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Nicosia, Cyprus

Santamouris M.,National and Kapodistrian University of Athens | Santamouris M.,Cyprus Institute
Energy and Buildings | Year: 2014

Urban heat island and global warming increase ambient temperature and modify the energy budget of buildings. The magnitude of the modification has been evaluated in a large number of articles, under different climatic and building boundary conditions. This paper collects, analyzes and classifies existing knowledge regarding the energy impact of urban heating to buildings and calculates preliminary indicators and impact figures. Based on the analysis of the impact studies, it is found that in average the cooling load of typical urban buildings is by 13% higher compared to similar buildings in rural areas. Four specific energy impact indicators, the global energy penalty per m2, the global energy penalty per m2 and degree of UHI, the global energy penalty per person and the global energy penalty per person and per degree of the UHI are defined and calculated. The variability of the heating and cooling loads of typical buildings is evaluated for the period 1970-2010. The average increase of the cooling demand is 23% while the corresponding average reduction of the heating is 19%. In total, the average energy consumption of typical buildings for heating and cooling purposes increased by 11% for the same period. © 2014 Elsevier B.V.

De Arellano J.V.-G.,Wageningen University | Van Heerwaarden C.C.,Max Planck Institute for Meteorology | Lelieveld J.,Max Planck Institute for Chemistry | Lelieveld J.,Cyprus Institute
Nature Geoscience | Year: 2012

Cumulus clouds in the atmospheric boundary layer play a key role in the hydrologic cycle, in the onset of severe weather by thunderstorms and in modulating Earth's reflectivity and climate. How these clouds respond to climate change, in particular over land, and how they interact with the carbon cycle are poorly understood. It is expected that as a consequence of rising atmospheric CO 2 concentrations the plant stomata will close, leading to lower latent heat fluxes and higher sensible heat fluxes. Here we show that this causes a decline in boundary-layer cloud formation in middle latitudes. This could be partly counteracted by the greater ability of a warmer atmosphere to take up water and by a growth in biomass due to CO 2 fertilization. Our results are based on a new soil-water-atmosphere-plant model supported by comprehensive observational evidence, from which we identify the dominant atmospheric responses to plant physiological processes. They emphasize the intricate connection between biological and physical aspects of the climate system and the relevance of short-term and small-scale processes in establishing this connection.

Lelieveld J.,Max Planck Institute for Chemistry | Lelieveld J.,Cyprus Institute | Kunkel D.,Max Planck Institute for Chemistry | Lawrence M.G.,Max Planck Institute for Chemistry | Lawrence M.G.,Institute for Advanced Sustainability Studies
Atmospheric Chemistry and Physics | Year: 2012

Major reactor accidents of nuclear power plants are rare, yet the consequences are catastrophic. But what is meant by "rare"? And what can be learned from the Chernobyl and Fukushima incidents? Here we assess the cumulative, global risk of exposure to radioactivity due to atmospheric dispersion of gases and particles following severe nuclear accidents (the most severe ones on the International Nuclear Event Scale, INES 7), using particulate 137Cs and gaseous 131I as proxies for the fallout. Our results indicate that previously the occurrence of INES 7 major accidents and the risks of radioactive contamination have been underestimated. Using a global model of the atmosphere we compute that on average, in the event of a major reactor accident of any nuclear power plant worldwide, more than 90% of emitted 137Cs would be transported beyond 50 km and about 50% beyond 1000 km distance before being deposited. This corroborates that such accidents have large-scale and trans-boundary impacts. Although the emission strengths and atmospheric removal processes of 137Cs and 131I are quite different, the radioactive contamination patterns over land and the human exposure due to deposition are computed to be similar. High human exposure risks occur around reactors in densely populated regions, notably in West Europe and South Asia, where a major reactor accident can subject around 30 million people to radioactive contamination. The recent decision by Germany to phase out its nuclear reactors will reduce the national risk, though a large risk will still remain from the reactors in neighbouring countries. © Author(s) 2012. CC Attribution 3.0 License.

Asproulis N.,Cranfield University | Drikakis D.,Cyprus Institute
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

This paper investigates the combined effects of surface stiffness κ and wall particles' mass mw on the slip length. It aims to enhance our understanding of the momentum and energy transfer across solid-liquid interfaces. Elastic spring potentials are employed to simulate the thermal solid walls and model the surface stiffness κ. The thermal oscillation amplitude is primarily dictated by values of stiffness, whereas the oscillating frequency is proportional to √κ/mw. It is shown that for cases with variable wall mass the relation of slip length and thermal oscillating frequencies can be approximated by a "master" curve according to which the length initially increases, then approaches a peak value, and afterwards is reduced toward an asymptotic value. ©2011 American Physical Society.

Lawrence M.G.,Max Planck Institute for Chemistry | Lawrence M.G.,University of Mainz | Lelieveld J.,Max Planck Institute for Chemistry | Lelieveld J.,Cyprus Institute
Atmospheric Chemistry and Physics | Year: 2010

Southern Asia, extending from Pakistan and Afghanistan to Indonesia and Papua New Guinea, is one of the most heavily populated regions of the world. Biofuel and biomass burning play a disproportionately large role in the emissions of most key pollutant gases and aerosols there, in contrast to much of the rest of the Northern Hemisphere, where fossil fuel burning and industrial processes tend to dominate. This results in polluted air masses which are enriched in carbon-containing aerosols, carbon monoxide, and hydrocarbons. The outflow and long-distance transport of these polluted air masses is characterized by three distinct seasonal circulation patterns: the winter monsoon, the summer monsoon, and the monsoon transition periods. During winter, the near-surface flow is mostly northeasterly, and the regional pollution forms a thick haze layer in the lower troposphere which spreads out over millions of square km between southern Asia and the Intertropical Convergence Zone (ITCZ), located several degrees south of the equator over the Indian Ocean during this period. During summer, the heavy monsoon rains effectively remove soluble gases and aerosols. Less soluble species, on the other hand, are lifted to the upper troposphere in deep convective clouds, and are then transported away from the region by strong upper tropospheric winds, particularly towards northern Africa and the Mediterranean in the tropical easterly jet. Part of the pollution can reach the tropical tropopause layer, the gateway to the stratosphere. During the monsoon transition periods, the flow across the Indian Ocean is primarily zonal, and strong pollution plumes originating from both southeastern Asia and from Africa spread across the central Indian Ocean. This paper provides a review of the current state of knowledge based on the many observational and modeling studies over the last decades that have examined the southern Asian atmospheric pollutant outflow and its large scale effects. An outlook is provided as a guideline for future research, pointing out particularly critical issues such as: resolving discrepancies between top down and bottom up emissions estimates; assessing the processing and aging of the pollutant outflow; developing a better understanding of the observed elevated pollutant layers and their relationship to local sea breeze and large scale monsoon circulations; and determining the impacts of the pollutant outflow on the Asian monsoon meteorology and the regional hydrological cycle, in particular the mountain cryospheric reservoirs and the fresh water supply, which in turn directly impact the lives of over a billion inhabitants of southern Asia. © Author(s) 2010.

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