C. Tzanis

Tropospheric aerosol forcing of climate: a case study for the greater area of Greece

Although greenhouse gas forcing has global significance, the aerosol forcing is regional and seasonal, associated with the much shorter aerosol residence times in the atmosphere, and could become dominant on a regional scale. Several studies indicate that aerosol radiative forcing is among the highest in the world over the Mediterranean in the summer. In this study, the aerosol impact (forcing) on the short‐wave and long‐wave fluxes, as well as the radiative heating rate due to aerosols for different altitudes in the atmosphere over Athens, Greece, was estimated using satellite data and SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model. The short‐wave aerosols radiative forcing at the surface in cloud‐free conditions during the period 2000–2001 ranged from 10.8 to 20.1 W m−2 in the winter and from 15.2 to 16.6 W m−2 in the summer. The radiative heating rates near the surface due to aerosols were found to be in the range of 0.2–0.5 K day−1 during the winter period and 0.4 K day−1 during the summer period simultaneous with enhanced heating in the lower troposphere (below 5 km). The long‐wave radiative forcing (clear sky) at the top of the atmosphere induced by aerosols during night‐time was estimated to be only 0.02–0.04 W m−2 and 0.04–0.05 W m−2 for the winter and summer months, respectively.

The Long-Term Coupling between Column Ozone and Tropopause Properties

Abstract The observational data of the vertical temperature distribution and column ozone, obtained from 10 main stations in the Northern Hemisphere, are analyzed in order to explore the tropopause variations in conjunction with the dynamical variability in column ozone. From the analysis presented, it is evident that the summer distribution of the frequency of occurrence of the tropopause over Greece, apart from its main maximum (around 12 km), is also characterized by a secondary one around 16 km. It is proposed that this elevated maximum possibly originates from the height variation of the tropopause from 12 to 16 km depending on whether the Athens station is located below the cyclonic shear side or below the anticyclonic shear side of the subtropical jet stream. It is also suggested that the transport in the upper troposphere and lower stratosphere that originated in the equatorial region forces the appearance of the multiple tropopauses above Greece. Furthermore, the observational analysis of the ver...

On the longitude dependence of total ozone trends over middle-latitudes

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.

Aircraft observations of the solar ultraviolet irradiance throughout the troposphere

Observations of the biological effective solar ultraviolet irradiance, made by instrumentation flown on a Falcon aircraft over the entire Greek area, from the sea up to the tropopause level, obtained in the frame of the Radiation Field in the Troposphere-Scientific Training and Access to Aircraft for Atmospheric Research Throughout Europe project, are presented to discuss among others its altitude dependence. The experimental data of the biological effective solar UV irradiance as a function of height, throughout the troposphere, showed an average increase of about 7.2±1.2% km−1, which is in close agreement with the theoretically derived one, by using an appropriate algorithm, providing the biological effective solar UV irradiance at various altitudes from the Earths surface. This increase rate has also been compared with the burden ozone content at each height level as it was derived from ozone concentration measurements obtained by both balloon ascents and the aircrafts instrumentation. This comparison showed a strong anticorrelation (correlation coefficient r = −0.98) between the biological effective solar UV irradiance and the integrated ozone content above each height level corresponding to 0.25% increase in UV per 1 Dobson Unit (1DU = 0.001 atm cm) decrease in total ozone column, approximately.

Effects of air pollution on materials and cultural heritage: ICP materials celebrates 25 years of research

An overview is given of all results from the International Co-operative Programme on Effects on Materials including Historic and Cultural Monuments (ICP Materials), which was launched in 1985. Since then, about twenty different materials have been exposed repeatedly in a network of test sites consisting of more than twenty sites with an extensive environmental characterisation and more than sixty official reports have been issued. Recent results on trends in corrosion, soiling, and pollution show that corrosion of carbon steel, zinc, and limestone is today substantially lower than 25 years ago, but while corrosion of carbon steel has decreased until today, corrosion of zinc and limestone has remained more or less constant since the turn of the century. Unique data are given on measured HNO3 concentrations from 2002-2003, 2005-2006, and 2008-2009, and the relative average decrease was about the same from 2002-2003 to 2005-2006 as it was from 2005-2006 to 2008-2009.

