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Under the background of global warming, occurrence of heat waves has increased in most part of Europe, Asia and Australia along with enhanced ozone level. In this paper, observational air temperature and surface ozone in the Yangtze River Delta (YRD) region of China during summer of 2013, and the regional chemistry-climate model (RegCM-CHEM4) were applied to explore the relationship between heat wave and elevated ground-level ozone. Observations indicated that YRD experienced severe heat waves with maximum temperature up to 41.1°C, 6.1°C higher than the definition of heat wave in China, and can last for as long as 27days. Maximum ozone reached 160.5ppb, exceeding the national air quality standard (secondary level) as 74.7ppb. Moreover, ozone was found to increase at a rate of 4-5ppbK-1 within the temperature range of 28-38°C, but decrease by a rate of -1.3~-1.7ppbK-1 under extremely high temperature. A typical heat wave case (HW: 24/7-31/7) and non-heat wave case (NHW: 5/6-12/6) were selected to investigate the mechanism between heavy ozone and heat waves. It was found that chemical reactions play the most important role in ozone formation during HW days, which result in 12ppb ozone enhancement compared to NHW days. Chemical formation of ozone can be influenced by several factors. During heat waves, a more stagnant condition, controlled by anti-cyclone with sink airflow, led to less water vapor in YRD from south and contributed to less cloud cover, which favored a strong solar radiation environment and ozone significantly increasing. High temperature also slightly promote the effect of vertical turbulence and horizontal advection, which beneficial to ozone remove, but the magnitude is much smaller than chemical effect. Our study suggests that the chemical reaction will potentially lead to substantial elevated ozone in a warmer climate, which should be taken into account in future ozone related issues.

In the current work, a numerical model for the prediction of temperature, air velocity, relative humidity and ammonia distribution released by sheep and goats manure inside a naturally ventilated livestock building is presented. Given that noteworthy amount of gaseous pollutants are emitted by the agricultural and animal husbandry activities, the study of the indoor microclimate is essential to be investigated for the healthy growth of the breeding livestock. The developed numerical model is satisfactory validated by recorded measurements in the building. The analysis reveals that the natural ventilation of the building is effective, although it is observed relative high temperatures in the cores of the recirculations inside the building. ACh (Air Changes per hour) and internal climate indexes like THI (Temperature Humidity Index) and Twc (Wind Chill Index) were calculated in order to reveal the existence of areas where cold or heat stress conditions hold. According to the developed flow pattern, it is estimated the ammonia distribution internally. Due to the adequate ventilation of examined cases, no areas with excessive ammonia concentration are predicted neither marked areas with heat or cold stress climatic conditions are found. In buildings with relative geometry, areas away from openings, are candidates for the appearance of hot stress conditions, even when the required ventilation rates are satisfied. However, this is expected to be happened for higher external temperatures from the examined. This implies that, large and concentrated openings cannot substitutes, in terms of efficiency, the smaller and equally distributed over a building's sides openings.

Meteorological (T and RH values) and air pollution data (PM10, NO2 and O3 concentrations) observed in Athens, Thessaloniki and Volos were analyzed to assess the air quality and the thermal comfort conditions and to study their synergy, when extreme hot weather prevailed in Greece during the period 2001–2010. The identification of a heat wave day was based on the suggestion made by the IPCC to define an extreme weather event. According to it, a heat wave day is detected when the daily maximum hourly temperature value exceeds its 90th percentile. This temperature criterion was applied to the data recorded at the cities center. Air quality was assessed at three sites in Athens (city center, near the city center, suburb), at two sites in Thessaloniki (city center, suburb) and at one site in Volos (city center), while thermal comfort conditions were assessed at the cities center. Mean pollution levels during the heat wave days and the non-heat wave days were calculated in order to examine the impact of the extreme hot weather on air quality. For this purpose, the distributions of the common air quality index and the exceedances of the air quality standards in force during the heat wave days and the non-heat wave days were also studied. Additionally, the variation of the daily maximum hourly value of Thom's discomfort index was studied in order to investigate the effect of extreme hot weather on people's thermal comfort. Moreover, the values of the common air quality index and Thom's discomfort index were comparatively assessed so as to investigate their synergy under extreme hot weather.

