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There is much debate today about the role of carbon dioxide in global warming. In this study we examine the intrinsic dynamics of the temporal evolution of the carbon dioxide amount and temperature by analyzing instrumental measurements data and paleo-reconstructed data to see if this dynamics remains stable in terms of its internal properties. The paleoecological data were based on over 20,000 sea surface temperature point reconstructions obtained from ocean sediment cores using alkenone unsaturation indices, applying ratios of Mg/Ca in planktonic foraminifera, and based upon microfossil abundances. The results of the analysis of the instrumental data fluctuations in land-ocean temperature and carbon dioxide in the period March 1958–April 2017, showed that the long-term dynamics of the fluctuations of these two parameters exhibit persistent power-law type behavior. This type of behavior also emerges from the same analysis of the reconstructed global mean sea temperature and carbon dioxide amount fluctuations over the past 805 thousand years. In addition, the time series of both parameters are characterized by multifractality for time scales of less than 4 years. Consequently, the intrinsic properties of carbon dioxide and global temperature have not changed over the past nearly one million years.

Atmospheric pollutants and environmental indicators are often used to reconstruct historic atmospheric pollution from peat, as it accumulates over time by decomposing plant material, thus recording a history of air pollution. In the present study, three key parameters related to the peat bogs&rsquo, surface wetness dynamics in European Russia during the Holocene were investigated using modern statistical analysis. These parameters are: (i) the water table depth (WTD) in relation to the surface, which is reconstructed based on the community structure of the subfossil testate amoeba assemblages, (ii) the peat humification estimated as absorption of alkaline extract that directly reflects moisture at which the peat was formed, (iii) the Climate Moisture Index (CMI) and the Aridity Index derived from pollen-based reconstructions of the mean annual temperature and precipitation and classifying moisture conditions as the ratio between available annual precipitation and potential land surface evapotranspiration. All these parameters provide useful information about the paleoclimate (atmospheric moisture component) dynamics. High values of WTD and peat humification appear to comply with Gutenberg&ndash, Richter law. It is noteworthy that this law also seems to reproduce the high values of the modeled climate moisture and aridity indices. The validity of this new result is checked by replacing &ldquo, conventional time&rdquo, with &ldquo, natural time&rdquo, On this basis, a new nowcasting tool is developed to more accurately estimate the average waiting time for the extreme values of these climate parameters. This will help to understand climate variability better to address emerging development needs and priorities by implementing empirical studies of the interactions between climatic effects, mitigation, adaptation, and sustainable growth.

The temporal evolution of the temperature of the lower troposphere, middle troposphere, tropopause and lower stratosphere on a global, hemispheric and latitudinal basis is studied using the recent Version 6 of the UAH MSU/AMSU global satellite temperature data set. The analysis showed that any long-term increase or decrease in temperature is not smooth and uniform, i.e., it is not slow and monotonous. In contrast, it grows or decreases monotonously in a short period, then almost stabilizes for some time, and then repeats the same pattern. In other words, the long-term temperature trend is not linear but follows the stepwise increase or decrease. In more concrete, the temperature time series over the period 12/1978–07/2018 is composed by a noisy pattern superposed on a stepwise function with abrupt shifts in 1986, 1994 and 2014. In addition, we noticed that the superposition of the stepwise function on the ENSO time series provides a new composite time series, which fits very well with the observed temperature. If the latter is delayed for almost 4 months this fit is even better. This pattern applies to the temperature of the troposphere on a global, hemispheric and tropical basis. It does not apply to the temperature of the troposphere over the extratropics and polar regions, as well as to the temperature of the lower stratosphere. In particular, the extra-tropics of the northern hemisphere displays an Arctic Oscillation stair-shaped behaviour. Perhaps the stepwise pattern in temperature evolution may be due to the fact that the gradual changes in the periodic or quasi-periodic tropospheric temperature components may trigger sudden changes which with positive feedbacks, lead to a self-enhancing change. This can be so strong that the temperature reaches critical values and then with sudden changes goes from one equilibrium state to another.

The enhancement of the atmospheric greenhouse effect due to the increase in the atmospheric greenhouse gases is often considered as responsible for global warming (known as greenhouse hypothesis of global warming). In this context, the temperature field of global troposphere and lower stratosphere over the period 12/1978–07/2018 is explored using the recent Version 6 of the UAH MSU/AMSU global satellite temperature dataset. Our analysis did not show a consistent warming with gradual increase from low to high latitudes in both hemispheres, as it should be from the global warming theory. In addition, in the lower stratosphere the temperature cooling over both poles is lower than that over tropics and extratropics. To study further the thermal field variability we investigated the long-range correlations throughout the global lower troposphere-lower stratosphere region. The results show that the temperature field displays power-law behaviour that becomes stronger by going from the lower troposphere to the tropopause.This power-law behaviour suggests that the fluctuations in global tropospheric temperature at short intervals are positively correlated with those at longer intervals in a power-law manner. The latter, however, does not apply to global temperature in the lower stratosphere. This suggests that the investigated intrinsic properties of the lower stratospheric temperature are not related to those of the troposphere, as is expected by the global warming theory.

