Synoptic and mesoscale weather conditions during air pollution episodes in Athens,Greece

Based on regular climatological and air quality data from the Greater Athens Area (GAA), the air pollution episodes observed in Athens during the period 1983–1990 were analysed and classified. The main characteristics of atmospheric conditions during days with high air pollution concentrations are summarized too. Model simulations show that the worst air pollution episodes in Athens occur during days with a critical balance between synoptic and mesoscale circulations and/or during days with warm advection in the lower troposphere.     

Mean monthly air temperatures in Athens, Greece

Summary  In this paper some statistical parameters of the mean monthly air temperatures in Athens are examined, namely trends, periodicities and cross-correlations between months. It is found that there is not any significant trend for most of the months and the periodicities don’t allow the extraction of any general conclusion. On the other hand, cross-correlation analysis shows that some correlation between the temperature in certain months exists. Received March 10, 2000     

The conductivity of the air and other electrical parameters in relation to meteorological elements and air pollution in Athens

Summary The annual and diurnal variation of the conductivity near the ground at Athens, based on long-term data, are presented. The diurnal double oscillation is a characteristic of the atmospheric electric climate of Athens. In addition, the influence of air pollution due to smoke and sulfur dioxide and of wind speed (as an element affecting the dispersion of pollulants) on large ion concentration and on conductivity has been examined. The air pollution, which is often severe in Athens area, results in decreasing conductivity and increasing large ion concentration, while the influence of wind speed is also pronounced. The results justify the use of conductivity as a pollution index. Finally the plausible influence of air temperature and relative humidity and of their rate of change on air electrical conductivity, has been examined. The results are ambiguous and depending on the season, especially for relative humidity.With 3 Figures     

Study of small ions concentration in the air above Athens, Greece

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/cm³ for positive ions and n₋ = 151.1 ions/cm³ 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.     

Evidence of katabatic flows deduced from a 84 m meteorological tower in Athens,Greece

The identification of katabatic flows and their characteristics observed on a simple slope (the western side of Hymettos mountain) for a six-month period (January to June, 1990) are presented. This is the first application of data obtained from an 84 m high meteorological research tower recently erected at the National Center for Scientific Research Demokritos in Athens, Greece. The tower is described with respect to construction and instrumentation. The topography of the region and the observational site are also described. Criteria for the identification of katabatic flows are presented, while the frequency of occurrence of such flows is estimated. Finally, two case studies are analysed in order to reveal the special characteristics of the katabatic flows.     

The effect of air temperature and human thermal indices on mortality in Athens, Greece

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.     

Mesoscale and macroscale aspects of the morning Urban Heat Island around Athens,Greece

Summary This paper examines the characteristics of the morning Urban Heat Island (UHI) in Athens basin, Greece. The study is performed by using and analyzing mesoscale and synoptic data covering the period 1990–2001. The UHI was estimated using the 0600 Local Time (LT) minimum temperature differences between rural and urban areas of the city. The analysis results in 7 UHI classes. A strong UHI was found for the 1/3 of days. The specific meteorological characteristics (surface and upper air, cooling rate) of each UHI class were revealed and examined. The spatial and temporal characteristics of the UHI were also identified. The UHI is largest on nights with clear skies and low relative humidity. In all seasons the UHI switches on rapidly in afternoon. During spring and summer, sea breeze commonly reduces and delays the UHI. Cases documenting the sensitivity and rapidity of changes of the UHI to changes in classes (cloud cover, wind) are also presented. The cooling rate is higher in the urban area under negative and lower under positive UHI conditions. Mesoscale and macroscale phenomena were examined during the different UHI classes through a weather type scheme. It was emerged that high UHI classes are associated with anticyclonic conditions or advection in the lower troposphere, while low UHI classes are associated with strong northeasterly winds. Anticyclonic conditions which frequently occur in spring and early summer, reduce or reverse the UHI to Urban Cooling Island.     