This article studied the potential seasonal heat-stress of dairy ewes housed in a typical naturally ventilated sheep barn located close to the east coast of central Greece. Heat stress was assessed using the Temperature Humidity Index (THI) and the Seasonal THI-hrs index. Dairy ewes were exposed to potential heat-stress (THI ≥ 22.2) in 79%, 17%, and 11% of summer, autumn, and spring hours, respectively, whereas no heat-stress was present during winter. The monthly means of the daily maximum hourly THI values remained above the extreme severe heat-stress threshold (i.e. 25.6) during the summer months and above the severe heat-stress threshold (i.e., 23.3) during May and September. During all summer days the minimum daily maximum hourly THI value was 24.6 indicating that sheep experienced severe heat-stress (THI ≥ 23.3). THI levels remained very high (usually above the extreme severe heat-stress threshold) during daytime and dropped below the heat-stress threshold (i.e., 22.2) only for a few hours during night-time. The values of the Seasonal THI-hrs index under heat-stress conditions (THI ≥ 22.2) were 6596, 975, 0, and 516 during summer, autumn, winter, and spring, respectively. These findings suggest that under summer conditions in the east coast of central Greece, dairy ewes were exposed to severe or extremely severe heat-stress conditions, while they were also partially exposed to severe or extremely severe heat-stress conditions during autumn and spring.

China experienced major heat waves in summer 2013, being the worst the last 140 years in Eastern China. The RegCM-Chem4 climate-chemistry model was applied over China for the summer 2013 with a spatial resolution of 60 km and hourly temporal analysis. This study focuses on the examination of the RegCM-Chem4 performance in the simulation of ozone levels during two prolonged heat wave periods (24/07/2013–31/07/2013 and 07/08/2013–14/08/2013) and a non heat wave period (05/06/2013–12/06/2013) in Central and Eastern China. Near surface model results for ozone are compared with hourly observational data from 45 monitoring stations of the Chinese air quality network. The RegCM-Chem4 validation in the non-HW period presents good results. In August HW, the model underestimates the O3 values and variability, in line with RegCM-Chem4 temperature values underestimation in the same period, showing at almost all stations a performance that is not as good as that in the non-HW period. The performance of the model in the July HW requires further analysis; RegCM-Chem4 also underestimates the O3 levels and variability at almost all stations, however the model performance is not as good as that in the non-HW period only at a part of the AQ stations.

The heat waves (HWs) that hit Central and Eastern China in July and August 2013 brought record-breaking high temperatures. People died, water resources were depleted and regional power grids were strained. The aim of this paper was to assess the capability of RegCM4 model to predict temperature at 2 m above ground (T2m) and relative humidity (RH) values during the HWs that occurred in China in the summer 2013. T2m data recorded by 32 meteorological stations (MSs) distributed in the whole country were analyzed to identify HW events. Two 8-day periods were selected (24/7–31/7, 7/8–14/8), when the daily maximum hourly value (DMHV) of T2m continuously exceeded 35 °C. Additionally, an 8-day non HW period was selected (5/6–12/6) for comparison purposes. These prolonged HW events were occurred in Hunan, Hubei, Anhui, Jiangsu and Shanghai Provinces, therefore data recorded by the MSs located in these Provinces were further exploited. Model’s results were evaluated against measurements by applying common statistical indices. RegCM4 showed generally sufficient performance in capturing the main characteristics of the HWs in summer 2013 at Central and Eastern China.

It is well documented that heat-stress burdens sheep welfare and productivity. Peak heat-stress levels are observed when high temperatures prevail, i.e. during heat waves; however, continuous measurements inside livestock buildings are not usually available for long periods so as to study the variation of summer heat-stress levels for several years, especially during extreme hot weather. Α methodology to develop a long time series of summer temperature and relative humidity inside naturally ventilated sheep barns is proposed. The accuracy and the transferability of the developed linear regression models were verified. Temperature Humidity Index (THI) was used to assess sheep's potential heat-stress. Τhe variation of THI inside a barn during heat wave and non-heat wave days was examined, and the results were comparatively assessed. The analysis showed that sheep were exposed to moderate, severe, and extreme severe heat-stress in 10, 21 and 66 % of hours, respectively, during heat wave days, while the corresponding values during non-heat wave days were 14, 33 and 43 %, respectively. The heat load on sheep was much higher during heat wave events than during non-heat wave periods. Additionally, based on the averaged diurnal variation of THI, it was concluded that extreme severe heat-stress conditions were prevailing between 1000 and 2400 hours local time during heat wave days. Cool off night periods were never and extremely rarely detected during heat wave and non-heat wave days, respectively.

