2 research outputs found
Aerosol optical properties from columnar data during the second Aerosol Characterization Experiment on the south coast of Portugal
Measurements of aerosol optical properties over the atmospheric column (aerosol
optical thickness, spectral angular sky radiance (sky brightness), and downwelling
hemispheric flux) have been used to derive climate-relevant aerosol parameters such as the
phase function, the broadband single-scattering albedo, and the refractive index. These
parameters are needed to estimate the direct short-wave radiative forcing by aerosols and
to validate aerosol models in the satellite retrieval algorithms. Values of the broadband
single-scattering albedo obtained in this study range between w0 = 0.98 (marine aerosols)
and 0.90 (continental pollution aerosols). The columnar ambient broadband refractive
index is found to be m = 1.39 卤 0.044 i (<0.003) for marine conditions and m = 1.48 卤
0.058 i (0.01 卤 0.003) for polluted continental aerosols. Nonsphericity is shown to be
important in the case of marine aerosols. Moreover, aerosol nonsphericity gives an
additional contribution to the negative short-wave radiative forcing of marine aerosols
under clear-sky conditions, which can be estimated as being 30 up to 50% of the radiative
forcing estimated for spherical marine aerosols. In the case of continental polluted aerosols
the optical properties can be represented by spherical particles, and no additional shape
effect has to be considered. However, the aerosol absorption leads to an increase of about
40% of the radiative forcing estimated for nonabsorbing aerosol of the same size
distribution