Intraventricular hemorrhage (IVH) is a major cause of morbidity and mortality in preterm neonates. Elucidation of the mechanisms underlying IVH and/or development of disease biomarkers is essential. The aim of the study was to investigate the urine metabolic profile of preterm neonates (gestational age 32 weeks) IVH and explore the role of metabolomics in understanding pathophysiological mechanisms of the disease from which novel biomarkers could be derived. In this single-center, prospective, case-control study, urine samples were collected from seven preterm infants with early IVH (IVH group) and from 11 preterm ones without IVH (control group) on days 1, 3 and 9 of life. Urine metabolites were evaluated using targeted liquid chromatography-tandem mass spectrometry. Demographic and perinatal-clinical characteristics were recorded. Univariate and multivariate statistical analyses were performed. Orthogonal Partial Least Squares-Discriminant Analysis showed that the study groups differed significantly due to alternation in 20 out of the 40 metabolites detected in the urine. Elevated differentiated metabolites included energy intermediates and other important compounds, whereas reduced ones various amino acids, hypoxanthine and nicotinamide. A set of metabolites showed high performance as indicators of IVH, especially during day 1. As evidenced by metabolomics, preterm neonates with IVH demonstrate significant metabolism perturbations. Potentially, a selected panel of metabolites could be used as urine biomarkers of IVH development and/or progression in high-risk preterm infants.

Very recently, it has been found that intense anomalies of the mesospheric ozone occur a few days before major earthquakes. This paper explores the credibility of this finding in the case of the last two major earthquakes in Greece. Indeed, the study of the mesospheric ozone vertical distribution showed that unusual anomalies occurred a few days before these two earthquakes. However, at time periods with no significant seismicity the same unusual changes in the mesospheric ozone vertical distribution were observed. Consequently, significant temporal changes of the mesospheric ozone can not be considered as precursors for upcoming significant seismic activity.

Satellite and ground-based observations are used to explore the composite oceanic–atmospheric link known as the El Nino/La Nina Southern Oscillation (ENSO) phenomenon, which is closely associated w...

In this paper we investigate the evolution of the energy emitted by CO2 and NO from the Earth's thermosphere on a global scale using both observational and empirically derived data. In the beginning, we analyze the daily power observations of CO2 and NO received from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) equipment on the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite for the entire period 2002–2016. We then perform the same analysis on the empirical daily power emitted by CO2 and NO that were derived recently from the infrared energy budget of the thermosphere during 1947–2016. The tool used for the analysis of the observational and empirical datasets is the detrended fluctuation analysis, in order to investigate whether the power emitted by CO2 and by NO from the thermosphere exhibits power-law behavior. The results obtained from both observational and empirical data do not support the establishment of the power-law behavior. This conclusion reveals that the empirically derived data are characterized by the same intrinsic properties as those of the observational ones, thus enhancing the validity of their reliability.

Since February 2016, the equatorial quasi-biennial oscillation (QBO) in zonal wind of the lower stratosphere exhibited anomalous behavior. In more detail, it broke down from its typical pattern and the eastward stratospheric winds unexpectedly reversed to a westward direction. We herewith attempt to detect whether this unprecedented event could be considered as a result of plausible long-range correlations in the QBO temporal evolution. The analyses performed using all the available QBO data sets showed that such an interpretation could not be inferred, because the temporal evolution of the equatorial zonal wind in the lower stratosphere does not exhibit power-law behavior. Further, the natural time analysis of the QBO data indicates precursory behavior before the maximization of the zonal wind velocity and that the recent strong El Nino event might be related with the aforementioned unprecedented behavior.

A number of recent studies suggest that atmospheric changes that precede an earthquake might offer the hope of providing early warning. This study attempts to examine seismo-atmospheric anomalies around the time and the location of some of the major earthquakes in Greece in the period 2001–2015. Daily values of aerosol optical depth (AOD) and total ozone column (TOZ) obtained from satellite observations are used, in the time window between 25 days before and 14 days after each of these events, in a 1° × 1° area centred on the epicentre of each earthquake. For some of these earthquake events, abnormal increases in time series of AOD and TOZ data were detected before and after the occurrence of the earthquake. Nevertheless, in other cases, no clear anomalies were observed around the earthquake date. In addition, examining the statistics of AOD and TOZ daily values, there were many cases of prominent abnormal variations, without, however, being associated with an earthquake event. Therefore, no clear association was found between AOD and TOZ fluctuations and recent earthquakes in Greece.

According to recent findings the tropospheric-stratospheric temperature in the tropical atmosphere exhibits long range power-law persistence, which becomes stronger as the altitude increases. Because the ozone content is closely associated with the solar radiation and temperature we explore this effect in the vertical ozone distribution. We therefore analyze the tropical monthly mean ozone volume mixing ratios during `1980–2014, which is based on model simulations at heights 30−50 km. The results obtained confirm that the modeled ozone data do not exhibit long-range power law correlations and therefore are not biased by a persistent signal.

The main objective of the present study is to develop a model for the prediction of the extreme events of air pollution in megacities using the concept of so-called "natural time" instead of the "conventional clock time". In particular, we develop a new nowcasting technique based on a statistically significant fit to the law of Gutenberg-Richter of the surface concentration of ozone (O3), particles of the size fraction less than 10 μm (PM-10) and nitrogen dioxide (NO2). Studying the air pollution over Athens, Greece during the period 2000–2018, we found that the average waiting time between successive extreme concentrations values varied between different atmospheric parameters accounted as 17 days in case of O3, 29 days in case of PM-10 and 28 days in case of NO2. This average waiting time depends on the upper threshold of the maximum extreme concentrations of air pollutants considered. For instance, considering the NO2 concentrations over Athens it was found that the average waiting time is 13 days for 130 μg/m3 and 2.4 years for 200 μg/m3. Remarkably, the same behaviour of obedience to the Guttenberg-Richter law characterizing the extreme values of the air pollution of a megacity was found earlier in other long-term ecological and paleoclimatic variables. It is a sign of self-similarity that is often observed in nature, which can be used in the development of more reliable nowcasting models of extreme events.