This study explores the ideas of Greek prospective primary teachers about the anthropogenic greenhouse effect, particularly about its causes, consequences and cures. For this purpose, a survey was conducted: 265 prospective teachers completed a closed-form questionnaire. The results showed serious misconceptions in all areas (causes, consequences and cures). The most prominent misconception found by this survey is the conflation between the greenhouse effect and the ozone layer depletion, which is widely reported in the literature. There is also the notion that ‘good things’ (like clean beaches) can help ameliorate the greenhouse effect, whereas ‘bad things’ (like insecticides) can enhance it. One of the secondary results of the survey is that prospective teachers’ main source of information about the greenhouse effect is school. This calls for educational interventions to fight misconceptions at the source. Some suggestions are presented in this paper. The results of this study are compared with the results of two similar studies conducted in the UK and in Turkey.

The short–term prediction of near surface ozone levels is very important due to the negative impacts of ozone on human health, climate and vegetation. The objective of this paper is to develop and test an analytical model that could be applied to predict next day's maximum ozone concentration for the first time in Tirana, Albania, where ozone's monitoring has been recently started. The relationship of the daily maximum hourly ozone values with meteorological variables, including near surface air temperature and relative humidity and with air pollution variables like the persistency of ozone levels and its seasonal variation is examined. The data analysis reveals that the pollution persistency and the near surface air temperature are the factors that mainly affect the peak ozone levels. Multiple linear regression analysis has been performed to establish the relationship between the above mentioned parameters and peak ozone concentration. The agreement between observed and predicted daily maximum hourly ozone values is very good, with a correlation coefficient (R) of 0.87. The model slightly under–predicts the ozone concentration while no significant mispredictions are observed. Additionally, the model’s ability to predict the exceedances of a specific ozone limit value is examined. The model successfully predicts the exceedances of 105 μg m −3 , a value that corresponds to the 75 th percentile, in the 86% of the cases applied.

Data referring to an approximately 8-year period (1999–2007) are analyzed in order to estimate the trend of the daily maximum hourly value of ozone concentration at the east coast of central Greece, where the summer background ozone concentration is high. A Kolmogorov–Zurbenko filter is applied to remove the short-term component from the raw time series of ozone and meteorological variables. Regression models are developed in order to produce meteorologically adjusted ozone time series, involving the noise-free temperature, relative humidity, and wind speed as independent variables. The analysis verifies that the meteorological adjustment provides better results on estimating ozone’s trend, which is found to be increasing (α = 0.001) with an annual rate of 1.34 ± 0.07 μg/m3. This trend could mainly be attributed to policy and changes in the emissions of ozone’s precursors. Additionally, the short-term component of ozone concentration is also meteorologically adjusted and its impact on the trend is examined. The analysis shows that its contribution is of minor importance when the ozone trend is adjusted by temperature, relative humidity, and wind speed. Moreover, the sea breeze circulation system that is frequently developed in the area influences the short-term and seasonal ozone variation, and therefore, it should be taken into account when producing meteorologically adjusted time series. The study’s conclusions could be exploited by environmental and agricultural authorities in order to develop their long-term strategies towards the air quality management.

