Time filter

Source Type

Varotsos K.V.,National and Kapodistrian University of Athens | Tombrou M.,National and Kapodistrian University of Athens | Giannakopoulos C.,Institute for Environmental Research and Sustainable Development
Journal of Geophysical Research: Atmospheres | Year: 2013

A statistical model to examine the potential impact of increasing future temperatures due to climate change on ozone exceedances (days with daily maximum 8 h average ≥ 60 ppb) is developed for Europe. We employ gridded observed daily maximum temperatures and hourly ozone observations from nonurban stations across Europe, together with daily maximum temperatures for 2021-2050 and 2071-2100 from three regional climate models, based on the Intergovernmental Panel on Climate Change Special Reports on Emissions Scenarios A1B scenario. A rotated principal components analysis is applied to the ozone stations yielding five principal components, which divide the study domain in five subregions. The historical ozone-temperature relationship is examined and then used to provide estimates of future ozone exceedance days under current emissions and under the assumption that this relationship will retain its main characteristics. Results suggest that increases in the upper temperature percentiles lead to statistically significant increases (95% statistical significance level) of the ozone exceedances for both future periods. The greatest average increases depending on the particular regional climate model range from 5 to 12 extra ozone days/yr for 2021-2050 and from 16 to 25 for 2071-2100, in southeast Europe. The lowest average increases range from 0 to 2 extra ozone days/yr for 2021-2050 and from 2 to 4 for 2071-2100 and are seen in northwest Europe. The simulations with the dynamical Goddard Institute of Space Studies/GEOS-CHEM climate chemistry modeling system shows decreases instead of increases in eastern Europe, higher increases in northwest Europe, whereas for the other subregions similar results to the statistical model are obtained. Key Points Statistical models can complement the dynamical ones Statistical models could provide useful tools for policymakers Greatest increases of climate change impact on ozone are seen in Southern Europe © 2013. American Geophysical Union. All Rights Reserved.

Dascalaki E.G.,Institute for Environmental Research and Sustainable Development | Sermpetzoglou V.G.,School Buildings Organization
Energy and Buildings | Year: 2011

School buildings constitute a major part of the non-residential building stock, though due to their operational characteristics, they represent a low percentage of the overall energy balance of the building sector. Although health and productivity of pupils and teachers is strongly affected by the indoor environmental quality of their school, poor indoor air quality has been reported in published literature, even so for recently constructed school buildings. The same applies for the energy consumption, with large amounts of energy being wasted because no energy saving measures are applied for the operation of schools. This paper presents the outcome of a study on the energy performance of Hellenic school buildings. The general features of the contemporary building stock are presented along with the results from an energy survey in 135 Hellenic schools. The derived energy consumption benchmarks are compared with published literature. Finally, the energy performance and indoor environmental quality of a representative sample of schools in metropolitan Athens are assessed in a holistic approach to the "energy efficiency - thermal comfort - indoor air quality" dilemma. The IEQ assessment was based on an objective evaluation by monitoring crucial indoor conditions and a subjective occupant evaluation using standardized questionnaires. The potential of several energy conservation measures is evaluated in terms of energy savings and reduction of greenhouse gas emissions along with the related payback periods. © 2010 Elsevier B.V. All rights reserved.

Moriondo M.,CNR Institute for Biometeorology | Giannakopoulos C.,Institute for Environmental Research and Sustainable Development | Bindi M.,University of Florence
Climatic Change | Year: 2011