秦皇岛市空气污染与气象要素的关系

利用多因子分析和多元回归模型,对1998—2004年秦皇岛市城区空气污染物浓度逐日监测数据及气象要素进行分析,并调查污染源,得出主要污染物与气象要素的关系,建立当地空气质量预报。结果表明：上游西北地区是对秦皇岛市空气质量影响最大的污染源地;空气质量首要污染物PM10的峰值出现在4月,SO2的峰值出现在采暖季,NO2浓度全年稳定少变; SO2和PM10的浓度受风场影响较大,NO2最小;春季“南高北低”型气压场造成PM10污染指数全年最高;大于等于1 mm的降水对空气净化作用效果较小于1 mm的降水显著;春季气旋控制下,5级以上西风可形成中度以上污染,而非气旋控制下,6级以上西风才可形成中度以上污染。     

盱眙县空气污染特征及其气象条件分析

采用盱眙县环境监测站 2014年1—12月PM₁₀、PM_2.5、SO₂、NO₂、O₃逐日质量浓度资料及盱眙国家基本气象站同期气象资料,分析不同气象条件下盱眙县空气质量变化.结果表明:盱眙县主要污染物是PM_2.5、PM₁₀,污染较轻的是SO₂、NO₂、O₃;盱眙县空气质量变化趋势为春冬季污染严重,夏秋季污染较轻.气象条件中的降水因子对改善空气质量、清除颗粒物具有明显作用;当温度在0 ℃以下或30 ℃以上时空气质量相对较好,0～20 ℃时空气污染情况较为严重;偏东风时大气环境质量较差,偏北风时大气环境质量较好.     

德阳市区空气污染气象指数预报

根据空气污染与气象条件的关系分析,引入一个空气污染气象指数,用T213数值预报产品相关资料作为空气污染气象因子输入,从而作出空气污染气象指数预报.     

德阳市区空气污染气象指数预报

根据空气污染与气象条件的关系分析，引入一个空气污染气象指数，用T213数值预报产品相关资料作为空气污染气象因子输入，从而作出空气污染气象指数预报。     

Indications of change of climate from the analysis of air temperature time series in Athens,Greece

Air temperature data of Athens are analysed to point out the variations caused by natural controls and anthropogenic activities. The study of the temperature records from 1858 to 1982 at Athens, on the southeast coast of Greece, supports the findings of earlier studies which indicate that the period of the 1920's to the 1950's were, climatologically, warmer than the preceding 60 yr and after about 1960. In particular, minimum temperatures show an increase from the 1920's to the 1980's, possibly due to the urbanization of the area. The climatological trends are clearly indicated in the data, when averaged over 30 yr and/or a numerical low-pass filtering technique is used. However, the sizes of the trends in climate are smaller than the interannual variations in the temperature measures. Over periods of several generations these small variations in climate cannot have had any effect on human activity when compared with the large effects caused by the interannual variability in the temperature.     

厦门空气污染指数与地面气象要素的关系分析

利用相关统计法分析2006—2008年厦门市地面气象要素对空气污染指数变化的影响规律。结果表明：风速、气温、降水、相对湿度和水汽压对空气污染指数有显著负效应作用,气压起显著正效应作用;风向影响较为复杂, NNW-N-E-ESE风起正效应作用, SE-S-W风起负效应作用,厦门风向总体不利于空气质量提高,全年仅夏季盛行SE-S-W风。API指数与风向、气温、降水、气压、相对湿度和水汽压的季节变化规律有高相关性。API指数与气象要素中的水汽压关系最相关,其次是气压。     

A statistical analysis of air pollution data in terms of meteorological conditions

