diverse and depend on the chemical and physical properties of the aerosol particles.
Aerosols have a strong impact on climate both due to scattering and absorption of
incoming solar radiation (direct effect) and through their effects on cloud properties
and associated cloud albedo (first indirect effect) and precipitation (second indirect
effect). Aerosol radiative forcing is a critical, however, variable and still quite
unrecognized, component of the global climate, which results in the fact that climate
models have to rely on incomplete information of the aerosol optical properties (Eck
et al. 2010). The multiyear, multi-instrument observations show robust differentiation in both the magnitude and spectral dependence of the absorption—a property
driving aerosol climate forcing, for desert dust, biomass burning, urban–industrial,
and marine aerosols (Dubovik et al. 2002). Moreover, we observe significant variability of the absorption for the same aerosol type due to different meteorological and
source characteristics as well as different emission characteristics.
Atmospheric aerosols consist of a suspension of particles whether they occur as
particles or as droplets, i.e. chemicals in their liquid phase, or dissolved in a liquid
in the air. Aerosols are an important constituent of the atmospheric boundary layer.
Aerosol particles provide surfaces for heterogeneous chemical processes, they also
act as a condensation sink for atmospheric trace gases, while hygroscopic particles
serve as cloud condensation nuclei. Aerosol particle sizes vary from a few nanometres to some tens of micrometres and the “large” particles are sufficiently heavy
that their atmospheric residence time is very short and hence their concentrations
are negligible. Still in very strong wind conditions (hurricanes) these large sea spray
particles may be important in the ocean–atmosphere transfer of heat and water
vapour (Andreas et al. 2008).
As a result of various interacting processes, the most abundant aerosol particles
in the atmosphere are those with a radius of a few tenths of microns, which are often
referred to as accumulation mode particles. Their atmospheric lifetime is relatively
long (few days to a few weeks) and it depends on their surface roughness and
related deposition velocity, and their main removal mechanism is wet deposition.
Atmospheric aerosols originate from a wide variety of sources in both marine
and continental environments. Aerosol content varies significantly depending upon
whether the air mass is natural or modified anthropogenically, marine or continental, rural or urban (Zielinski and Zielinski 2002). Aerosols formed over land by
either primary or secondary formation processes are transported over the oceans and
contribute substantially to the aerosol concentrations over the oceans (Kastendeuch
and Najjar 2003; Smirnov et al. 2003; Zielinski 2004). Sea spray aerosol is directly
produced at the sea surface through the interactions between wind and surface
waves (Hobbs 2000). Ship emissions and volcanoes also contribute to primary
aerosol in the marine atmosphere.
Secondary aerosol formation from gases released from the sea surface also
contribute significantly to marine atmosphere aerosol loading. Estimates of the mass
concentrations show that the largest aerosol contributions on a global scale are from
sea spray aerosol and desert dust (Andreae and Rosenfeld 2008; Jickells et al. 2005).
The chemical and physical properties of aerosols vary both in space and time and
depend on the proximity of sources and sinks. Additionally they strongly depend on
2
T. Zielinski et al.
Aerosols have a strong impact on climate both due to scattering and absorption of
incoming solar radiation (direct effect) and through their effects on cloud properties
and associated cloud albedo (first indirect effect) and precipitation (second indirect
effect). Aerosol radiative forcing is a critical, however, variable and still quite
unrecognized, component of the global climate, which results in the fact that climate
models have to rely on incomplete information of the aerosol optical properties (Eck
et al. 2010). The multiyear, multi-instrument observations show robust differentiation in both the magnitude and spectral dependence of the absorption—a property
driving aerosol climate forcing, for desert dust, biomass burning, urban–industrial,
and marine aerosols (Dubovik et al. 2002). Moreover, we observe significant variability of the absorption for the same aerosol type due to different meteorological and
source characteristics as well as different emission characteristics.
Atmospheric aerosols consist of a suspension of particles whether they occur as
particles or as droplets, i.e. chemicals in their liquid phase, or dissolved in a liquid
in the air. Aerosols are an important constituent of the atmospheric boundary layer.
Aerosol particles provide surfaces for heterogeneous chemical processes, they also
act as a condensation sink for atmospheric trace gases, while hygroscopic particles
serve as cloud condensation nuclei. Aerosol particle sizes vary from a few nanometres to some tens of micrometres and the “large” particles are sufficiently heavy
that their atmospheric residence time is very short and hence their concentrations
are negligible. Still in very strong wind conditions (hurricanes) these large sea spray
particles may be important in the ocean–atmosphere transfer of heat and water
vapour (Andreas et al. 2008).
As a result of various interacting processes, the most abundant aerosol particles
in the atmosphere are those with a radius of a few tenths of microns, which are often
referred to as accumulation mode particles. Their atmospheric lifetime is relatively
long (few days to a few weeks) and it depends on their surface roughness and
related deposition velocity, and their main removal mechanism is wet deposition.
Atmospheric aerosols originate from a wide variety of sources in both marine
and continental environments. Aerosol content varies significantly depending upon
whether the air mass is natural or modified anthropogenically, marine or continental, rural or urban (Zielinski and Zielinski 2002). Aerosols formed over land by
either primary or secondary formation processes are transported over the oceans and
contribute substantially to the aerosol concentrations over the oceans (Kastendeuch
and Najjar 2003; Smirnov et al. 2003; Zielinski 2004). Sea spray aerosol is directly
produced at the sea surface through the interactions between wind and surface
waves (Hobbs 2000). Ship emissions and volcanoes also contribute to primary
aerosol in the marine atmosphere.
Secondary aerosol formation from gases released from the sea surface also
contribute significantly to marine atmosphere aerosol loading. Estimates of the mass
concentrations show that the largest aerosol contributions on a global scale are from
sea spray aerosol and desert dust (Andreae and Rosenfeld 2008; Jickells et al. 2005).
The chemical and physical properties of aerosols vary both in space and time and
depend on the proximity of sources and sinks. Additionally they strongly depend on
2
T. Zielinski et al.