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Validation is critical for quantifying accuracy, errors and limitations of models’ results. This study examines the ability of ENVI-met model to simulate thermal conditions in high spatial resolution. Field measurements from 11 central sites (squares and parks) across the greater area of Athens, Greece, incorporating 15 days of campaigns in July and August were used. Air temperature, relative humidity, wind speed, grey globe temperature and total solar radiation were monitored at 1.1 m above the ground using a mobile meteorological station. In addition, Mean Radiant Temperature, Physiologically Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) were calculated incorporating in-situ measurements. The full force method for ENVI-met initial conditions was applied, using hourly data from the nearest meteorological stations. Validation metrics including Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and the index of agreement (d) were used to measure the model accuracy. The results showed that air temperature is simulated with adequate accuracy (MAE = 1.6 ⁰C and d = 0.8) while PET and UTCI also present a high percentage of agreement (MAE = 5.3 ⁰C and 3.3 ⁰C; d = 0.7 and 0.8, respectively). Overall, the study provides further confidence that the ENVI-met can be utilized as a reliable model for further research analysis.

Thermal indices are commonly used to assess outdoor thermal environments. This study aims to examine the applicability of popular thermal indices for the assessment of thermal sensation in Cyprus. Field surveys were conducted in outdoor public sites in five districts of the Republic of Cyprus. The surveys involved environmental monitoring and questionnaire-based interviews of pedestrians. The pedestrians reported their thermal sensation using a nine-point scale, the actual thermal sensation (ATS). Thermal sensation predicted by Discomfort Index, Heat Index, Humidex (HU), Physiologically Equivalent Temperature (PET), Predicted Mean Vote (PMV), Standard Effective Temperature, Universal Thermal Climate Index, and Wet-Bulb Globe Temperature (WBGT), was compared to ATS. Spearman’s rho, Goodman and Kruskal's gamma, percentage of correct predictions, and distribution of indices’ predictions per category of ATS were used to assess indices’ applicability and find the index that best predicts thermal sensation. The analysis was performed for participants living in Cyprus (locals) and for visitors (non-locals). The indices predicted successfully a low percentage of ATS ranging in locals between 9.6% (HU) and 20.7% (PMV), and in non-locals between 13.9% (WBGT) and 29.9% (DI). Overall, PET performed better predicting successfully 16.8% of ATS in locals and 27.3% in non-locals.

Public open spaces improve the quality of life in cities and form places for community gatherings and outdoor activities. This study examines the preference of pedestrians for the design features of urban squares. Field surveys on the perception of environmental stimuli were conducted in five squares in Athens, Greece in three seasons (summer, autumn and winter), while a mobile station monitored environmental conditions at the moment of the interview. The questionnaire included an item on the preference for improvement of urban design features (i.e., vegetation, water elements, view, and sport spaces) at the monitoring sites. Overall, 1,858 pedestrians participated in the survey. Of these, 84.4% reported a preference for the monitoring site to be improved for urban design. More vegetation (60.7%) and adding water elements (28.9%) were the most popular suggestions. The preference for increasing vegetation was prevalent in all three seasons (summer, 63.8%; autumn, 61.5%; winter, 57.3%; p=0.05). The preference for water elements was more prevalent in summer (39.6%) than autumn (31.5%) and winter (17.3%; p

Several thermal indices have been proposed for quantification of various aspects of the thermal environment. Their applicability however is a methodological conundrum. The aim of the present study (part of the Biometeorological Aspect of Thermal environment and Health (BeAT Heat) project) was to assess the outdoor thermal environment using data on thermal sensation. In particular, the study tried to identify the thermal index that best simulates thermal sensation in the temperate and dry Mediterranean climate of Cyprus. Field surveys were conducted in summer 2019 in public urban spaces of five districts in Cyprus. These surveys involved monitoring of micrometeorological conditions and conducting questionnaire-based interviews with pedestrians in order to collect data on actual thermal sensation (ATS), demographics, and physiological and psychological variables. The study participants, using a predefined thermal sensation scale, reported their ATS. Variations of thermal sensation across the participants were studied in relation to the outdoor thermal environment and to physiological factors. ATS was compared with simulated thermal sensation (STS) produced by operationally used thermal indices under matching weather conditions, i.e., Heat Index, Humidex, and Wet-Bulb Globe Temperature. Physiologically Equivalent Temperature was additionally considered. All indices showed low predictability of ATS. The thermal index that performed best to the temperate and dry Mediterranean climate of Cyprus was the Heat Index using an assessment scale modified for the Mediterranean climate.