This paper studies the maximum intensity of the urban heat island (UHI) that develops in Volos urban area, a medium-sized coastal city in central Greece. The maximum temperature difference between the city center and a suburb is 3.4°C and 3.1°C during winter and summer, respectively, while during both seasons the average maximum UHI intensity is 2.0°C. The UHI usually starts developing after sunset during both seasons. It could be attributed to the different nocturnal radiative cooling rate and to the different anthropogenic heat emission rate that are observed at the city center and at the suburb, as well as to meteorological conditions. The analysis reveals that during both seasons the daily maximum hourly (DMH) UHI intensity is positively correlated with solar radiation and with previous day’s maximum hourly UHI intensity and negatively correlated with wind speed. It is also negatively correlated with relative humidity during winter but positively correlated with it during summer. This difference could be attributed to the different mechanisms that mainly drive humidity levels (i.e., evaporation in winter and sea breeze (SB) in summer). Moreover, it is found that SB development triggers a delay in UHI formation in summer. The impact of atmospheric pollution on maximum UHI intensity is also examined. An increase in PM10 concentration is associated with an increase in maximum UHI intensity during winter and with a decrease during summer. The impact of PM10 on UHI is caused by the attenuation of the incoming and the outgoing radiation. Additionally, this study shows that the weekly cycle of the city activities induces a weekly variation in maximum UHI intensity levels. The weekly range of DMH UHI intensity is not very large, being more pronounced during winter (0.4°C). Moreover, a first attempt is made to predict the DMH UHI intensity by applying regression models, whose success is rather promising.

Atmospheric pollutants from livestock operations influence air quality inside livestock buildings and the air exhausted from them. The climate that prevails inside the building affects human and animal health and welfare, as well as productivity, while emissions from the building contribute to environmental pollution. The aim of this study was to examine the variation of two climatic parameters (namely temperature and relative humidity) and the levels of particulate matter of different sizes (PM10-PM2.5-PM1), as well as the relationships between them, inside a typical Greek naturally ventilated livestock building that hosts mainly sheep. The concentration of particles was recorded during a 45-day period (27/11-10/1), while temperature and relative humidity were observed during an almost 1-year period. The analysis revealed that the variation of outdoor weather conditions significantly influenced the indoor environment, as temperature and relative humidity inside the building varied in accordance to the outside climate conditions. Temperature remained higher indoors than outdoors during the winter and extremely low values were not recorded inside the building. However, the tolerable relative humidity levels recommended by the International Commission of Agricultural Engineering (CIGR) were fulfilled only in 47% of the hours during the almost 1-year period that was examined. This fact indicates that although temperature was satisfactorily controlled, the control of relative humidity was deficient. The concentration of particulate matter was increased during the cold winter days due to poor ventilation. The maximum daily average value of PM10, PM2.5 and PM1 concentration equaled to 363, 61 and 30 μg/m(3) respectively. The concentration of the coarse particles was strongly influenced by the farming activities that were daily taking place in the building, the dust resuspension being considered as the dominant source. A significant part of the fine particles were secondary, which the production of could be attributed to an increase in relative humidity levels. It is concluded that measures have to be adopted in order to achieve sufficient ventilation and to reduce particulate matter levels.

Weather Research and Forecast (WRF) model is applied to study the wind field over the east coast of central Greece under typical summer conditions. This study aims at identifying the major features of the sea breeze circulation that is very frequently developing in the area during the warm period of the year and at verifying the model's ability to simulate the complex flow that is strongly influenced by the complicated coastline and very steep terrain. The simulation is carried out for a five-day period, characterized by sea breeze development. It is found that a complex meteorological phenomenon is evolving in the area, as two circulation systems are successively developing, the first over Pagasitikos Gulf, which is overridden by the system that develops later over the Aegean Sea. The major characteristics of the wind patterns and especially the sea breeze systems are identified and discussed. Additionally, the impact of topography and slope on sea breeze circulation is also commented. Model predictions agree fairly well with the observations taken at a near-surface meteorological station.

During the summer of 2007 several Greek regions suffered periods of extreme heat, with midday temperatures of over 40 degrees C on several consecutive days. High temperatures were also recorded on the east coast of central Greece, where a complex sea breeze circulation system frequently develops. The more intense events occurred at the end of June and July. The highest temperatures were observed on 26 June and 25 July, while the sea breeze developed only on 25 July. Meteorological data collected at two sites-a coastal urban location and an inland suburban site that is not reached by the sea breeze flow-as well as pollution data collected at the urban site, were analysed in order to investigate the relationship between sea breeze development and the prevailing environmental conditions during these two heat wave events. The analysis revealed that sea breeze development affects temperature and pollution levels at the shoreline significantly, causing a decrease of approximately 4 degrees C from the maximum temperature value and an increase of approximately 30% in peak PM10 levels. Additionally, several stress indices were calculated in order to assess heat comfort conditions at the two sites. It was found that nocturnal comfort levels are determined mainly by the urban heat island effect, the intensity of which reaches up to 8 degrees C, while the applied indices do not demonstrate any significant daytime thermal stress relief due to sea breeze development.

