Seasonal evolution of the tropospheric aerosol vertical profile in the central Mediterranean and role of desert dust

Abstract

[1] The seasonal evolution of the aerosol vertical distribution in the Central Mediterranean is studied using measurements made in the period 1999-2008 at Lampedusa with an aerosol Lidar and a multi filter rotating shadowband radiometer (MFRSR). Measurements show that the aerosol vertical distribution is largely influenced by Saharan dust, which produces a strong annual cycle both in aerosol vertical extension and optical depth. Dust layers are present in the profile in 38% of the cases throughout the year, and in 57% in summer. The dust top altitude peaks in late spring, up to 9 km. The monthly average optical depth at 500 nm for dust cases shows a main peak in July (0.38), and values exceeding 0.2 throughout March-September. Conversely, non-dust cases show a very limited seasonality, both in vertical distribution and aerosol optical depth. The monthly average optical depth for non-dust cases is smaller than 0.17 throughout the year. During winter, the vertical distribution and optical depth are very similar for both dust and non-dust cases. The seasonal average extinction coefficient profiles for dust and non-dust cases show remarkable differences in spring and summer, when values of the extinction coefficient exceed 0.5 Â 10 À4 m À1 throughout the altitude range 0-4.5 km for dust cases, and 0-1 km altitude for non-dust cases, respectively. Estimates of the Lidar Ratio are derived by combining Lidar and MFRSR measurements. The average Lidar Ratio at 532 nm is about 30 sr.

Long-range transport and mixing of aerosol sources during the 2013 North American biomass burning episode: analysis of multiple lidar observations in the western Mediterranean basin

“…The layer optical parameters are consistent with a dust plume with a large depolarization, while a large variability is observed for LR. The large depolarization ratio and the low LR value at 355 nm are quite similar to previous observations by Di Iorio et al (2009) in fresh dust exported over the Mediterranean Sea. The strong variation in the LR values between layer C of the LNG lidar at 13.5 • E and the Lampedusa observations at 12.5 • E suggests an increase of the mixing between the northward African dust outflow and the BB plume as the aircraft moved across the boundary between layer IV and II between Lampedusa and the southern cape of Sicily.…”

Evidence for heavy fuel oil combustion aerosols from chemical analyses at the island of Lampedusa: a possible large role of ships emissions in the Mediterranean

“…Figure 3 shows a marked seasonal pattern with springsummer maxima of the AOD and of the tree chemical markers. As discussed by Di Iorio et al (2009), the dust optical depth and vertical distribution show a large seasonal cycle, with elevated AOD and a wider vertical extension in spring and summer; the seasonal change is mainly controlled by dust transport occurring over the boundary layer. On the contrary, non dust cases and boundary layer aerosols display a very limited seasonal change (black dots and blue line in Fig.…”

Optical, physical and chemical properties of aerosols transported to a coastal site in the western Mediterranean: a focus on primary marine aerosols

“…The transport time of air masses from northern Africa to Ersa ranges between 2 and 6 days. Such air masses contain significant concentrations of mineral dust particles, which are usually transported at higher altitudes over the Mediterranean Basin, in the free troposphere and up to 9 km in altitude Hamonou et al, 1999;Dulac and Chazette, 2003;Di Iorio et al, 2009;Mona et al, 2006;Gómez-Amo et al, 2011). Thus, we also performed simulations starting at 4000 m a.s.l., that show that the air masses arriving at Cap Corse on 19 and 20 June were within the boundary layer (< 1000 m) over Tunisia and Algeria from 2 to 3 days before.…”

“…This high variability in terms of PMA loading and optical, physical and chemical properties leads to significant uncertainties in the quantification of regional radiative impact, both for direct and indirect effects (Forster et al, 2007;Stevens and Feingold, 2009). Finally, it should be noted that most past studies have documented aerosol properties in the eastern part of the Mediterranean Basin (Crete Mihalopoulos et al, 1997;Bardouki et al, 2003;Sciare et al, 2003;Koulouri et al, 2008;Greece Chabas and Lefèvre, 2000), even though many studies also took place in the central (Meloni et al, 2004;Di Iorio et al, 2009) and western (Sellegri et al, 2001;Cros et al, 2004;Pey et al, 2009;Guerrero-Rascado et al, 2009) Mediterranean Basin.…”