The large-scale surface-water monitoring infrastructure for Greece Open Hydrosystem Information Network (Openhi.net) is presented in this paper. Openhi.net provides free access to water data, incorporating existing networks that manage their own databases. In its pilot phase, Openhi.net operates three telemetric networks for monitoring the quantity and the quality of surface waters, as well as meteorological and soil variables. Aspiring members must also offer their data for public access. A web-platform was developed for on-line visualization, processing and managing telemetric data. A notification system was also designed and implemented for inspecting the current values of variables. The platform is built upon the web 2.0 technology that exploits the ever-increasing capabilities of browsers to handle dynamic data as a time series. A GIS component offers web-services relevant to geo-information for water bodies. Accessing, querying and downloading geographical data for watercourses (segment length, slope, name, stream order) and for water basins (area, mean elevation, mean slope, basin order, slope, mean CN-curve number) are provided by Web Map Services and Web Feature Services. A new method for estimating the streamflow from measurements of the surface velocity has been advanced as well to reduce hardware expenditures, a low-cost ‘prototype’ hydro-telemetry system (at about half the cost of a comparable commercial system) was designed, constructed and installed at six monitoring stations of Openhi.net.

The Price-Rind 92 parameterization (Price and Rind, 1992) that utilizes cloud top height as predictor for the estimation of lightning density is widely used by modelers in an attempt to forecast electrical activity in thunderstorms. In the present paper new parameterizations for the estimation of lightning density of convective clouds are formulated. LINET lightning data, NWC SAF (Satellite Application Facility on support to Nowcasting and Very Short-Range Forecasting) products and ERA-Interim (ECMWF-Re Analysis) data, covering the summer of 2016 over continental Europe, are used. The proposed models estimate the lightning density of convective clouds, using cloud top height, cloud top pressure and cold cloud depth as predictors. Model efficiency statistics calculated over an independent dataset, suggest that the proposed models can be considered successful over the specific area (continental Europe) and period (summer). The new cloud top height model differs from the PR92 and other parameterizations, which is not an unexpected result, since every model has its own characteristics, strengths and weaknesses. The new parameterizations could be utilized in numerical model simulations to produce quantitative estimations of the amount of strokes over convective areas.

The Hydro-telemetric Network, HYDRO-NET, is a pilot streamflow monitoring network established and operated by the Institute for Environmental Research and Sustainable Development of the National Observatory of Athens (NOA) within the HYDRO-NET Project (2018-2021): Hydro-Telemetric Network of Surface Waters: Gauging instruments, smart technologies, installation and operation. An aim of the project is that HYDRO-NETs’ principles of design, installation and operation will guide establishing of hydrometric networks in the Hellenic territory. HYDRO-NET provides a comprehensive framework for collection, transmission, handling and free use of data that combines technological innovations and advanced scientific methods with efficient use of resources. It particularly responds to the need of estimating the discharge at cross-sections of streams where no prior data exist by inexpensive means.Technological innovations concern the design and construction of a prototype hydro-telemetry system that combines custom built firmware and intelligent measuring technologies with telecommunication at low cost, ~50% the price of a commercial station. This prototype is equipped with an ultrasonic sensor for measuring stage, a thermometer, a GPRS modem, a camera and a data logger (it can also receive input from a rain gauge), and is powered by a solar panel; data and photos are transmitted to NOA’s server via mobile internet. The systems’ additional advantages are flexibility in programming, low maintenance costs, and the possibility of extending its monitoring capabilities with additional sensors (e.g. for monitoring water quality, video camera).Progress in streamflow estimation is achieved through the development of a maximum-entropy based method that calculates the discharge, at a cross-section of known bathymetry, using measurements of water stage and surface velocity by SVR (Surface Velocity Radar) and/or video cameras. Rating curves at monitoring stations can be thus constructed by inexpensive field campaigns, and safely under flooding. HYDRO-NET currently operates 16 hydro-telemetric stations, six of which are of NOA’s design, in the Peloponnese and in Attica, Greece. Measured data are transmitted to NOAs’ Server, where they are automatically processed (Quality Controlled) and stored in a Data Base; the data are freely available to users through the OpenHi.net platform (openhi.net), or upon request (hydronet@noa.gr). A prime service prospect of the HYDRO-NET system, with its real-time observations, is Flood Warning. Acknowledgment: The Hellenic General Secretariat for Research & Technology has provided financial support, under the National Strategic Reference Framework (2014-2020), for the project HYDRO-NET: Hydro-Telemetric Networks of Surface Waters: Gauging instruments, smart technologies, installation and operation, as a part of the Hellenic Integrated Marine and Inland Water Observing, Forecasting and Offshore Technology System, HIMIOFoTS (MIS5002739) (https://www.himiofots.gr/).

