Ångström coefficient as an indicator of the atmospheric aerosol type for a well-mixed atmospheric boundary layer : Part 1: Model development
article
The physical and optical properties of an atmospheric aerosol mixture depend
on a number of factors. The relative humidity influences the size of hydroscopic
particles and the effective radius of an aerosol mixture. In consequence, values of
the aerosol extinction, the aerosol optical thickness and the Ångström coefficient
are modified. A similar effect is observed when the aerosol composition changes.
A higher content of small aerosol particles causes the effective radius of an aerosol
mixture to decrease and the Ångström coefficient to increase. Both effects are
analysed in this paper. The parameters of the size distribution and the type
of components used to represent natural atmospheric aerosol mixtures are based
on experimental data. The main components are sea-salts (SSA), anthropogenic
salts (WS, e.g. NH4HSO4, NH4NO3, (NH4)2SO4), organic carbon (OC) and black
carbon (BC). The aerosol optical thickness is modelled using the external mixing
approach. The influence of relative humidity on the optical and physical properties
of the following aerosol mixtures is investigated: (SSA&WS), (SSA&OC),
(SSA&BC), (SSA, WS&OC) and (WS, OC&BC). It is demonstrated that the
Ångström coefficient can be used as a rough indicator of the aerosol type.
on a number of factors. The relative humidity influences the size of hydroscopic
particles and the effective radius of an aerosol mixture. In consequence, values of
the aerosol extinction, the aerosol optical thickness and the Ångström coefficient
are modified. A similar effect is observed when the aerosol composition changes.
A higher content of small aerosol particles causes the effective radius of an aerosol
mixture to decrease and the Ångström coefficient to increase. Both effects are
analysed in this paper. The parameters of the size distribution and the type
of components used to represent natural atmospheric aerosol mixtures are based
on experimental data. The main components are sea-salts (SSA), anthropogenic
salts (WS, e.g. NH4HSO4, NH4NO3, (NH4)2SO4), organic carbon (OC) and black
carbon (BC). The aerosol optical thickness is modelled using the external mixing
approach. The influence of relative humidity on the optical and physical properties
of the following aerosol mixtures is investigated: (SSA&WS), (SSA&OC),
(SSA&BC), (SSA, WS&OC) and (WS, OC&BC). It is demonstrated that the
Ångström coefficient can be used as a rough indicator of the aerosol type.
Topics
TNO Identifier
242074
Source
Oceanologia, 51(1), pp. 5-38.
Pages
5-38
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