A new nowcasting method is herewith proposed to monitor the crucial components of the variability of the stratospheric ozone depletion. A demonstration of this method is performed considering the daily measurements of the minimum air temperature in the latitude range 50oN – 90oN, at 50 hPa, during the period 1/1/1979-06/04/2020. The motivation for choosing this geographical area is the fact that unusual dynamic conditions in the winter in the Arctic region this year resulted in a record-low ozone level in much of central Arctic, with an area about three times that of Greenland. In addition, discussion on whether the Arctic stratospheric temperature in the winter of 2020 was indeed the lowest in the record is presented. Comparing the temporal evolution of the winter-spring minimum temperature in the year 2019–2020 of the unprecedented ozone hole showed that it resembles that of 2010–2011, when, however, no such ozone hole occurred. This fact suggests that this phenomenon is complex and does not depend solely on the temperature regime of the polar stratosphere. The interactive combination of possible factors that contributed to the appearance of the first ozone hole over the Arctic during the winter-spring period of 2019–2020, such as the long-lasting of the strong and stable polar vortex, the large extent and duration of polar stratospheric clouds, are discussed in detail.

Hypoxic-ischemic encephalopathy (HIE), a serious complication of perinatal asphyxia, is commonly associated with an unfavorable outcome. In-depth research is important not only for the interpretation of the underlying biological alternations but may also provide the basis for the development of novel diagnostic and therapeutic tools. The application of metabolomics in perinatal asphyxia/HIE is a relatively new approach. We performed a narrative, non-systematic review in the literature of metabolomic studies involving newborn animals and humans exposed to hypoxia-ischemia or developing perinatal asphyxia/HIE. Fifteen animal studies, nine studies in human neonates, and two review articles were evaluated. Changes in the metabolomic profile of newborn animals exposed to hypoxia-ischemia and of asphyxiated neonates with HIE are presented in relation to the underlying pathophysiology. The clinical relevance of these findings is further discussed in a comprehensible to the bedside clinician manner. Metabolomics may provide an explanation for the various metabolic alternations occurring in perinatal asphyxia/HIE, elucidate the biological background of the applied therapeutic interventions and promote the development of novel diagnostic-prognostic biomarkers of the disease. HIPPOKRATIA 2017, 21(3): 115-123.

Metabolomics could provide valuable insights into hypoxemic-ischemic encephalopathy (HIE) revealing new disease-associated biochemical derangements. The study aimed to investigate urine metabolic changes in neonates with HIE compared to healthy controls, using targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS).In this prospective, single-center study we enrolled neonates born at ≥ 36 weeks gestation with HIE (HIE group) and healthy controls (control group). We collected urine samples for metabolomic analysis on days one, three, and nine of life.Twenty-one full-term newborns were studied, 13 in the HIE group and eight in the control group. Six of the affected neonates had moderate/severe HIE and seven mild HIE. Therapeutic hypothermia was applied only in four neonates with moderate/severe HIE. Multivariate and univariate statistical analysis showed a clear separation between the HIE and the control groups. Discriminant metabolites involved pyruvic acid, amino acids, acylcarnitines, inositol, kynurenine, hippuric acid, and vitamins.We have identified a specific metabolic profile in neonates with HIE, adding to the existing knowledge on the disease biochemistry that may potentially help in biomarker development. HIPPOKRATIA 2017, 21(2): 80-84.

A substantial weakness of several climate studies on long-range dependence is the conclusion of long-term memory of the climate conditions, without considering it necessary to establish the power-law scaling and to reject a simple exponential decay of the autocorrelation function. We herewith show one paradigmatic case, where a strong long-range dependence could be wrongly inferred from incomplete data analysis. We firstly apply the DFA method on the solar and volcanic forcing time series over the tropical Pacific, during the past 1000 years and the results obtained show that a statistically significant straight line fit to the fluctuation function in a log-log representation is revealed with slope higher than 0.5, which wrongly may be assumed as an indication of persistent long-range correlations in the time series. We argue that the long-range dependence cannot be concluded just from this straight line fit, but it requires the fulfilment of the two additional prerequisites i.e. reject the exponential decay of the autocorrelation function and establish the power-law scaling. In fact, the investigation of the validity of these prerequisites showed that the DFA exponent higher than 0.5 does not justify the existence of persistent long-range correlations in the temporal evolution of the solar and volcanic forcing during last millennium. In other words, we show that empirical analyses, based on these two prerequisites must not be considered as panacea for a direct proof of scaling, but only as evidence that the scaling hypothesis is plausible. We also discuss the scaling behaviour of solar and volcanic forcing data based on the Haar tool, which recently proved its ability to reliably detect the existence of the scaling effect in climate series.

The present paper uses characteristics of the marine interstitial ciliate community in the White Sea intertidal sandflat during the period of 1991–2011, in order to study its long-term dynamics, investigating in particular whether it exhibits scaling behaviour into its fluctuations, which is a characteristic feature of the climate system. To this aim, a recently proposed version of the detrended fluctuation analysis is herewith employed which has been successfully applied to a wide range of simulated and physiologic time series in recent years. In case that the fluctuations of the ciliate community present self-similarity processes, an ideal field test for the currently proposed biological models will be established, allowing to evaluate their reliability. Indeed, we show for the first time that different ciliate species exhibit long-range power-law persistent correlations. This means that ciliate fluctuations in different intervals are positively correlated, obeying a power-law behaviour. Although the origin of power-law temporal evolution of ciliates should be further investigated, this finding is probably associated with the self-organized criticality of ciliates. It should be noted that the long-range correlations obtained do not imply the presence of specific cycles but rather the existence of dynamic links between long-term and short-term temporal evolution. The scaling behaviour found in marine interstitial ciliate community should be taken into account in the investigation of their response to the present or future climate change.

