310
A. di Sarra, M. Cacciani, J. DeLuisi, L. De Silvestri, T. Di Iorio, G. Fiacco, P. Grigioni
to wind erosion in arid regions, and the average size of transported particles depends
on wind strength; dust mobilization also depends on the nature of soil and other
parameters, and complex mechanisms, as saltation of relatively large dust grains,
are involved (Gillette et aI., 1974). Anthropic activity, through modification of the
land use and/or by inducing changes of climate (primarily through changes of
precipitation and temperature regime), may contribute to the production of mineral
aerosols. The Sahara desert is one of the main sources of mineral aerosols: the dust
particles are captured by the wind at the surface, are raised to considerable altitudes
in the troposphere by the strong convective regimes that develop over the desert
(Dubief, 1979), and may be transported to large distances. Saharan dust is
commonly observed over southern Europe, and, at far distances, in the Carribean,
and South America. In rare occasions, Saharan dust reaches northern Europe.
North and central African regions have suffered severe droughts in the recent
past (e.g. Middleton, 1985; Prospero and Nees, 1986; Dai et aI., 1998), and an
increase of the dust export has been correspondingly observed (Middleton, 1985;
Prospero and Nees, 1986). The droughts appear to be connected to large scale
phenomena occuring in the ocean-atmosphere system, like El Nino and the North
Atlantic Oscillation (NAO). A correlated behavior of the dust export from Sahara
to the North Atlantic and to the Mediterranean with these phenomena has been also
observed (Prospero and Nees, 1986; Moulin et aI., 1997). Dust aerosols strongly
influence the radiative balance, and affect the solar irradiance reaching sea and land
surface. In its turn, a change of the solar irradiance may influence evaporative fluxes
and, on a basin-wide scale, its hydrological budget (see e.g. Gilman and Garrett,
1994).
In the Mediterranean dust particles, that are non-hygroscopic and are not
expected to interact with clouds, may encounter and mix with different aerosol types.
Continental and anthropogenic particles originating from Europe, as well as marine
aerosols from the North Atlantic and the Mediterranean itself, are commonly present
in the basin. Dust particles coated with sulphate have been recently observed;
mixing of the dust with sulphate is believed to occur as a consequence of cloud
evaporation processes (Levin et aI., 1996). In this way, dust particles become
hygroscopic, and may influence the cloud formation and properties. Saharan dust
constitutes one of the most relevant inputs of trace elements to the Mediterranean
(e.g. Kubilay and Saydam, 1995), and an important source of nutrients for oceanic
microorganisms. Desert aerosols may also affect the precipitation acidity (Loye-Pilot
et aI., 1986).
In this paper we discuss some measurements carried out from the Station for
Climate Observations of the National Agency for New Technology, Energy, and
Environment of Italy (ENEA) in the island of Lampedusa (3505' N, 12.6' E).
Lampedusa is a small, rocky island, relatively isolated in the central-southern
Mediterranean, approximately 100 km east of Tunisia, and 200 km North of Libya.
The island is 10 km long, has a surface area of about 20 km 2 , and its maximum
elevation is 120 m. The ENEA station is located on the north-eastern coast of
Lampedusa, on a 45 m high cliff. At the station total ozone, ultraviolet spectral
A. di Sarra, M. Cacciani, J. DeLuisi, L. De Silvestri, T. Di Iorio, G. Fiacco, P. Grigioni
to wind erosion in arid regions, and the average size of transported particles depends
on wind strength; dust mobilization also depends on the nature of soil and other
parameters, and complex mechanisms, as saltation of relatively large dust grains,
are involved (Gillette et aI., 1974). Anthropic activity, through modification of the
land use and/or by inducing changes of climate (primarily through changes of
precipitation and temperature regime), may contribute to the production of mineral
aerosols. The Sahara desert is one of the main sources of mineral aerosols: the dust
particles are captured by the wind at the surface, are raised to considerable altitudes
in the troposphere by the strong convective regimes that develop over the desert
(Dubief, 1979), and may be transported to large distances. Saharan dust is
commonly observed over southern Europe, and, at far distances, in the Carribean,
and South America. In rare occasions, Saharan dust reaches northern Europe.
North and central African regions have suffered severe droughts in the recent
past (e.g. Middleton, 1985; Prospero and Nees, 1986; Dai et aI., 1998), and an
increase of the dust export has been correspondingly observed (Middleton, 1985;
Prospero and Nees, 1986). The droughts appear to be connected to large scale
phenomena occuring in the ocean-atmosphere system, like El Nino and the North
Atlantic Oscillation (NAO). A correlated behavior of the dust export from Sahara
to the North Atlantic and to the Mediterranean with these phenomena has been also
observed (Prospero and Nees, 1986; Moulin et aI., 1997). Dust aerosols strongly
influence the radiative balance, and affect the solar irradiance reaching sea and land
surface. In its turn, a change of the solar irradiance may influence evaporative fluxes
and, on a basin-wide scale, its hydrological budget (see e.g. Gilman and Garrett,
1994).
In the Mediterranean dust particles, that are non-hygroscopic and are not
expected to interact with clouds, may encounter and mix with different aerosol types.
Continental and anthropogenic particles originating from Europe, as well as marine
aerosols from the North Atlantic and the Mediterranean itself, are commonly present
in the basin. Dust particles coated with sulphate have been recently observed;
mixing of the dust with sulphate is believed to occur as a consequence of cloud
evaporation processes (Levin et aI., 1996). In this way, dust particles become
hygroscopic, and may influence the cloud formation and properties. Saharan dust
constitutes one of the most relevant inputs of trace elements to the Mediterranean
(e.g. Kubilay and Saydam, 1995), and an important source of nutrients for oceanic
microorganisms. Desert aerosols may also affect the precipitation acidity (Loye-Pilot
et aI., 1986).
In this paper we discuss some measurements carried out from the Station for
Climate Observations of the National Agency for New Technology, Energy, and
Environment of Italy (ENEA) in the island of Lampedusa (3505' N, 12.6' E).
Lampedusa is a small, rocky island, relatively isolated in the central-southern
Mediterranean, approximately 100 km east of Tunisia, and 200 km North of Libya.
The island is 10 km long, has a surface area of about 20 km 2 , and its maximum
elevation is 120 m. The ENEA station is located on the north-eastern coast of
Lampedusa, on a 45 m high cliff. At the station total ozone, ultraviolet spectral