This article presents data collected during a web-based survey on expressions used to describe thermal sensation and comfort in the Greek language. The survey used a structured questionnaire and delivered through Google Forms. The survey was promoted through social networks and conducted in spring 2019. The data presented herein comprise of the participants’ responses to the questionnaire. A total of 359 questionnaires were completed. The participants were Greek speakers, older than 12, with at least a basic knowledge of the English language. The participants were asked to: (a) select the most appropriate translation, from English to Greek, of the nine-point ISO 10551 scale of perceptual judgment on personal thermal state, (b) formulate five, seven and nine-point thermal sensation scales, (c) report the category of the thermal sensation scale that signifies thermal comfort and (d) to assess the relative distances between the thermal sensation categories of the five, seven and nine-point thermal sensation scales. For the translation of the ISO 10551, the respondents were allowed to choose from a list of 30 Greek wordings. The data have been analysed in the research article entitled “Native influences on the construction of thermal sensation scales” [1] .

People exposed to heat experience symptoms of varying severity, from mild manifestations to heat stroke. Due to global warming, interest in the impact of heat exposure on human health has been increasing. This study investigated the association between outdoor thermal conditions and heat-related symptoms experienced by pedestrians in a temperate-Mediterranean and hot semi-arid climate. In the study, pedestrians participated in questionnaire-based surveys at outdoor sites in Cyprus in summer and autumn 2019 while the weather conditions at the sites were recorded. In the surveys, pedestrians reported whether they had experienced heat-related symptoms. The physiologically equivalent temperature (PET) was used to estimate the effect of the thermal environment. Statistical analyses of the data included the use of multivariable logistic regression models. In total, 1880 individuals (999 males, 54.2%; mean age ± standard deviation 38.4 ± 18.4 years) responded to the surveys of heat-related symptoms. An increase of 1 °C in air temperature (adjusted odds ratio (aOR): 1.10, 95% confidence interval (CI): 1.04–1.16) or PET (aOR: 1.04, 95% CI: 1.01–1.07) was associated with an elevated probability of reporting heat-related symptoms. The magnitude of the association of PET with the reporting of heat-related symptoms was found to be higher for nonpermanent residents in Cyprus (aOR: 1.11, 95% CI: 1.02–1.21). Females were more likely than males to report heat-related symptoms (aOR: 2.36, 95% CI: 1.82–3.06). Visiting the monitoring site for work (aOR: 1.69, 95% CI: 1.26–2.26) or reporting a medical history of respiratory disease (aOR: 3.60, 95% CI: 2.39–5.42) were associated with an increased likelihood of reporting heat-related symptoms. The thermal conditions and participant characteristics were associated with increased reporting of heat-related symptoms during non-heat-wave but warm periods in Cyprus. These results could have implications for adaptation measures, healthcare delivery, and public health services.

The Open Hydrosystem Information Network (OpenHi.net) is a state-of-the-art information infrastructure for the collection, management and free dissemination of hydrological and environmental information related to Greece’s surface water resources. It was launched two years ago as part of a the national research infrastructure “Hellenic Integrated Marine Inland water Observing, Forecasting and offshore Technology System” (HIMIOFoTS), which also comprises a marine-related component (https://www.himiofots.gr/). The OpenHi.net system receives and processes real-time data from automatic telemetric stations that are connected to a common web environment (https://openhi.net/). In particular, for each monitoring site it accommodates stage measurements, raw and automatically post-processed. Furthermore, in some specially selected sites time series related to water quality characteristics (pH, water temperature, salinity, DO, electrical conductivity) are provided. The web platform also offers automatically-processed information in terms of discharge data, statistics, and graphs, alerts for extreme events, as well as geographical data associated with surface water bodies. At the present time, the network comprises about 20 stations. However, their number is continuously increasing, due to the open access policy of the system (the platform is fully accessible to third-parties uploading their data). In the long run, it is envisioned that a national-scale hydrometric infrastructure will be established, covering all important rivers, lakes and reservoirs of the country.

Thermal scales assess thermal environments in terms of thermal sensation and comfort. The number of scale’s categories and their verbal realization/labels, especially when translated for local applications, are subjects of research. This study examined variations from the ISO 10551 thermal scale when translated into Greek language. We conducted an online survey asking participants to translate the English ISO 10551 scale, develop their own scales (five, seven and nine-point), report a wording for thermal comfort, and assign discrete values to scales’ categories proportional to their perceived distances. Overall, 357 participants enrolled in the survey while data from 321 questionnaires included in the analysis. The interpretations of ISO 10551 categories varied (6–18) although the majority consisted of the exact translation. The wordings of the formulated scales differed from ISO 10551 scale indicating a more intense expression mode. The labels overlapped in the extreme categories of the nine-point scale supporting the use of the seven-point scale. Most participants (~ 65%) reported thermal comfort equivalent to neutrality. About half of the participants reported equal distances between the categories of the scales. The results can be applied on thermal sensation studies having a possible impact on the use of outdoor spaces under various contexts, i.e., public health, urban design, and energy conservation.

