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Pantavou K.,National and Kapodistrian University of Athens | Lykoudis S.,Institute of Environmental Research and Sustainable Development
International Journal of Biometeorology | Year: 2014

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. © 2013 ISB.


Kitsara G.,National and Kapodistrian University of Athens | Papaioannou G.,National and Kapodistrian University of Athens | Papathanasiou A.,National and Kapodistrian University of Athens | Retalis A.,Institute of Environmental Research and Sustainable Development
Water Resources Management | Year: 2013

Evidence of global dimming/brightening is mainly based upon few measurements of solar radiation. A need for more research supported and extended with the use of other climatic variables, such as sunshine duration, recorded for a longer time period and successfully used as a proxy for solar radiation over the past 80 years, has already been urged. Thus, in this study, residual sunshine duration series computed after removal of the cloudiness-related variability, from daily sunshine duration and cloudiness data measured at the National Observatory of Athens are used for highlighting global dimming or brightening periods in Athens, during the period 1951-2001. Furthermore, the consistency of trends in radiation records and their implications for the hydrological cycle and especially the trends in reference evapotranspiration are examined, during the period 1951-2001. The analysis focuses on the seasonal decadal variations, determines and explains the causes of the seasonal trends from the inter-annual and decadal variability of the sunshine duration during the last half past century, with a special emphasis in detecting possible sub-periods in Athens. The signs of trends in the modeled annual and seasonal reference evapotranspiration are estimated, according to the indicated global dimming/brightening periods. © 2012 Springer Science+Business Media Dordrecht.


Dotsika E.,Greek National Center For Scientific Research | Lykoudis S.,Institute of Environmental Research and Sustainable Development | Lykoudis S.,University of Patras | Poutoukis D.,General Secretariat for research and Technology
Global and Planetary Change | Year: 2010

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- < 200 ppm and T < 25 °C) δ18O reveals several interesting features such as an orographic shadow effect induced by the Pindos Mountains, a strong climatic signal in southern Greece and a local city-microclimate effect around Athens. © 2009 Elsevier B.V. All rights reserved.


Droutsa K.G.,Institute of Environmental Research and Sustainable Development | Kontoyiannidis S.,Institute of Environmental Research and Sustainable Development | Dascalaki E.G.,Institute of Environmental Research and Sustainable Development | Balaras C.A.,Institute of Environmental Research and Sustainable Development
Energy | Year: 2016

Residential buildings are the vast majority of the building sector and play a significant role in the energy and environmental footprint of the whole building stock. This paper presents an overview of the energy performance of the existing Hellenic residential building stock, by exploiting data from the EPCs (energy performance certificates) of buildings issued in accordance to national EPBD (energy performance in buildings directive) provisions. The analysis is performed for different building size (i.e. single- and multi-family houses), construction periods and locations (i.e. at the four national climate zones). In addition, implemented energy conservation measures are investigated in order to define the most common refurbishment actions for each building type. According to 650,000 EPCs that have been issued in Greece by August 2015, 15% are for single-family houses and 85% for multi-family houses (buildings or building units). About 34% of the residential buildings are ranked at the lowest energy class-G, while only 3% are ranked in energy class-B or higher. The average calculated primary energy is 261.6kWh/m2 and the average CO2 emissions 70.3 kg/m2. Replacing the windows is the most popular retrofit action, followed by the installation of solar collectors for domestic hot water. © 2016 Elsevier Ltd.


Kotroni V.,Institute of Environmental Research and Sustainable Development | Lagouvardos K.,Institute of Environmental Research and Sustainable Development
Environmental Research Letters | Year: 2016

Here we present the analysis of lightning activity over the Mediterranean, based on a 10 year long dataset (2005-2014) provided by the ZEUS long-range lightning detection system. The major hot-spots of lightning activity are identified, with a clear predominance during the warm period of the year over land in the vicinity of the major topographic features of the area. Special emphasis is also given on the discussion of the seasonal distribution of lightning. In addition, we investigate the relationship of lightning with sea-surface temperature, obtained by high-resolution satellite measurements and we conclude that the number of lightning strokes is positively correlated with the sea-surface temperature during autumn when also the maximum lightning activity over the sea is depicted. We suggest that higher sea surface temperature further destabilises the lower tropospheric layers, enhancing thus convection and therefore lightning. © 2016 IOP Publishing Ltd.


Dascalaki E.G.,Institute of Environmental Research and Sustainable Development | Droutsa K.G.,Institute of Environmental Research and Sustainable Development | Balaras C.A.,Institute of Environmental Research and Sustainable Development | Kontoyiannidis S.,Institute of Environmental Research and Sustainable Development
Energy and Buildings | Year: 2011

Successful strategies towards minimizing the energy consumption and greenhouse gas emissions attributed to the building sector require knowledge on the energy-related characteristics of the existing building stock. Despite the numerous studies on energy conservation applications in buildings, current knowledge on the energy-related characteristics of the building stock still remains limited. Building typologies can be a useful instrument to facilitate the energy performance assessment of a building stock. This work is based on a harmonised structure for European building typologies (TABULA) developed for residential buildings, but the methodology may be extended to the tertiary sector as well. National typologies are sets of model buildings with characteristic energy-related properties representative of a country's building stock. The model buildings are used as a showcase for demonstrating the energy performance and the potential energy savings from typical and advanced energy conservation measures (ECMs) on the thermal envelope and the heat supply system. The proposed Hellenic residential building typology is presented for the first time along with an assessment of various ECMs that are used for an estimate of the energy performance of building stock in Greece in an effort to meet the 9% indicative national energy savings target by 2016. © 2011 Elsevier B.V.


