Abstract. Aerosol optical depth andÅngström exponent were obtained from multi filter rotating shadowband radiometer (MFRSR) observations carried out at the island of Lampedusa, in the Central Mediterranean, in the period July 2001-September 2003. The average aerosol optical depth at 495.7 nm, τ , is 0.24±0.14; the averageÅngström exponent, α, is 0.86±0.63. The observed values of τ range from 0.03 to 1.13, and the values of α vary from −0.32 to 2.05, indicating a large variability in aerosol content and size. In cloudfree conditions, 36% of the airmasses come from Africa, 25% from Central-Eastern Europe, and 19% from Western patterns over the Mediterranean, the efficiency of the aerosol production mechanisms, and the variability of the particles' residence time produce a distinct seasonal cycle of aerosol optical depths andÅngström exponent values. Particles originating from all sectors show a summer maximum in aerosol optical depth. The summer increase in optical depth for European aerosols is linked with an increment in the values of α, that indicates an enhancement in the number of fine particles. The summer maximum of τ for African particles is associated with a weak reduction in theÅngström exponent, suggesting an increase in the total number of particles and a relatively more intense transport of large particles. The observations were classified according to the aerosol optical properties, and two main classes have been identified: desert dust and biomass burning/urban-industrial aerosols. Values of τ and α averaged over the whole observing period are 0.37 and 0.15 for desert dust, and 0.27 and 1.77 for urbanindustrial/biomass burning aerosols.

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The atmospheric concentration of carbon dioxide and other greenhouse gases has been measured weekly since 1992 at the island of Lampedusa, in the Mediterranean sea. Lampedusa is a small island located approximately 100 km east of Tunisia, and 250 km south of Sicily. The 10-yr CO 2 data set has been analysed to quantify trends, and characterize semi-annual, annual and inter-annual variability. The data show an average trend of +1.7 ppmv yr −1 ; the average annual cycle has an amplitude of about 9 ppmv. In the period of investigation the annual growth rate varies between 0.5 and 4.5 ppmv yr −1 , and the amplitude of the annual cycle between 7 and 11 ppmv yr −1 . By comparing the observed growth rate with recent estimates of carbon dioxide emissions, it is calculated that 58-61% of the emitted CO 2 remains in the atmosphere. The CO 2 growth rate appears to be related to large-scale dynamic phenomena, primarily El Niño/Southern Oscillation (ENSO). An evident signature of the 1997-98 El Niño is apparent in the CO 2 record, and corresponds to a weakening of the exchange with the biosphere. A high correlation between the global average temperature and the 12-month average carbon dioxide growth rate is also found. Wind direction displays a significant inter-annual variability throughout the measurement period, possibly influencing the observed evolution of the CO 2 concentration.