The article was published without special issue designation resulting in regular issue compilation. The author group and publisher regret the error and ask the article be considered for Special Issue: Subjective approaches to thermal perception.

The influence of physiological acclimatization and psychological adaptation on thermal perception is well documented and has revealed the importance of thermal experience and expectation in the evaluation of environmental stimuli. Seasonal patterns of thermal perception have been studied, and calibrated thermal indices' scales have been proposed to obtain meaningful interpretations of thermal sensation indices in different climate regions. The current work attempts to quantify the contribution of climate to the long-term thermal adaptation by examining the relationship between climate normal annual air temperature (1971-2000) and such climate-calibrated thermal indices' assessment scales. The thermal sensation ranges of two thermal indices, the Universal Thermal Climate Index (UTCI) and the Physiological Equivalent Temperature Index (PET), were calibrated for three warm temperate climate contexts (Cfa, Cfb, Csa), against the subjective evaluation of the thermal environment indicated by interviewees during field surveys conducted at seven European cities: Athens (GR), Thessaloniki (GR), Milan (IT), Fribourg (CH), Kassel (DE), Cambridge (UK), and Sheffield (UK), under the same research protocol. Then, calibrated scales for other climate contexts were added from the literature, and the relationship between the respective scales' thresholds and climate normal annual air temperature was examined. To maintain the maximum possible comparability, three methods were applied for the calibration, namely linear, ordinal, and probit regression. The results indicated that the calibrated UTCI and PET thresholds increase with the climate normal annual air temperature of the survey city. To investigate further climates, we also included in the analysis results of previous studies presenting only thresholds for neutral thermal sensation. The average increase of the respective thresholds in the case of neutral thermal sensation was about 0.6 °C for each 1 °C increase of the normal annual air temperature for both indices, statistically significant only for PET though.

This data article presents the data collected through an extensive research work conducted in urban areas in the city of Athens (Greece) during the period 2010–2012. Data concerns 2287 questionnaires and microclimatic data collected through interviews to the visitors of the examined areas with parallel monitoring of the urban microclimatic characteristics. The field surveys carried out occasionally throughout the year covering as much as possible the different seasons under Mediterranean climate conditions. These data are related to the research articles with the titles: Seasonal differences in thermal sensation in the outdoor urban environment of Mediterranean climates–the example of Athens, Greece (Tseliou et al., 2017) and Outdoor thermal sensation in a Mediterranean climate (Athens): The effect of selected microclimatic parameters (Tseliou et al., 2016).

This work exploits available data from energy audits of about 350 Hellenic school buildings from the national electronic repository that have been performed for issuing energy performance certificates The average construction characteristics of the building’s envelope and technical characteristics of the electromechanical installations are defined in order to gain a better understanding of the existing condition of school buildings. The resulting final and primary energy use intensities are calculated, as well as the respective energy ratings. Building envelopes are not thermally insulated or partly insulated, and the prevailing central heating systems are oil-fired boilers. Schools are commonly ranked at energy class-D, with average energy use intensity 98.8 kWh/m2 for final and 158.9 kWh/m2 for primary energy. Generally, space heating is the most significant service, followed by lighting and space cooling. In addition, available data on actual energy use of the buildings is analysed and used to generate empirical correction factors that relate the calculated energy consumption with the actual energy use. On average, actual thermal energy use is about twenty percent higher than calculated, while the actual electricity consumption is about half of the calculated value.

During the last 10 years, the Institute for Environmental Research and Sustainable Development of the National Observatory of Athens has developed and operates a network of automated weather stations across Greece. The motivation behind the network development is the monitoring of weather conditions in Greece with the aim to support not only the research needs (weather monitoring and analysis, weather forecast skill evaluation) but also the needs of various communities of the production sector (agriculture, constructions, leisure and tourism, etc.). By the end of 2016, 335 weather stations are in operation, providing real-time data at 10-min intervals. This paper provides information about the logistics of this network, including real-time applications of the collected data as well as information on the quality control protocols, the construction of the station data and metadata repository and the means through which the data are made available to users.