The intrinsic features of the temporal evolution of the air pollution are of crucial importance for its reliable modeling. In this regard, Varotsos et al. (2012) suggested that the surface ozone fluctuations at Athens since 1900, exhibit long-range dependence (long-memory), despite its present-day doubling. We herewith establish the long-memory in surface ozone concentrations that assumed in Varotsos et al. (2012), by employing recent analytical tools.

In the present analysis, we study the North Atlantic hurricanes and the tropical cyclones over the Atlantic, attempting to statistically contribute to the study of the recently observed rapid shifts of sea surface temperature anomalies (SSTa) and hurricane activity. Indeed, the annual values of hurricane count (HC), during 1900–2012, seem to show two abrupt increasing events which temporally coincide with the SST shifts. Moreover, the superposition of a staircase function on the Southern Oscillation Index (SOI) after removing the effect of the Pacific Decadal Oscillation (PDO) and the quasi-biennial oscillation (QBO) provides a good fit to the observed HC values. In addition, the annual values of the tropical cyclone count (TCC), during 1900–2006, analyzed with the same procedure as that of HC exhibit similar features to those of the HC values, revealing abrupt shifts in the same years. Furthermore, the application of two shift detection statistical methods determines more accurately the intervals where the shifts occur for each of the three parameters (SSTa, HC, and TCC). Nevertheless, the undersampling of hurricane numbers during early and mid-twentieth century due to the observing capabilities may have contributed to the first rapid shift in hurricane activity.

In the present study, the investigation of the levels of the local and regional oxidants concentration at Athens, Greece, is attempted by analyzing the observations obtained at an urban and a rural station, during 2001-2011 and 2007-2011, respectively. A progressive increase of the daytime and nighttime average of [NO2]/[Ox] versus [NOx] is observed showing a larger proportion of Ox in the form of NO2 when the level of NOx increases. Similar results are observed when studying the variation of mean values of [NO2]/[NOx] versus [NOx]. The results obtained when compared with those that have earlier detected elsewhere, revealed similarities and discrepancies that are discussed in detail. The parameterized curves that are presented for the first time in this paper may be used by the air quality planners to track the trends in other cities also, and to understand what is or was driving them.

[1] We hereby attempt to detect plausible reasons for the discrepancies between the measured and modeled tropospheric temperature anomalies in the tropics. For this purpose, we calculate the trends of the upper-minus-lower tropospheric temperature anomaly differences (TAD) for both the measured and modeled time series during 1979–2010. The modeled TAD trend is significantly higher than that of the measured ones, confirming that the vertical amplification of warming is exaggerated in models. To investigate the cause of this exaggeration, we compare the intrinsic properties of the measured and modeled TAD by employing detrended fluctuation analysis (DFA). The DFA exponent obtained for the measured values reveals white noise behavior, while the exponent for the modeled ones shows that they exhibit long-range power law correlations. We suggest that the vertical amplification of warming derived from modeled simulations is weighted with a persistent signal, which should be removed in order to achieve better agreement with observations.

The annual and the monthly mean values of the land-surface air temperature anomalies from 1880–2011, over both hemispheres, are used to investigate the existence of long-range correlations in their temporal evolution. The analytical tool employed is the detrended fluctuation analysis, which eliminates the noise of the non-stationarities that characterize the land-surface air temperature anomalies in both hemispheres. The reliability of the results obtained from this tool (e.g., power-law scaling) is investigated, especially for large scales, by using error bounds statistics, the autocorrelation function (e.g., rejection of its exponential decay) and the method of local slopes (e.g., their constancy in a sufficient range). The main finding is that deviations of one sign of the land-surface air temperature anomalies in both hemispheres are generally followed by deviations with the same sign at different time intervals. In other words, the land-surface air temperature anomalies exhibit persistent behaviour, i.e., deviations tend to keep the same sign. Taking into account our earlier study, according to which the land and sea surface temperature anomalies exhibit scaling behaviour in the Northern and Southern Hemisphere, we conclude that the difference between the scaling exponents mainly stems from the sea surface temperature, which exhibits a stronger memory in the Southern than in the Northern Hemisphere. Moreover, the variability of the scaling exponents of the annual mean values of the land-surface air temperature anomalies versus latitude shows an increasing trend from the low latitudes to polar regions, starting from the classical random walk (white noise) over the tropics. There is a gradual increase of the scaling exponent from low to high latitudes (which is stronger over the Southern Hemisphere).

The investigation of the intrinsic properties of the annual tropical cyclone count over Atlantic, during 1870–2006, is herewith attempted. The motivation behind this exploration is to contribute to the current understanding about the dynamics of these disastrous events, as tropical cyclones create destructive impacts for people living around tropical areas. The analytical tool used is the detrended fluctuation analysis, and the exponent obtained reveals that the time series of the annual tropical cyclone count over Atlantic obeys the classical random walk (white noise). In other words, the number of tropical cyclones seems to exhibit neither persistent nor antipersistent behavior. The reliability of the lack of scaling dependence in the time series of the annual tropical cyclone count is confirmed, by applying error bounds statistics and studying the decay of the autocorrelation function (i.e., not rejected exponential decay) and the variability of local slopes (i.e., lack of constancy in a sufficient range). In addition, the fact that the series used is fractional Gaussian noise depicts that the results obtained are reliable, despite the fact that the available data set is still limited. The indication of a nearly white noise signal in the tropical cyclone count fluctuations does not suggest that the climate change phenomenon does not exist.

