Saharan dust profiles measured by lidar at Lampedusa

Sarra, Alcide di; Iorio, Tatiana Di; Cacciani, Marco; Fiocco, G.; Fuà, D.

doi:10.1029/2000jd900734

Cited by 108 publications

(96 citation statements)

References 42 publications

(5 reference statements)

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“…They found that the largest values of α correspond to airmasses coming from Eastern Europe and Russia. The aerosol origin sector can be identified by considering the time spent in the different sectors along the trajectory (di Sarra et al, 2001;Gerasopoulos et al, 2003), or by more sophisticated correlation methodologies (Formenti et al, 2001). Previous results (di Sarra et al, 2001), as well as a preliminary analyses of this dataset, indicate that dust is loaded in the air column even after a marginal passage over the African continent.…”

Section: Identification Of the Aerosol Originmentioning

confidence: 99%

“…In this study we use trajectories that end over Lampedusa at 750, 2000, and 4000 m. Previous investigations based on spring-summer lidar observations (di Sarra et al, 2001) and model results (e.g. Alpert et al, 2004) have shown that African airmasses are generally loaded with desert dust up to at least 4 km, and often up to 7-8 km.…”

Section: Identification Of the Aerosol Originmentioning

confidence: 99%

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Aerosol optical properties at Lampedusa (Central Mediterranean). 1. Influence of transport and identification of different aerosol types

et al. 2006

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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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Section: Identification Of the Aerosol Originmentioning

confidence: 99%

Section: Identification Of the Aerosol Originmentioning

confidence: 99%

Aerosol optical properties at Lampedusa (Central Mediterranean). 1. Influence of transport and identification of different aerosol types

et al. 2006

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“…The first two years of regular observations by the EARLINET stations showed frequent transport of Saharan dust from southern Europe to central and northern Europe. It has been shown that dust plumes may be found in heights well above the surface [Hamonou et al, 1999;Gobbi et al, 2000;Di Sarra et al, 2001;Mattis et al, 2002b;Welton et al, 2000]. Observations of mineral dust in different parts of the Mediterranean region revealed significantly different optical properties, as the result of highly variable physical and chemical properties [e.g., Sokolik et al, 1998;von Hoyningen-Huene et al, 1999;Tanré et al, 2001].…”

Section: Introductionmentioning

confidence: 99%

Saharan dust over a central European EARLINET‐AERONET site: Combined observations with Raman lidar and Sun photometer

et al. 2003

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Combined observations with an advanced aerosol water‐vapor temperature Raman lidar and a Sun photometer are used for a detailed characterization of geometrical and optical properties of a continental‐scale Saharan dust event observed over Leipzig (51.3°N, 12.4°E), Germany, from 13 to 15 October 2001. The Raman lidar is part of the European Aerosol Research Lidar Network (EARLINET). Automatic observations of aerosol optical depth and sky brightness are made with the Sun photometer in the framework of the worldwide operating Aerosol Robotic Network (AERONET). The dust plume reached a top height of 6000 m. Sun photometer and lidar observations showed a constant increase of columnar optical depth at 532 nm from 0.25 on 13 October 2001 to a maximum of ∼0.63 on 14 October 2001. According to observations with lidar, up to 90% of the optical depth at the wavelength of 532 nm was contributed by the dust layer above 1000‐m height. Ångström exponents from Sun photometer observations between 380 and 1020 nm were ∼0.45 at the beginning of the dust period, and dropped to minimum values of 0.14 during the peak of the dust outbreak. Vertically resolved Ångström exponents derived from lidar profiles of the extinction coefficients at 355 and 532 nm showed a strong variability with values as low as −0.2 in the center of the dust plume. Below 1000‐m height column‐averaged Ångström exponents strongly varied between 1.0 in the beginning of the dust period and 0.39 on 14 October 2001 when the dust penetrated into the boundary layer. Comparison of column‐averaged optical depth and Ångström exponents derived from lidar and Sun photometer observations showed excellent agreement. Particle depolarization ratios of up to 25% were derived from lidar observations at 532 nm. Scattering phase functions retrieved from Sun photometer observations indicated particles of nonspherical shape. This shape caused unusually large particle extinction‐to‐backscatter (lidar) ratios at 532 nm in the range from 50 to 80 sr. There were substantial deviations of the lidar ratio at 532 nm derived from both measurement methods. They are explained by the effect of particle shape.

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“…A challenge in the creation of an adequate data set was the adjustment between optical measurements made through the total atmospheric column and aerosol sampling at ground level. Representativeness of surface sampling for dust events is problematic due to the fact that dust maybe transported at high altitudes (Hamonou et al, 1999;di Sarra et al, 2001;Tsidulko et al, 2002;Dulac and Chazette, 2003;Alpert et al, 2004) and not be adequately sampled at the surface. An additional problem is that the aerosolsampling unit collects particles during two or three days on one filter, thus it may contain particles from different events and sources.…”

Section: Data Integrationmentioning

confidence: 99%

The role of iron and black carbon in aerosol light absorption

et al. 2008

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Abstract. Iron is a major component of atmospheric aerosols, influencing the light absorption ability of mineral dust, and an important micronutrient that affects oceanic biogeochemistry. The regional distribution of the iron concentration in dust is important for climate studies; however, this is difficult to obtain since it requires in-situ aerosol sampling or simulation of complex natural processes. Simultaneous studies of aerosol chemical composition and radiometric measurements of aerosol optical properties, which were performed in the Negev desert of Israel continuously for about eight years, suggest a potential for deriving a relationship between chemical composition and light absorption properties, in particular the spectral single-scattering albedo.The two main data sets of the present study were obtained by a sun/sky radiometer and a stacked filter unit sampler that collects particles in coarse and fine size fractions. Analysis of chemical and optical data showed the presence of mixed dust and pollution aerosol in the study area, although their sources appear to be different. Spectral SSA showed an evident response to increased concentrations of iron, black carbon equivalent matter, and their mixing state. A relationship that relates the spectral SSA, the percentage of iron in total particulate mass, and the pollution components was derived. Results calculated, using this relationship, were compared with measurements from dust episodes in several locations around the globe. The comparison showed reasonable agreeCorrespondence to: Y. Derimian (derimian@loa.univ-lille1.fr) ment between the calculated and the observed iron concentrations, and supported the validity of the suggested approach for the estimation of iron concentrations in mineral dust.

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Saharan dust profiles measured by lidar at Lampedusa

Cited by 108 publications

References 42 publications

Aerosol optical properties at Lampedusa (Central Mediterranean). 1. Influence of transport and identification of different aerosol types

Aerosol optical properties at Lampedusa (Central Mediterranean). 1. Influence of transport and identification of different aerosol types

Saharan dust over a central European EARLINET‐AERONET site: Combined observations with Raman lidar and Sun photometer

The role of iron and black carbon in aerosol light absorption

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