The air pollution in the planetary boundary layer (PBL) at a height of about 1 km is considered. Assuming stationarity and horizontal homogeneity of the underlying surface, the turbulent state in the PBL is completely determined by the following external parameters: the Rossby number, one parameter for thermal stratification and two for baroclinicity. The turbulent state in the PBL under the same conditions is also determined completely by the following internal parameters: one for thermal stratification and two for baroclinicity. If the internal or external parameters completely determine the PBL turbulent state, then they should completely determine the diffusion processes in it. That is why for the analysis of pollution data, it is recommended that these representative meteorological parameters should be used rather than selected ones. The external parameters which may be obtained from synoptic data have a definite advantage for statistical processing of air pollution data. This is clearly of importance for forecasting. On the other hand, the connection between pollution and the internal parameters is comparatively well-studied theoretically. That is why for the prediction of pollution, it is necessary to know the dependence between the internal and external parameters, as given by the resistance law. An example of statistical processing of air pollution data in the PBL is treated in terms of the external parameters. In addition, an example is given of a theoretical prediction of pollution using synoptic data.     

Temporal variations of atmospheric tides over Athens,Greece

Summary The mean daily march of pressure (hourly values) for each month of the 96 year period 1894–1989 in Athens, Greece is studied using Fourier analysis. The annual variation of the harmonic parameters (amplitude, time of maximum,x andy-components) is examined. The globally excited 2nd and 3rd harmonics show in general the same behaviour as in other places of the Earth. Similar features show the corresponding parameters of the daily solar radiation march. The first harmonic displays some local characteristics. The long period fluctuations study revealed statistically significant trends in most parameters of the 2nd harmonic, most strikingly the 0.5 h shift in the time of its maximum during the 20th century. Power spectrum analysis showed the existence of a biennial oscillation inB ₁, thex-component of the first harmonic, but this oscillation is mainly confined to the second half of the entire period. A periodicity of about 6 years which could be associated to the Southern Oscillation was also found inB ₁ while inA ₁, they-component, a periodicity close to the 11-year solar cycle and another one close to the nutation of the Earth's axis are present. The lunar tides are too small to be detected by the same methods. However the semilunar tide was revealed to be 10–20 times smaller than the semisolar.With 8 Figures     

A note on smoke concentration prediction in Athens,Greece

Summary In this paper an attempt for predicting smoke concentration levels in Athens for spring and autumn is presented. The regression models are based on equations relating wind speed and smoke values. It is found that both of them become more effective if corrections related to wind speed categories are applied to the equations. In this way good prediction is achieved for the next 24 hours.With 4 Figures     

Chemical composition of wet deposition in a Mediterranean site Athens,Greece related to the origin of air masses

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° 58′ N, longitude: 23° 47′ E) inside the Athens University Campus and in a site at Heraklio Attica, a northern suburb of Athens (latitude: 38° 03′ N, longitude: 23° 45′ E). The concentrations (μeq l⁻¹) of the major cations (H⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺) and anions (Cl⁻, , και ), 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 μS cm⁻¹. The analysis showed that Ca²⁺ ions are abundant within all examined samples, while and 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.     

Analysis of the long-term precipitation series at Athens,Greece

In this paper, the characteristics of the long-term precipitation series at Athens (1858–1985) have been statistically analyzed. This study covers both the history and the analysis of the data. The ten-year mean amounts, the monthly and annual amounts averaged over the intervals 1858–1890, 1891–1985, 1951–1980, 1858–1985, the mean number of hours of precipitation and the precipitation intensity are given. The analysis of long-term time series of climatic data (in particular precipitation) is a useful tool for the study of past climate. Different statistical techniques are used in order to depict monthly, seasonal and annual variations, as well as trends, periodicities and recurrence intervals of the amount, intensity and number of precipitation days. The analysis reveals many interesting characteristics. These characteristics of the precipitation regime are extended to a time scale from seasonal variation to a semi-secular trend. The study of such long-term series may be helpful not only in practical applications of rainfall, but also for explaining the possible physical or anthropogenic mechanisms of climatic fluctuations and tendencies. The series of precipitation at Athens is one of the longest in south-eastern Europe.