Stratospheric ozone variations in the northern and the southern hemisphere during the period 1957–1990     

John Xanthakis  Constantine Poulakos  Christos S. Zerefos 《Earth, Moon, and Planets》1993,60(2):109-125

The fluctuation and the periodicities of the total ozone layer for the period 1957–1990 is studied. Monthly total ozone data from 32 ground based stations have been analysed. It is shown that the maxima and the minima of the monthly values of total ozone for each year and for the whole period in question do not necessarily occur in March or in April and in September or October but range from March till July and from September till December respectively. Periodicities of 3, 4 and 6 months have been revealed. Finally the maxima and the minima of the total ozone data were examined. The variation of the whole phenomenon is analytically expressed with the help of an algebraic formula and can represent the observed monthly ozone values with an accuracy of 97%.  相似文献   

Climate change impact assessment: the role of climate extremes in crop yield simulation   总被引：6，自引：2，他引：4  

M. Moriondo  C. Giannakopoulos  M. Bindi 《Climatic change》2011,104(3-4):679-701

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?C2100) 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?C1990). 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.  相似文献   

An empirical analysis of IOPCF oil spill cost data     

Christos A. Kontovas  Harilaos N. Psaraftis  Nikolaos P. Ventikos 《Marine pollution bulletin》2010,60(9):1455-18097

This paper reports on recent analysis of oil spill cost data assembled by the International Oil Pollution Compensation Fund (IOPCF). Regression analyses of clean-up costs and total costs have been carried out, after taking care to convert to current prices and remove outliers. In the first place, the results of this analysis have been useful in the context of the ongoing discussion within the International Maritime Organization (IMO) on environmental risk evaluation criteria. Furthermore, these results can be useful in estimating the benefit of regulations that deal with the protection of marine environment and oil pollution prevention.  相似文献   

Conflicts at sea between artisanal and industrial fishers: Inter-sectoral interactions and dispute resolution in Senegal     

Carolyn DuBois  Christos Zografos 《Marine Policy》2012

Conflicts between artisanal and industrial fishermen—targeting increasingly scarce resources in Senegal—are posing a serious threat to human security and are only symbolically addressed by the country's fisheries governance regime. Severely outmatched in terms of political influence and size, artisanal fishermen are more vulnerable to the fallout of conflicts at sea. The loss of fishing materials threatens the livelihoods of fishermen and their families; collisions and violence between members of the two sectors often result in injury and death. This study examines at-sea interactions between Senegal's artisanal and industrial sectors and the formal and informal mechanisms in place for managing them. Conflictive interactions are found to co-exist alongside cooperative ones and both emerge in response to changes in marine resource abundance and management. Formal systems in place to mediate at-sea conflicts are ineffective and seldom used by artisanal fishermen, who either accept their losses, attempt to informally resolve conflicts with industrial actors or resort to violence.  相似文献   

Appropriate SCF basis sets for orbital studies of galaxies and a 'quantum-mechanical' method to compute them     

Constantinos Kalapotharakos  Christos Efthymiopoulos  Nikos Voglis 《Monthly notices of the Royal Astronomical Society》2008,383(3):971-988

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Ordered and chaotic Bohmian trajectories     

George Contopoulos  Christos Efthymiopoulos 《Celestial Mechanics and Dynamical Astronomy》2008,102(1-3):219-239

We discuss the issue of ordered and chaotic trajectories in the Bohmian approach of Quantum Mechanics from points of view relevant to the methods of Celestial Mechanics. The Bohmian approach gives the same results as the orthodox (Copenhagen) approach, but it considers also underlying trajectories guided by the wave. The Bohmian trajectories are rather different from the corresponding classical trajectories. We give examples of a classical chaotic system that is ordered quantum-mechanically and of a classically ordered system that is mostly chaotic quantum mechanically. Then we consider quantum periodic orbits and ordered orbits, that can be represented by formal series of the “third integral” type, and we study their asymptotic properties leading to estimates of exponential stability. Such orbits do not approach the “nodal points” where the wavefunction ψ vanishes. On the other hand, when an orbit comes close to a nodal point, chaos is generated in the neighborhood of a hyperbolic point (called X-point). The generation of chaos is maximum when the X-point is close to the nodal point. Finally we remark that high order periodic orbits may behave as “effectively ordered” or “effectively chaotic” for long times before reaching the period.  相似文献   

