Abstract. Dust samples from rainfall residues have been collected in southeast Italy (40 • 20 N, 18 • 6 E) during dust outbreaks occurred from April to June 2002 to characterize morphological and elemental particle composition by different techniques, and investigate the dependence of particle properties on source regions. Four-day analytical back trajectories and satellite images have been used to infer source regions of the investigated dust samples.It has been found that the TOMS absorbing aerosol index was in the range 0.7-2.2 over Southern Italy when samples have been collected. The particle-size and -shape analysis by a scanning electron microscope (SEM) has revealed either that the particle-diameter distribution was between 0.3 and 30 µm with median-diameter values between 1.7-2.4 µm, and that the particles were characterized by a roundness factor varying from 0.8 to 2.5. The infrared transmission spectra have allowed recognizing that all dust samples contained a significant amount of illite. The X-ray energy dispersive (EDX) measurements have revealed that the Al/Si ratio of the transported dust varies from 0.41 to 0.50, and that the Al/Si,
Abstract. The all-sky direct radiative effect by anthropogenic aerosol (DRE a ) is calculated in the solar (0.3-4 µm) and infrared (4-200 µm) spectral ranges for six Mediterranean sites. The sites are differently affected by pollution and together reflect typical aerosol impacts that are expected over land and coastal sites of the central Mediterranean basin. Central to the simulations are aerosol optical properties from AERONET sun-/sky-photometer statistics for the year 2003. A discussion on the variability of the overall (natural + anthropogenic) aerosol properties with site location is provided. Supplementary data include MODIS satellite sensor based solar surface albedos, ISCCP products for high-mid-and low cloud cover and estimates for the anthropogenic aerosol fraction from global aerosol models. Since anthropogenic aerosol particles are considered to be smaller than 1 µm in size, mainly the solar radiation transfer is affected with impacts only during sun-light hours. At all sites the (daily average) solar DRE a is negative all year round at the top of the atmosphere (ToA). Hence, anthropogenic particles produce over coastal and land sites of the central Mediterranean a significant cooling effect. Monthly DRE a values vary from site to site and are seasonally dependent as a consequence of the seasonal dependence of available sun-light and microphysical aerosol properties. At the ToA the monthly average DRE a is −(4±1) W m −2 during spring-summer (SS, AprilSeptember) and −(2±1) W m −2 during autumn-winter (AW, October-March) at the polluted sites. In contrast, it varies between −(3±1) W m −2 and −(1±1) W m −2 on SS and AW, respectively at the less polluted site. Due to atmospheric absorption the DRE a at the surface is larger than at the ToA. At the surface the monthly average DRE a varies between the most and the least polluted site between −(7±1) W m −2 and −(4±1) W m −2 during SS, and between −(4±3) W m −2Correspondence to: M. R. Perrone (perrone@le.infn.it) and −(1±1) W m −2 during AW. The DRE a at infrared wavelengths is positive but negligible, especially at the ToA (<0.3 W m −2 ). The average of DRE a monthly-means referring to all sites has allowed getting a ToA-and sfc-DRE a yearly-mean value of −(3±2) and −(5±3) W m −2 , respectively at solar wavelengths. Last data, even if refer to a particular year, indicate that the radiative energy-balance of Central Mediterranean land and coastal sites is quite affected by anthropogenic particles.
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