Perception plays a significant role on people's response to preventive measures. In the view of public awareness, the aim of this study was to explore factors that affect air quality perception and to reveal its potential patterns. Air quality perception of individuals, in terms of dust and overall air quality, was examined in relation to air pollutants concentrations, meteorological variables, personal characteristics as well as their thermal sensation and health condition. The data used were obtained from environmental measurements, in situ and from stations, and questionnaire surveys conducted in an outdoor urban Mediterranean area, Athens, Greece. The participants were asked to report their air quality perception and thermal sensation based on predefined scales. A thermal index, Physiological Equivalent Temperature (PET), was estimated to obtain an objective measure of thermal sensation. Particulate matter (PM10) and nitrogen oxide (NO) were associated with dust perception. Nitrogen oxides (NOx) and carbon monoxide (CO) were associated to air quality perception. Age, area of residence, health symptoms and thermal sensation also affected the perception of air quality. Dusty or poor air quality conditions were more likely to be reported when pollutants' concentrations were increased. Younger people, participants residing in the city center, experiencing health symptoms or warm thermal sensation showed a trend towards reporting more unfavorable air quality conditions.

We review the stable isotopic data of recovered Greek bones from the Early Neolithic to the Late Bronze period in order to examine dietary changes over time. As an isotopic baseline we use the published fauna data of the periods. The analysis revealed a diet that included a significant proportion of foods based on C3 plants, and the bulk of the animal protein must have been provided by terrestrial mammals with a small but detectable proportion of marine protein for coastal and island populations. A more significant contribution of marine protein is observed for Bronze Age populations while the enrichment in both C and N isotopes is connected, for some areas, to the introduction of millet during the Bronze Age, and to freshwater consumption. An extensive database of Greek food sources is presented and compared to the fauna from the prehistoric periods (Early Neolithic to Late Bronze Age) of the literature. We propose that this database can be used in palaeodiet reconstruction studies.

Image velocimetry is a popular remote sensing method mainly because of the very modest cost of the necessary equipment. However, image velocimetry methods employ parameters that require high expertise to select appropriate values in order to obtain accurate surface flow velocity estimations. This introduces considerations regarding the subjectivity introduced in the definition of the parameter values and its impact on the estimated surface velocity. Alternatively, a statistical approach can be employed instead of directly selecting a value for each image velocimetry parameter. First, probability distribution should be defined for each model parameter, and then Monte Carlo simulations should be employed. In this paper, we demonstrate how this statistical approach can be used to simultaneously produce the confidence intervals of the estimated surface velocity, reduce the uncertainty of some parameters (more specifically, the size of the interrogation area), and reduce the subjectivity. Since image velocimetry algorithms are CPU-intensive, an alternative random number generator that allows obtaining the confidence intervals with a limited number of iterations is suggested. The case study indicated that if the statistical approach is applied diligently, one can achieve the previously mentioned threefold objective.

The objective of the following paper is to identify weather-related thresholds for wildfire danger, i.e., the potential extent of fire, based on local weather conditions. The target area is Greece, a wildfire prone Mediterranean country which experienced on average 2000 wildfires annually over the last two decades. Initially, the Fire Weather Index (FWI) component of the Canadian Fire Weather Index (FWI) System (FWI System) adopted by the European Forest Fire Information System (EFFIS), is evaluated with respect to its wildfire danger predictive ability. Hence, weather and wildfire data at municipality level and on a daily basis, for the period 2000–2016 are exploited. The analysis showed that the FWI thresholds proposed by EFFIS for assessing the level of fire danger in Europe are too low for the case of Greece and, therefore, are not representative of the country's fire weather conditions. Two statistical approaches, cluster analysis and non-linear least-squares regression, are subsequently applied to determine the most appropriate FWI thresholds for discrete levels of wildfire danger. The results are presented in 4 sets of FWI thresholds and they are further evaluated on the basis of verification measures. All sets of FWI thresholds were found to significantly improve the predictability of wildfire danger compared to the EFFIS fire danger class thresholds. In particular, two of them were found to meet selected performance requirements for a balanced predictive performance, namely a reduced overestimation of wildfire danger and increased reliability in danger classification. The results are expected to have significant practical implications for wildfire prevention and risk mitigation strategies implemented by the forest fire control agencies of the country.

This work exploits data from the energy performance certificates (EPCs) of the national electronic repository, to characterize the energy use intensity (EUI) of non-residential (NR) buildings in Greece and investigate the gap between the nominal needs and the actual energy use. Over the past eight years, a total of about 1,500,000 EPCs have been issued for various building types, out of which 17.5% for NR buildings. As the national EPC database is progressively enriched with more data, the work considers the time evolution of the average EUI and analyse the available data in order to determine whether they can be regarded as typical and representative for the Hellenic building stock. When available, data on actual energy use of the buildings is used in an attempt to close the gap between calculated (asset) and actual (operational) energy use. The data is organized in terms of different end uses and used to generate empirical correction factors that relate the normative calculated heating energy consumption with the actual energy use. These factors can be used to make more realistic estimates of the energy performance of buildings that undergo different refurbishments at national level.