The investigation of the intrinsic properties of the solar spectral irradiance as a function of the ultraviolet (UV) wavelength is attempted by exploiting rare observations performed at the Villard St. Pancrace station of the Lille University of Sciences and Technology ranging from 278 to 400 nm with a step of 0.05 nm every half an hour from nearly sunrise to sunset. To achieve this goal, the modern method of the detrended fluctuation analysis was applied on the solar spectral irradiance values versus wavelength. This analysis revealed that the solar incident flux at the top of the atmosphere and the solar spectral irradiance at the ground during two overcast sky days fluctuate with the UV wavelength exhibiting persistent long-range power-law behavior. More interestingly, the exponent of the power-law relationship between the fluctuations of the solar spectral irradiance versus UV wavelength at both the top of the atmosphere and the ground is consistently close to unity (of 1/f-type) throughout the day. This 1/f behavior has been detected in many complex dynamical systems, but despite much effort to derive a theory for its widespread occurrence in nature, it remains unexplained so far. According to the above-mentioned findings we speculate that the 1/f property of the incident solar UV flux at the top of the atmosphere could probably drive both the 1/f behavior depicted in the atmospheric components and the solar UV irradiance at the Earth's surface. The latter could influence the UV-sensitive biological ecosystems, giving rise to a 1/f-type variability in the biosphere, which has already been proven by recent observational data. We finally propose that Wien approximation could be multiplied by a 1/f function of wavelength (e.g., of the type of the fractional Brownian motion) in order to reproduce the aforementioned 1/f feature of the solar UV flux.

Recent studies have suggested that variation of the total ozone content may be a precursor tool for earthquake forecasts. The main aim of this analysis is to examine whether the total ozone variability before and after the eight large earthquakes (M w ≥ 6.0) of the decade 2001–2010 in Greece could be related with these earthquake events. The results clearly show that the association of total ozone fluctuation with earthquake occurrence in the time window of 2 weeks before and after each of these large earthquake events is not statistically significant.

The estimation of the future projected precipitation and rainfall on short- and long-term basis is crucial because their substantial changes are closely associated with severe socioeconomic and ecological consequences. For this reason, the detrended fluctuation analysis is applied on the Sahel precipitation and standardized rainfall anomalies in order to explore the intrinsic properties of their temporal variability. The results obtained show that the Sahel precipitation anomalies the period 1900–2010 exhibit persistent long-range correlations for all the time lags between 4 months and 28 years. This result states that the fluctuations of the Sahel precipitation anomalies in small time intervals are positively correlated to those in longer time intervals in a power law fashion. In opposite, the Sahel standardized rainfall fluctuations during the periods 1948–2001 show an almost random walk behavior. It should be emphasized that these findings could substantially contribute to the precipitation forecast and the advanced simulation of the variability of the global climate system. For instance, the data of the precipitation forecast modeling must exhibit the long-range correlations dictated by the precipitation data in the past. A detailed analysis on this topic will be published elsewhere.

The main aim of the present study is to investigate further the association between total ozone (TOZ) and the 11 year solar cycle (SC) during the period 1979–2010, by employing satellite observations of TOZ made by Nimbus-7, Meteor-3, Earth Probe Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) instrumentation. A statistically significant correlation between the annual mean TOZ over both hemispheres and sunspot number (SN) is found. On the contrary, focusing on the January and February mean monthly TOZ fluctuations from the equator to the high latitudes of the Northern Hemisphere, no association between TOZ and SN is derived. This is attributed to the existence of the quasi-biennial-oscillation (QBO) and the El Nino-Southern oscillation (ENSO) in the TOZ time series. The latter oscillation is herewith expressed by the recently introduced Ozone ENSO Index (OEI). However, when considering the TOZ zonal means centred at 17.5 and 27.5°N during the east phase years of the QBO in the equatorial zonal wind at 50 hPa, a statistically significant correlation between TOZ and SN is revealed. It is an indication that the quasi-periodic fluctuations (i.e. QBO, ENSO) strongly contaminate the relationship between TOZ and solar activity. Plausible mechanisms are discussed, exploring the momentum flux (MF) measurements between 45 and 75°N, in the periods of increased dynamical variability. The findings obtained point to the conclusion that the 11 year solar cycle response in TOZ is caused by dynamical changes which are caused by solar activity. These are of crucial importance because solar radiation is a major driving force of the climate system. Copyright © 2012 Royal Meteorological Society

The main aim of this study is to investigate whether the main components of the photochemical smog episodes over megacities obey the Gaussian distribution or do they follow the distribution of the Gutenberg-Richter law. To this end, a case study has been implemented for Athens, Greece, which is among the most densely populated capitals in the middle latitudes of the Northern Hemisphere. The data employed are hourly mean values of surface ozone and nitrogen dioxide concentrations collected by the National Air Pollution Monitoring Network during the period 1988–2008. The results obtained show that the surface ozone and nitrogen dioxide concentrations obey the Gutenberg-Richter law, while their extreme values follow the Generalized Pareto distribution. This finding is important for current efforts to reliably forecast the air pollutants concentrations and to quantify their contribution to climate change. Finally, the plausible mechanisms involved in air pollution dynamics leading to the above-mentioned behaviour are also discussed, assuming the air pollution system governed by non-linear processes.

The aim of this study is to investigate the potential effects of increased urbanization in the Athens city, Greece on the intrinsic features of the temporal fluctuations of the surface ozone concentration (SOC). The detrended fluctuation analysis was applied to the mean monthly values of SOC derived from ground-based observations collected at the centre of Athens basin during 1901–1940 and 1987–2007. Despite the present-day SOC doubling in respect to SOC historic levels, its fluctuations exhibit long-range power-law persistence, with similar features in both time periods. This contributes to an improved understanding of our predictive powers and enables better environmental management and more efficient decision-making processes. The extensive photochemistry enhancement observed in the Athens basin from the beginning of the twentieth century until the beginning of the twenty-first century seems not to have affected the long memory of SOC correlations. The strength of this memory stems from its temporal evolution and provides the limits of the air pollution predictability at various time scales.