Ambient aerosol concentrations have been implicated in human health effects, in visibility reduction in urban and regional areas, in acid deposition and in perturbing the Earth’s radiation balance. The main concern of the air quality managers is to achieve compliance to the established air quality standards (AQS). As AQS are exceeded in numerous sites worldwide, it is essential to reduce the emissions. Having decided which statistical distribution fits well to the PM10 parent distribution, it is feasible to estimate the reduction in emissions that is required in order to meet AQS. In this study, it is verified that the PM10 concentration distribution can be adequately simulated by lognormal distribution, a conclusion drawn by the calculation of several statistical indexes. The study area is the city of Volos in central Greece, which is experiencing an unpleasant situation concerning the levels of PM10 pollution. The probability density function of lognormal distribution is capable to predict the number of days when the European Union (EU) AQS for PM10 concentration are exceeded in Volos area. Furthermore, the minimum reduction in current emission sources of PM10 required in order to meet the air quality regulations that are established by the EU is calculated for the study area and is found to be ~33%. The results could be utilized as reference for air pollution control strategy.

The atmospheric boundary layer (ABL) is characterized by the turbulence eddies that transport heat, momentum, gaseous constituents and particulate matter from Earth’s surface to the atmosphere and vice versa. Thus, the determination of its height has a great importance in a wide range of applications like air quality forecasting and management. This study aims at estimating the height of the ABL in a suburban environment and at investigating its temporal variation and its relationship with meteorological variables, like temperature and wind. For this purpose, radiosonde data from the suburban area of Thessaloniki, Greece, are analyzed. The data analysis reveals that ABL height is usually below 200 m in the morning hours during all seasons of the year and that is also low when near-surface temperature and wind speed are low too. Additionally, noon ABL height exhibits a strong seasonal variation, reaching higher values during summer than during winter.Very high values of ABL height, of the order of ~3,000 m, are occasionally observed in Thessaloniki during summer. Moreover, sea breeze development during summer is related to a slight reduction of the ABL height.

The aims of this paper are to investigate the characteristics of the sea breeze that is developing in Volos area, a medium sized coastal city in central Greece, and to study the influence of sea breeze on concentration levels of ozone and PM10, during the period 2001–2005. The identification of sea breeze days is based on a set of strict, objective criteria, which include the wind direction and its diurnal reversal, the wind direction difference between the surface winds and the winds in the free atmosphere and the thermal contrast between the sea and the land surface. The statistical analysis reveals that sea breeze is developing in 85.6% of days from May until July, with maximum frequency of occurrence 89% in June. Its most frequent onset and cessation time periods are 09:00–11:00 and 20:00–22:00 LST respectively and its usual duration is approximately 10 h. The average maximum strength is 2.6 m/s, usually between 14:00 and 17:00 LST, while the maximum observed value equals 5.9 m/s. Studying the variation of ozone and PM10 levels during the cold and the warm period of the year (October–April and May–September respectively), it is concluded that sea breeze development is associated with an increase of the concentration of both pollutants. This increase is more pronounced during the cold period and is attributed to unfavourable meteorological conditions. Copyright © 2008 Royal Meteorological Society

Suspended particulate matter is significantly related to the degradation of air quality in urban agglomerations, generating adverse health effects. Therefore, the ability to make accurate predictions of particulate ambient concentrations is important in order to improve public awareness and air quality management. This study aims at developing models using multiple regression and neural network (NN) methods that might produce accurate 24-h predictions of daily average (DA) value of PM10 concentration and at comparatively assessing the above mentioned techniques. Pollution and meteorological data were collected in the urban area of Volos, a medium-sized coastal city in central Greece, whose population and industrialization is continuously increasing. Both models utilize five variables as inputs, which incorporate meteorology (difference between daily maximum and minimum hourly value of ground temperature and DA value of wind speed), persistency in PM10 levels and weekly and annual variation of PM10 concentration. The validation of the models revealed that NN model showed slightly better skills in forecasting PM10 concentrations, as the regression and the NN model can forecast 55 and 61% of the variance of the data, respectively. In addition, several statistical indexes were calculated in order to verify the quality and reliability of the developed models. The results showed that their skill scores are satisfying, presenting minor differences. It was also found that both are capable of predicting the exceedances of the limit value of 50 μg/m3 at a satisfactory level.