In the frame of this paper a wind climatology has been built for Greece, based on high resolution model simulations performed for a typical year of wind conditions over the area. The methodology followed includes: (a) the development of a typical wind year, (b) the definition of a modeling strategy and the performance of the appropriate simulations, (c) the verification of the 10-m wind speed simulated by the model against observations, (d) the statistical analysis of the wind simulations for the construction of the wind atlas. The analysis is performed at 50 m and includes gridded wind speeds, the parameters of the respective Weibull distributions, and the potential power production. Finally a discussion on the effect of the topography height and slope on the wind distribution and consequently on the wind potential density is provided.

In this paper, the characteristic properties of inversions formed inside the lower boundary layer over Athens, Greece, were studied using 35-year radiosonde measurements of temperature, humidity, and atmospheric pressure. The analysis revealed that the inversion parameters demonstrate considerable seasonal variation. Specifically, inversions associated with weak anticyclonic conditions are more frequent during the winter and summer months, while during spring, weak lows are more probable to produce inversions. Some theoretically expected associations between synoptic circulation patterns and certain inversion parameters were also identified.

A simple thermo-physiological model of outdoor thermal sensation adjusted with psychological factors is developed aiming to predict thermal sensation in Mediterranean climates. Microclimatic measurements simultaneously with interviews on personal and psychological conditions were carried out in a square, a street canyon and a coastal location of the greater urban area of Athens, Greece. Multiple linear and ordinal regression were applied in order to estimate thermal sensation making allowance for all the recorded parameters or specific, empirically selected, subsets producing so-called extensive and empirical models, respectively. Meteorological, thermo-physiological and overall models - considering psychological factors as well - were developed. Predictions were improved when personal and psychological factors were taken into account as compared to meteorological models. The model based on ordinal regression reproduced extreme values of thermal sensation vote more adequately than the linear regression one, while the empirical model produced satisfactory results in relation to the extensive model. The effects of adaptation and expectation on thermal sensation vote were introduced in the models by means of the exposure time, season and preference related to air temperature and irradiation. The assessment of thermal sensation could be a useful criterion in decision making regarding public health, outdoor spaces planning and tourism.

Bones and teeth samples of Ursus ingressus from Loutra Arideas Cave (Greece) were used to determine the diet of this extinct species and to reconstruct the palaeoclimatic conditions. The age range of the fossil layers is from 32 ka BP to a maximum of 38 ka BP (radiocarbon dating). The method used was the isotopic analysis of carbonate bioapatite of fossil cave bear ( U. ingressus ) and brown bear ( Ursus arctos ) bone and tooth fragments, as well as water samples from springs of the Pindos area, the modern bear habitat. Several possible effects that may affect the isotopic composition of apatite were investigated, including age, sex, tooth type and diagenesis. The comparison of isotopic values of Greek U. ingressus to other Pleistocene Ursidae species in Europe, exhibit more positive and more variable δ 13 C values. These positive values are attributed mainly to diet, to bear physiology (differences among species) and to climate conditions. The diet of U. ingressus apparently was based mainly on vegetable matter, however with a variable component of animal protein. The variation observed in the δ 18 O values of U. arctos tooth enamel samples were attributed to environmental conditions, and through the spring waters isotopic gradient for the region of Northeastern Pindos, to differences in the bear’s habitat elevation. Assuming similarity of the metabolism of modern and fossil bear species and incorporating only the effect of drinking water on the isotopic composition of body water, an equation has been derived that could be used to provide palaeoclimatic information.

This paper reviews all available stable isotopic data concerning precipitation and spring water in Greece, from the 1960s until today. Spatial variability is investigated in order to provide basic information and identify the locally significant parameters that affect isotopic distributions. The area of interest was partitioned into eight sections according to geographical location and climatic characteristics. The distance of the station from the sea and the altitude are the main factors imprinted in the isotopic signature of precipitation. Local meteoric water meteoric line (LMWL) for precipitation and spring water were calculated for each section and for Greece as a whole. Precipitation LMWLs differ from the Global Meteoric Water Line (GMWL) in various ways across Greece. Elevated deuterium excess values are observed, probably due to water vapour originating from the Aegean or the Mid-eastern Mediterranean. Spring LMWLs are more or less consistent throughout the country. Furthermore, a high resolution map of precipitation and freshwater spring (Cl−

