+, Ca2+ and Mg2+) and anions (Cl-, NO3-, HCO3- kappa alpha L SO2- (4)), as well as pH and conductivity of rain in 39 total samples were determined. The figures of pH range from 6.4 to 8.4 and conductivity from 8 to 207 mu S cm(-1). The analysis showed that Ca2+ ions are abundant within all examined samples, while HCO3- and SO42- present the highest concentrations from the anions. In order to find out the origin of the air masses, the air mass back trajectories were calculated. Five sectors of the origin of air masses were revealed: the North, the South, the Local, the West and the East sector. Multivariate methods included Factor Analysis and Discriminant Analysis were applied to the examined ion concentrations and three main factors were extracted, which discriminated the ions according to their origin. The first group of ions is interpreted as the result of the anthropogenic activity, the second group represents the acidity - alkalinity independently of their source and the third one the marine influence.
Abstract: In the present study the involvement of human activities is assessed in the revalorization of groundwater quality. The groundwater quality was assessed on the basis of physical and chemical analysis (electric conductivity, pH, total dissolved solids (TDS), total hardness, NO3-, NO2-, SO4-2, Fe, Mn, Zn, Cu, B, residual sodium absorption (RSC) and sodium absorption ratio (SAR) for the period 2000-2004. From the analysis of results, it emerges that there are significant differences on the quality of water among the sample areas studied. The degradation of groundwater quality is mainly due to the pollution caused by the rural use of land, as well as its intensive exploitation. The salination and toxicity are potential problems of groundwater quality, especially in some areas, indicating that there is a need to take direct actions for the purpose of the optimum management of water resources in the Region of Thessaly.
Abstract: Two periods of transboundary transport of volcanic aerosols and debris following recent eruptions of Mount Etna, Italy, were examined using ground-based and satellite spectrophotometric measurements together with Light Detection And Ranging (LiDAR) and aerosol filter observations in Athens and Thessaloniki, Greece. Independent columnar SO2 measurements from ground and space identified peaks at Greek sites after the volcanic eruptions. LiDAR measurements of the aerosol extinction at Thessaloniki and Athens performed in July 2001 have shown the height of the volcanic plume to be about 3.5 km asl and the optical thickness of the dust layer to be of the order of 3 x 10(-3) at 532nm. Strong ozone depletion observed at the volcano plume level by using ozonesonde ascents may be attributed to the in-plume processes that generate reactive halogens, which in turn destroy ozone. The chemical and elemental composition of aerosol samples, taken at the Earth's surface, was analysed and confirmed the volcanic origin of the dust.
Abstract: In this study the contribution of meteorological parameters to the total variability of respiratory infections (RI) is analysed. For this purpose, data on the daily numbers of general practitioner (GP) consultations for RI during the year 2002 were used. This dataset has been compiled by the Local Health Service in the surroundings of Athens, Greece (Acharnes city). The meteorological data obtained by the Meteorological Station of the National Observatory of Athens comprise daily values of mean, maximum, and minimum air temperature, air temperature range, relative humidity, absolute humidity, sunshine, surface atmospheric pressure, wind speed, as well as day-to-day changes of these parameters. Furthermore, the following biometeorological parameters and thermal indices were also evaluated: mean radiant temperature (T-mrt), predicted mean vote (PMV), physiologically equivalent temperature (PET) and standard effective temperature (SET*) as well as their day-to-day changes. First, the relationship between every meteorological-biometeorological parameter and consultations for RI was examined by applying the Pearson Chi-Square Test (chi(2)) to the data of the 25 compiled contingency tables. In the second stage, the application of generalised linear models (GLM) with Poisson distribution to the data revealed how much the weather variability leads to statistically important changes in consultations for RI. The results of this study contribute to the evidence that there is an association between weather conditions and the number of GP consultations for RI. More specifically, the influence of air temperature and absolute humidity on consultations on the same day is weaker than the lag effect (similar to 2 weeks) related to cold existence and absolute humidity, while a strong wind during the preceding 3 days drives a peak in GP consultations.