The enhanced deterioration of the cultural heritage monuments due to air pollution.

Atmospheric pollution is an accelerating factor in the material deterioration of buildings and other structures as well as objects of cultural heritage; this is exemplified by three papers being published round about now in this journal (Chapoulie et al. 2008; Aulinas et al. 2009; Harrison et al. accepted for Environ Sci Pollut Res 2009) The study of the corrosive effects of gaseous SO2, NOx, O3, HNO3, particulate matter, and acid rainfall in combination with climatic parameters (the latter is influencing the carbonization rate) are of crucial importance, especially for mega-cities like Athens with unique historic monuments (Cartalis and Varotsos 1994). Greece (University of Athens, Faculty of Physics) has been involved in the European research project MULTIASSESS when exposure started at one test site in Athens in 2002 near the Acropolis which was formally proclaimed as the pre-eminent monument on the European Cultural Heritage list of monuments on 26 March 2007. One of the principal results obtained from the MULTIASSESS experimental campaign is the comparison of nitric acid concentration measured at the Athens station with that monitored at other historic cities in Europe (Ferm et al. 2005; Final Report 2005). This is presented in Fig. 1. Black columns and black and white columns denote, respectively, the cities and rural areas (background stations) where observation stations are located. The weathering (erosion) rate of stone types is determined by their compositional/physical properties. Figure 2 shows the surface recession rates for natural stone materials for 1and 2-year exposure. The surface recession differs from one stone type to another exposed to the same conditions depicting different weathering processes prevailing in each test site. As expected, the presence of air pollution increases the rate of natural weathering by about one to two times. Another important finding is that there is an increase in recession rates in the second year exposure at all test sites by one to two times, with exceptions for the weakest materials, Baumberger sandstone and Saaremaa dolomite, which showed three times increase, and moderately sensitive, namely Gotland sandstone, Portland limestone and Carrara marble (Final Report 2005; Ferm et al. 2006). The International Co-operative Programme on Effects on Materials including Historic and Cultural Monuments (ICP Materials) is being performed within the United Nations and the Economic Commission for Europe (UN/ECE) Convention in Geneva on Long-Range Transboundary Air Pollutants (LRTAP) with Greece as one of the signatories. The aim of the programme is to perform a quantitative evaluation of the effect of sulphur pollutants in combination with NOx and other pollutants as well as climatic parameters on the atmospheric corrosion of important materials and materials used in historical and cultural monuments. The two main objectives are the assessment of (a) dose–response functions (used for the calculation of deterioration rates) based on long-term exposures and (b) trend analysis based on repeated 1-year exposures (Kucera et al. 2005). This assessment is performed by statistical analysis of data on corrosion of materials and measurements of the environment. ATask Force is organising the programme with Sweden Environ Sci Pollut Res (2009) 16:590–592 DOI 10.1007/s11356-009-0114-8

New features of land and sea surface temperature anomalies

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.

On the limits of the air pollution predictability: the case of the surface ozone at Athens, Greece

PurposeThe 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).MethodsThe 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.ResultsDespite 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.ConclusionsThe 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.

Ground‐based observations of ozone at Athens, Greece during the solar eclipse of 1999

Measurements of column ozone were carried out at Athens, Greece, using a Dobson spectrophotometer during the solar eclipse of 11 August 1999. Taking into account the performance of the Dobson spectrophotometer during an eclipse event, the observation analysis showed positive and negative fluctuations of the column ozone of ca 2% within a period of two hours, approximately. Furthermore, observations of the surface ozone concentration and solar ultraviolet radiation reaching the ground during the eclipse event are presented.

The exceptional ozone depletion over the Arctic in January–March 2011

The largest ozone losses ever recorded over the Arctic have been measured by an international network of over 30 ground-based stations and satellite-borne sensors during January–March 2011. We study whether this was an exceptional event or whether it is part of the evolution of an ozone hole in the Arctic. The main finding is that the 2010–2011 winters record-breaking ozone loss was instigated by the extremely low stratospheric temperatures that are linked to climate change, that is, the coldest winters at the Arctic region have been getting colder leading to larger ozone losses there, which are progressively reaching the levels of the Antarctic ozone hole.