Climate change effects on the marine characteristics of the Aegean and Ionian Seas     

Christos Makris  Panagiota Galiatsatou  Konstantia Tolika  Christina Anagnostopoulou  Katerina Kombiadou  Panayotis Prinos  Kondylia Velikou  Zacharias Kapelonis  Elina Tragou  Yannis Androulidakis  Gerasimos Athanassoulis  Christos Vagenas  Ioannis Tegoulias  Vassilis Baltikas  Yannis Krestenitis  Theodoros Gerostathis  Kostantinos Belibassakis  Eugen Rusu 《Ocean Dynamics》2016,66(12):1603-1635

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The exceptionally hot summer of 2007 in Athens, Greece — A typical summer in the future climate?     

D. Founda  C. Giannakopoulos   《Global and Planetary Change》2009,67(3-4):227-236

Summer 2007 was abnormally warm for many areas of southeastern Europe, the Balkan peninsula and parts of Asia Minor with departures from the seasonal means exceeding 4 °C in some areas but also distinct periods of extremely hot weather. Greece experienced very likely the warmest summer of its instrumental history with record breaking temperatures being observed at a number of stations. The historical air temperature record of the National Observatory of Athens (NOA), extending back to the 19th century, was used in order to highlight the rarity of the event. Seasonal (June to August) temperature anomalies at NOA exceeded 3 °C corresponding to more than 3 standard deviations with respect to the 1961–1990 reference period. The record value of 44.8 °C was observed at NOA on 26 June 2007 (previous record 43 °C in June 1916) during the first and most intense heat wave that affected the area. The study places summer 2007 in the climatology of the previous century and also examines whether the statistics of summer 2007 have similarities with Mediterranean summers of the future. An ensemble of regional climate model simulations undertaken for the European domain indicate that summer 2007 reflects the daily maximum temperatures that are projected to occur in the latter part of the 21st century. The analysis of temperature data from other less urbanized stations indicates that the urban heat effect in Athens contributed positively to the anomalies of the nocturnal temperatures. The abnormally hot summer of 2007 is perhaps not the proof but a strong indicator of what eastern Mediterranean summers could resemble in future.  相似文献   

Impacts of climate extremes on activity sectors – stakeholders’ perspective     

Z. W. Kundzewicz  C. Giannakopoulos  M. Schwarb  I. Stjernquist  P. Schlyter  M. Szwed  J. Palutikof 《Theoretical and Applied Climatology》2008,93(1-2):117-132

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Winter convective precipitation variability in southeastern Europe and its connection to middle tropospheric circulation for the 60-year period, 1950–2009     

Christos J. Lolis 《Theoretical and Applied Climatology》2012,107(1-2):189-200

The inter-annual variability of winter convective precipitation rate (CPR) in southeastern Europe and its connection to 500?hPa geopotential height (GH) is examined for the period 1950–2009 by using factor analysis and canonical correlation analysis. Two GH centers of action for CPR are found. The first one is located over Italy and it is associated with the typical winter depression activity regime over the Mediterranean Sea, controlling CPR in southern Italy, the southern Balkans, west Asia Minor, and the adjacent seas. The second one is located over the British Isles and it is associated with blocking activity over western Europe being responsible for a CPR seesaw teleconnection between (1) northern Italy, the Alps and the northwestern Balkans and (2) the south central Mediterranean Sea, south of Sicily. A CPR decrease in most of the areas under study and a CPR increase in the south central Mediterranean Sea are found.  相似文献