This work was aimed at assessing the role of climate extremes in climate change impact assessment of typical winter and summer Mediterranean crops by using Regional Circulation Model (RCM) outputs as drivers of a modified version of the CropSyst model. More specifically, climate change effects were investigated on sunflower (Helianthus annuus L.) and winter wheat (Triticum aestivum L.) development and yield under the A2 and B2 scenarios of the IPCC Special Report on Emissions Scenarios (SRES). The direct impact of extreme climate events (i. e. heat stress at anthesis stage) was also included. The increase in both mean temperatures and temperature extremes under A2 and B2 scenarios (2071-2100) resulted in: a general advancement of the main phenological stages, shortening of the growing season and an increase in the frequency of heat stress during anthesis with respect to the baseline (1961-1990). The potential impact of these changes on crop yields was evaluated. It was found that winter and summer crops may possess a different fitting capacity to climate change. Sunflower, cultivated in the southern regions of the Mediterranean countries, was more prone to the direct effect of heat stress at anthesis and drought during its growing cycle. These factors resulted in severe yield reduction. In contrast, the lower frequency of heat stress and drought allowed the winter wheat crop to attain increased yields with respect to the baseline period. It can be concluded that the impact of extreme events should be included in crop-modelling approaches, otherwise there is the risk of underestimating crop yield losses, which in turn would result in the application of incorrect policies for coping with climate change. © 2010 Springer Science+Business Media B.V.

The estimation of transient streamflow from stage measurements is indeed important and the study of Dottori, Martina and Todini (2009) (henceforth DMT) is useful, however, DMT seem to miss certain of its practical aspects. The goal is to infer the discharge from measurements of the stage conveniently and with accuracy adequate for practical work. This comment addresses issues of the applicability of the DMT method in the field. DMT also advocate their method as a replacement of the widely used Jones Formula. The Jones Formula was modified by Thomas (Henderson, 1966) to include the temporal derivative of the depth, instead of the spatial one, to specifically allow discharge estimation from at-a-section stage observations. The outcome of the comparison is not surprising in view of this approximation. However, this discussion intends to show that, properly evaluated, the praxis-oriented Jones Formula, which did well in the tests, can perform better than DMT imply. It will be also documented that the DMT methodology relates to a known method for computing flood depth profiles. © 2010 Author(s).

Retalis A.,Institute for Environmental Research and Sustainable Development | Sifakis N.,Institute for Space Applications and Remote Sensing
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2010

Low and moderate spatial resolution satellite sensors (such as TOMS, AVHRR, SeaWiFS) have already shown their capability in tracking aerosols at a global scale. Sensors with moderate to high spatial resolution (such as MODIS and MERIS) seem also to be appropriate for aerosol retrieval at a regional scale. We investigated in this study the potential of MERIS-ENVISAT data to resolve the horizontal spatial distribution of aerosols over urban areas, such as the Athens metropolitan area, by using the differential textural analysis (DTA) code. The code was applied to a set of geo-corrected images to retrieve and map aerosol optical thickness (AOT) values relative to a reference image assumed to be clean of pollution with a homogeneous atmosphere. The comparison of satellite retrieved AOT against PM10 data measured at ground level showed a high positive correlation particularly for the AOT values calculated using the 5th MERIS' spectral band (R2=0.83). These first results suggest that the application of the DTA code on cloud free areas of MERIS images can be used to provide AOT related to air quality in this urban region. The accuracy of retrieved AOT mainly depends on the overall quality, the pollution cleanness and the atmospheric homogeneity of the reference image. © 2009 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).

Founda D.,Institute for Environmental Research and Sustainable Development
Advances in Building Energy Research | Year: 2011

This study explores research carried out on the effect of climate change on the air temperature of Athens. The main features of the Athens base-line climate and related synoptic systems are presented first. Studies based on the available historical airtemperature records for the city, extending back to the mid 19th century, as well as more recent studies concerning the detection and quantification of the urban heat island are reviewed. Air-temperature fluctuations and trends for different periods, as well as their relationship to changes in large-scale atmospheric circulation, are discussed and emphasis is given to studies examining the evolution of air-temperature extremes in Athens. Perhaps the dominating features of the recent climate of Athens are the pronounced increase in air temperature in the summer and the increase in frequency of exceptionally hot days and persistent large-scale systems, leading to more frequent heat waves in the area. The air-temperature regime in the city is determined by the parallel evolution and combined effect of both natural and anthropogenic driving forces. The study attempts to provide a more complete picture of the temporal temperature variability in Athens, in the context of global climate change and changes inherent to urbanization effects. © 2011 Earthscan.