Abstract: The aim of this study was to investigate the influence of weather conditions on the number of admissions for childhood asthma in Athens, Greece. Daily counts of childhood asthma admissions (2764) of the three main Children's Hospitals in Athens, from hospital registries during a 3-year period (2001-2003), were obtained. The meteorological data reviewed consists of daily values of 20 parameters recorded at the National Observatory of Athens during the study period: maximum temperature (T-max); minimum temperature (T-min); mean temperature (T-mean); diurnal temperature range (T-range = T-max - T-min); day-to-day change in maximum temperature (Delta T-max); day-to-day change in minimum temperature (Delta T-min); day-to-day change in mean temperature (Delta T-mean); day-to-day change in diurnal temperature range (Delta T-range); mean relative humidity (RH); day-to-day change in mean relative humidity (Delta RH); mean water vapor pressure (e); day-to-day change in mean water vapor pressure (Delta e); mean atmospheric pressure at sea level (P); day-to-day change in mean atmospheric pressure (Delta P); mean irradiance (1); day-to-day change in mean irradiance (Delta I); mean sunshine (S); day-to-day change in mean sunshine (Delta S); mean wind speed (v) and day-to-day change in mean wind speed (Delta v). The performed statistical methods were: (i) Pearson's chi(2) test, using contingency tables and (ii) Factor and Cluster analysis. The application of this 2-part analysis revealed the relationship between the extracted weather types and the frequency of childhood asthma admissions in Athens. The results showed that weather conditions with low temperature, low water vapor pressure and cold anticyclonic presence were significantly correlated with an increase in the number of asthma admissions among children in Athens. The impact of these specific weather conditions on asthma exacerbation should be interpreted either by the asthmogenic effect of humid weather per se or the association with respiratory viral infection, mold's and mites' allergy.
Abstract: A multivariate analysis of 4797 cases of patients who were cured of their psychological symptoms and their notes filed by the psychiatric clinic of the Eginition Hospital in Athens, during the year 1994, has been done. The results of this analysis imply significant contribution of environmental variations, expressed by a discomfort index, in the aggravation of psychological symptoms like depression, sleep disturbances, anxiety, aggressiveness, etc. Moreover, geomagnetic field variations expressed by the international geomagnetic index (DST) manifest significant indications that they contribute to the aggravation of sleep disturbances. A clear seasonal variation, with a maximum around August and a minimum at the end of the year, appears in the environmental index, while a double oscillation with a period of about six months is obvious in the geomagnetic index. The same more or less seasonal variation was mirrored in most of the psychological symptoms we analysed in the present study.
Abstract: In this study the contribution of meteorological parameters to the total variability of respiratory infections (RI) is analysed. For this purpose, data on the daily numbers of general practitioner (GP) consultations for RI during the year 2002 were used. This dataset has been compiled by the Local Health Service in the surroundings of Athens, Greece (Acharnes city). The meteorological data obtained by the Meteorological Station of the National Observatory of Athens comprise daily values of mean, maximum, and minimum air temperature, air temperature range, relative humidity, absolute humidity, sunshine, surface atmospheric pressure, wind speed, as well as day-to-day changes of these parameters. Furthermore, the following biometeorological parameters and thermal indices were also evaluated: mean radiant temperature (T (mrt)), predicted mean vote (PMV), physiologically equivalent temperature (PET) and standard effective temperature (SET*) as well as their day-to-day changes. First, the relationship between every meteorological-biometeorological parameter and consultations for RI was examined by applying the Pearson Chi-Square Test (chi (2)) to the data of the 25 compiled contingency tables. In the second stage, the application of generalised linear models (GLM) with Poisson distribution to the data revealed how much the weather variability leads to statistically important changes in consultations for RI. The results of this study contribute to the evidence that there is an association between weather conditions and the number of GP consultations for RI. More specifically, the influence of air temperature and absolute humidity on consultations on the same day is weaker than the lag effect ( approximately 2 weeks) related to cold existence and absolute humidity, while a strong wind during the preceding 3 days drives a peak in GP consultations.
Abstract: In this work, the characteristics of the long-term precipitation time series in Athens area (1891-2000). Statistical analysis shows that higher values of annual precipitation observed in the 1930s, while the lowest values were observed in the 1890s and 1980s. There is no significant trend in the annual precipitation time series. Moreover, the annual number of days with high precipitation (ANDHP) remains constant, during the investigated period. Spectral analysis by the Blackman-Tukey method that applied to the time series of ANDHP, showed in most cases peaks at frequencies corresponding to the following time periods: about 2.6 and 4.0 years.