Global mean land and sea surface temperature (LSST) anomalies were analysed statistically with detrended fluctuation analysis (DFA), for the period from January 1850 to August 2008, for both hemispheres, individually. Persistent long-range power-law correlations were revealed within the time series of the LSST anomalies, for all time lags between 4 months and 39 years. In addition, the derived 'long memory' in the time series of the LSST anomalies was examined to determine whether they are derived from their time evolution or from the distribution of their own values. The results obtained could be taken into consideration for the prediction of basic climate variables through the use of future climate modelling.

Detrended fluctuation analysis is applied to the mean monthly temperature values, over different heights of the global troposphere, during 1980-2004, to search for self-similarity properties. The results show that the tropospheric temperature anomalies obey persistent long-range power-law correlations for time-scales longer than about four months and shorter than about six years. This suggests that the temperature fluctuations over small time periods (i.e. a few months) are related to those over longer time periods (i.e. a few years). In addition, the long-range power-law persistence in the global tropospheric temperature fluctuations becomes stronger as the altitude increases.

The recently constructed retrospective time-series of total ozone content at Arosa (46.47°N, 9.40°E) and Poluy River (66.1°N, 68.3°E) are used to detect the existence of long-range correlations. The multifractal detrended fluctuation analysis applied to the mean yearly values of the reconstructed total ozone content over both locations showed that the fluctuations of the total ozone content exhibit persistent long-range power-law correlations, for all time lags between 4 and 90 years. In addition, the same analysis applied to the yearly increments of the reconstructed total ozone values shows that it exhibits a crossover at approximately 11 years and persistent (antipersistent) long-range power-law correlations before (after) the crossover point.

Detrended fluctuation analysis is applied to the time series of the global tropopause height derived from the 1980–2004 daily radiosonde data, in order to detect long-range correlations in its time evolution. Global tropopause height fluctuations in small time-intervals are found to be positively correlated to those in larger time intervals in a power-law fashion. The exponent of this dependence is larger in the tropics than in the middle and high latitudes in both hemispheres. Greater persistence is observed in the tropopause of the Northern than in the Southern Hemisphere. A plausible physical explanation of the fact that long-range correlations in tropopause variability decreases with increasing latitude is that the column ozone fluctuations (that are closely related with the tropopause ones) exhibit long range correlations, which are larger in tropics than in the middle and high latitudes at long time scales. This finding for the tropopause height variability should reduce the existing uncertainties in assessing the climatic characteristics. More specifically the reliably modelled values of a climatic variable (i.e. past and future simulations) must exhibit the same scaling behaviour with that possibly existing in the real observations of the variable under consideration. An effort has been made to this end by applying the detrended fluctuation analysis to the global mean monthly land and sea surface temperature anomalies during the period January 1850–August 2008. The result obtained supports the findings presented above, notably: the correlations between the fluctuations in the global mean monthly land and sea surface temperature display scaling behaviour which must characterizes any projection.

Detrended fluctuation analysis (DFA) was applied to the total ozone planetary waves 1 and 2 at the middle and high latitudes of the southern hemisphere that had been acquired by daily Total Ozone Mapping Spectrometer (TOMS) total ozone observations since 1979. The main aim of the analysis was to examine the ozone layer as a system invariant in a wide range of scales characterized by the fractal structure, and to search for the existence of long-range correlations. The results show that fluctuations in the amplitude of wave 1 obey persistent long-range power-law correlations for time scales greater than about 4 days and less than about 3 months. This suggests that these fluctuations in small time intervals are closely related to the fluctuations in longer time intervals in a power-law fashion (when the time intervals vary from about 4 days to about 3 months). Similar analysis applied to the amplitude of wave 2 revealed that this wave does not exhibit long-range correlations.

Detrended fluctuation analysis (DFA) was applied to zonal mean daily Aerosol Index (AI) values derived from satellite observations during 1979–2003 to search for self‐similarity properties. The results show that the detrended and deseasonalized AI fluctuations in both hemispheres and globally obey persistent long‐range power‐law correlations for time scales longer than about 4 days and shorter than about 2 years. This suggests that the AI fluctuations in small time intervals are related to the AI fluctuations in longer time intervals in a power‐law fashion (when the time intervals vary from about 4 days to about 2 years). In other words, an anomaly in AI in one time frame continues into the next, exhibiting a power‐law evolution. The influence of the annual and semiannual cycles on the scaling behaviour of the AI time series in both hemispheres is discussed. A plausible mechanism for the time scale of about 2 years in AI time series could be the modulation of the Brewer–Dobson cell by the quasi‐biennial o...

An investigation was made into the characteristic features of the signature of the quasi‐stationary planetary waves in ozone over Antarctica during recent years, where the Antarctic ozone hole exhibits peculiar behaviour. To this end, mean monthly ozone data, collected by the Total Ozone Mapping Spectrometer (TOMS) flown on the Earth‐Probe satellite over 75.5° S during September of four successive years (2000–2003), were used. Planetary waves in total ozone seem to have been much stronger during 2002 than during the other years investigated. The latter agrees fairly well with the substantial reduction in the spatial extent of the polar vortex and the limited ozone hole size in 2002.