article i nfo The water cycle is one of the key parameters that determine the climatic character of a region. Stable isotopes have long been established as a valuable tracer in the study of the origin, dynamics and interactions between the various components of the hydrologic cycle, both of the present and of the past. Even though significant efforts have been made, the spatial and temporal coverages of the available water isotope data are far from satisfactory. Statistical modeling and interpolation of existing measurements is a possible answer to this problem. This work is based on the experience gained by several recent studies in order to generate 0.5°×0.5° gridded monthly time series of δ 18 O in the precipitation of the Eastern Mediterranean. The empirical model incorporates geographical and topographical data in order to capture the main modes of the spatial variability of the isotopic composition of precipitation, while the incorporation of meteorological data time series provides the necessary temporal variability. Overall, despite the rather coarse spatial resolution of the existing isotopic data, the applied methodology provides a satisfactory reproduction of the measurements.

This study investigates the potential for passive cooling patterns inside the urban fabric in the Mediterranean climate city of Athens (Greece), especially with regard to quantify air temperature reduction and thermal comfort amelioration at the neighbourhood scale. Using both field measurements and an urban microclimate simulation model, we assessed cooling and warming patterns in various sites of an Athens residential neighbourhood. Results show that, under Mediterranean climate conditions, urban design elements such as wooded courtyards and appropriately oriented urban design elements such as galleries have a considerable cooling effect and can be used as cool places inside the neighbourhood for occupants' comfort amelioration and also as passive cooling tools for buildings to reduce summer energy consumption. They may then function as passive design strategies to adapt the urban site form to different climate change scenarios.

This study examines the effect of the total solar eclipse of March 29 th 2006, on some parameters of the atmospheric surface layer. The eclipse effects on the mean, but also turbulent parameters of the wind were studied at Kastelorizo, a small island of southeastern Greece situated within the totality path of the eclipse. Although the eclipse effect on the mean flow was partly masked by the synoptic situation, the analysis of the intensive (high frequency) wind measurements showed a decrease of the turbulent processes with reduced values of the turbulent kinetic energy and shear stress for a short period around the maximum phase of the eclipse. The buoyancy flux decreased by one order of magnitude during the phenomenon. The power spectra of the three wind components were found to be lower by almost one order of magnitude near the total phase when compared to spectra after the end of the eclipse.

In the frame of this work, “current” climate (1961–1990) simulations using the regional climate change model PRECIS were performed 25 km grid spacing. The 30-year simulations are compared with the available surface station data, focusing on near-surface air temperature and precipitation. The analysis has shown that the model overestimates the diurnal temperature variation during the cold period of the year (DJF) in the majority of the stations. During the warm period (JJA) the simulated daily temperature range is shifted towards warmer values, while during the transient periods of the year (MAM and SON) it is shifted towards cooler values. Both usual goodness of fit indices and tests and some more advanced methods for comparing statistical distributions were used. The latter indicate that both a scale and location adjustment needs to be applied on the model results distribution in order to sufficiently describe the observed temperature distribution. Regarding rainfall, it was found that the model underestimates the seasonal rainfall during DJF and SON, mainly over the stations of the Mediterranean coast that receive most of the yearly rainfall during autumn and, mainly, winter. An interesting feature is that, during JJA, the model was able to reproduce quite efficiently the seasonal rainfall in the central Balkans that receive as much rain during summer as during winter.

This paper examines the effect of the total solar eclipse of 29 March 2006 on meteorological variables across Greece. Integrated micrometeorological measurements were conducted at Kastelorizo, a small island within the path of totality, and other sites within the Greek domain, with various degrees of solar obscuration. The observations showed a dramatic reduction in the incoming global radiation and subsequent, pronounced changes in surface air temperature with the lowest temperature values occurring about 15 min after the full phase. The amplitude of the air temperature drop was not analogous to the obscuration percentage but was principally determined by the surrounding environment (mainly the sea influence), the background meteorological conditions and local cloudiness. Surface wind-speed decreased in most sites as a result of the cooling and stabilization of the atmospheric boundary layer. This perturbation provided a unique opportunity to apply a sensitivity analysis on the effect of the eclipse to the Weather Research and Forecast (WRF) numerical mesoscale meteorological model. Strong anomalies, not associated with a dynamic response, were simulated over land especially in surface air temperature. The simulated temperature drop pattern was consistent with the observations.

In this paper, the thermal performance of a ventilated roof component is investigated during the winter period. The ventilated roof component consists of a conventional roof structure—reinforced concrete with a layer of thermal insulation—an air gap that allows the movement of the ambient air and an external layer made of a prefabricated concrete slab. The experimental results of the ventilated roof component during the winter period are presented and its thermal performance is analysed. The effect of key construction parameters like the height of the air gap and the use of a radiant barrier in the air gap is also investigated. Analysis of the results showed that the performance of a ventilated roof component is comparable to a conventional structure during winter. The ventilated component is shown to be in compliance with Greek regulatory requirements in terms of U-value.