Abstract: Objective: We examined the association between climatologic parameters and daily admissions for non-fatal acute coronary syndromes (ACS) to emergency units of hospitals in the greater Athens area, from January 2001 to August 2002. Methods: Daily mean, maximum and minimum temperatures, relative humidity, wind speed, barometric pressure and a thermo-hydrological index (T.H.I.) were measured at the meteorological station of the Laboratory of Climatology of the Geology Department of the University of Athens. In addition, the daily number of admissions for acute myocardial infarction or unstable angina in the five major general hospitals in the greater Athens area was recorded. Generalized additive models (GAM) were applied to regress-time-series of daily numbers of outpatients with acute cardiac events against climatological variations, after controlling for possible confounders and adjustment for over dispersion and serial correlation. Results: Five thousand four hundred fifty-eight Athenians with non-fatal acute cardiac events were admitted to the selected hospitals during the period of the study, 4093 (75%) males and 1365 (25%) females. There was a negative correlation between hospital admissions and mean daily temperature (MDT) with a I degreesC decrease in mean air temperature yielding a 5% increase in hospital admissions (P<0.05). This association was stronger in females and the elderly (P<0.01). Relative humidity was positively correlated with hospital admissions (P<0.05). Conclusion: Despite the relatively short study period (<2 years), these findings suggest a significant association between cold weather and increased coronary heart disease incidence, especially in the elderly and females. (C) 2003 Elsevier Ireland Ltd. All fights reserved.
Abstract: The goal of this study is to estimate the relation between air temperature and precipitation in Greece and, thereafter, to define the regions of the covariability of the two parameters. For that purpose, the air temperature and precipitation mean monthly data of 30 meteorological stations, for the period 1950-2000, are analyzed. The first step is the application of Factor Analysis (FA) to each of the two variable groups of the seasonal air temperature and precipitation. The aim is to reduce the number of variables in each group and, more specific, to define the main significant factors for each parameter. The second step is the application of Canonical Correlation Analysis (CCA) to the factor scores of each parameter, derived by the use of PCA, so that the canonical pairs are extracted and the number of the pairs are equal to the minimum number of variables in either set. In the process, the computed canonical scores are correlated to the respective original data, aiming to define regions of positive and negative correlations between the canonical roots of the air temperature and precipitation.
Abstract: The effects of urbanization on the Athens National Observatory (NOA) long records are investigated, in the present study, examining the mean monthly maximum and minimum air temperature for the period 1925-1996, for NOA and the corresponding time series for Aliartos (ALI), a rural station located 70 km NW of Athens. The existing small urbanization effect in NOA before the second world war period increased after the war and up to about 1990, when the effect became stationary. The urbanization effect in NOA referred mainly to maximum temperature and to the warmer seasons of the year. It is attributed to the extensive building of Athens after the war around NOA site and up to the sea which increases the temperature of the sea breeze. The effect is also attributed to the rapid increase of the population and the number of motor vehicles mainly after 1970. Moreover the decreasing trend of precipitation during the period 1970-1990 may have contributed to the increase of maximum air temperature. The urbanization effect on maximum temperatures of NOA amounts about 2 degrees C in spring, summer and less in fall, while no urbanization effect is clear in winter.
Abstract: The patterns of monthly precipitation distributions in Greece, during the months of the year, are studied. Using factor analysis T-mode on mean monthly precipitation for a long period, we try to establish characteristic patterns of precipitation distribution. Only two of the eigenvectors (factors) were found statistically significant, namely factor I, explaining 67% of total variance and referring to the months of the period from October to March (cold period) and factor II, explaining 23% of total variance and referring to the months from April to September (warm period). During the cold period precipitation is maximum on Western Greek mainland and along the Western Asia Minor coast and islands while minima are shown in Cyclades islands, Attika, Thessaly, Macedonia and Thrace. On the other hand, during the warm period precipitation shows maxima in Central and North continental areas and the interior of Peloponese while minima appeared again in Cyclades, Dodecanese and Crete. Finally, the various areas of the country are distributed in 4 categories, depending on the combination of plus or minus of the normalized factor scores, for each period.
Abstract: In this paper, we deal with the ARIMA (Box-Jenkins) model of the gridded mean annual air temperature for the area included by the co-ordinates :20 degrees - 30 degrees W, 35 degrees - 45 degrees N, (thus the South Balkan area, the most of its percentage covered by Creek peninsula). We analyse the gridded temperature time series which existed from 1851 to 1996. With the theoretical model's construction, we try to forecast the annual temperature till the year 2006, and the results were satisfactory enough. Also, from the analysis we found that the autocorrelation function (ASF) and the partial autocorrelation function (PASF) of the residuals were not significant, and the ARIMA model is quite reliable.