Detrended fluctuation analysis is applied to the Athens air-pollution time-series consisting of hourly observations of ozone, nitrogen oxides, and particulate matter obtained at five air-pollution monitoring stations during 1987–2003. Persistent power-law correlations in the fluctuations of daytime and nighttime ozone concentrations with lag times ranging from 1 week to 5 years were detected with more intense correlations (“stronger memory”) during daytime. The fluctuations of nitrogen oxide concentrations exhibit similar behavior. Finally, persistent power-law correlations from about 4 h to 9 months were found in PM10 fluctuations in Athens. Long-range correlations for lag times from about 4 h to 2 weeks were also detected for PM2.5 fluctuations in a 6-month data set collected at the University of Maryland “Supersite” in East Baltimore. Although the origin of the long-range behaviour of air-pollution merits further investigation, these findings presumably, reflect short and longer term source/meteorological features that are probably related to the self-organized critical behavior of the atmosphere. These findings provide power-law relationships which may substantially contribute to the development of more reliable simulating models for the ozone, nitrogen oxides, and particulate matter fluctuations.

A major shortcoming of many climate studies on long-range dependence is the inference of long-term memory from climate data without considering that the power-law scaling needs to be established and a simple exponential decay of the autocorrelation function has to be rejected (Efstathiou and Varotsos 2010; Maraun et al. 2004; Varotsos 2005a; Varotsos and Kirk-Davidoff 2006; Varotsos et al. 2003a, b, 2005, 2006, 2007, 2008, 2009, 2013). Very recently, Varotsos et al. (2013), studying the highresolution observations of the spectral solar incident flux (SIF) reaching the ground and the top of the atmosphere, concluded that SIF versus ultraviolet wavelengths (WL) exhibit 1/f-type power-law correlations. This result was based on the slope (i.e., 1.02±0.02) of the log–log plot of the root mean square fluctuation function Fd(τ) of SIF versus the WL segment size τ, after the application of the detrended fluctuation analysis (DFA). However, the reader of the paper by Varotsos et al. (2013) may argue that the afore-mentioned power-law scaling should be established by employing the two criteria suggested by Maraun et al. (2004), notably the rejection of the exponential decay of the autocorrelation function and the constancy of “local slopes” in a certain range towards the low frequencies. In this respect, we herewith plot the profile of the power spectral density (i.e., the distribution of the variance over frequency) versus logτ for the detrended SIF-WL data set (depicted in Fig. 1a). This plot shows that in a WL scale range from logτ≈0.3 (given that the measurement step is 0.05, the value of τ≈10×0.05≈0.1 nm) to maximally logτ≈1.46 (τ≈10×0.05≈1.4 nm), the power spectral density is better fitted exponentially, while for larger scales, it turns into an algebraically (power-law) fit (i.e., satisfying thus the first criterion of Maraun et al. (2004) for the rejection of the exponential fit). On the other hand, we apply the method of local slopes, suggested by Maraun et al. (2004), in order to examine the establishment of the 1/f noise in the UV solar spectral irradiance. Since the single straight line of the DFA plot for the detrended SIF-WL data set that established in the whole range of scales may be biased, we evaluate the local slopes of logFd(τ) versus logτ detecting for constancy in a sufficient range. Along these lines, we first fit a straight line to logFd(τ) versus logτ within a specific window of WL scale range. This window is then shifted successively over all calculated scales τ. At this point, it should be noted that Maraun et al. (2004) state verbatim: “Choosing the optimal window size, one has to trade bias for variance: For small windows, the bias is small, but the variability renders the interpretation difficult, whereas for large windows, the variance is reduced at the cost of a biased estimate of a.” Figure 1b illustrates the local slope a versus logτ for two different window sizes. In addition, we compute the standard deviations, sa, of each estimated local slope over all the scales, along with the error bounds of each local slope a, defined as a±1.96⋅sa. Inspection of Fig. 1b shows that for small scales, the variance of the local slopes is low, while for large scales, the variance is increased with a values reaching to a constant threshold (a≈0.92) at a range that coincides with that in Fig. 1a, where the power-law behavior prevails (establishing thus the long-range dependence). Similar results were obtained by considering other windows. C. A. Varotsos (*) :M. N. Efstathiou :C. Tzanis Climate Research Group, Division of Environmental Physics and Meteorology, Faculty of Physics, University of Athens, University Campus Bldg. Phys. V, Athens 15784, Greece e-mail: covar@phys.uoa.gr

Intention, Goal, Scope, Background. Photochemical pollution is a very complex process involving meteorological, topographic, emission and chemical parameters. The most important chemical mechanisms involved in the atmospheric process have already been identified and studied. However, many unknown parameters still exist because of the large number of participating chemical reactions.

It has recently been observed that the total ozone trends derived from certain geographical regions such as the Mediterranean and Athens (Greece) show similar values to those derived from the 40°N zonal averaged column ozone data. In this Letter, the total ozone concentration, collected by the Total Ozone Mapping Spectrometer (TOMS) flown on Nimbus-7 and Meteor-3 during the time-period January 1979-December 1993, as well as by Earth Probe during the time-period January 1997-May 2001, for the Mediterranean, Athens (Greece) and Srinagar (India), is analysed. Further, the harmonic analysis performed on total ozone time-series provides a proper tool to interpret the observed similarity in total ozone seasonal trends, which may probably be attributed to the effect of planetary waves on the ozone distribution.