Dascalaki E.G.,Institute of Environmental Research and Sustainable Development | Balaras C.A.,Institute of Environmental Research and Sustainable Development | Gaglia A.G.,Institute of Environmental Research and Sustainable Development | Droutsa K.G.,Institute of Environmental Research and Sustainable Development | Kontoyiannidis S.,Institute of Environmental Research and Sustainable Development
Energy Policy | Year: 2012

Transposition of the European Directive on the energy performance of buildings (EPBD) in Greece was enacted in 2008 by a national law. A follow-up regulation on the energy performance in the building sector-KENAK released in 2010, outlines the overall approach in accordance to European standards and EPBD mandates. All necessary technical specifications and detailed information for the implementation of KENAK are included in four new technical guidelines prepared in 2010, which are supported by an official national software. Issues related to the energy experts are handled by presidential decrees published in 2010; over 5400 temporary energy inspectors are already in place, while permanent accreditation is in progress. Energy performance design study of new buildings for obtaining a building permit is in place since October 2010 and issuing energy performance certificates as of January 2011. This paper presents an overview of the development and current EPBD stage of implementation in Greece, along with a first assessment of the lessons learned and experiences gained. © 2012 Elsevier Ltd.


Papagiannaki K.,Institute of Environmental Research and Sustainable Development | Lagouvardos K.,Institute of Environmental Research and Sustainable Development | Kotroni V.,Institute of Environmental Research and Sustainable Development
Natural Hazards and Earth System Science | Year: 2013

This paper introduces the development of a database of high-impact weather events that occurred in Greece since 2001. The selected events are related to the occurrence of floods, flash floods, hail, snow/frost, tornados, windstorms, heat waves and lightning with adverse consequences (excluding those related to agriculture). The database includes, among others, the geographical distribution of the recorded events, relevant meteorological data, a brief description of the induced impacts and references in the press. This paper further offers an extensive analysis of the temporal and spatial distribution of high-impact weather events for the period 2001-2011, taking into account the intensity of weather conditions and the consequent impact on the society. Analysis of the monthly distribution of high-impact weather events showed that they are more frequent during October and November. More than 80 people lost their lives, half of which due to flash floods. In what concerns the spatial distribution of high-impact weather events, among the 51 prefectures of the country, Attica, Thessaloniki, Elia and Halkidiki were the most frequently affected areas, mainly by flash floods. Significant was also the share of tornados in Elia, of windstorms in Attica, of lightning and hail events in Halkidiki and of snow/frost events in Thessaloniki. © 2013 Author(s).


Kalogiros J.,Institute of Environmental Research and Sustainable Development
Journal of Atmospheric and Oceanic Technology | Year: 2012

A least squares method for the reconstruction of Doppler spectra of weather radars with irregular pulse repetition time used to increase the range of unambiguous velocity is presented and evaluated. This method is a robust spectral method that is based on the least squares minimum norm principle and reconstructs both the magnitude and the phase of the discrete Fourier transform of the signal. The phase spectrum is useful in the estimation of the differential phase in dual-polarization radars with staggered sampling schemes, which is a case of irregular sampling. A computationally efficient iterative algorithm for estimating the mean frequency of the signal, which is required for the reconstruction of the spectrum, is described for possible realtime applications. Aclutter filter method based on spectral interpolation, which can be applied to echoes with generally nonzero mean velocity, is also described and combined with the spectrum reconstruction method. Using simulated data it is shown that the least squares reconstruction method with or without the presenceof clutter gives results with small bias and standard error and can be applied to wide spectra. The application of the method to real X-band radar data with a low signal-to-noise ratio and a high stagger ratio value of 5/6 showed that the least squares method has low sensitivity to the stagger ratio and satisfactorily gives spectral reconstruction for signal-to-noise ratio values as low as 10 dB. © 2012 American Meteorological Society.


Lagouvardos K.,Institute of Environmental Research and Sustainable Development | Kotroni V.,Institute of Environmental Research and Sustainable Development
Journal of Grid Computing | Year: 2010

Numerical weather prediction applications require considerable processing power and data storage resources, and thus can benefit from the offerings of Grid technologies. In this paper we discuss the porting of such an application on the Grid infrastructure provided by the SEE-GRID-SCI European research project. This study explores the regional ensemble forecasting technique as a means to contribute to the improvement of weather forecasting in the Mediterranean. Indeed, a regional ensemble system was built, based on the use of two limited area models that are run using a multitude on initial and boundary conditions over the Mediterranean. This large-scale application involves the use of large infrastructures that are not easily available and thus its porting to the Grid at production level has been proved to be a challenging endeavour. The application workflow, the operational and Grid infrastructure requirements, and also the problems encountered are presented. Multiple requirements mainly related to the characteristics of the implemented workflow, the model characteristics and the limitations imposed by the Grid infrastructure itself, had to be satisfied. The paper concludes with a recent result of the implemented application. Indeed the regional scale ensemble forecasting system provided useful probabilistic forecasts for a severe thunderstorm case that affected Central Europe during the summer 2009 (with damages, casualties and several injuries). © 2010 Springer Science+Business Media B.V.

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