An experimental methodology was developed to measure the non-volatile particle number concentration using a thermodenuder (TD). The TD was coupled with a high-resolution time-of-flight aerosol mass spectrometer, measuring the chemical composition and mass size distribution of the submicrometer aerosol and a scanning mobility particle sizer (SMPS) that provided the number size distribution of the aerosol in the range from 10 to 500 nm. The method was evaluated with a set of smog chamber experiments and achieved almost complete evaporation (> 98 %) of secondary organic as well as freshly nucleated particles, using a TD temperature of 400 °C and a centerline residence time of 15 s. This experimental approach was applied in a winter field campaign in Athens and provided a direct measurement of number concentration and size distribution for particles emitted from major pollution sources. During periods in which the contribution of biomass burning sources was dominant, more than 80 % of particle number concentration remained after passing through the thermodenuder, suggesting that nearly all biomass burning particles had a non-volatile core. These remaining particles consisted mostly of black carbon (60 % mass contribution) and organic aerosol, OA (40 %). Organics that had not evaporated through the TD were mostly biomass burning OA (BBOA) and oxygenated OA (OOA) as determined from AMS source apportionment analysis. For periods during which traffic contribution was dominant 50–60 % of the particles had a non-volatile core while the rest evaporated at 400 °C. The remaining particle mass consisted mostly of black carbon (BC) with an 80 % contribution, while OA was responsible for another 15–20 %. Organics were mostly hydrocarbon-like OA (HOA) and OOA. These results suggest that even at 400 °C some fraction of the OA does not evaporate from particles emitted from common combustion processes, such as biomass burning and car engines, indicating that a fraction of this type of OA is of extremely low volatility.

Meteorological and air pollution data observed during the last decade in Athens, Thessaloniki and Volos were analyzed to assess the air quality during heat waves. The identification of a heat wave day was based on two temperature criteria applied to the data recorded at the cities centre: the daily maximum and the daily average temperature value are at least 37°C and 31°C, respectively. Heat wave days were identified every year in Athens but only in 2007 in Thessaloniki and Volos. Air quality was aggravated during heat wave days, a fact that was verified by the means of the common air quality index. PM10 concentration levels increased 30% in the centre of Athens and more than 100% in Thessaloniki and Volos, while O3 concentration levels increased 29% in Thessaloniki’s suburb. The increase of pollution levels triggered exceedances of the air quality standards. Temperature and pollution levels during the heat waves occurred in 2007 were separately examined.

This paper studies the heat stress conditions imposed onto sheep housed in a naturally ventilated sheep barn during the four seasons of a year. The barn is located near the east coast of central Greece. Heat stress is assessed by means of the hourly temperature-humidity index (THI). The analysis shows that animals were exposed to heat stress in 11%, 80% and 17% of spring, summer and autumn hours, respectively, whereas no heat stress was identified during winter. As expected, animals are more prone to severe heat stress during summer, as the daily maximum hourly values of THI remained higher than the extreme severe heat stress threshold (i.e. THI = 25.6) in 90% of the summer days. Additionally, THI remained higher than 25.6 during the vast majority of the summer daytime hours. Measures have to be taken so as to improve the indoor climate conditions and to alleviate animal’s heat stress.

A statistical analysis of ozone and PM10 concentration levels in the area of Volos, a medium-sized Greek coastal city, was carried out for the period 2001-2003. The data analysis revealed that the Daily Maximum Hourly (DMH) value of ozone concentration reaches a maximum of 160 µg/m³ during summer; it is observed during afternoon hours and is associated usually with winds from southern directions. This is attributed to the impact of the sea breeze on pollution levels. Concerning PM10 concentration, it was found that its DMH values are quite high and that its Daily Average (DA) value exceeds the limit value of 50 µg/m³ for approximately 38% of the days. The daily cycle shows two maxima (morning-evening) and in these cases the wind is typically from north-northwest directions. The weekly and seasonal variance of DA values of PM10 concentration is not very significant.