A full-scale ventilated roof component was tested under real climatic conditions. Key constructional parameters, such as the air gap height and application or not of a layer of a radiant barrier, were examined during the tests and the performance of the component was assessed by direct comparison to a simultaneously operating conventionally constructed roof. The experimental results of the summer period are presented in this paper. The direct comparison with the conventional roof indicates significantly improved performance of the ventilated component.

It is well known that air pollution is one of the major factors affecting human health and the activities in a town. Among the various air pollutants an interesting one, especially for sunny climates, is the reactive O3. O3 varies significantly through the year; it is therefore very important to know the onset and the duration of the warm period of the year since at that time O3 concentrations increase significantly. In this work, an attempt was made to determine the onset of warm season of the year as well as its duration in various sites located in Northeastern Mediterranean. For this purpose, a fuzzy clustering method is used. The method was applied on the isobaric thickness between 1000 and 500 hPa for the period from 1974 to 1997. The results were compared to conventional methods based on synoptic classification and were found to be in good agreement.

In a conventional construction, the ventilation air enters the building through a combination of pathways, such as windows and vents, via cracks around external openings, joints between building materials, etc. By contrast, in a dynamic insulation construction, the ventilation air is drawn into the building through the insulation material of the building envelope. Structures with dynamic insulation incorporate porous insulating material in the envelope and air passes through the porous material. The aim of this paper is to present the experimental work carried out on a wall component that is a combination of dynamic insulation panel and a ventilated facade, tested under real weather conditions. The wall component consisted of two main sub-layers: the ventilated external envelope and the dynamic insulation (DI) sub-layer. The DI component consisted of layers of breathing materials that let the air enter the room at a reasonable pressure difference between the interior and exterior. The paper describes the experimental work carried out and the results drawn from the tests performed in the linked wall component under: (i) various differential pressure regimes between the interior and the exterior of the test cell and (ii) controlled and floating internal air temperature. In summary, the performance of the component was effective, since conduction losses were decreasing.

Coupling a building to the ground as a heat sink through earth-to-air heat exchangers can reduce the cooling energy demand during summer. The fans for circulating the air through the heat exchangers are usually grid connected. However, given that the cooling loads are almost in phase with the available solar irradiance, an innovative system coupling an earth-to-air heat exchanger with a simple photovoltaic array has been designed. The experimental results are presented and discussed in this paper. The system was installed and studied in Athens, Greece during a summer period. The obtained results showed that the overall thermal performance of the system and the efficiencies involved indicate that earth-to-air heat exchangers are an interesting hybrid cooling technique and another field of application of photovoltaics.

The impact of shading devices on the airflow across large openings during single-sided natural ventilation is investigated through an extensive experimental campaign. To quantify this impact the approach of the correction coefficient, already applied in non-shaded openings is used. The proposed methodology is independent from the climatic conditions of the test site. The correction coefficient and the corresponding Archimedes number are determined experimentally. The regression equations to determine the correction coefficient as a function of the Archimedes number are determined using a regression technique that takes into account the errors in both axes. The combined standard uncertainties of the parameters of these equations are estimated according to the widely accepted guidelines of the International Standardization Organization. The methodology followed is presented in detail. The proposed equations improve the accuracy of network models in buildings thermal simulations.

National and international authorities recommend a variety of air-quality standards that should not be exceeded in local and regional scales currently. With this work a uniform indexing scale is introduced which characterises several urban pollutants in a simple and comparable manner. The “indicators” proposed are implemented at the Athens Metropolitan Area (AMA) which is an area with serious pollution problems. Hourly data from all available monitoring stations are analysed during 1983 and 1995. This analysis demonstrates that the status of air quality in Athens can be characterised as acute with regards to photochemical pollutants while strong spatial and temporal variability is encountered for all pollutants.

The need of accurate Test Reference Years (TRYs) for simulations has been well recognised over the years. Various methods for deriving TRYs have been developed, but their final results can be significantly different. In this paper, the major methodologies reported in literature were applied to 20-year hourly measurements of weather data from Athens, covering the period 1977 to 1996. Seventeen TRYs were produced in total. The basis to select the “best” performing TRY includes meteorological criteria (inherent in the selection process used by each method) and comparisons of results from various simulations for typical energy systems (i.e. a solar water heater, a building, a large scale solar heating system with interseasonal storage and a photovoltaic system). Based on the results of each simulation exercise, a scoring system was developed and applied. The best performing TRY was found to be the one produced by a modified Festa-Ratto method.