We have recently suggested that the warming in the sea surface temperature (SST) since 1900, did not occur smoothly and slowly, but with two rapid shifts in 1925/1926 and 1987/1988, which are more obvious over the tropics and the northern midlatitudes. Apart from these shifts, most of the remaining SST variability can be explained by the El Nino Southern Oscillation and the Pacific Decadal Oscillation (PDO). Here, we provide evidence that the timing of these two SST shifts (around 60 years) corresponds well to the quasi-periodicity of many natural cycles, like that of the PDO, the global and Northern Hemisphere annual mean temperature, the Atlantic Multi-decadal Oscillation, the Inter-Tropical Convergence Zone, the Southwest US Drought data, the length of day, the air surface temperature, the Atlantic meridional overturning circulation and the change in the location of the centre of mass of the solar system. In addition, we show that there exists a strong seasonal link between SST and ENSO over the tropics and the NH midlatitudes, which becomes stronger in autumn of the Northern Hemisphere. Finally, we found that before and after each SST shift, the intrinsic properties of the SST time series obey stochastic dynamics, which is unaffected by the modulation of these two shifts. In particular, the SST fluctuations for the time period between the two SST shifts exhibit 1/f-type long-range correlations, which are frequently encountered in a large variety of natural systems. Our results have potential implications for future climate shifts and crossing tipping points due to an interaction of intrinsic climate cycles and anthropogenic greenhouse gas emissions.

An attempt has been made to examine the seasonal variation of the surface ozone mixing ratio in Athens, Greece during the periods 1901–1940 and 1987–1998. The first finding is that in July and August while the daytime surface ozone mixing ratio from the beginning until the end of the 20th century has increased by approximately 1.8 times, the nighttime surface ozone mixing ratio remained approximately at the same level. The second finding is that the increase in the mean daytime mixing ratio during the transition period from winter to summer is equal to the increase in the maximum daytime mixing ratios, whilst the enhancement of the nighttime surface ozone maxima is stronger than that of the nighttime mean surface ozone mixing ratio. Plausible explanation for this finding is given through mechanisms like long-range transport and photochemical processes occurring in the boundary layer, free troposphere and lower stratosphere.

The annual and the monthly mean values of the land-surface air temperature anomalies during 1880–2011, over both hemispheres, are used to investigate the existence of long-range correlations in their temporal march. The analytical tool employed is the detrended fluctuation analysis which eliminates the noise of the non-stationarities that characterize the land-surface air temperature anomalies in both hemispheres. The main result obtained is that deviations of one sign of the land-surface air temperature anomalies in both hemispheres are generally followed by deviations with the same sign at different time intervals. In other words the land-surface air temperature anomalies exhibit persistent behaviour i.e., deviations tend to keep the same sign. Specifically, the scaling exponents of the annual (monthly) mean land-surface air temperature anomalies, α = 0.65 (0.73–0.75), are roughly equal in both hemispheres approaching to that of the global annual (monthly) mean land-surface air temperature anomalies, α =0.68 (0.80). Taking into account our earlier study according to which the land and sea surface temperature anomalies obey scaling exponents α =0.78 and α = 0.89 in the Northern and Southern Hemisphere, respectively, we conclude that the difference between the scaling exponents in both sea and land contributions to the surface air temperature stems mainly from the sea surface temperature, which exhibits stronger memory in the Southern than in the Northern Hemisphere. This conclusion may be attributed to the fact that oceans have the greatest capacity to store heat, being thus able to regulate the temperature on land with less pronounced persistence. Moreover, the variability of the scaling-exponents of the annual mean values of the land-surface air temperature anomalies versus latitude shows an increasing trend from the low to polar regions starting from the classical random walk (white noise) over tropics. The gradual increase of the scaling exponent from the low to high latitudes (which is stronger over the Southern Hemisphere) could be associated with the poleward increase in climate sensitivity predicted by the global climate models. In this context, the persistence in the land-surface air temperature enhances the feasibility of its reliable long-term forecast, which is very important for various climate applications.

Changes in solar ultraviolet radiation (SUVR) have many different effects on global biogeochemistry. Nowadays, there is an increasing interest in the interactions and feedbacks between climate change and surface UV radiation. The amount of the UV radiation reaching the ground depends on a number of atmospheric and surface parameters such as the atmospheric ozone variability, the time of the day, the latitude, the season, the cloud cover, the meteorological conditions, the aerosol and gases concentrations. Ground-based and airborne measurements of the SUVR were carried out with various instruments in Athens, Greece to study the solar ultraviolet irradiance as a function of height and the influence of the air pollution and forest fires on the UV doses reaching the ground. Additionally, the relationship between SUVR at the Earth’s surface and total ozone content during the summertime period has been investigated. To perform the above-mentioned studies a recently developed theoretical algorithm for the calculation of the UV irradiance at the Earth’s surface was also employed. Finally, implications to the adverse human health effects will be discussed.

Traditionally healthcare providers have determined how healthcare resources should be allocated. However, in recent years, healthcare users have increasingly been invited to identify those priorities important to them. Yet, healthcare users' priorities do not always match the priorities set by healthcare providers. In Greece, there has not been any research to measure the extent of agreement between healthcare providers and users on cancer care priorities. This project aimed to identify the priorities of healthcare users and providers with regards to the areas of cancer care that needed to be developed or improved in Greece and to examine the extent of agreement between the two groups. Two parallel Delphi surveys were conducted to identify the priorities and arrive at a consensus. Thirty participants formed the panel of healthcare providers and 30 participants the panel of healthcare users. The participants identified 18 key cancer care areas that require development or improvement; however, there were significant differences on the prioritisation between the two panels. It is encouraging that 18 key areas were shared by both panels. These areas can form an agenda for further exploration. Healthcare users can participate in developing priorities for cancer care; however, education is required so that they are better able to make informed choices.

The enhanced UVB radiation causes adverse effects on human health such as eye abnormalities. According to relevant studies, although the risk for eye damage can be estimated fairly reliably, many uncertainties still remain. In the present study the existing archive of a research centre in Greece has been used to examine relationships between the frequency of well-known ocular effects and the SUVR exposure.