Spyropoulos G.N.,Aristidou | Balaras C.A.,Institute for Environmental Research and Sustainable Development
Energy and Buildings | Year: 2011

Energy performance of non-residential buildings and in particular of office buildings used as bank branches is very limited. This paper presents new data from 39 representative bank branches and results from a more in-depth analysis of information from energy audits in 11 typical bank branches throughout Greece. The data was used to derive practical energy benchmarks and assess various energy conservation measures. Accordingly, the average annual total energy consumption is 345 kWh/m2. The breakdown of the different end-uses reveals that HVAC averages 48% of the final energy consumption, lighting averages 35% and other office and electronic equipment average 17%. The most effective energy conservation measures reach annual energy savings of 56 kWh/m2 by regulating the indoor set point temperature, while the use of HF electronic ballasts and CFL lamps may save about 22 kWh/m2 and 29 kWh/m2 with and without the use of the external marquee sign, respectively. © 2010 Elsevier B.V. All rights reserved.

Mirasgedis S.,Institute for Environmental Research and Sustainable Development | Tourkolias C.,National Technical University of Athens | Tzovla E.,National Technical University of Athens | Diakoulaki D.,National Technical University of Athens
Renewable and Sustainable Energy Reviews | Year: 2014

This study presents an application of the Contingent Valuation Method (CVM) for valuing the landscape externalities associated with the large-scale exploitation of wind power at the local level. The survey was undertaken in South Evia, Greece, which is a region with rich wind energy potential and a considerable number of wind farms in operation during the period of the study. The results showed that 57% of the households are not willing to contribute financially in order to implement interventions to mitigate the visual impact of wind farms. He mean willingness to pay per household to avoid the visual impact attributed to the installation of new wind farms in the area in question was estimated at €41.6/year taking into account all households of the sample. This estimate is relatively lower compared to the results of other relevant studies. As shown by a meta-analysis developed based on these studies, this is mainly attributed to the great recession in Greece and the reduced available income of households. © 2014 Elsevier Ltd.

Papanastasiou D.K.,Center for Research and Technology Hellas | Melas D.,Aristotle University of Thessaloniki | Kambezidis H.D.,Institute for Environmental Research and Sustainable Development
Atmospheric Research | Year: 2015

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. © 2014 Elsevier B.V.

Tourkolias C.,National Technical University of Athens | Mirasgedis S.,Institute for Environmental Research and Sustainable Development
Renewable and Sustainable Energy Reviews | Year: 2011

This paper formulates and implements an integrated approach for estimating the employment benefits associated with the exploitation of renewable energy sources (RES) in the power sector. It builds up on well-known techniques and makes all the necessary modifications in order to take into account the specific conditions of the RES market. More specific, the proposed approach exploits the input-output methodology for estimating the direct, indirect and induced employment effects associated with the energy technologies in question and the "opportunity cost of labour" approach for expressing these effects in monetary terms. This framework has been implemented to estimate the employment benefits resulting from the development of different RES technologies in Greece, taking into account both the construction and operation phases of the relative projects. The results of the analysis clearly show that the exploitation of RES in the Greek power sector presents significant employment benefits, which are at the same order of magnitude or in several cases even higher compared to the corresponding benefits attributed to the operation of fossil-fueled power plants (e.g. lignite and natural gas). Therefore, the fulfillment of the national target for increasing the penetration of RES into the Greek power sector from approximately 12% today to 40% in 2020, will contribute, apart from the significant environmental improvements, to the overall economic development and the increase of the employment. © 2011 Elsevier Ltd. All rights reserved.

Loading Institute for Environmental Research and Sustainable Development collaborators
Loading Institute for Environmental Research and Sustainable Development collaborators